Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2014; 15: 93–97
ORIGINAL ARTICLE
Spinal cord atrophy correlates with disease duration and severity in amyotrophic lateral sclerosis
LUCAS M. T. BRANCO, MILENA DE ALBUQUERQUE, HELEN MAIA T. DE ANDRADE, FELIPE P. G. BERGO, ANAMARLI NUCCI & MARCONDES C. FRANÇA JR. Department of Neurology and Neuroimaging Laboratory, Faculty of Medicine, University of Campinas – UNICAMP, Campinas, SP, Brazil
Abstract Our objective was to investigate spinal cord (SC) atrophy in amyotrophic lateral sclerosis (ALS) patients, and to determine whether it correlates with clinical parameters. Forty-three patients with ALS (25 males) and 43 age- and gender-matched healthy controls underwent MRI on a 3T scanner. We used T1-weighted 3D images covering the whole brain and the cervical SC to estimate cervical SC area and eccentricity at C2/C3 level using validated software (SpineSeg). Disease severity was quantified with the ALSFRS-R and ALS Severity scores. SC areas of patients and controls were compared with a Mann-Whitney test. We used linear regression to investigate association between SC area and clinical parameters. Results showed that mean age of patients and disease duration were 53.1 ⫾ 12.2 years and 34.0 ⫾ 29.8 months, respectively. The two groups were significantly different regarding SC areas (67.8 ⫾ 6.8 mm² vs. 59.5 ⫾ 8.4 mm², p ⬍ 0.001). Eccentricity values were similar in both groups (p ⫽ 0.394). SC areas correlated with disease duration (r ⫽ ⫺0.585, p ⬍ 0.001), ALSFRS-R score (r ⫽ 0.309, p ⫽ 0.044) and ALS Severity scale (r ⫽ 0.347, p ⫽ 0.022). In conclusion, patients with ALS have SC atrophy, but no flattening. In addition, SC areas correlated with disease duration and functional status. These data suggest that quantitative MRI of the SC may be a useful biomarker in the disease. Key words: ALS, motor neuron diseases, MRI, cord atrophy
Introduction Amyotrophic lateral sclerosis (ALS) is the most relevant adult motor neuron disease (MND) involving both upper and lower motor neurons. The disease is found worldwide and incidence is around 2–16 per 100,000 person-years (1). It is a disabling neurodegenerative disease characterized by progressive weakness, generalized muscular atrophy, diffuse cramps, fasciculations and sometimes spasticity (1). The disease is uniformly fatal, but survival times may vary widely between subjects (1). Early ALS diagnosis is hampered by the large number of diseases with similar symptoms; the usual delay between symptom onset and diagnosis is around one year (2,3). In addition, it is often difficult to determine prognosis for an individual patient at the first appointment (1). Therefore, the identification of reliable biomarkers in ALS would be extremely
helpful both for diagnosis and disease monitoring. Several possible candidates have been investigated, including serum and CSF markers, neurophysiological parameters and especially MRI data (4–7). The great strength of MRI based studies in ALS is the ability to non-invasively assess the integrity of the corticospinal tracts (8). There are several studies based on DTI and volumetric analyses of brain scans, with promising results (9,10). Although spinal cord damage is a pathological hallmark of ALS, there are not many MRI studies specifically devoted to investigate spinal cord impairment in the disease (11–13). Recent advances in MRI, including high field devices and advanced post-processing techniques, now enable reliable quantitative analyses of the spinal cord that have already proven useful in similar neurodegenerative disorders (14).
Correspondence: M. C. França Jr, Department of Neurology, University of Campinas – UNICAMP, Rua Tessá lia Vieira de Camargo, 126 Cidade Universitaria ‘Zeferino Vaz’, Campinas SP, Brazil 13083-887. Fax: 55 19 3521 7933. E-mail: [email protected] (Received 11 June 2013 ; accepted 3 October 2013) ISSN 2167-8421 print/ISSN 2167-9223 online © 2014 Informa Healthcare DOI: 10.3109/21678421.2013.852589
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We thus hypothesize that ALS patients have cord atrophy amenable to detection by modern MRI based techniques. The anatomical substrate for this abnormality is mostly the damage to the lateral corticospinal tracts (upper motor neurons). Therefore, in those patients with limb onset and marked pyramidal signs, quantification of cord area might be an interesting candidate biomarker for follow-up or prognosis. For those subjects with bulbar onset, such analyses may provide evidence of more widespread damage, earlier than clinical signs appear. In this setting, we have designed a transversal MRI based study in order to investigate and quantify spinal cord atrophy in patients with ALS. We also evaluated whether cord damage correlates with clinical parameters. Our ultimate objective is to evaluate the usefulness of quantitative MRI of the cervical spinal cord as a biomarker in ALS. Material and methods Subjects selection We selected a group of 43 consecutive patients regularly followed at UNICAMP hospital with ALS. Each patient fulfilled the El Escorial revised criteria for definite or probable ALS (15). We excluded subjects under 18 years of age or those who had another concomitant neurological disease not related to ALS. We also excluded those who were not able to perform MRI examination. Imaging findings were compared to a control group of 43 healthy individuals with similar age-andgender distribution. These controls had no relevant past medical or family history of neurological disease. This study was approved by our institution ethics committee and written informed consent was obtained from all participants.
semi-automatically using the SpineSeg software tool, developed at UNICAMP neuroimaging laboratory and previously validated (14,18). SpineSeg resamples the MR images to correct for variations in imaging angle and neck position, segments cross-sections of the spinal cord semi-automatically, and fits an ellipse to the segmentation. The only interactive inputs in SpineSeg are a few nodes that define an approximation of the spine and neck curvature and a single point inside the spinal cord. The boundary of the spinal cord is segmented by automatic tree pruning, which consistently segments the object with minimal interaction, and an ellipse is fitted to the segmented object boundary (18). Two measurements were used for all further analyses: spinal cord area (CA), expressed in mm2, and spinal cord eccentricity (CE), which is defined as the square root of 1–(a/b)2, where a is the smaller diameter of the cord and b is the larger diameter of the cord. CE is thus a measure of antero-posterior cord flattening, and might be useful to give some insight into the anatomical substrate of cord atrophy. Diseases with marked atrophy and gliosis of the posterior columns, for example, result in atrophy combined with flattening (14). We used the mean values obtained from three consecutive levels measurements at the mid-section of the intervertebral disc between C2 and C3 in each subject (Figure 1). This level was chosen because it includes the cervical intumescence thus making the cord larger and enabling easier detection of atrophy. In addition, it is the region most commonly employed for MRI based cord area measurements, which permits comparison of our own data with previous data (19). All measurements were performed by a single investigator (LMTB) who was blind for the clinical status of the patients.
Clinical evaluation Patients with ALS underwent neurological evaluation on the same day MRI scans were obtained, and data on age at examination and disease duration were recorded. Disease severity was quantified using the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) (16) and ALS Severity scale (17). MRI analyses Acquisition. Patients and controls underwent MRI on a 3 T Achieva PHILIPS Scanner using a standard head coil. We used T1-weighted images covering the whole brain and the cervical spinal cord with the following acquisition parameters: TE ⫽ 3.2 ms, TR ⫽ 7.1 ms, flip angle ⫽ 80, voxel size ⫽ 1.0 ⫻ 1.0 ⫻ 1.0 mm and FOV ⫽ 240 ⫻ 240. Measurements and segmentation. Spinal cord segmentation and measurements were performed
Statistical analysis Comparative analyses of CA and CE between patients and controls were obtained using a MannWhitney test. We also used Pearson coefficients to investigate the association between cord measurements and clinical parameters (ALSFRS-R scale, ALS Severity scale and disease duration) in the ALS group. Level of significance was set at p ⫽ 0.05 for all comparisons. SYSTAT software version 9.0 was used to perform these analyses. Results In the ALS group there were 23 patients with definite disease and 20 with probable disease, according to the El Escorial criteria. Demographic data and spinal cord measurements of all subjects are shown on Table I. Patients with ALS had significant reduction of CA compared to controls (p ⬍ 0.001), but CE
Spinal cord atrophy in ALS
95
Figure 1. SpineSeg layout showing segmentation of spinal cord at C2 – C3 level.
was not statistically different (p ⫽ 0.394) (Table I, Figures 2, 3). In addition, we found that CA was directly associated both with the ALSFRS-R score (r ⫽ 0.309, p ⫽ 0.044) and ALS Severity scale (r ⫽ 0.347, p ⫽ 0.022). After removing bulbar subscore from ALSFRS-R, the direct association with CA persisted (r ⫽ 0.302, p ⫽ 0.049). Disease duration was inversely
associated to CA (r ⫽ ⫺0.585, p ⬍ 0.001). CA was not associated with age of the patients (p ⫽ 0.688). Discussion We have shown that ALS patients have cord atrophy amenable to detection with MRI based analyses. This is especially relevant if we consider that a 3T
Table I. Demographic and MRI data of patients and controls.
Age (mean ± SD, years) Gender (M/F) Duration of disease (mean ± SD, months) Bulbar onset (%) Limb onset (%) ALSSS (mean ± SD) ALSFRS-R total score (mean ± SD) ALSFRS-R without bulbar scores (mean ± SD) ALSFRS-R bulbar subscore (mean ± SD) ALSFRS-R arm subscore (mean ± SD) ALSFRS-R leg subscore (mean ± SD) ALSFRS-R respiratory subscore (mean ± SD) Cord area (mean ± SD, mm²) Cord eccentricity (mean ± SD)
ALS (n ⫽ 43)
Controls (n ⫽ 43)
p
53.1 ⫾ 12.2 25/18 34.0 ⫾ 29.9 8 (18.6%) 35 (81.4%) 26.5 ⫾ 7.5 29.9 ⫾ 9.8 20.7 ⫾ 8.6 9.2 ⫾ 2.5 5.0 ⫾ 3.6 5.5 ⫾ 4.2 10.2 ⫾ 2.2 59.6 ⫾ 8.5 0.79 ⫾ 0.05
53.2 ⫾ 12.3 23/20 – – – – – – – – – – 67.8 ⫾ 6.8 0.78 ⫾ 0.05
0.979 0.664 – – – – – – – – – – 0.001 0.394
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AREA
70 60 50 40 30
1
GROUP
2
Figure 2. Box-and-whiskers plot showing the distribution of CA. Patients with ALS are represented by Group 1, and controls are represented by Group 2.
scanner and validated software were employed in our study. This is in line with pathological reports on the disease, which describe extensive motor neuron loss in anterior horns as well as corticospinal damage (20). Our results also indicate that cord damage in ALS is not characterized by flattening. We hypothesize that this pattern of atrophy without anteroposterior shortening occurs because tissue loss is mostly located at the lateral corticospinal tracts. There are few previous MRI based studies devoted to spinal cord damage in ALS, and available results are conflicting (10,21,22). Sperfeld et al. failed to identify cord atrophy in a series of 39 patients with ALS. In that study, however, scans were performed on a 1.5T device and authors employed linear measurements of the cord as surrogate markers for atrophy. We think that these are
major limitations and help to explain the discrepancy between our results. More recent studies using cord area measurements and high field devices also found atrophy in patients with ALS (10,22). Our findings also show a correlation between spinal cord atrophy and disease severity in patients with ALS. Since ALS determines a progressive impairment of motor structures, concomitant worsening of clinical parameters would be expected. A recent study (22) found association between specific muscle deficits and local spinal cord atrophy in ALS. These data agree with our expectation of clinical worsening as a result of cumulative injury in ALS progression. In contrast, another MRI based study (10), also using a 1.5T scanner, found significant reduction of cord cross-sectional area in a longitudinal setting with 17 patients, but did not find association between cord atrophy and worsening of disability and rate of disease progression in ALS, using the ALSFRS-R score. The authors allegedly hypothesize that those results might have been compromised by the small number of subjects, and also by the high drop-out rate (39%) in the study. They also reported that the ALSFRS-R score may have low specificity to spinal involvement in the disease. However, since the ALSFRS-R scale includes bulbar scores (which are not directly related to cord damage), the full scale may not be very accurate with MRI findings. Thus, we also performed correlation tests using a modified ALSFRS-R scale that did not include bulbar parameters, and still found an association with CA. We have also shown a correlation between spinal cord atrophy and disease duration in patients with ALS. This is in accordance with the findings of a recent longitudinal study (22). Taken together, these results strongly suggest that cord area may be a reliable prognostic marker in ALS. However, it is first
Figure 3. Comparison of cervical spinal cord sections between a patient with ALS (left) and a healthy control (right), obtained by software SpineSeg.
Spinal cord atrophy in ALS necessary to determine whether cord atrophy follows a linear progression or whether it varies according to clinical stage of the disease. Novel MRI protocols for cord imaging, including spectroscopy and DTI, are very promising in ALS (11,13). These techniques enable detection of biochemical and microstructural damage to motor tracts in the cord. We thus believe that they can complement morphometric studies and provide a comprehensive analysis of cord damage in ALS. Despite this, there are still major limitations in these new techniques mostly because of the small size of the spinal cord (and its tracts) as well as the lack of standardized acquisition protocols (5,7). Perhaps ultra-high field scanners may help to improve quality and reliability of these advanced techniques (12). Acknowledgements This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). Declaration of interest: The authors report no confl icts interest regarding this research. The authors alone are responsible for the content and writing of the paper. References 1. Kiernan MC, Vucic S, Cheah BC, Turner MR, Eisen A, Hardiman O, et al. Amyotrophic lateral sclerosis. Lancet. 2011;377:942–55. 2. Kraemer M, Buerger M, Berlit P. Diagnostic problems and delay of diagnosis in amyotrophic lateral sclerosis. Clin Neurol Neurosurg. 2010;112:103–5. 3. Chieia MA, Oliveira AS, Silva HC, Gabbai AA. Amyotrophic lateral sclerosis: considerations on diagnostic criteria. Arq Neuropsiquiatr. 2010;68:837–42. 4. Rocha AJ, Maia ACM Jr. Is magnetic resonance imaging a plausible biomarker for upper motor neuron degeneration in amyotrophic lateral sclerosis/primary lateral sclerosis or merely a useful paraclinical tool to exclude mimic syndromes? A critical review of imaging applicability in clinical routine. Arq Neuropsiquiatr. 2012;70:532–9. 5. Turner MR, Kiernan MC, Leigh PN, Talbot K. Biomarkers in amyotrophic lateral sclerosis. Lancet Neurol. 2009; 8:94–109. 6. Turner MR, Grosskreutz J, Kassubek J, Abrahams S, Agosta F, Benatar M, et al. Towards a neuroimaging biomarker for amyotrophic lateral sclerosis. Lancet Neurol. 2011;10:400–3. 7. Turner MR. MRI as a frontrunner in the search for amyotrophic lateral sclerosis biomarkers? Biomark Med. 2011;5:79–81.
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8. Kollewe K, Korner S, Dengler R, Petri S, Mohammadi B. Magnetic resonance imaging in amyotrophic lateral sclerosis. Neurol Res Int. 2012;2012:608501. Epub. 9. Bashat BD, Artzi M, Tarrasch R, Nefussy B, Drory VE, Aizenstein O. A potential tool for the diagnosis of ALS based on diffusion tensor imaging. Amyotroph Lateral Scler. 2011;12:398–405. 10. Agosta F, Rocca MA, Valsasina P, Sala S, Caputo D, Perini M, et al. A longitudinal diffusion tension MRI study of the cervical cord and brain in amyotrophic lateral sclerosis patients. J Neurol Neurosurg Psychiatry. 2009;80:53–5. 11. Valsasina P, Agosta F, Benedetti B, Caputo D, Perini M, Salvi F, et al. Diffusion anisotropy of the cervical cord is strictly associated with disability in amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry. 2007;78:480–4. 12. Cohen-Adad J, Zhao W, Keil B, Ratai EM, Triantafyllou C, Lawson R, et al. 7-T MRI of the spinal cord can detect lateral corticospinal tract abnormality in amyotrophic lateral sclerosis. Muscle Nerve. 2013;47:760–2. 13. Carew JD, Nair G, Pineda-Alonso N, Usher S, Hu X, Benatar M, et al. Magnetic resonance spectroscopy of the cervical cord in amyotrophic lateral sclerosis. Amyotroph Lateral Scler. 2011;12:185–91. 14. Chevis CF, da Silva CB, D’Abreu A, Lopes-Cendes I, Cendes F, Bergo FP, et al. Spinal cord atrophy correlates with disability in Friedreich’s ataxia. Cerebellum. 2013;12:43–7. 15. World Federation of Neurology research group on motor diseases. El Escorial revisited: revised criteria for the diagnosis of ALS. A consensus conference held at Airlie House. Worrenton. 1998;2–4 16. Cedarbaum JM, Stambler N, Malta E, Fuller C, Hilt D, Thurmond B, et al. The ALSFRS-R: a revised ALS functional rating scale that incorporates assessments of respiratory function. BDNF ALS Study Group (Phase III). J Neurol Sci. 1999;169:13–21. 17. Hillel AD, Miller RM, Yorkston K, McDonald E, Norris FH, Konikow N. Amyotrophic lateral sclerosis severity scale. Neuroepidemiology. 1989;8:142–50. 18. Bergo FPG, França MC Jr, Chevis CF, Cendes F. SpineSeg: A Segmentation and Measurement Tool for Evaluation of Spinal Cord Atrophy. In: CISTI’2012 (7ª Conferencia Ibérica de Sistemas y Tecnologia de Información). Madrid, Spain: IEEE; 2012. pp 400–3. 19. França MC Jr, d’Abreu A, Zanardi VA, Faria AV, Lopes-Cendes I, Nucci A, et al. MRI shows dorsal lesions and spinal cord atrophy in chronic sensory neuronopathies. J Neuroimaging. 2008;18:168–72. 20. Sasaki S, Iwata M. Impairment of fast axonal transport in the proximal axons of anterior horn neurons in amyotrophic lateral sclerosis. Neurology. 1996;47:535–40. 21. Sperfeld AD, Bretschneider V, Flaith L, Unrath A, Hanemann CO, Ludolph AC, et al. MR-Pathologic Comparison of the Upper Spinal Cord in the Different Motor Neuron Diseases. Eur Neurol. 2005;53:74–7. 22. Cohen-Adad J, El Mendili MH, Morizot-Koutlidis R, Lehéricy S, Meininger V, Blancho S, et al. Involvement of spinal sensory pathway in ALS and specificity of cord atrophy to lower motor neuron degeneration. Amyotroph Lateral Scler Frontotemporal Degener. 2013;14;30–8.
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ORIGINAL ARTICLE
Spinal cord atrophy correlates with disease duration and severity in amyotrophic lateral sclerosis
LUCAS M. T. BRANCO, MILENA DE ALBUQUERQUE, HELEN MAIA T. DE ANDRADE, FELIPE P. G. BERGO, ANAMARLI NUCCI & MARCONDES C. FRANÇA JR. Department of Neurology and Neuroimaging Laboratory, Faculty of Medicine, University of Campinas – UNICAMP, Campinas, SP, Brazil
Abstract Our objective was to investigate spinal cord (SC) atrophy in amyotrophic lateral sclerosis (ALS) patients, and to determine whether it correlates with clinical parameters. Forty-three patients with ALS (25 males) and 43 age- and gender-matched healthy controls underwent MRI on a 3T scanner. We used T1-weighted 3D images covering the whole brain and the cervical SC to estimate cervical SC area and eccentricity at C2/C3 level using validated software (SpineSeg). Disease severity was quantified with the ALSFRS-R and ALS Severity scores. SC areas of patients and controls were compared with a Mann-Whitney test. We used linear regression to investigate association between SC area and clinical parameters. Results showed that mean age of patients and disease duration were 53.1 ⫾ 12.2 years and 34.0 ⫾ 29.8 months, respectively. The two groups were significantly different regarding SC areas (67.8 ⫾ 6.8 mm² vs. 59.5 ⫾ 8.4 mm², p ⬍ 0.001). Eccentricity values were similar in both groups (p ⫽ 0.394). SC areas correlated with disease duration (r ⫽ ⫺0.585, p ⬍ 0.001), ALSFRS-R score (r ⫽ 0.309, p ⫽ 0.044) and ALS Severity scale (r ⫽ 0.347, p ⫽ 0.022). In conclusion, patients with ALS have SC atrophy, but no flattening. In addition, SC areas correlated with disease duration and functional status. These data suggest that quantitative MRI of the SC may be a useful biomarker in the disease. Key words: ALS, motor neuron diseases, MRI, cord atrophy
Introduction Amyotrophic lateral sclerosis (ALS) is the most relevant adult motor neuron disease (MND) involving both upper and lower motor neurons. The disease is found worldwide and incidence is around 2–16 per 100,000 person-years (1). It is a disabling neurodegenerative disease characterized by progressive weakness, generalized muscular atrophy, diffuse cramps, fasciculations and sometimes spasticity (1). The disease is uniformly fatal, but survival times may vary widely between subjects (1). Early ALS diagnosis is hampered by the large number of diseases with similar symptoms; the usual delay between symptom onset and diagnosis is around one year (2,3). In addition, it is often difficult to determine prognosis for an individual patient at the first appointment (1). Therefore, the identification of reliable biomarkers in ALS would be extremely
helpful both for diagnosis and disease monitoring. Several possible candidates have been investigated, including serum and CSF markers, neurophysiological parameters and especially MRI data (4–7). The great strength of MRI based studies in ALS is the ability to non-invasively assess the integrity of the corticospinal tracts (8). There are several studies based on DTI and volumetric analyses of brain scans, with promising results (9,10). Although spinal cord damage is a pathological hallmark of ALS, there are not many MRI studies specifically devoted to investigate spinal cord impairment in the disease (11–13). Recent advances in MRI, including high field devices and advanced post-processing techniques, now enable reliable quantitative analyses of the spinal cord that have already proven useful in similar neurodegenerative disorders (14).
Correspondence: M. C. França Jr, Department of Neurology, University of Campinas – UNICAMP, Rua Tessá lia Vieira de Camargo, 126 Cidade Universitaria ‘Zeferino Vaz’, Campinas SP, Brazil 13083-887. Fax: 55 19 3521 7933. E-mail: [email protected] (Received 11 June 2013 ; accepted 3 October 2013) ISSN 2167-8421 print/ISSN 2167-9223 online © 2014 Informa Healthcare DOI: 10.3109/21678421.2013.852589
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We thus hypothesize that ALS patients have cord atrophy amenable to detection by modern MRI based techniques. The anatomical substrate for this abnormality is mostly the damage to the lateral corticospinal tracts (upper motor neurons). Therefore, in those patients with limb onset and marked pyramidal signs, quantification of cord area might be an interesting candidate biomarker for follow-up or prognosis. For those subjects with bulbar onset, such analyses may provide evidence of more widespread damage, earlier than clinical signs appear. In this setting, we have designed a transversal MRI based study in order to investigate and quantify spinal cord atrophy in patients with ALS. We also evaluated whether cord damage correlates with clinical parameters. Our ultimate objective is to evaluate the usefulness of quantitative MRI of the cervical spinal cord as a biomarker in ALS. Material and methods Subjects selection We selected a group of 43 consecutive patients regularly followed at UNICAMP hospital with ALS. Each patient fulfilled the El Escorial revised criteria for definite or probable ALS (15). We excluded subjects under 18 years of age or those who had another concomitant neurological disease not related to ALS. We also excluded those who were not able to perform MRI examination. Imaging findings were compared to a control group of 43 healthy individuals with similar age-andgender distribution. These controls had no relevant past medical or family history of neurological disease. This study was approved by our institution ethics committee and written informed consent was obtained from all participants.
semi-automatically using the SpineSeg software tool, developed at UNICAMP neuroimaging laboratory and previously validated (14,18). SpineSeg resamples the MR images to correct for variations in imaging angle and neck position, segments cross-sections of the spinal cord semi-automatically, and fits an ellipse to the segmentation. The only interactive inputs in SpineSeg are a few nodes that define an approximation of the spine and neck curvature and a single point inside the spinal cord. The boundary of the spinal cord is segmented by automatic tree pruning, which consistently segments the object with minimal interaction, and an ellipse is fitted to the segmented object boundary (18). Two measurements were used for all further analyses: spinal cord area (CA), expressed in mm2, and spinal cord eccentricity (CE), which is defined as the square root of 1–(a/b)2, where a is the smaller diameter of the cord and b is the larger diameter of the cord. CE is thus a measure of antero-posterior cord flattening, and might be useful to give some insight into the anatomical substrate of cord atrophy. Diseases with marked atrophy and gliosis of the posterior columns, for example, result in atrophy combined with flattening (14). We used the mean values obtained from three consecutive levels measurements at the mid-section of the intervertebral disc between C2 and C3 in each subject (Figure 1). This level was chosen because it includes the cervical intumescence thus making the cord larger and enabling easier detection of atrophy. In addition, it is the region most commonly employed for MRI based cord area measurements, which permits comparison of our own data with previous data (19). All measurements were performed by a single investigator (LMTB) who was blind for the clinical status of the patients.
Clinical evaluation Patients with ALS underwent neurological evaluation on the same day MRI scans were obtained, and data on age at examination and disease duration were recorded. Disease severity was quantified using the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) (16) and ALS Severity scale (17). MRI analyses Acquisition. Patients and controls underwent MRI on a 3 T Achieva PHILIPS Scanner using a standard head coil. We used T1-weighted images covering the whole brain and the cervical spinal cord with the following acquisition parameters: TE ⫽ 3.2 ms, TR ⫽ 7.1 ms, flip angle ⫽ 80, voxel size ⫽ 1.0 ⫻ 1.0 ⫻ 1.0 mm and FOV ⫽ 240 ⫻ 240. Measurements and segmentation. Spinal cord segmentation and measurements were performed
Statistical analysis Comparative analyses of CA and CE between patients and controls were obtained using a MannWhitney test. We also used Pearson coefficients to investigate the association between cord measurements and clinical parameters (ALSFRS-R scale, ALS Severity scale and disease duration) in the ALS group. Level of significance was set at p ⫽ 0.05 for all comparisons. SYSTAT software version 9.0 was used to perform these analyses. Results In the ALS group there were 23 patients with definite disease and 20 with probable disease, according to the El Escorial criteria. Demographic data and spinal cord measurements of all subjects are shown on Table I. Patients with ALS had significant reduction of CA compared to controls (p ⬍ 0.001), but CE
Spinal cord atrophy in ALS
95
Figure 1. SpineSeg layout showing segmentation of spinal cord at C2 – C3 level.
was not statistically different (p ⫽ 0.394) (Table I, Figures 2, 3). In addition, we found that CA was directly associated both with the ALSFRS-R score (r ⫽ 0.309, p ⫽ 0.044) and ALS Severity scale (r ⫽ 0.347, p ⫽ 0.022). After removing bulbar subscore from ALSFRS-R, the direct association with CA persisted (r ⫽ 0.302, p ⫽ 0.049). Disease duration was inversely
associated to CA (r ⫽ ⫺0.585, p ⬍ 0.001). CA was not associated with age of the patients (p ⫽ 0.688). Discussion We have shown that ALS patients have cord atrophy amenable to detection with MRI based analyses. This is especially relevant if we consider that a 3T
Table I. Demographic and MRI data of patients and controls.
Age (mean ± SD, years) Gender (M/F) Duration of disease (mean ± SD, months) Bulbar onset (%) Limb onset (%) ALSSS (mean ± SD) ALSFRS-R total score (mean ± SD) ALSFRS-R without bulbar scores (mean ± SD) ALSFRS-R bulbar subscore (mean ± SD) ALSFRS-R arm subscore (mean ± SD) ALSFRS-R leg subscore (mean ± SD) ALSFRS-R respiratory subscore (mean ± SD) Cord area (mean ± SD, mm²) Cord eccentricity (mean ± SD)
ALS (n ⫽ 43)
Controls (n ⫽ 43)
p
53.1 ⫾ 12.2 25/18 34.0 ⫾ 29.9 8 (18.6%) 35 (81.4%) 26.5 ⫾ 7.5 29.9 ⫾ 9.8 20.7 ⫾ 8.6 9.2 ⫾ 2.5 5.0 ⫾ 3.6 5.5 ⫾ 4.2 10.2 ⫾ 2.2 59.6 ⫾ 8.5 0.79 ⫾ 0.05
53.2 ⫾ 12.3 23/20 – – – – – – – – – – 67.8 ⫾ 6.8 0.78 ⫾ 0.05
0.979 0.664 – – – – – – – – – – 0.001 0.394
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70 60 50 40 30
1
GROUP
2
Figure 2. Box-and-whiskers plot showing the distribution of CA. Patients with ALS are represented by Group 1, and controls are represented by Group 2.
scanner and validated software were employed in our study. This is in line with pathological reports on the disease, which describe extensive motor neuron loss in anterior horns as well as corticospinal damage (20). Our results also indicate that cord damage in ALS is not characterized by flattening. We hypothesize that this pattern of atrophy without anteroposterior shortening occurs because tissue loss is mostly located at the lateral corticospinal tracts. There are few previous MRI based studies devoted to spinal cord damage in ALS, and available results are conflicting (10,21,22). Sperfeld et al. failed to identify cord atrophy in a series of 39 patients with ALS. In that study, however, scans were performed on a 1.5T device and authors employed linear measurements of the cord as surrogate markers for atrophy. We think that these are
major limitations and help to explain the discrepancy between our results. More recent studies using cord area measurements and high field devices also found atrophy in patients with ALS (10,22). Our findings also show a correlation between spinal cord atrophy and disease severity in patients with ALS. Since ALS determines a progressive impairment of motor structures, concomitant worsening of clinical parameters would be expected. A recent study (22) found association between specific muscle deficits and local spinal cord atrophy in ALS. These data agree with our expectation of clinical worsening as a result of cumulative injury in ALS progression. In contrast, another MRI based study (10), also using a 1.5T scanner, found significant reduction of cord cross-sectional area in a longitudinal setting with 17 patients, but did not find association between cord atrophy and worsening of disability and rate of disease progression in ALS, using the ALSFRS-R score. The authors allegedly hypothesize that those results might have been compromised by the small number of subjects, and also by the high drop-out rate (39%) in the study. They also reported that the ALSFRS-R score may have low specificity to spinal involvement in the disease. However, since the ALSFRS-R scale includes bulbar scores (which are not directly related to cord damage), the full scale may not be very accurate with MRI findings. Thus, we also performed correlation tests using a modified ALSFRS-R scale that did not include bulbar parameters, and still found an association with CA. We have also shown a correlation between spinal cord atrophy and disease duration in patients with ALS. This is in accordance with the findings of a recent longitudinal study (22). Taken together, these results strongly suggest that cord area may be a reliable prognostic marker in ALS. However, it is first
Figure 3. Comparison of cervical spinal cord sections between a patient with ALS (left) and a healthy control (right), obtained by software SpineSeg.
Spinal cord atrophy in ALS necessary to determine whether cord atrophy follows a linear progression or whether it varies according to clinical stage of the disease. Novel MRI protocols for cord imaging, including spectroscopy and DTI, are very promising in ALS (11,13). These techniques enable detection of biochemical and microstructural damage to motor tracts in the cord. We thus believe that they can complement morphometric studies and provide a comprehensive analysis of cord damage in ALS. Despite this, there are still major limitations in these new techniques mostly because of the small size of the spinal cord (and its tracts) as well as the lack of standardized acquisition protocols (5,7). Perhaps ultra-high field scanners may help to improve quality and reliability of these advanced techniques (12). Acknowledgements This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). Declaration of interest: The authors report no confl icts interest regarding this research. The authors alone are responsible for the content and writing of the paper. References 1. Kiernan MC, Vucic S, Cheah BC, Turner MR, Eisen A, Hardiman O, et al. Amyotrophic lateral sclerosis. Lancet. 2011;377:942–55. 2. Kraemer M, Buerger M, Berlit P. Diagnostic problems and delay of diagnosis in amyotrophic lateral sclerosis. Clin Neurol Neurosurg. 2010;112:103–5. 3. Chieia MA, Oliveira AS, Silva HC, Gabbai AA. Amyotrophic lateral sclerosis: considerations on diagnostic criteria. Arq Neuropsiquiatr. 2010;68:837–42. 4. Rocha AJ, Maia ACM Jr. Is magnetic resonance imaging a plausible biomarker for upper motor neuron degeneration in amyotrophic lateral sclerosis/primary lateral sclerosis or merely a useful paraclinical tool to exclude mimic syndromes? A critical review of imaging applicability in clinical routine. Arq Neuropsiquiatr. 2012;70:532–9. 5. Turner MR, Kiernan MC, Leigh PN, Talbot K. Biomarkers in amyotrophic lateral sclerosis. Lancet Neurol. 2009; 8:94–109. 6. Turner MR, Grosskreutz J, Kassubek J, Abrahams S, Agosta F, Benatar M, et al. Towards a neuroimaging biomarker for amyotrophic lateral sclerosis. Lancet Neurol. 2011;10:400–3. 7. Turner MR. MRI as a frontrunner in the search for amyotrophic lateral sclerosis biomarkers? Biomark Med. 2011;5:79–81.
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