Journal of Neural Transmission
J Neural Transm [GenSect] (1992) 89:219-232
9 Springer-Verlag 1992 Printed in Austria
B l o o d - C S F barrier permeability and central nervous s y s t e m immunoglobulin G in schizophrenia D. G. Kirch 1' 2, R. C. Alexander2, R. L. Suddath2, N. M. Papadopoulos 3, C. A. Kaufmann2, D. G. Daniel 4, and R. J. Wyatt z
1Division of Clinical Research, 2Neuropsychiatry Branch, and 4Clinical and Research Services Branch, National Institute of Mental Health, Rockville, Maryland and Washington, D. C., and 3Chemistry Service, National Institutes of Health, Bethesda, Maryland, U.S.A. Accepted February 21, 1992
Summary. The ratio of albumin in cerebrospinal fluid (CSF) to serum may serve as an index of the integrity of the blood-CSF barrier, with increases in this ratio indicating increased permeability. The ratio of immunoglobulin G (IgG) in CSF to serum (divided by the albumin ratio to correct for variance in blood-CSF permeability) represents an index of the endogenous production of IgG in the central nervous system (CNS), with increases reflecting a possible infectious and/or autoimmune process stimulating central IgG synthesis. We analyzed simultaneously collected CSF and serum samples from 46 schizophrenic subjects, 8 of whom were studied both on and off neuroleptic treatment, and samples from 20 normal controls. The data indicated increases in CSF/ serum albumin ratios or CSF/serum IgG indices in 22% and 20%, respectively, of the schizophrenic patients. Only 3 patients showed elevations in both indices. Comparison of values on and off neuroleptics indicated no significant effect of neuroleptics on these indices. Keywords: Blood-CSF barrier, albumin, immunoglobulin G, schizophrenia. Introduction
In the effort to elucidate the pathophysiologic and etiologic factors involved in schizophrenia, the analysis of cerebrospinal fluid (CSF) has been a primary method of assessing central nervous system (CNS) function in living subjects. Studies of neurotransmitters, metabolites, proteins, and other CSF constituents in schizophrenia have been extensively pursued for many years with mixed results (van Kammen and Sternberg, 1980). Among the abnormalities reported at an early point in the course of biological investigations of schizophrenia was
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an apparent increase in total CSF protein concentrations (Bruetsch et al., 1942), although subsequent studies of specific CSF proteins yielded divergent findings (Pearson, 1973; Bock and Rafaelson, 1974; Bock, 1978; Kirch et al., 1985; DeLisi and Crow, 1986; Torrey and Kaufmann, 1986). Many disorders of the CNS, including meningitis, neoplasms, polyneuropathies, disk herniations, and infarctions lead to elevated concentrations of CSF proteins (Papadopoulos et al.; 1984). The primary component of CSF protein is albumin, which is usually at a concentration about 200 times lower in CSF compared with serum (Tibbling et al., 1977). Since synthesis of albumin within the mature CNS is not thought to occur (Ganrot and Laurell, 1974), all albumin in the CSF is derived from serum. The ratio of CSF to serum albumin, in the absence of significant disturbances in CSF flow, is therefore thought to reflect the overall permeability of those structures that separate the serum from the CSF compartment (Schliep and Felgenhauer, 1978). Immunoglobulin G (IgG) concentration in the CSF is measured because of the important clinical implications of increased production within the CNS. The ratio between the concentration of IgG in CSF to IgG in serum (corrected for the ratio of albumin in CSF to serum) has been proposed as an index that can distinguish endogenous CNS IgG production from elevation of CSF IgG from other causes (Ganrot and Laurell, 1974). Use of the CSF IgG index to identify endogenous CNS IgG synthesis is supported by the finding of abnormally high values in 80% of multiple sclerosis patients (Link and Tibbling, 1977). We previously reported data showing some schizophrenic patients to have abnormalities in the albumin ratio and/or the IgG index (Kirch etal., 1985). We have now expanded the number of schizophrenic patients studied. By including patients studied both on and off neuroleptic treatment, these data also allow an assessment of the effect, if any, of neuroleptics on these CSF protein indices.
Subjects and methods Subjects The patient group consisted of 46 individuals (31 males and 15 females) who were inpatients in the research program of the National Institute of Mental Health (NIMH) Neuropsychiatric Research Hospital, located at the Neuroscience Center at Saint Elizabeths in Washington, D.C. All met DSM-III (American Psychiatric Association, 1980) criteria for schizophrenia, and were determined to be free of significant coexisting medical disorders. Clinical data gathered on each subject included age of onset and duration of illness, past drug and/or alcohol abuse (patients with active substance abuse being excluded from participation), past treatment with electroconvulsive therapy (ECT), and the presence or absence of tardive dyskinesia. Testing of intelligence(IQ) using the WAIS-R was performed in 33 patients. Of the 46 patients, 38 underwent a singlelumbar puncture and venipuncture procedure. Of these, 15 were on chronic neuroleptic treatment at the time of study, while 23 had been withdrawn from neuroleptic treatment for a period of at least 4 weeks. The remaining 8
Blood-CSF barrier and CSF immunoglobulin G in schizophrenia
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patients were studied in paired fashion both on and at least 4 weeks after withdrawal from chronic neuroleptic treatment. Of the total of 46 patients, 24 had been included in our earlier study (Kirch etal., 1985). All individuals participating in these studies provided informed consent. In addition, previously published (Papadopoulos et al., 1984) comparison CSF protein data were available for 20 healthy individuals (16 males and 4 females) ranging in age from 20 to 87 (mean 4- SD = 54.1 4- 20.5). These individuals were evaluated as inpatients at the Clinical Center of the National Institutes of Health and were free of any significant neuropsychiatric diagnosis or other medical disorders. Normal subjects spanning a wide age range had been selected in order to validate the normal ranges for the CSF albumin ratio and IgG index in adults proposed by other investigators using "neurologic" controls (Tibbling etal., 1977; Killingsworth, 1982).
Methods Each patient underwent a lumbar puncture in the lateral decubitus position early in the morning while at bedrest. CSF was collected under sterile conditions with the initial fraction sent for routine laboratory studies. No patients whose CSF on microscopic examination showed evidence of a traumatic lumbar puncture was included in this study. As noted above, 8 patients underwent paired lumbar punctures, one on and one off neuroleptic. A total of 54 lumbar punctures were performed in the 46 patients, 23 while patients were medicated and 31 after neuroleptic withdrawal. Patient CSF samples from the second fraction, together with serum samples collected at the time of lumbar puncture, were stored at - 70 ~ Analyses of the concentrations of albumin and IgG in CSF and serum in the samples from the 46 patients and the 20 control subjects were performed in the same laboratory by one of the authors (N.M.P.). Patient samples were assayed using rate nephelometry, while control values were determined by radial immunodiffusion (Papadopoulos etal., 1984). These methods have been demonstrated to correlate well with one another (Christenson etal., 1988). The albumin ratio was calculated as [(CSF albumin~serum albumin) x 1000], while the IgG index was calculated as [ (CSF IgG/serum IgG) / (CSF albumin/serum albumin)]. The denominator in the IgG index serves to correct the IgG index for any variance in the blood-CSF barrier which might allow more or less peripheral IgG to enter the CSF, resulting in a more accurate representation of endogenous CNS IgG production. All 46 patients underwent a computed tomographic (CT) brain scan as part of their evaluation on admission to the research program, allowing calculation of the ventricularbrain ratio (VBR) by planimetry as previously described (Synek and Reuben, 1976; Shelton etal., 1988). All scans were nonenhanced and consisted of 12 parallel planes 10mm thick with a pixel size of 0.5 by 0.5 mm and matrix size of 512 • 512. No patients had diagnostic abnormalities on CT scan, and all scans were screened for evidence of asymmetric head placement in the CT scanner. Insofar as the CT scan was typically part of the initial admission evaluation, it usually preceded the lumbar puncture by several weeks.
Statistical analysis The individual patient and control values for the albumin ratio were compared in terms of whether they were within or outside previously determined, age-adjusted reference ranges for adults (Tibbling et al., 1977) using Fisher's exact test. Patient and control data for the IgG index, which is constant across the age span, were compared using a t-test. For both the albumin quotient and the IgG index, the descriptive data on patients whose CSF protein index was outside the normal range versus those who fell within the normal range were compared using a t-test or Fisher's exact test, depending on the variable. Lastly, data on
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the albumin ratio and IgG index in the 8 subjects tested on versus off neuroleptic treatment were analyzed using a matched-pairs t-test.
Results
The demographic and other relevant data on the 46 patients are summarized in Table 1. Although the patients were relatively young, with a mean age of 29.9, they were characteristic of patients referred to the N I M H research program insofar as they were chronically ill and relatively treatment-refractory, with most having a history of repeated hospitalizations and constant neuroleptic treatment throughout the duration of their illnesses. Their mean age of onset was 20.1 years, with a mean duration of illness of 9.8 years. Of the 46 schizophrenic patients, 18 had a history of past drug and/or alcohol abuse, 5 had received ECT (although none had received ECT within several months prior to lumbar puncture), and 9 had persistent tardive dyskinesia. The mean VBR in the patient group as a whole was 5.73, a value similar to that found in a larger cumulative series of CT scans in schizophrenic patients from the N I M H program (Shelton et al., 1988). The results of IQ testing in 33 of the 46 patients revealed the group to be somewhat impaired, with a mean full-scale IQ of 89.3, and a gap between higher verbal and lower performance scores. Albumin ratio Individual data regarding the calculated albumin ratio for the 46 patients and 20 healthy control subjects are displayed in Fig. 1, which also includes the normal ranges for the albumin ratio across the adult age span determined by Tibbling etal. (1977). For the 8 patients who underwent paired lumbar punctures, the value used was the mean of the two analyses. It is apparent from both the previously established reference values and the data from our own 20 control
Table 1. Descriptive information for 46 schizophrenic patients participating in study of CSF proteins Age* Gender Age of onset of illness* Duration of illness (years)* Past substance abuse ECT Tardive dyskinesia CT scan VBR* IQ (N = 33)* Full scale Verbal Performance * mean -4- SD
29.9 -t- 6.0 31 male / 15 female 20.1 + 3.3 9.8 4- 5.8 18 yes / 28 no 5 yes / 41 no 9 yes / 37 no 5.73 + 3.33 89.3 4- 13.3 94.4 4- 15.9 84.8 4- l 1.1
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Fig. 1. Albumin ratio for 46 schizophrenicpatients and 20 healthy control subjects. Enclosed boxes represent age-specific reference values established by Tibbling et al. (1977) subjects that there is an increase in the CSF/serum albumin ratio with normal aging~ For the albumin ratio, 10 of 46 patients and 1 of 20 control subjects exceeded the originally reported control values (p = 0.08; one-tailed Fisher's exact test). Table 2 presents an analysis of clinical variables for the 10 patients with albumin ratios above the normal range versus the 36 patients falling within the normal range, with comparisons of age, onset, duration, VBR, and IQ by ttest and of past substance abuse, ECT, and tardive dyskinesia by Fisher's exact test. None of the comparisons indicated a statistically significant difference between the two groups.
Immunoglobulin G index Figure 2 shows the data for the IgG index for the 46 patients (with the mean value shown for those patients having two lumbar punctures) and the 20 control subjects. The normal range for the IgG index has been shown to be constant across the age span (Tibbling etal., 1977; Killingsworth, 1982). For the 20 control subjects, the mean (4- SD) IgG index was 0.44 (4- 0.095). These values
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Table 2. Assessment of patients with elevated albumin ratio versus those within the normal range
Age* Gender Age of onset of illness* Duration of illness (years)* Past substance abuse ECT Tardive dyskinesia CT scan VBR* IQ* Full scale Verbal Perfomance
Elevated (N = 10)
Normal (N = 36)
28.9 4- 4.5 9 male / 1 female 19.1 4- 1.8
30.2 4- 6.3 22 male / 14 female 20.4 4- 3.6
9.8 4- 4.8
9.8 4- 6.1
6 yes
4 no
12 yes / 24 no
2 yes 2 yes
8 no 8 no
3 yes / 33 no 7 yes / 29 no
5.58 + 3.34 ( N = 8) 89.3 4- 16.5 93.1 4- 18.2 85.9 + 13.1
5.77 4- 3.37 ( N = 25) 89.4 4- 12.5 94.8 4- 15.5 84.5 4- 10.7
* mean 4- SD
are comparable to those reported by other investigators (Tibbling et al., 1977; Killingsworth, 1982). The mean (-4- SD) IgG index for the 46 patients was 0.54 (+ 0.24), which was significantly (p < 0.01, one-tailed t-test) higher than that of the 20 controls (0.44 + 0.095). Of the 46 patients, 9 had an IgG index greater than 0.63 (the mean for the 20 control subjects plus two SD) versus none of the control subjects (p < 0.05; one-tailed Fisher's exact test). Table 3 shows an assessment of clinical variables for these 9 patients versus those who fell within the normal range. Using the same variables and statistical analyses as for the albumin ratio data in Table 2, the only significant difference was that patients with elevated IgG indices were significantly (p < 0.003; two-tailed Fisher's exact test) more likely to have undergone ECT in the past. Of the 46 patients studied, only 3 showed coexisting elevations of both the albumin ratio and the IgG index.
Effect of neuroleptics The data from paired lumbar punctures performed on and off chronic neuroleptic treatment in 8 of the patients allowed an evaluation of the potential effect of drug treatment on the albumin ratio (Fig. 3) and IgG index (Fig. 4). As illustrated by both figures, there was no significant difference between the neuroleptic-treatment and neuroleptic-withdrawal state for either CSF protein index in these 8 patients. Of the total 54 lumbar punctures performed on the
Blood-CSF barrier and CSF immunoglobulin G in schizophrenia
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46 patients, 23 were done while the patients were being treated with neuroleptic and 31 were done at least 4 weeks after neuroleptic withdrawal. As shown in Table 4, there was no significant difference in either the albumin ratio or IgG index between the two groups. Thus, neither the paired analysis in 8 subjects nor the group analysis in 46 subjects indicated that either the albumin quotient or IgG index are significantly affected by neuroleptic treatment. Discussion
Blood-CSF barrier permeability The blood-brain barrier (BBB) was first discovered by Paul Ehrlich, who observed that injecting aniline dye into the blood stream of animals stained all of the body organs except the brain (Goldstein and Betz, 1986). Modern studies have refined the anatomical understanding of this barrier, revealing tight junctions between endothelial cells (Reese and Karnovsky, 1967). Although commonly thought to be equivalent, the blood-CSF barrier is distinct from the
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Table 3. Assessment of patients with elevated I g G index versus those within the normal range
Age* Gender Age of onset of illness* Duration of illness (years)* Past substance abuse ECT Tardive dyskinesia CT scan VBR* IQ* Full scale Verbal Performance
Elevated (N = 9)
Normal (N = 37)
31.8 + 6.1 7 male / 2 female 18.8 4- 3.1
29.5 + 5.9 24 male / 13 female 20.4 4- 3.3
13.0 4- 8.0
9.1 • 4.9
4 yes / 5 no
14 yes / 23 no
4 yes / 5 no 2 yes / 7 no 5.77 4- 3.81 (N = 4) 85.5 4- 17.7 90.3 • 16.8 80.8 • 17.7
1 yes / 36 no** 7 yes / 30 no 5.71 • 3.26 (N = 29) 89.9 4- 12.9 95.0 • 16.0 85.4 • 10.3
* mean • SD ** p < 0.003
ALBUMIN QUOTIENT
OFF
ON NEUROLEPTIC
Fig. 3. Albumin ratio in 8 schizophrenic patients on and off chronic neuroleptic treatment (p = 0.13, matched pairs t-test)
Blood-CSF barrier and CSF immunoglobulin G in schizophrenia
227
0,8
0,7
0.6 IGG INDEX 0.5
0.4
0.3
ON
OFF
NEUROLEPTIC
Fig. 4. IgG index in 8 schizophrenic patients on and off chronic neuroleptic treatment (p = 0.35, matched pairs t-test) Table 4. Albumin ratio and IgG index (mean • SD) in 23 CSF samples collected from patients on neuroleptics compared with 31 samples collected from patients withdrawn from neuroleptics
Albumin ratio IgG index
Neuroleptic treatment
Neuroleptic withdrawal
4.75 • 1.77
4.92 + 1.80
0.59 • 0.31
0.49 • 0.14
BBB. The capillaries of the choroid plexus, where CSF is created, are fenestrated and allow the passage of large protein molecules into the choroid plexus stroma. The epithelial cells that separate the stroma from the CSF and the arachnoid cells lining the subarachnoid space, separating the blood and CSF, however, have tight junctions and exclude the passage of proteins (Shapiro, 1988). Despite these distinctions, there do not appear to be differences in the mechanisms of transport between the BBB and blood-CSF barrier (Cutler, 1980). The correlation between concentration ratios and hydrodynamic protein radii indicate that passive exchange is the major mode of entry of serum proteins into the CSF (Felgenhauer, 1974). The CSF/serum albumin ratio reflects the steady state equilibrium between the serum and CSF compartments. An increased CSF/serum albumin ratio may be the result of increased permeability
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of barrier structures or alterations in CSF flow (Schliep and Felgenhauer, 1978). By convention, elevations in the CSF/serum albumin ratio have been interpreted as evidence of "impaired BBB permeability" in the absence of evidence of abnormalities of CSF flow (as might be caused by space occupying lesions). In support of this interpretation, the CSF/albumin ratio is clearly elevated in disorders causing increased BBB permeability through facilitated transvascular exchange, including meningitis, general acidosis, uremia, and hypothyroidism (Schliep and Felgenhauer, 1978). The data presented here on a relatively large group of chronic schizophrenic subjects not only serve to extend our own earlier preliminary results (Kirch etal., 1985), but are also consistent with other studies of psychotic subjects (most of whom were schizophrenic) indicating a number of patients with presumed increased blood-CSF or BBB permeability (Axelsson et al., 1982; Torrey etal., 1985; Bauer and Kornhuber, 1987). It is important to note that an abnormality of the CSF/serum albumin ratio is found only in a minority of patients in these studies. In the between-groups analysis of the present data, the number of patients versus controls falling outside the age-adjusted reference range fell just short of statistical significance (p = 0.08). Nevertheless, the patients with increased CSF/serum albumin ratios should not simply be dismissed as "outliers", but may possibly represent a pathophysiologically distinct subgroup of patients. Increased blood-CSF permeability in some schizophrenic patients may explain earlier findings (Bruetsch et al., 1942) in large numbers of patients showing increased CSF total protein. In another recent quantitative analysis of CSF proteins in schizophrenia (Roos et al., 1985), the investigators did not specifically examine the albumin ratio. While they did not observe any significant difference in mean CSF albumin concentrations between schizophrenic and control subjects, it must be noted that the mean and range of albumin concentrations they report for both serum and CSF in patients and controls are clearly higher than the normal values typically described (Papadopoulos et al., 1984; Killingsworth, 1982). It is also of interest to note that recent functional imaging studies using a dynamic computed tomographic method have identified possible blood-brain permeability alterations in some psychotic subjects (Burns etal., 1987; Dysken etal., 1987). The present study also goes beyond earlier CSF protein investigations by offering a within-subjects analysis of the CSF/serum albumin ratio on versus off neuroleptics. As shown in Fig. 3, there is no significant difference on versus off medication. While the trend (p = 0.13) in this within-subjects assessment was in the direction of patients being more likely to have a higher albumin ratio while on neuroleptics, the data for all 54 lumbar punctures in 46 subjects (23 on and 31 off neuroleptics) were in the opposite direction, as shown in Table 4. While some drugs, especially those affecting CNS adrenergic systems, are known to affect BBB permeability (Braun et al., 1980; Preskorn et al., 1981), to our knowledge this has not been reported to occur with the use of neuroleptics in humans. At this point, therefore, any alteration in the CSF/serum albumin
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ratio in schizophrenia cannot simply be attributed to the effects of neuroleptics. Whether or not neuroleptics are able to alter the albumin ratio, it is apparent that any increase in the CSF/serum albumin ratio has potential clinical implications in terms of the entry of drugs into the CNS and may have research implications, for example, in functional imaging studies involving passage of radiolabelled ligands into the brain or high-resolution electrophoretic studies of CSF proteins (Harrington et al., 1985). It would seem important that future studies of schizophrenic subjects which might be influenced by changes in diffusion-transport between the periphery and CSF should quantify and, if necessary, correct for individual variance in permeability. While a possible functional elevation in blood-CSF or BBB permeability appears to occur in some schizophrenic patients, as with the structural observation of increased VBR, the etiology and pathophysiologic relevance of this finding remains unknown. Moreover, an increased CSF/albumin ratio does not appear to distinguish a clinical subgroup of schizophrenia patients. Central nervous system immunoglobulin G production As noted above, the information provided by the IgG index focuses on a different aspect of pathology than the albumin quotient. The IgG index may provide more specific information regarding the potential etiologic involvement of CNS infection and/or autoimmunity in schizophrenia. Increases in CNS immunoglobulin production and the IgG index are seen in infectious states, such as acute viral meningoencephalitides, and in CNS disorders known or suspected to be autoimmune, including lupus cerebritis (Winfield et al., 1983) and multiple sclerosis (Ganrot and Laurell, 1974; Link and Tibbling, 1977; Caroscio etal., 1983; Papadopoulos et al., 1987). The latter is a disorder that has been noted to have interesting clinical similarities to schizophrenia (Stevens, 1988). In addition, there are many possible links between viral infection and immune dysfunction. Preexisting immune impairment may be permissive to viral infection, or immune abnormalities may be the sequelae of prior viral infection. Viral infections are also known to be able to trigger a subsequent autoimmune reaction, a process that may be relevant to schizophrenia (Knight, 1982; Pert et al., 1988). Viewed in the light of existing data, the fact that the majority of patients in the current study showed IgG indices within the normal range certainly must be taken as further evidence that most cases of chronic schizophrenia do not involve an active CNS infection by a common neurotropic virus or an acute autoimmune reaction. This was the conclusion drawn by Roos etal. (1985), who used a different method (Tourtellotte et al., 1980) to calculate endogenous CNS IgG production and did not identify increases in a group of schizophrenic subjects. Another group which did find an elevated albumin index reported no increase in the IgG index in schizophrenia (Bauer and Kornhuber, 1987), although they did not cite their mean value or variance. In a study of 5 first episode or acutely psychotic patients, Stevens et al. (1990) found no increase in
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IgG index. Nevertheless, the fact that the patients in the present study did have a significantly higher mean IgG index compared with normal controls is difficult to ignore. Moreover, as indicated by the data in Fig. 4 and Table 4, this cannot be attributed to neuroleptic treatment. The finding of an increased IgG index in some patients is consistent with the presence of CSF immunoglobulin oligoclonal bands in occasional cases of schizophrenia, as found by some investigators (Ahokas etal., 1985), but not others (Stevens etal., 1990). As shown in Table 3, the only demographic variable that appears to differ in the 9 patients with IgG index elevations compared with the 37 with values in the normal range is that the former were more likely to have had ECT. Insofar as the number of subjects who had ECT was small (N = 5), given that there is no intuitively obvious reason to suspect that ECT stimulates immunoglobulin synthesis, and noting that none of the patients had recently undergone ECT, this finding must certainly be viewed with caution. None of the other variables examined differed between the groups with high and normal IgG indices. It should also be noted that only 3 patients had elevations in both the albumin ratio and the IgG index. Whatever the cause of elevated CSF/serum albumin ratio and elevated IgG production, they do not appear to be directly linked to each other. Passive exposure to blood-borne antigens apparently does not induce Class I major histocompatibility antigen expression (Lampson, 1987) and would not necessarily be expected to stimulate IgG production within the CNS. In summary, the data indicate that some schizophrenic patients have CSF protein findings possibly reflecting increased blood-CSF permeability or increased CNS IgG production. As has been the case with all other biological markers studied in schizophrenia, however, these abnormalities are neither specific to the diagnosis nor present in all patients. Nevertheless, the findings do represent clues in the formidable task of unraveling the pathophysiology and probable etiologic heterogeneity of a complex disorder.
Acknowledgements The authors gratefully acknowledgethe assistance of R. Costello, J. Gold, M. Coggiano, and S. Marley, and the commitmentof the staff and patients of the NIMH Neuropsychiatric Research Hospital.
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Bauer K, Kornhuber J (1987) Blood-cerebrospinal fluid in schizophrenic patients. Eur Arch Psychiatr Neurol Sci 236:257-259 Bock E (1978) Immunoglobulins, prealbumin, transferrin, albumin, and alpha2-macroglobulin in cerebrospinal fluid and serum in schizophrenic patients. Birth Defects 14: 283-295 Bock E, Rafaelson OJ (1974) Schizophrenia: proteins in blood and cerebrospinal fluid. Dan Med Bull 21:93-105 Braun U, Braun G, Sargent T (1980) Changes in the blood-brain barrier permeability resulting from d-amphetamine, 6-hydroxydopamine and pimozide measured by a new technique. Experientia 36:207-209 Bruetsch VL, Bahr MA, Skobba JS, Dieter VJ (1942) The group of dementia praecox patients with an increase of the protein content of the cerebrospinal fluid. J Nerv Ment Dis 95:669-679 Burns EM, Nasrallah HA, Kathol M, Kruckeberg TW, Coffman JA (1987) Right vs. left hemispheric blood-brain barrier permeability in schizophrenia: a dynamic computed tomographic study. Psychiatry Res 22:229-241 Caroscio JT, Kochwa S, Sacks H, Cohen JA, Yahr MD (1983) Quantitative CSF IgG measurements in multiple sclerosis and other neurological diseases. Arch Neurol 40: 409-413 Christenson RH, Russel ME, Bell YL (1988) Immunoassays for immunoglobulin G (IgG) in cerebrospinal fluid (CSF) compared. Clin Chem 34:1158 Cutler RWP (1980) Neurochemical aspects of blood-brain-cerebrospinal fluid barriers. In: Wood JH (ed) Neurobiology of cerebrospinal fluid. Plenum, New York, pp41-51 DeLisi LE, Crow TJ (1986) Is schizophrenia a viral or immunologic disorder? Psychiatr Clin North Am 9:115-132 Dysken M, Patlak CS, Dobben GD, Pettigrew KD, Bartko JJ, Burns EM, Davis J, Regier DA (1987) Rapid dynamic CT scanning to distinguish schizophrenic from normal subjects. Psychiatry Res 20:165-175 Felgenhauer K (1974) Protein size and cerebrospinal fluid composition. Klin Wochenschr 52:1158-1164 Ganrot K, Laurell CB (1974) Measurement of IgG and albumin content of cerebrospinal fluid, and its interpretation. Clin Chem 20:571-573 Goldstein GW, Betz AL (1986) The blood-brain barrier. Sci Am 255:74-83 Harrington MG, Merril CR, Torrey EF (1985) Differences in cerebrospinal fluid proteins between patients with schizophrenia and normal persons. Clin Chem 31:722-726 Killingsworth LM (1982) Clinical applications of protein determinations in biological fluids other than blood. Clin Chem 28:1093-1102 Kirch DG, Kaufmann CA, Papadopolous NM, Martin B, Weinberger DR (1985) Abnormal cerebrospinal fluid protein indices in schizophrenia. Biol Psychiatry 20:1039-1046 Knight JG (1982) Dopamine-receptor-stimulating autoantibodies: a possible cause of schizophrenia. Lancet: 1073-1076 Lampson LA (1987) Molecular bases of the immune response to neural antigens. TINS 10:211-216 * Link H, Tibbling G (1977) Principles of albumin and IgG analyses in neurological disorders. III. Evaluation of IgG synthesis within the central nervous system in multiple sclerosis. Scand J Clin Lab Invest 37:397-401 Papadopoulos NM, Costello R, Kay AD, Cutler NR, Rapaport SI (1984) Combined immunochemical and electrophoretic determinations of proteins in paired serum and cerebrospinal fluid samples. Clin Chem 30:1814-1816 Papadopoulos NM, McFarlin DE, Patranas NJ, McFarland HF, Costello R (1987) A comparison between chemical analysis and magnetic resonance imaging with the clinical diagnosis of multiple sclerosis. Am J Clin Pathol 88:365-368
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Pearson EK (1973) Study of cerebrospinal fluid in schizophrenics: a review of the literature. Psychopharmacol Bull 9:59-62 Pert CB, Knight JC, Laing P, Markwell MAK (1988) Scenarios for a viral etiology of schizophrenia. Schizophr Bull 14:243-247 Preskorn SH, Irwin GH, Simpson S, Friesen D, Rinne J, Jerkovich G (1981) Medical therapies for mood disorders alter the blood-brain barrier. Science 213:469471 Reese TS, Karnovsky MJ (1967) Five structural localizations of a blood-brain barrier to exogeneous peroxidase. J Cell Biol 34:207-217 Roos RP, Davis K, Meltzer HY (1985) Immunoglobulin studies in patients with psychiatric diseases. Arch Gen Psychiatry 42:124-128 Schliep G, Felgenhauer K (1978) Serum-CSF protein gradients, the blood-CSF barrier and local immune response. J Neurol 218:77-96 Shapiro WR (1988) Cerebrospinal fluid circulation and the blood-brain barrier. Ann NY Acad Sci 531:9-14 Shelton RC, Karson CN, Doran AR, Pickar D, Bigelow LB, Weinberger DR (1988) Cerebral structural pathology in schizophrenia: evidence for a selective prefrontal cortical deficit. Am J Psychiatry 145:154-163 Stevens JR (1988) Schizophrenia and multiple sclerosis. Schizophr Bull 14:231-241 Stevens JR, Papadopoulos NM, Resnick M (1990) Oligoclonal bands in acute schizophrenia: a negative search. Acta Psychiatr Scand 81:262-264 Synek W, Reuben JR (1976) The ventricular brain ratio using planimetric measurement of EMI scans. Br J Radiol 49:233-237 Tibbling G, Link H, Ohman S (1977) Principles of albumin and IgG analyses in neurological disorders. I. Establishment of reference values. Scand J Clin Lab Invest 37:385-390 Torrey EF, Kaufmann CA (1986) Schizophrenia and neuroviruses. In: Nasrallah HA, Weinberger DR (eds) The neurology of schizophrenia. Elsevier, Amsterdam, pp 361376 Torrey EF, Albrecht P, Behr DE (1985) Permeability of the blood-brain barrier in psychiatric patients. Am J Psychiatry 142:657-658 Tourtellotte WW, Potvin AR, Fleming JO, Murphy KN, Levy K, Syndulko K, Potvin JH (1980) Multiple sclerosis: measurement and validation of central nervous system IgG synthesis rate. Neurology 30:240-244 van Kammen DP, Sternberg DE (1980) Cerebrospinal fluid studies in schizophrenia. In: Wood JH (ed) Neurobiology of cerebrospinal fluid. Plenum, New York, pp 719-742 Winfield JB, Shaw M, Silverman LM, Eisenberg RA, Wilson HA, Koffier D (1983) Intrathecal IgG synthesis and blood-brain barrier impairment in patients with systemic lupus erythematosus and central nervous system dysfunction. Am J Med 74:837-844 Authors' address: D. G. Kirch, M.D., Division of Clinical Research, National Institute of Mental Health, 5600 Fishers Lane - Room 10-105, Rockville, Maryland 20857, U.S.A. Received August 8, 1991
J Neural Transm [GenSect] (1992) 89:219-232
9 Springer-Verlag 1992 Printed in Austria
B l o o d - C S F barrier permeability and central nervous s y s t e m immunoglobulin G in schizophrenia D. G. Kirch 1' 2, R. C. Alexander2, R. L. Suddath2, N. M. Papadopoulos 3, C. A. Kaufmann2, D. G. Daniel 4, and R. J. Wyatt z
1Division of Clinical Research, 2Neuropsychiatry Branch, and 4Clinical and Research Services Branch, National Institute of Mental Health, Rockville, Maryland and Washington, D. C., and 3Chemistry Service, National Institutes of Health, Bethesda, Maryland, U.S.A. Accepted February 21, 1992
Summary. The ratio of albumin in cerebrospinal fluid (CSF) to serum may serve as an index of the integrity of the blood-CSF barrier, with increases in this ratio indicating increased permeability. The ratio of immunoglobulin G (IgG) in CSF to serum (divided by the albumin ratio to correct for variance in blood-CSF permeability) represents an index of the endogenous production of IgG in the central nervous system (CNS), with increases reflecting a possible infectious and/or autoimmune process stimulating central IgG synthesis. We analyzed simultaneously collected CSF and serum samples from 46 schizophrenic subjects, 8 of whom were studied both on and off neuroleptic treatment, and samples from 20 normal controls. The data indicated increases in CSF/ serum albumin ratios or CSF/serum IgG indices in 22% and 20%, respectively, of the schizophrenic patients. Only 3 patients showed elevations in both indices. Comparison of values on and off neuroleptics indicated no significant effect of neuroleptics on these indices. Keywords: Blood-CSF barrier, albumin, immunoglobulin G, schizophrenia. Introduction
In the effort to elucidate the pathophysiologic and etiologic factors involved in schizophrenia, the analysis of cerebrospinal fluid (CSF) has been a primary method of assessing central nervous system (CNS) function in living subjects. Studies of neurotransmitters, metabolites, proteins, and other CSF constituents in schizophrenia have been extensively pursued for many years with mixed results (van Kammen and Sternberg, 1980). Among the abnormalities reported at an early point in the course of biological investigations of schizophrenia was
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an apparent increase in total CSF protein concentrations (Bruetsch et al., 1942), although subsequent studies of specific CSF proteins yielded divergent findings (Pearson, 1973; Bock and Rafaelson, 1974; Bock, 1978; Kirch et al., 1985; DeLisi and Crow, 1986; Torrey and Kaufmann, 1986). Many disorders of the CNS, including meningitis, neoplasms, polyneuropathies, disk herniations, and infarctions lead to elevated concentrations of CSF proteins (Papadopoulos et al.; 1984). The primary component of CSF protein is albumin, which is usually at a concentration about 200 times lower in CSF compared with serum (Tibbling et al., 1977). Since synthesis of albumin within the mature CNS is not thought to occur (Ganrot and Laurell, 1974), all albumin in the CSF is derived from serum. The ratio of CSF to serum albumin, in the absence of significant disturbances in CSF flow, is therefore thought to reflect the overall permeability of those structures that separate the serum from the CSF compartment (Schliep and Felgenhauer, 1978). Immunoglobulin G (IgG) concentration in the CSF is measured because of the important clinical implications of increased production within the CNS. The ratio between the concentration of IgG in CSF to IgG in serum (corrected for the ratio of albumin in CSF to serum) has been proposed as an index that can distinguish endogenous CNS IgG production from elevation of CSF IgG from other causes (Ganrot and Laurell, 1974). Use of the CSF IgG index to identify endogenous CNS IgG synthesis is supported by the finding of abnormally high values in 80% of multiple sclerosis patients (Link and Tibbling, 1977). We previously reported data showing some schizophrenic patients to have abnormalities in the albumin ratio and/or the IgG index (Kirch etal., 1985). We have now expanded the number of schizophrenic patients studied. By including patients studied both on and off neuroleptic treatment, these data also allow an assessment of the effect, if any, of neuroleptics on these CSF protein indices.
Subjects and methods Subjects The patient group consisted of 46 individuals (31 males and 15 females) who were inpatients in the research program of the National Institute of Mental Health (NIMH) Neuropsychiatric Research Hospital, located at the Neuroscience Center at Saint Elizabeths in Washington, D.C. All met DSM-III (American Psychiatric Association, 1980) criteria for schizophrenia, and were determined to be free of significant coexisting medical disorders. Clinical data gathered on each subject included age of onset and duration of illness, past drug and/or alcohol abuse (patients with active substance abuse being excluded from participation), past treatment with electroconvulsive therapy (ECT), and the presence or absence of tardive dyskinesia. Testing of intelligence(IQ) using the WAIS-R was performed in 33 patients. Of the 46 patients, 38 underwent a singlelumbar puncture and venipuncture procedure. Of these, 15 were on chronic neuroleptic treatment at the time of study, while 23 had been withdrawn from neuroleptic treatment for a period of at least 4 weeks. The remaining 8
Blood-CSF barrier and CSF immunoglobulin G in schizophrenia
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patients were studied in paired fashion both on and at least 4 weeks after withdrawal from chronic neuroleptic treatment. Of the total of 46 patients, 24 had been included in our earlier study (Kirch etal., 1985). All individuals participating in these studies provided informed consent. In addition, previously published (Papadopoulos et al., 1984) comparison CSF protein data were available for 20 healthy individuals (16 males and 4 females) ranging in age from 20 to 87 (mean 4- SD = 54.1 4- 20.5). These individuals were evaluated as inpatients at the Clinical Center of the National Institutes of Health and were free of any significant neuropsychiatric diagnosis or other medical disorders. Normal subjects spanning a wide age range had been selected in order to validate the normal ranges for the CSF albumin ratio and IgG index in adults proposed by other investigators using "neurologic" controls (Tibbling etal., 1977; Killingsworth, 1982).
Methods Each patient underwent a lumbar puncture in the lateral decubitus position early in the morning while at bedrest. CSF was collected under sterile conditions with the initial fraction sent for routine laboratory studies. No patients whose CSF on microscopic examination showed evidence of a traumatic lumbar puncture was included in this study. As noted above, 8 patients underwent paired lumbar punctures, one on and one off neuroleptic. A total of 54 lumbar punctures were performed in the 46 patients, 23 while patients were medicated and 31 after neuroleptic withdrawal. Patient CSF samples from the second fraction, together with serum samples collected at the time of lumbar puncture, were stored at - 70 ~ Analyses of the concentrations of albumin and IgG in CSF and serum in the samples from the 46 patients and the 20 control subjects were performed in the same laboratory by one of the authors (N.M.P.). Patient samples were assayed using rate nephelometry, while control values were determined by radial immunodiffusion (Papadopoulos etal., 1984). These methods have been demonstrated to correlate well with one another (Christenson etal., 1988). The albumin ratio was calculated as [(CSF albumin~serum albumin) x 1000], while the IgG index was calculated as [ (CSF IgG/serum IgG) / (CSF albumin/serum albumin)]. The denominator in the IgG index serves to correct the IgG index for any variance in the blood-CSF barrier which might allow more or less peripheral IgG to enter the CSF, resulting in a more accurate representation of endogenous CNS IgG production. All 46 patients underwent a computed tomographic (CT) brain scan as part of their evaluation on admission to the research program, allowing calculation of the ventricularbrain ratio (VBR) by planimetry as previously described (Synek and Reuben, 1976; Shelton etal., 1988). All scans were nonenhanced and consisted of 12 parallel planes 10mm thick with a pixel size of 0.5 by 0.5 mm and matrix size of 512 • 512. No patients had diagnostic abnormalities on CT scan, and all scans were screened for evidence of asymmetric head placement in the CT scanner. Insofar as the CT scan was typically part of the initial admission evaluation, it usually preceded the lumbar puncture by several weeks.
Statistical analysis The individual patient and control values for the albumin ratio were compared in terms of whether they were within or outside previously determined, age-adjusted reference ranges for adults (Tibbling et al., 1977) using Fisher's exact test. Patient and control data for the IgG index, which is constant across the age span, were compared using a t-test. For both the albumin quotient and the IgG index, the descriptive data on patients whose CSF protein index was outside the normal range versus those who fell within the normal range were compared using a t-test or Fisher's exact test, depending on the variable. Lastly, data on
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the albumin ratio and IgG index in the 8 subjects tested on versus off neuroleptic treatment were analyzed using a matched-pairs t-test.
Results
The demographic and other relevant data on the 46 patients are summarized in Table 1. Although the patients were relatively young, with a mean age of 29.9, they were characteristic of patients referred to the N I M H research program insofar as they were chronically ill and relatively treatment-refractory, with most having a history of repeated hospitalizations and constant neuroleptic treatment throughout the duration of their illnesses. Their mean age of onset was 20.1 years, with a mean duration of illness of 9.8 years. Of the 46 schizophrenic patients, 18 had a history of past drug and/or alcohol abuse, 5 had received ECT (although none had received ECT within several months prior to lumbar puncture), and 9 had persistent tardive dyskinesia. The mean VBR in the patient group as a whole was 5.73, a value similar to that found in a larger cumulative series of CT scans in schizophrenic patients from the N I M H program (Shelton et al., 1988). The results of IQ testing in 33 of the 46 patients revealed the group to be somewhat impaired, with a mean full-scale IQ of 89.3, and a gap between higher verbal and lower performance scores. Albumin ratio Individual data regarding the calculated albumin ratio for the 46 patients and 20 healthy control subjects are displayed in Fig. 1, which also includes the normal ranges for the albumin ratio across the adult age span determined by Tibbling etal. (1977). For the 8 patients who underwent paired lumbar punctures, the value used was the mean of the two analyses. It is apparent from both the previously established reference values and the data from our own 20 control
Table 1. Descriptive information for 46 schizophrenic patients participating in study of CSF proteins Age* Gender Age of onset of illness* Duration of illness (years)* Past substance abuse ECT Tardive dyskinesia CT scan VBR* IQ (N = 33)* Full scale Verbal Performance * mean -4- SD
29.9 -t- 6.0 31 male / 15 female 20.1 + 3.3 9.8 4- 5.8 18 yes / 28 no 5 yes / 41 no 9 yes / 37 no 5.73 + 3.33 89.3 4- 13.3 94.4 4- 15.9 84.8 4- l 1.1
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Fig. 1. Albumin ratio for 46 schizophrenicpatients and 20 healthy control subjects. Enclosed boxes represent age-specific reference values established by Tibbling et al. (1977) subjects that there is an increase in the CSF/serum albumin ratio with normal aging~ For the albumin ratio, 10 of 46 patients and 1 of 20 control subjects exceeded the originally reported control values (p = 0.08; one-tailed Fisher's exact test). Table 2 presents an analysis of clinical variables for the 10 patients with albumin ratios above the normal range versus the 36 patients falling within the normal range, with comparisons of age, onset, duration, VBR, and IQ by ttest and of past substance abuse, ECT, and tardive dyskinesia by Fisher's exact test. None of the comparisons indicated a statistically significant difference between the two groups.
Immunoglobulin G index Figure 2 shows the data for the IgG index for the 46 patients (with the mean value shown for those patients having two lumbar punctures) and the 20 control subjects. The normal range for the IgG index has been shown to be constant across the age span (Tibbling etal., 1977; Killingsworth, 1982). For the 20 control subjects, the mean (4- SD) IgG index was 0.44 (4- 0.095). These values
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Table 2. Assessment of patients with elevated albumin ratio versus those within the normal range
Age* Gender Age of onset of illness* Duration of illness (years)* Past substance abuse ECT Tardive dyskinesia CT scan VBR* IQ* Full scale Verbal Perfomance
Elevated (N = 10)
Normal (N = 36)
28.9 4- 4.5 9 male / 1 female 19.1 4- 1.8
30.2 4- 6.3 22 male / 14 female 20.4 4- 3.6
9.8 4- 4.8
9.8 4- 6.1
6 yes
4 no
12 yes / 24 no
2 yes 2 yes
8 no 8 no
3 yes / 33 no 7 yes / 29 no
5.58 + 3.34 ( N = 8) 89.3 4- 16.5 93.1 4- 18.2 85.9 + 13.1
5.77 4- 3.37 ( N = 25) 89.4 4- 12.5 94.8 4- 15.5 84.5 4- 10.7
* mean 4- SD
are comparable to those reported by other investigators (Tibbling et al., 1977; Killingsworth, 1982). The mean (-4- SD) IgG index for the 46 patients was 0.54 (+ 0.24), which was significantly (p < 0.01, one-tailed t-test) higher than that of the 20 controls (0.44 + 0.095). Of the 46 patients, 9 had an IgG index greater than 0.63 (the mean for the 20 control subjects plus two SD) versus none of the control subjects (p < 0.05; one-tailed Fisher's exact test). Table 3 shows an assessment of clinical variables for these 9 patients versus those who fell within the normal range. Using the same variables and statistical analyses as for the albumin ratio data in Table 2, the only significant difference was that patients with elevated IgG indices were significantly (p < 0.003; two-tailed Fisher's exact test) more likely to have undergone ECT in the past. Of the 46 patients studied, only 3 showed coexisting elevations of both the albumin ratio and the IgG index.
Effect of neuroleptics The data from paired lumbar punctures performed on and off chronic neuroleptic treatment in 8 of the patients allowed an evaluation of the potential effect of drug treatment on the albumin ratio (Fig. 3) and IgG index (Fig. 4). As illustrated by both figures, there was no significant difference between the neuroleptic-treatment and neuroleptic-withdrawal state for either CSF protein index in these 8 patients. Of the total 54 lumbar punctures performed on the
Blood-CSF barrier and CSF immunoglobulin G in schizophrenia
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46 patients, 23 were done while the patients were being treated with neuroleptic and 31 were done at least 4 weeks after neuroleptic withdrawal. As shown in Table 4, there was no significant difference in either the albumin ratio or IgG index between the two groups. Thus, neither the paired analysis in 8 subjects nor the group analysis in 46 subjects indicated that either the albumin quotient or IgG index are significantly affected by neuroleptic treatment. Discussion
Blood-CSF barrier permeability The blood-brain barrier (BBB) was first discovered by Paul Ehrlich, who observed that injecting aniline dye into the blood stream of animals stained all of the body organs except the brain (Goldstein and Betz, 1986). Modern studies have refined the anatomical understanding of this barrier, revealing tight junctions between endothelial cells (Reese and Karnovsky, 1967). Although commonly thought to be equivalent, the blood-CSF barrier is distinct from the
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Table 3. Assessment of patients with elevated I g G index versus those within the normal range
Age* Gender Age of onset of illness* Duration of illness (years)* Past substance abuse ECT Tardive dyskinesia CT scan VBR* IQ* Full scale Verbal Performance
Elevated (N = 9)
Normal (N = 37)
31.8 + 6.1 7 male / 2 female 18.8 4- 3.1
29.5 + 5.9 24 male / 13 female 20.4 4- 3.3
13.0 4- 8.0
9.1 • 4.9
4 yes / 5 no
14 yes / 23 no
4 yes / 5 no 2 yes / 7 no 5.77 4- 3.81 (N = 4) 85.5 4- 17.7 90.3 • 16.8 80.8 • 17.7
1 yes / 36 no** 7 yes / 30 no 5.71 • 3.26 (N = 29) 89.9 4- 12.9 95.0 • 16.0 85.4 • 10.3
* mean • SD ** p < 0.003
ALBUMIN QUOTIENT
OFF
ON NEUROLEPTIC
Fig. 3. Albumin ratio in 8 schizophrenic patients on and off chronic neuroleptic treatment (p = 0.13, matched pairs t-test)
Blood-CSF barrier and CSF immunoglobulin G in schizophrenia
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0,8
0,7
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0.4
0.3
ON
OFF
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Fig. 4. IgG index in 8 schizophrenic patients on and off chronic neuroleptic treatment (p = 0.35, matched pairs t-test) Table 4. Albumin ratio and IgG index (mean • SD) in 23 CSF samples collected from patients on neuroleptics compared with 31 samples collected from patients withdrawn from neuroleptics
Albumin ratio IgG index
Neuroleptic treatment
Neuroleptic withdrawal
4.75 • 1.77
4.92 + 1.80
0.59 • 0.31
0.49 • 0.14
BBB. The capillaries of the choroid plexus, where CSF is created, are fenestrated and allow the passage of large protein molecules into the choroid plexus stroma. The epithelial cells that separate the stroma from the CSF and the arachnoid cells lining the subarachnoid space, separating the blood and CSF, however, have tight junctions and exclude the passage of proteins (Shapiro, 1988). Despite these distinctions, there do not appear to be differences in the mechanisms of transport between the BBB and blood-CSF barrier (Cutler, 1980). The correlation between concentration ratios and hydrodynamic protein radii indicate that passive exchange is the major mode of entry of serum proteins into the CSF (Felgenhauer, 1974). The CSF/serum albumin ratio reflects the steady state equilibrium between the serum and CSF compartments. An increased CSF/serum albumin ratio may be the result of increased permeability
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of barrier structures or alterations in CSF flow (Schliep and Felgenhauer, 1978). By convention, elevations in the CSF/serum albumin ratio have been interpreted as evidence of "impaired BBB permeability" in the absence of evidence of abnormalities of CSF flow (as might be caused by space occupying lesions). In support of this interpretation, the CSF/albumin ratio is clearly elevated in disorders causing increased BBB permeability through facilitated transvascular exchange, including meningitis, general acidosis, uremia, and hypothyroidism (Schliep and Felgenhauer, 1978). The data presented here on a relatively large group of chronic schizophrenic subjects not only serve to extend our own earlier preliminary results (Kirch etal., 1985), but are also consistent with other studies of psychotic subjects (most of whom were schizophrenic) indicating a number of patients with presumed increased blood-CSF or BBB permeability (Axelsson et al., 1982; Torrey etal., 1985; Bauer and Kornhuber, 1987). It is important to note that an abnormality of the CSF/serum albumin ratio is found only in a minority of patients in these studies. In the between-groups analysis of the present data, the number of patients versus controls falling outside the age-adjusted reference range fell just short of statistical significance (p = 0.08). Nevertheless, the patients with increased CSF/serum albumin ratios should not simply be dismissed as "outliers", but may possibly represent a pathophysiologically distinct subgroup of patients. Increased blood-CSF permeability in some schizophrenic patients may explain earlier findings (Bruetsch et al., 1942) in large numbers of patients showing increased CSF total protein. In another recent quantitative analysis of CSF proteins in schizophrenia (Roos et al., 1985), the investigators did not specifically examine the albumin ratio. While they did not observe any significant difference in mean CSF albumin concentrations between schizophrenic and control subjects, it must be noted that the mean and range of albumin concentrations they report for both serum and CSF in patients and controls are clearly higher than the normal values typically described (Papadopoulos et al., 1984; Killingsworth, 1982). It is also of interest to note that recent functional imaging studies using a dynamic computed tomographic method have identified possible blood-brain permeability alterations in some psychotic subjects (Burns etal., 1987; Dysken etal., 1987). The present study also goes beyond earlier CSF protein investigations by offering a within-subjects analysis of the CSF/serum albumin ratio on versus off neuroleptics. As shown in Fig. 3, there is no significant difference on versus off medication. While the trend (p = 0.13) in this within-subjects assessment was in the direction of patients being more likely to have a higher albumin ratio while on neuroleptics, the data for all 54 lumbar punctures in 46 subjects (23 on and 31 off neuroleptics) were in the opposite direction, as shown in Table 4. While some drugs, especially those affecting CNS adrenergic systems, are known to affect BBB permeability (Braun et al., 1980; Preskorn et al., 1981), to our knowledge this has not been reported to occur with the use of neuroleptics in humans. At this point, therefore, any alteration in the CSF/serum albumin
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ratio in schizophrenia cannot simply be attributed to the effects of neuroleptics. Whether or not neuroleptics are able to alter the albumin ratio, it is apparent that any increase in the CSF/serum albumin ratio has potential clinical implications in terms of the entry of drugs into the CNS and may have research implications, for example, in functional imaging studies involving passage of radiolabelled ligands into the brain or high-resolution electrophoretic studies of CSF proteins (Harrington et al., 1985). It would seem important that future studies of schizophrenic subjects which might be influenced by changes in diffusion-transport between the periphery and CSF should quantify and, if necessary, correct for individual variance in permeability. While a possible functional elevation in blood-CSF or BBB permeability appears to occur in some schizophrenic patients, as with the structural observation of increased VBR, the etiology and pathophysiologic relevance of this finding remains unknown. Moreover, an increased CSF/albumin ratio does not appear to distinguish a clinical subgroup of schizophrenia patients. Central nervous system immunoglobulin G production As noted above, the information provided by the IgG index focuses on a different aspect of pathology than the albumin quotient. The IgG index may provide more specific information regarding the potential etiologic involvement of CNS infection and/or autoimmunity in schizophrenia. Increases in CNS immunoglobulin production and the IgG index are seen in infectious states, such as acute viral meningoencephalitides, and in CNS disorders known or suspected to be autoimmune, including lupus cerebritis (Winfield et al., 1983) and multiple sclerosis (Ganrot and Laurell, 1974; Link and Tibbling, 1977; Caroscio etal., 1983; Papadopoulos et al., 1987). The latter is a disorder that has been noted to have interesting clinical similarities to schizophrenia (Stevens, 1988). In addition, there are many possible links between viral infection and immune dysfunction. Preexisting immune impairment may be permissive to viral infection, or immune abnormalities may be the sequelae of prior viral infection. Viral infections are also known to be able to trigger a subsequent autoimmune reaction, a process that may be relevant to schizophrenia (Knight, 1982; Pert et al., 1988). Viewed in the light of existing data, the fact that the majority of patients in the current study showed IgG indices within the normal range certainly must be taken as further evidence that most cases of chronic schizophrenia do not involve an active CNS infection by a common neurotropic virus or an acute autoimmune reaction. This was the conclusion drawn by Roos etal. (1985), who used a different method (Tourtellotte et al., 1980) to calculate endogenous CNS IgG production and did not identify increases in a group of schizophrenic subjects. Another group which did find an elevated albumin index reported no increase in the IgG index in schizophrenia (Bauer and Kornhuber, 1987), although they did not cite their mean value or variance. In a study of 5 first episode or acutely psychotic patients, Stevens et al. (1990) found no increase in
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IgG index. Nevertheless, the fact that the patients in the present study did have a significantly higher mean IgG index compared with normal controls is difficult to ignore. Moreover, as indicated by the data in Fig. 4 and Table 4, this cannot be attributed to neuroleptic treatment. The finding of an increased IgG index in some patients is consistent with the presence of CSF immunoglobulin oligoclonal bands in occasional cases of schizophrenia, as found by some investigators (Ahokas etal., 1985), but not others (Stevens etal., 1990). As shown in Table 3, the only demographic variable that appears to differ in the 9 patients with IgG index elevations compared with the 37 with values in the normal range is that the former were more likely to have had ECT. Insofar as the number of subjects who had ECT was small (N = 5), given that there is no intuitively obvious reason to suspect that ECT stimulates immunoglobulin synthesis, and noting that none of the patients had recently undergone ECT, this finding must certainly be viewed with caution. None of the other variables examined differed between the groups with high and normal IgG indices. It should also be noted that only 3 patients had elevations in both the albumin ratio and the IgG index. Whatever the cause of elevated CSF/serum albumin ratio and elevated IgG production, they do not appear to be directly linked to each other. Passive exposure to blood-borne antigens apparently does not induce Class I major histocompatibility antigen expression (Lampson, 1987) and would not necessarily be expected to stimulate IgG production within the CNS. In summary, the data indicate that some schizophrenic patients have CSF protein findings possibly reflecting increased blood-CSF permeability or increased CNS IgG production. As has been the case with all other biological markers studied in schizophrenia, however, these abnormalities are neither specific to the diagnosis nor present in all patients. Nevertheless, the findings do represent clues in the formidable task of unraveling the pathophysiology and probable etiologic heterogeneity of a complex disorder.
Acknowledgements The authors gratefully acknowledgethe assistance of R. Costello, J. Gold, M. Coggiano, and S. Marley, and the commitmentof the staff and patients of the NIMH Neuropsychiatric Research Hospital.
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