LETTERS TO THE EDITOR

MULTIFOCAL CONDUCTION BLOCK IN A PATIENT WITH BORRELIA BURGDORFERI INFECTION Th e most common neurophysiological abnormalities in lymphocytic meningoradiculitis in spirochete Borrelia burgdorferi infection are abnormalities of sensory conduction and motor terminal l a t e n ~ y ”while ~ signs of demyelination occur only very rarely.’ Sural nerve biopsy may show perivascular inflammation and mild axonal loss.*.” We report multifocal conduction block of motor and sensory nerves in a patient with unilateral brachial plexus neuritis due to B . burgdorferi infection. A 71-year-old man experienced a stinging pain in his Ieft little finger, which after a few days radiated to the whole arm. Sensation and strength of his left hand were impaired. He also had a slight loss of sensation in his right fingertips. There was no history of a tick-bite or erythematous skin lesion. On neurological examination 7 weeks later, there was paresis of the left biceps and triceps brachii muscles, MRC grade 4, and of the wrist and finger extensors and flexors, MRC grade 2. Sensation was impaired in the left C6-8 dermatomes. T h e tendon reflexes of

the left arm were diminished. Routine laboratory analysis of blood and urine was normal; ANA and VDRL were negative and no paraproteinemia was detected. X-rays and CT-scan of the thorax and cervical spine were normal. T h e CSF showed a mononuclear pleocytosis of 35/mm3 and an elevated protein content of 1 g/L. With the enzyme-linked immunosorbent assay (ELISA), an optical density (OD) ratio of IgG antibodies against B. burgdorferi of 4.4 (normal < 2.5) was found in serum and of 3.9 (normal < 2.5) in CSF. T he patient received a 2-week course of intravenous penicillin 2.10” U/day. T h e pain diminished rapidly within a few days, but strength improved more gradually. One month after treatment, the CSF pleocytosis and protein content had declined. T h e OD ratio of antibodies against B . burgdorferi was 3.4 in seruni and 2.3 in CSF. Four weeks later he could extend his wrist against resistance. Nerve conduction studies were performed by using standard surface stimulation and recording techniques with limb temperature maintained at 36°C with infrared radiation. Motor conduction studies included median, ulnar, peroneal, and tibia1 nerves, and revealed prominent conduction blocks but normal distal laten-

Table 1. Needle examination Muscle*

Fibr. pot. recruitment MUAPs Musclet Fibr. pot. Recruitment MUAPs

Deltoideus L Biceps brachii L Hand inteross. dors. I R Tibialis anterior R 0 Interference pattern A; normal: D&P

Triceps brachii L Ext. digit. comm. L Ext. indic. prop. L

Flex. carp uln. L Flex. carp. rad. L Abd. poll brev. L

3+ No activity

3+ No activity

Ext. indic. prop. L

Abd. poll. brev. L 2+ Moderately reduced A; normal: D&P

I+ Markedly reduced A; normal: D&P

*On admission. t 4 weeks after initiation of therapy. Fibrillation potentials (fibr. pot). 0,none, I +, persistent trains, 2 areas, 2+, 3 or more areas; 3+, many. all areas. Motor unit action potentials (MUAPsj: A = amplitude, D = duration, P = percent polyphasia.

Letters to the Editor

MUSCLE & NERVE

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375

cies in the left ulnar and in both median nerves (Fig. 1 ) . The blocks were not located at usual sites of compression but were multifocal over the course of the nerves. A small conduction block was found in the right peroneal nerve at the head of the fibula. No F-waves were obtained after stimulation of the left ulnar and both median nerves. T h e minimal F-latency obtained after right ulnar nerve stimulation was normal; however, the F-latencies were too widely dispersed. Antidromic left median nerve sensory conduction in the wrist-second digit segment was normal. Nevertheless, no cervical o r cortical SEPs were obtained by left median nerve stimulation at the wrist o r elbow, indicating a conduction block in the upper arm, plexus, o r roots. N o SNAP o r SEPs could be recorded with left ulnar nerve stimulation at the wrist. O n the right side, sensory conduction and SEPs of the median and ulnar nerves were within normal limits. Needle examination revealed evidence of acute denervation without effort activity (Table 1). After treatment, these abnormalities rapidly improved.

s i n n Medianus

sin n Ulnaris

A

Conduction blocks had diminished and F-waves were present with all nerves examined (Fig. 1 , Table 1). T h e presence of specific antibodies against B . burgdorferi in serum and CSF and rapid improvement after treatment with penicillin confirmed the diagnosis. T h e pathogenesis of the peripheral nerve fiber injury in this patient is uncertain. T h e B. burgdorferi has been cultured from affected skin areas, blood, and CSF'.4 indicating direct invasion of the meninges, which may explain the meningitis and radiculopathy. Alternatively, a direct immunologic attack may explain the neurological abnormalities seen in this disease, based on the similarity of the clinical features of this disease to those of human serum sickness, a known immune-complex disease." Whatever the underlying mechanism, this treatable disorder should be considered when evaluating patients with clinical evidence of multifocal neuropathy. T h e multifocal demyelinating features detected in this patient by electrodiagnostic studies have not been re-

L MIS1

YRISI

BU6

ELBOY

i

nus

E __y___c_

nxitt

B B

YRISI

YVIO

L

"/Dl YRlSl

nu6

ELBOL

nu6

nxitti

AXlLLA

YRlSl

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Dv/D

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FIGURE 1. Surface recordings from the abductor digiti minimi and abductor pollicis brevis muscles with stimulation of the left ulnar, left median, and right median nerves, respectively. (A) At time of admission, (B)at 4 weeks, and (C) at 10 weeks after initiation of therapy; BUG: below ulnar groove, AUG: above ulnar groove.

376

Letters to the Editor

MUSCLE & NERVE

April 1991

A clinical classification with 6 grades was adopted: 1-sensory and/or disautonomic symptoms without neurological signs; 11-lower limbs (LI.) sensory signs; 111--1, motor signs, independent walk; 1V-upper limbs (UL) motor signs, walking with support; V-wheelchair; VI-bedridden. Electromyographic (EMG) evaluation was quantified according to a "score" We are grateful to Prof. Dr. A.C. van Huffelen for his valuable from 0 to 100 of abnormality."."." In this score, needle comments, Dr. T.U. Hoogenraad for referring the patient. Mrs. EMG of distal and proximal muscles of the LI, and UI., C. Dirckx-van den Berg and Mr. R.S. Schoobaar are acknowlsensory and motor conduction velocities and potentials edged for their secretarial assistance. were determined, taking into account the normal values P.L. Oey* of our laboratory 2 SD. EMG evolution scores consist H. Franssen* of the differences between EM(; scores at identical R.A.J.A.Y. Bernsent length of disease evolution time, spontaneously, and J.H.J. Wokket Departments of *Clinical Neurophysiology and under PE. +Neurology T h e PE program consisted of continuous flow cenUniversity Hospital Utrecht trifugation with substitution of 1.2 plasma volumes by 3584 CX Utrecht, The Netherlands plasma o r 4% albumin solution at each session. Nine of the 2 1 admitted patients was considered for statistical I . Renach J L , Uosler E M , Hanrahan ,]P,Coleman JI,, I-labicht evaluation under the following criteria: (a) each fortGS, bas( ' I T , Cameron DJ, Zieglei- JL, Barhour A(>, Burgdot-fer U', Edelnian K, Kaslow KA: Spirochetes isolated night, PE session with 4% albumin; and (b) treatment fr-om the blood of two patients with Lvme disease. r l ' k'~g1.1 length of time between 1.5 and 4.5 years, mean 3.1 2 l"Vfrr1 1983; 308:740-742. 1 . 1 , without intermissions. This group was compared 2. Halperin 1.1, Dattwylcr RJ: The spectrum o f Lynie neuropwith a control group during the same evolutioii tiwe athv. J UZJL ~Vno-c~p/~yzol 1989; 6:290. and with the patient's own previous evolution. 3. Reik I+ Steere AC, Bartenhagen N H , Stiope RF., Malawista SE: Neurologic abnormalities of L y n x discasc. ,\.fdicitic, From the 21 patients admitted to PE, 10 gave u p treatment (7 before 1.5 years and 3 after longer treat4. Steere AC, Groclzigki Kl., Korrtblatt A N , Ci-af.t JE, Rarboicr ment but with intermissions) because of reasons related A(;, Uurgdorfer W, Schtnid (;P, Johnson E, Malawista SE: to plasma as substitution fluid (allergic reactions, viral The spirochetal etiology of I~vntedisease. N EijgI ,] ;Wed 1983; 308:733- 740. infections, fear of AIDS, hepatitis, o r other blood trans5. Vallat ,]M,Hugon 1 , Lubeait M , Leboutet M,], 1)unias M. mitted diseases). Two patients started PE a short time l)esproges-(;otteron R: 'I'ick-bite m ~ n i t ~ g o r a t l i c ~ t l ~ ~ t t e ~ t ~ i t i s : ago with satisfactory results so far.

ported before. In this patient, the conduction block appeared to be a reversible abnormality, probably becausc most of the axons remained intact. In this respect, it should be noted how abundant fibrillation can be seen in muscles which are weak predominantly due to an associated conduction block, rather than to axonal loss.

*

Clinical, electrophysiologic, and histologic findings in 10 cases. 1Vu~7-cd0,~ 1987; 37:749-753.

TREATMENT OF FAMILIAL AMYLOIDOTIC POLYNEUROPATHY(P0RTUGUESE TYPE) BY PLASMA EXCHANGE* T h e possibility of treating familial amyloidotic polyneuropathy (FAP) (Portuguese type), by trying to remove 1'TK (Met 3 0 ) by plasma exchange (PE) has been considered but the results are inconclusive. 12.4,7 ''The aim of this study is to evaluate the therapeutic effect of' long-term PE on the evolution of FAP. To achieve this goal comparisons were made (1) between the evolution of treated and nontreated otherwise identical groups of patients and (2) between the evolution of treated patients before and after PE treatment. A total of 2 1 FAP patients ( 1 5 men and 6 women, ranging in age from 23 to 51 years, mean 36.5) were admitted to an open therapeutic trial with PE under the following inclusion criteria: (a) FAP diagnosis confirmed by positive biopsy for amyloid and presence of circulating T'TR (Met 3 0 ) , (b) disease onset before 5 0 years, (c) no contraindication for plasma exchange, and (d) express consent of the patient.

Table 1. Plasma exchange on FAP.

Number of patients Sex distribution Age at onset of symptoms Delay from first symptoms until diagnosis (years) Clinical grade at diagnosis EMG score at diagnosis Clinical grade pre-PE/precontrol period EMG score pre-PE/precontrol period Duration of PEicontrol period (years)

Treated group

Untreated group

9 6M,3F 33.8 ? 7.3 2.7 2 1.4

9 6M,3F 34.1 t 5.9 3 1 t 1.3

2.8 -t 0.5 36.9 2 12.6 2.8 t 0.6

2.6 5 0.5 36.1 5 5.5 2.7 2 0.7

43.0 t 13.9

40.5

3.1 t 1.1

2

9.6

3.2 t 0.5

The above 2 groups are statistically identical (p < 0.005). Final clinical grade Final EMG score Difference between initial and final scores

3.1 & 0.3 5 0 . 5 ? 12.3 7.5 2 8.7

3.2 t 0.5 56.1 t 11.4 15.6 2 7.7

~~

The difference between the evolution EMG scores of treated and untreated patients is statistically (P 4 0 05 using Student's t test for small samples)

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MUSCLE & NERVE

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377

Considering the groups under statistical arialysia, 9 treated and 9 untreated patients (Table I ) , the findings indicate: (1) from the clinical point of view, there was ;I worsening (change of grade) in 6 untreated patients and only in 3 treated patients. I n the PE group, ;I tendency for stabilization of weight and decrease of tiiarrhea was found; this was not observed in the spontarieous evolution group. (2) 'I'here is a statistically significant difference ( P < 0.05) between EM(; evoliition scores of treated (7.5 2 8.6) ant1 untreated patients (15.6 2 7.7). (3) EM(; evolution scores of' 5.6 ? 3.1 per year before treatment and 2.5 2 2.9 per year during treatment were found. We conclude that plasma exchange slows the progress of FAP, and some symptoms like diarrhea and weight loss have good response to PE. These results allow good expectations from selective pheresis.

M.L. Sales-Luis M. Galvao M. Carvalho 0. Sousa M.M. Alves R. Serrao Centro de Estudos Egas Moniz Neurology and lmmunohemotherapy Services Santa Maria Hospital 1600 Lisbon, Portugal 1. Costa PP, Saraiva MJM: PAP: Aniiloicle, ti-aiistirretina e nervo perifi-rico-estutlos etiopatogi-nicos (r tim d o Hospital dc Santo Aiit6nio 1088, 3 , 10% 126. 2. Coutinho P, Macedo E, Estlcio A: Familial amyloitlotic polyneuropathy. Clinical trial with plasniaphcresis. l'rocectlings of the Symposium on 1)ei-iptieraI Neuropathics, 1.isl)on, 1988, pp 241-244. 3. Sales-Luis ML: ~ , l e c t r o n c i i ~ o p l ~ ~ s i o l ostudies ~ i c a l i r i E'aniilial amyloid polyneiiropatliy- Portuguese type. J Ncurol A'uo osurg Psychiahy 1978; 41:847-8.50. 4. Sales-Luis M L , Serrzo R, (;alv;io M , Sousa (;, Quintas ,I. Espirito-Santo C: Therapeutic trials on fatiiilial aiiiyloidotic polyneuropathy (FAP) patients: Plasma exchange, gmgliosides. Proceedings of the Symposium on Peripheral Ncuropathies, Lisbon, 1988, pp 2445-250. 5. Sales-Luis ML, Alves M M , Set-rrio K, Saraiva M,], ( h t a PI', Coutinho P: Estudos clectroiicut-ofisiol6gicos cni litmiliai.es d e doentes con1 polineuroparia aniiloiclc liuiiiliar (PAP)correlaGrio coin a presenqa de trantirr-etina mol-mal (AE'p). Boletim d o Hospital tle Santo ,IntOiiio, 1088. 3 , 103- 108. 6 . Sales-Luis MI,, Set-rao K, Alves M M . Hasilio

B B B

0

> >

0 0 0 B B

0

B = blocked, NB = not blocked, D = diminished, >,< = predominance of one type of mechanical hyperalgesia over the other (at baseline), 0 = not present

time of block of myelinated fibers had various combinations of hyperalgesia, precluding any attempt t o identify a single sensory channel as responsible for both symptoms.

TOWARD MORE RATIONAL NERVE CONDUCTION INTERPRETATIONS: THE EFFECT OF HEIGHT:

Acknowledgment: Supported by NIH grants # R 0 i NS 24740 and 24766.

Rivner e t all recommend that nerve conduction velocity (NCV) measurenients be corrected for height. T h e y asked patients their body lengths- w e routinely measure body length-and have f o u n d that the patients’ reported lengths a r e often incorrect. As such errors may reach 5 cm, we feel that measurements must be preferred over reported lengths. In the discussion of F-waves, it is important to distinguish between F-wave latency, which is highly correlated with height, a n d F-wave conduction velocity, which shows no such relationship.““ F-wave conduction velocity measurements require a n indication o f axon length; Campbell e t al:’ used the distance from the L1 process to the knee. It is unknown how well such measurenients reflect t r u e axonal distances. A poor correspondence would a d d a source of variability rather than negate one, a n d a t r u e relation of‘ F-wave velocity with Iieight may be lost d u e to t h e a d d e d measurement error. For this reason, it may be preferable to use the highly reproducible body height nieasurement instead of a n approximated axonal length to correct F-wave latencies for height. Table 1 shows the relationships found in o u r laboratory f o r normal suJ?jects’ peroneal a n d tibia1 NCVs, F-waves, a n d f o r quadriceps a n d Achilles’ tendon j e r k latencies. We f o u n d inverse relationships between NCVs a n d height, b u t these did not reach statistical significance, probably because of small sample size. 1:-wave a n d reflex latencies show higher slope coefficients a n d stronger correlations, indicating a greater need for height correction. Kivner e t al give n o advice o n how to correct for height in clinical practice. Multiple regression formulae for a g e arid height have been described elsewhere,‘ but have, to o u r knowledge, not resulted in routine use of height (or age) corrections. A statistically correct correc-

David Yarnitsky, MD Jose L. Ochoa MD, DSc Department of Neurology Good Samaritan Hospital and Medical Center Oregon Health Sciences University Portland, Oregon 97210. Dr. Yarnitsky’s present address is Dept. of Neurology, Rambam Medical Center, Haifa 35254, Israel.

1. Brown AG, Iggo A: The structure and function of cutaneous “touch corpuscles” after nerve crush. J P h v d (Lond) 1963; 165328-29. 2. Fruhstorfer H, I.indblom U, Schmidt WG: Method for quantitative estimation of thermal thresholds on patients. j Neurol Neurosurg Psychiutq 1976; 39:1071- 1075. 3. Hoffmann P: Ueber eine methotie, den erfolg einer nervennalt zu beurteilen. Medlirinisrhr Klinik 1915; 11 :359360. 4. Konorski J , Lubinska L: Mechanical excitability of regenerating nerve fibers. Lancet 1946; 1:609-610. 5. Mackenzie RA, Burke D, Skuse NF, Lethlean AK: Fibre function and perception during cutaneous nerve block. J Neurol Neurosurg Pychiutjy 1975; 38:865- 873. 6 Ochoa JL, Torebjork HE, Culp W J , Schady W: Abnormal spontaneous activity in single sensory nerve fibers i n humans. Muscle N m i r 1982; 5(suppl):S74-S77. 7. Ochoa JL, Roberts WJ, Cline MA, Dotson R, Yarnitsky D: Two mechanical hyperalgesias in human neuropathy. A6.slr Soc Neuroxi 1989; l5:472. 8. Roberts W: A hypothesis on the physiological basis for causalgia and related pains. Puzn 1986; 24:297-311. 9. Sinclair DC, Hinshaw JR: A comparison of the dissociation produced by procaine and by limb ischaemia. Bruin 1950; 731480-498. 10. Tinel J: Le signe du “fourmillenient” dans les lesions des nerfs peripheriques. Lu Prvsse Medzccde 1915; 23:388389. 11. Wilkins RH, Brody IA: Tinel’s sign. Arch Neurol 1981; 24:573-575.

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Table 1. Relationships with height a NCV R. tibial NCV L. tibial NCV R. peroneal NCV L. peroneal NCV Latenctes R tibial F L tibia1 F R peroneal F L peroneal F A ATR L ATR R. knee jerk L knee jerk

-0.21 -0.18

-0.03 -0.12 0.30 0.20 0.35 0.47 0.25 0.25 0.13 0.15

b

P

n

r

86.1 78.3 52.6 71.4

NS NS NS NS

12 9 18 11

-0.29 -0.37 -0.07 -0.35

tl.

9 8 18 12 47 47 12 12

0.9 14.4 -11.3 -32.0 - 13.3 - 13.5 - 6.2 - 9.1 -

*** *** *** *** t** **t

0.78 0.71 0.82 0.93 0.78

0.82 0.73 0.79

r#

a#

0.00 --0.05 0.04 0.11 0.05 0.05 0.02 0.03

0.01 --0.39

0.26 0.73 0.37 0.42 0.27 0.46

For each variable (y) a linear relation with height ( x ) was assumed, and noted as y = ax + b. a and b refer to this formula. 'P < 0.05, **P < 0.02, "'P i0.01. n refers to the number of subjects, and r to Pearson's product-moment correlation coefficient. a# and r# refer to the same variables as above after correction for height was applied by dividing latencies by height R: right, L: left, ATR: Achilles tendon reflex.

tion for height involves the calculation from the regression formula of a NCV expected for a given height; the difference between the observed and the expected value then has to be compared to the spread around the line of best fit by dividing it by the standard deviation of the estimate (SE). Resulting values larger than 2 may be noted as abnormal. This laborious process will inhibit height correction in most laboratories. A simpler method involves dividing latencies by height; this changes the relationship with height from a linear to a hyperbolic one. T h e clinically relevant 150200 cm height range lies in the asymptotic part of the hyperbola, where it approximates a horizontal line. Table 1 shows that the relationship between this quotient and height has low slope and correlation coefficients, showing that the method largely negates the effect of height. T h e mean plus 2 standard deviations may be taken as a normality threshold value. This method has obvious disadvantages: it does not fully correct for height, and the resulting ms-per-meter parameter (the inverse of velocity) is unfamiliar. T h e method is simple, however, and may serve as a compromise between the need for statistically correct height correction and facility of use. J. Gert van Dijk Department of Clinical Neurophysiology Leiden University Hospital 2300 RC Leiden, The Netherlands 1. Rivner M H , Swift T R , Crout BO, Khodes KP: Toward nwre rational nerve conduction interpretations: ~l'he effect o f

height. Muscle Nerve 1990; 133232-239. 2 . Soudmand K,Ward LC, Swift T R : Effect o f height on nerve conduction velocity. Neulo~ogy1982; 32:407-4 1 0 .

3. Campbell WW, Ward LC, Swift T R : Nerve conduction velocity varies inversely with height. Mu.& Nenw I98 1 ; 4:520-523.

Letters to the Editor

TOWARD MORE RATIONAL NERVE CONDUCTION INTERPRETATIONS: THE EFFECT OF HEIGHT: A REPLY Since most subjects know their height and it remains constant, w e d o not routinely measure it. Initially, we measured the height of all o u r experimental subjects; however, we found that reported height compared almost exactly with measured height. In instances when we felt there was a discrepancy or the subject was unsure of their height, we measured the subject. We routinely measured axonal length, measured from the ankle to the xiphoid process. T h e measured axonal length correlated very well to the reported height (r = 0.9752). ' In addition, all nerve conductions and latencies which were correlated to height showed similar relationships to axonal length. In practice it is probably ideal to measure height. In the article by Campbell et al, both height and axonal length were measured and compared to F-wave latency.' T h e axonal length to the knee was only used when examining the F-wave latency from stimulation at the knee. In instances, where the F-wave at the ankle was used, the axonal length measured from the ankle was used instead." In our current article, we did not deal with F-waves or H-reflex latencies, even though based on our previous work, we agree that these are highly correlated to height. There are two reasons for this relationship. First, there is a relationship between nerve conduction velocity (NCV) and height; second, the length of' the nerve segment studied is longer in ta\l subjects. I n addition, Van Dijk's data show an inverse correlation between NCV and height. These correlations are not as significant as ours, but w e believe that is d u e to his small sample size. He examined between 9 and 18 sub-

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jects; we studied 104. In addition, w e d o not know the range of his subjects’ heights. I f this range was limited, the correlation coefficient would be reduced. While the method described by Van Dijk of dividing the F-wave latency by height would negate the effects of a longer axon segment, it would not correct for the slower conduction velocities seen in taller persons. Unfortunately, this method when used on our sural conduction velocity data failed to eliminate the effects of height. As stated in our article, the correlation between sural conduction velocity and height is -0.7104, when s u r d conduction is divided by height the correlation is -0.9056. In this instance, rather than eliniinating the effects of height, dividing the conduction velocity by height actually makes the correlation stronger. I n the case of sural latency, its correlation with height was 0.6518, when it is divided by height it beconies inversely correlated to height (1. = -0.2474). This is still a significant correlation ( P < 0.05). When testing distal nerves in tall patients, we believe it is important t o correlate the data with height. Dividing the data by height does not correct the data sufficiently to allow its use without correlation to height. Fortunately, the electrophysiologist has alterna-

382

Letters to the Editor

tives to using complicated equations. T h e first is to use the graphs in Figures 1 and 2 of our article.’ Using these graphs, it takes only a matter of seconds to determine the normal value of a nerve conduction. With modern computers, graphs such as these may be rapidly generated tly the electrophysiologist who wants to establish his own normal values. We also have a computer program available that calculates these normal values. Both of these methods are as easy as dividing the latency by height and are far more accurate. Michael H. Rivner, MD Thomas R. Swift, MD Barbara 0. Crout Karen P. Rhodes Department of Neurology Medical College of Georgia Augusta, Georgia 30912 Kivner M H , Swift ’l’K,