Transcranial magnetic stimulation studies in the Miller Fisher syndrome: evidence of corticospinal tract abnormality

Detecting spinal pyramidal tract of amyotrophic lateral sclerosis patients with diffusion tensor tractography

The objective of this study was to determine alteration of corticospinal tract in patients with amyotrophic lateral sclerosis (ALS) using diffusion tensor tractograhy (DTT) focusing on the cervical spinal cord (C5) and transcranial magnetic stimulation (TMS). We recruited 38 ALS, 6 spinal and bulbar muscular atrophy (SBMA), 7 spastic paraplegia (SP) patients, and 8 age-matched normal controls, and then ALS were divided into two subgroups according to their clinical type: 28 ALS-limb and 10 ALS-bulbar. DTT was performed using the diffusion tensor image (DTI) track module to reconstruct two fiber tracts via C5. The fractional anisotropy (FA) values of ALS-total and ALS-limb patients were significantly reduced compared with normal controls, and SBMA patients. On the other hand, the mean diffusivity (MD) values were not significantly different among normal controls and the three disease groups. The rate of disease progression (ΔFRS-R) of ALS patients was significantly correlated with FA values and central motor conduction time (CMCT). In conclusion, the present study demonstrated a significant reduction of FA values in ALS patients, and the ΔFRS-R of ALS patients showed distinct regressions with FA values and CMCT, suggesting that this DTT analysis could be useful for detecting disease progression of ALS patients.

Electrophysiology in Fisher syndrome

Fisher syndrome (FS), a variant of Guillain-Barré syndrome (GBS), is characterized by the clinical triad of ophthalmoplegia, ataxia, and areflexia. The lesion sites for these unique clinical features include the oculomotor nerves and group 1a neurons in the dorsal root ganglion, and the presence of FS is determined by the expression of ganglioside GQ1b in the human nervous system. Neurophysiological findings suggest that ataxia and areflexia are due to an impaired proprioceptive afferent system. Typically, the soleus H-reflex is absent and a body-sway analysis using posturography shows a 1-Hz peak, which indicates proprioception dysfunction. Sensory nerve action potentials and somatosensory-evoked potentials are abnormal in approximately 30% of FS patients, indicating the occasional involvement of cutaneous (group 2) afferents. During the disease course, approximately 15% of FS patients suffer an overlap of axonal GBS with nerve conduction abnormalities that reflect axonal dysfunction. This review summarizes electrophysiological abnormalities and their clinical significance in FS.

Cortical Reorganization Is Associated with Surgical Decompression of Cervical Spondylotic Myelopathy

Background. Cervical spondylotic myelopathy (CSM) results in sensorimotor limb deficits, bladder, and bowel dysfunction, but mechanisms underlying motor plasticity changes before and after surgery are unclear. Methods. We studied 24 patients who underwent decompression surgery and 15 healthy controls. Patients with mixed upper and lower limb dysfunction (Group A) and only lower limb dysfunction (Group B) were then analysed separately. Results. The sum amplitude of motor evoked potentials sMEP (p < 0.01) and number of focal points where MEPs were elicited (N) (p < 0.001) were significantly larger in CSM patients compared with controls. For Group A (16 patients), sMEP (p < 0.01) and N (p < 0.001) showed similar findings. However, for Group B (8 patients), only N (p = 0.03) was significantly larger in patients than controls. Group A had significantly increased grip strength (p = 0.02) and reduced sMEP (p = 0.001) and N (p = 0.003) after surgery. Changes in sMEP (cMEP) significantly correlated inversely with improved feeding (p = 0.03) and stacking (p = 0.04) times as was the change in number of focal points (NDiff) with improved writing times (p = 0.03). Group B did not show significant reduction in sMEP or N after surgery, or significant correlation of cMEP or NDiff with all hand function tests. No significant differences in H reflex parameters obtained from the flexor carpi radialis, or central motor conduction time changes, were noted after surgery. Discussion. Compensatory expansion of motor cortical representation occurs largely at cortical rather than spinal levels, with a tendency to normalization after surgery. These mirrored improvements in relevant tasks requiring utilization of intrinsic hand muscles.

Electrophysiological evidence of cerebellar fiber system involvement in the Miller Fisher syndrome

BACKGROUND

In the Miller Fisher syndrome (MFS), ataxia may be due involvement of Ia afferents and the cerebellum. Transcranial magnetic stimulation (TMS) over the cerebellum is known to interfere transiently with normal function.

METHODS

In this study, we utilized a previously described TMS protocol over the cerebellum in combination with ballistic movements to investigate cerebellar dysfunction in MFS patients.

RESULTS

The agonist (biceps) reaction time in MFS patients during a motor cancellation task was not significantly reduced during the initial TMS study. However, during the repeat TMS study, significant reduction was seen for all patients, in tandem with clinical recovery. There was significant correlation between anti-GQ1b IgG titers and change in agonist reaction time between the initial and repeat TMS studies.

CONCLUSIONS

TMS likely affected horizontally orientated parallel fibers in the cerebellar molecular layer. During disease onset, antibody binding may have interfered with facilitation of reaction time during motor cancellation tasks seen in normal subjects. Normalization of reaction time facilitation corresponded to resolution of antibody-mediated interference in the molecular layer. Our study has provided evidence suggesting parallel fiber involvement in MFS, and suggested a role of anti-GQ1b IgG antibody in these changes.

Clinical and immunological spectrum of the Miller Fisher syndrome

The Miller Fisher syndrome (MFS), characterized by ataxia, areflexia, and ophthalmoplegia, was first recognized as a distinct clinical entity in 1956. MFS is mostly an acute, self-limiting condition, but there is anecdotal evidence of benefit with immunotherapy. Pathological data remain scarce. MFS can be associated with infectious, autoimmune, and neoplastic disorders. Radiological findings have suggested both central and peripheral involvement. The anti-GQ1b IgG antibody titer is most commonly elevated in MFS, but may also be increased in Guillain-Barré syndrome (GBS) and Bickerstaff's brainstem encephalitis (BBE). Molecular mimicry, particularly in relation to antecedent Campylobacter jejuni and Hemophilus influenzae infections, is likely the predominant pathogenic mechanism, but the roles of other biological factors remain to be established. Recent studies have demonstrated the presence of neuromuscular transmission defects in association with anti-GQ1b IgG antibody, both in vitro and in vivo. Collective findings from clinical, radiological, immunological, and electrophysiological techniques have helped to define MFS, GBS, and BBE as major disorders within the proposed spectrum of anti-GQ1b IgG antibody syndrome.

The Role of Electrophysiology in the Diagnosis and Management of Cervical Spondylotic Myelopathy

Background: Cervical spondylotic myelopathy (CSM) is managed by conservative or surgical measures. While surgery is often performed in cases of longstanding or severe CSM, there is a lack of evidence concerning its efficacy. Transcranial magnetic stimulation (TMS) is a quick, safe, painless and non-invasive technique to study conduction in the descending corticospinal pathways in the spinal cord. The conduction time from the motor cortex to the anterior horn cell [central motor conduction time (CMCT)] is a measure of the integrity of corticospinal pathways. We have previously established the role of TMS in diagnosis and screening of CSM. In this study, we further investigate the use MEPs obtained with TMS in the outcome prediction of severe CSM patients requiring operative intervention. Methods: We prospectively evaluated 46 consecutive patients (mean age, 57.6 years; range, 36 to 84 years; 28 men) presenting with clinical features of CSM over a 2-year period. Disease duration ranged from 6 to 24 months. A total of 45 healthy controls were studied for comparison. All patients underwent clinical scoring. Patients’ initial clinical score (S1) and postoperative scoring at 6 months (S2) were based on a modified Japan Orthopedic Association Scoring Scale. A Modified Recovery Rate (MRR) was calculated based on the formula: (S2 – S1/17 – S1) x 100. We regarded a good surgical outcome as MRR of 50 or above. This was depicted as MRR50. The patients were separated into 4 groups according to the degree of cord compression by degenerative osteo-cartilaginous elements at the most significant level on MRI. TMS studies were performed before surgery. Each investigator was blinded to the results of the other investigators. Results: The upper limb (UL) CMCT (r = -0.507, P <0.0005) and lower limb (LL) CMCT (r = - 0.452, P = 0.002) were significantly and negatively correlated with S1. Similarly, UL MEP amplitude (r = 0.494, P <0005) and LL MEP amplitude (r = 0.305, P = 0.039) were significantly correlated with S1. Surgery consisted of anterior or posterior decompression with cervical laminoplasty, performed by an experienced team of orthopaedic surgeons. No significant intraoperative or postoperative complications were documented. Surgery resulted in significantly improved clinical scoring (unpaired t test, P <0.0005). No correlation between clinical scoring with patients’ age, disease duration, severity or levels of cord compression on MRI was found. ULCMCT and MEP amplitude abnormality were significantly associated with improvement in clinical scoring after surgery (Mann-Whitney test, P <0.05). The UL CMCT was the independent predictor of a good clinical outcome after surgery (odds ratio, 9.09; P = 0.011). Conclusions: In early CSM, lateral corticospinal tracts are first to be affected. It is thus possible that UL CMCT abnormality reflect more severe affectation of the corticospinal tracts placed relatively more medially in the cervical cord. Surgical intervention may have then effectively relieved the clinically significant compression, leading to a better outcome. This was further corroborated by our finding of negative correlation of S1 with UL CMCT, suggesting that patients who were clinically more severe were also electrophysiologically more abnormal, and subsequently benefited more from surgical decompression relative to patients with normal UL CMCT. This the largest series, to our knowledge, showing for the first time that UL CMCT abnormality obtained with TMS is an independent predictor of good surgical outcome in severe CSM. Key words: Cervical spondylosis, Surgery, Severe, Outcome, Transcranial magnetic stimulation, Motor-evoked potential, Magnetic resonance imaging

Cortico-hypoglossal and corticospinal conduction abnormality in Bickerstaff's brainstem encephalitis

The Miller Fisher syndrome, Guillain-Barre syndrome and Bickerstaff's brainstem encephalitis are related conditions in which anti-GQ1b antibody positivity occur in varied frequencies. This report demonstrates the presence of corticobulbar and corticospinal dysfunction in BBE, by means of a novel transcranial magnetic stimulation technique. It further supports the presence of protean manifestations in anti-GQ1b IgG antibody-positive spectrum of disorders.

Cutaneous silent periods in the evaluation of cord compression in cervical spondylosis

OBJECTIVE

The clinical diagnosis of cervical spondylotic myelopathy (CSM) may be challenging in patients with cervical spondylosis (CS). Routine nerve conduction studies (NCS) may not evaluate cord compression adequately.

METHODS

We obtained cutaneous silent periods (CSP) in 26 consecutive patients presenting with clinical features of CS, in comparison with 30 normal controls. The results were also compared with transcranial magnetic stimulation (TMS) findings, and magnetic resonance imaging of the cervical cord as the gold standard.

RESULTS

CSP findings showed similarly high sensitivity of up to 96% with TMS in evaluating cervical cord dysfunction.

CONCLUSION

In specific clinical settings, CSP is of value for the diagnosis of CSM in CS. CSP measurement is advocated as a simple and rapid diagnostic adjunct to NCS in evaluating CS patients with possible cord compromise.

Systematic correlation of transcranial magnetic stimulation and magnetic resonance imaging in cervical spondylotic myelopathy

STUDY DESIGN

A prospective study over a 3.5-year period involving transcranial magnetic stimulation and magnetic resonance imaging.

OBJECTIVES

To assess the correlation of transcranial magnetic stimulation and magnetic resonance imaging in cervical spondylotic myelopathy qualitatively and statistically.

SUMMARY OF BACKGROUND DATA

Cervical spondylotic myelopathy presents with different degrees of cord compression, which can be assessed by magnetic resonance imaging. There are no large studies correlating transcranial magnetic stimulation and magnetic resonance imaging findings in this condition.

METHODS

A total of 141 patients with a clinical diagnosis of cervical spondylotic myelopathy were prospectively studied over a 3.5-year period. They were classified into Groups 1 to 4 based on severity of cervical cord changes on magnetic resonance imaging. All had transcranial magnetic stimulation and central motor conduction time measurements within 2 months of the magnetic resonance imaging study.

RESULTS

Twenty-eight, 49, 28, and 36 patients were classified into Groups 1 to 4, respectively. Mean upper limb and lower limb central motor conduction times correlated with the severity of magnetic resonance cord compression. The absence of central motor conduction time abnormalities correlated reliably with the absence of cervical cord impingement as in Group 1. Statistically significant right left difference in central motor conduction time in the lower limbs was seen between Groups 1 (no cord changes) and Group 2 (mild cord impingement). Eight other patients with diagnoses other than cervical spondylotic myelopathy all showed central motor conduction time abnormalities. The sensitivity and specificity for transcranial magnetic stimulation for differentiating the presence from absence of magnetic resonance imaging cord abnormality were 100% and 84.8%, respectively.

CONCLUSIONS

Transcranial magnetic stimulation showed excellent correlation with magnetic resonance imaging findings and can be considered as an effective technique for screening patients for cervical cord abnormalities before magnetic resonance imaging in the clinical setting. The findings in this study have relevant implications in the pathophysiology, management, and health costs of cervical spondylotic myelopathy.

Acute ophthalmoparesis in the anti-GQ1b antibody syndrome: electrophysiological evidence of neuromuscular transmission defect in the orbicularis oculi

OBJECTIVE

To prospectively study anti-GQ1b antibody positive cases of acute ophthalmoparesis (AO) clinically and electrophysiologically.

METHODS

Nine consecutive cases presenting with predominantly acute ophthalmoplegia were assessed clinically and had stimulated single fibre electromyography (SFEMG) of the orbicularis oculi at presentation. All had magnetic resonance imaging brain scans and anti-GQ1b antibody titres determined.

RESULTS

Four cases had elevated anti-GQ1b antibody titres and abnormal SFEMG studies, which improved in tandem with clinical recovery over three months. Five other anti-GQ1b antibody negative cases were diagnosed as diabetic related cranial neuropathy, idiopathic cranial neuropathy, ocular myasthenia gravis, and Tolosa-Hunt syndrome. All five cases showed complete recovery over a three month period.

CONCLUSIONS

This study demonstrated electrophysiologically the dynamic improvement of neuromuscular transmission of anti-GQ1b antibody positive cases of AO, in tandem with clinical recovery. SFEMG is of value in differentiating weakness due to neuromuscular transmission defect from neuropathy in these clinical situations.

Corticobulbar dysfunction in the Miller Fisher syndrome

The Miller Fisher syndrome is an immunologically mediated condition with minimal motor manifestations. We describe a case showing mild reversible dysarthria and weak lingual movements with complete recovery over 2 months. Transcranial magnetic stimulation studies give an evidence of a reversible corticobulbar conduction abnormality which resolved with clinical improvement.

Nerve conduction studies in selected peripheral nerve disorders

PURPOSE OF REVIEW

The physiological properties of nerve and muscle are influenced by pathological changes and the aim of this review is to discuss recent contributions of electrophysiological studies to the understanding and diagnosis of selected peripheral nerve disorders. The relationships between pathology and physiology emphasize the close interdependence between electrophysiological studies, clinical deficits and other laboratory information. Attention should be paid to the strengths and limitations of electrophysiological methods, considering their impact on diagnosis and treatment of patients.

RECENT FINDINGS

Several studies have shown particular pathophysiological profiles associated with different antibody subtypes in autoimmune peripheral neuropathies and this association further supports the suggestion of pathological specificity in both acute and chronic neuropathy. The sensitivity and specificity of physiological profiles therefore become increasingly important since some of these neuropathies are accessible to treatment. On the other hand, the pathophysiological and clinical profiles may be heterogeneous in patients with some disorders. This could be related to a more indistinct division between different types of pathology with increased understanding of pathogenetic mechanisms. Moreover, new insights into disturbed axonal function have stimulated attempts to develop methods to explore normal and diseased human nerve function.

SUMMARY

The exploration of axonal membrane and ion-channel function has become accessible using studies of excitability and are of potential value where conventional studies only provide nonspecific evidence of the number of fibers and the integrity of myelin. These studies will presumably become increasingly important in the years ahead considering the lack of understanding of the functional disturbances in axonal neuropathies.