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.

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.

Mycophenolate mofetil - as an adjunctive immunosuppressive therapy in refractory myasthenia gravis: The Singapore experience.

We report our experience, using mycophenolate mofetil (MyM) as an adjunctive immunosuppressive therapy in patients with severe, refractory and high dose steroid-dependent myasthenia gravis (MG). Five patients were commenced on MyM in addition to other immunosuppressive therapies. All had significant clinical improvement and no subsequent myasthenic crisis requiring intensive care unit admission. MyM was well tolerated and no serious adverse effects were observed. MyM is an effective adjunctive therapy for the treatment of severe, refractory and steroid-dependent MG in our experience.

Superficial peroneal sensory and sural nerve conduction studies in peripheral neuropathy.

The objective of this study was to prospectively evaluate sensory nerve conduction studies (NCS) in the distal lower limbs in the electrodiagnosis of peripheral neuropathy. We prospectively studied 316 consecutive patients with surface stimulation and recording, in comparison with 90 control subjects. A total of 310 patients were found to have lower limb sensory NCS abnormalities. In these patients, the rate of detection of peripheral neuropathy with superficial peroneal NCS (88.5%) was significantly higher (P<0.001) compared with sural NCS (75%). The superficial peroneal NCS appeared to have a higher detection rate for peripheral neuropathy in our study, and its study can be adjunctive to sural NCS.

Transcranial magnetic stimulation screening for cord compression in cervical spondylosis.

OBJECTIVE: Cervical spondylosis (CS) often results in various degrees of cord compression, which can be evaluated functionally with transcranial magnetic stimulation (TMS). We investigate the use of TMS as a screening tool for myelopathy in CS. METHODS: We prospectively studied 231 patients classified into Groups 1 to 4 based on MRI grading of severity of cord compromise. TMS elicited central motor conduction times and motor evoked potential (MEP) amplitudes in all 4 limbs. The results were compared with those from 45 healthy controls. RESULTS: TMS showed 98% sensitivity and 98% specificity for cord abnormality using MRI as reference standard. CONCLUSIONS: MEP abnormalities are useful for electrophysiological evaluation of cord compression in CS. While TMS is not a substitute for MRI, it is of value as a rapid, inexpensive and non-invasive technique for screening patients before MRI studies.

Posterior antebrachial cutaneous nerve conduction study in radial neuropathy.

Radial neuropathy most commonly occurs as a result of external compression at the spiral groove region. The posterior antebrachial cutaneous nerve (PACN) conduction study was performed in 15 consecutive patients with radial palsy. Unilateral PACN abnormalities were present in 11 patients. A normal PACN study was correlated with clinical improvement at 3 months. Conversely, PACN abnormality was correlated with radial motor axon loss and a poorer prognosis. The PACN study is a simple adjunct which provides additional information relating to the diagnosis and prognosis of radial lesions.

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.

Decrement in area of muscle responses to repetitive nerve stimulation.

Measurement of the decremental muscle response to repetitive nerve stimulation (RNS) has low yields for the diagnosis of neuromuscular transmission defects compared with single fiber electromyography (SFEMG). We compared area and amplitude of muscle responses to RNS in 87 patients and 30 controls, using SFEMG as the reference standard. Decrement of response area provided additional diagnostic yields of 5.3% to 30% depending on the muscle examined and disease severity, and is recommended as a diagnostic adjunct to measurement of amplitude decrement during RNS.

Piribedil and bromocriptine in Parkinson's disease: a single-blind crossover study.

INTRODUCTION: Clinicians switch from one dopamine agonist to another for various reasons. However, each change may inadvertently result in certain potential risks such as decreased medication efficacy or new side-effects. OBJECTIVE: We evaluated the tolerability of a switch of bromocriptine to piribedil using two conversion ratios as a primary outcome measure, with motor function as a secondary outcome measure, in patients with mild to moderate Parkinson's disease (PD). METHODS: Twenty consecutive patients with mild to moderate PD (Hoehn and Yahr, stage II-III) on treatment with stable doses of bromocriptine and levodopa were randomized to two groups of 10 patients each, to receive piribedil based on 1:5 or 1:10 conversion ratios. Blinded evaluations were performed: 1) United Parkinson's Diseased Rating Scale (UPDRS) scores both in 'on' and 'off', 2) Open-ended interviews for adverse events, 3) Epworth Sleepiness Scale, 4) Purdue Pegboard assessment during 'on' and 'off', 5) Hand-arm movement test during 'on' and 'off', and 6) Walking test during 'on' and 'off'. RESULTS: Major adverse events included 'sleep attacks' in one patient and minor side-effects included giddiness, nausea, hallucinations, sleepiness and lethargy. However, these were mild and 19 (95%) of the 20 patients completed the study. There was a significant improvement in both the UPDRS 'off' total and motor scores at 1 month compared with baseline for the group on 1:10 ratio. The walking times during the 'off' state at 1 and 2 months were significantly better compared with baseline in the 1:5 group. There were otherwise no significant differences in the rating tests during both 'off' and 'on' states before and after the bromocriptine switch. CONCLUSIONS: We demonstrated that patients with mild to moderate PD who were on relatively low doses of bromocriptine can be safely switched to piribedil based on a conversion ratio of either 1:5 or 1:10. However, the higher conversion ratio has to be carried out with caution in patients with daytime somnolence.

Repetitive stimulation of the long thoracic nerve in myasthenia gravis: clinical and electrophysiological correlations.

OBJECTIVE: To investigate repetitive stimulation of the long thoracic nerve as a reliable and technically undemanding method for evaluating respiratory muscle function in myasthenia gravis. METHODS: 15 patients with myasthenia gravis and positive single fibre electromyography had repetitive stimulation of the long thoracic nerve together with serratus anterior recordings. There were 20 normal controls. RESULTS: Eight patients with respiratory symptoms all had abnormal results, with an increased response decrement. These patients required intensive monitoring and supplemental oxygen. The remaining seven cases with no respiratory symptoms all had negative studies. CONCLUSIONS: This is a simple well tolerated method that shows good correlation with respiratory symptoms and management requirements in myasthenia gravis. It can alert the physician to serious respiratory complications in this disease.

Repetitive hypoglossal nerve stimulation in myasthenia gravis.

OBJECTIVES: To assess the diagnostic efficacy of repetitive nerve stimulation (RNS) of the hypoglossal nerve in patients with myasthenia gravis (MG) and bulbar symptoms (dysphagia, dysarthria). METHODS: Twenty patients with MG and 25 normal controls had RNS of the hypoglossal nerve. All patients also had single fibre electromyography (SFEMG) of the orbicularis oculi and RNS with recordings of the nasalis, trapezius and abductor pollicis brevis muscles. RESULTS: All patients had positive SFEMG studies. Nine patients with bulbar symptoms had positive hypoglossal RNS, including 3 with negative RNS recordings in other muscles. Eleven patients with no bulbar symptoms showed negative hypoglossal RNS, including two with positive RNS recordings from other muscles. CONCLUSIONS: Abnormal RNS of the hypoglossal nerve correlates well with bulbar dysfunction and further characterises the extent of neuromuscular transmission defect in MG patients.

Clinical and electrophysiological aspects of distal ulnar neuropathy.

OBJECTIVES: To evaluate the use of fixed distance side to side comparison of abductor digiti minimi (ADM) and first dorsal interosseous (FDI) compound muscle action potential (CMAP) studies in the diagnosis of distal ulnar neuropathy. MATERIALS AND METHODS: Thirty normal controls underwent ADM and FDI CMAP studies bilaterally at a fixed ADM recording to stimulating point distance of 6 cm. Side to side mean latency differences to both muscles were calculated. Twenty patients with suspected unilateral distal ulnar neuropathy from routine nerve conduction studies had positive results when compared with controls. RESULTS: The upper limit of normal for side to side mean latency difference at 3 SD above the mean was 0.394 and 0.474 ms for ADM and FDI, respectively. All 20 patients had side to side mean CMAP latency difference above 3 SDs in the ADM, FDI or both muscles. Fifty percent of cases had involvement of the superficial sensory branch. CONCLUSIONS: Fixed distance side to side CMAP latency comparison is a useful electrodiagnostic adjunct for distal ulnar neuropathy. Trauma was the most common aetiology in the 20 reported cases. Correlation was found between aetiological factors and sites of lesions as localized with this method.

Segmental mixed nerve conduction studies in ulnar neuropathy at the elbow.

Conventional nerve conduction and electromyography may not be adequate in localizing ulnar neuropathy at the elbow, particularly in longstanding lesions with severe axon loss. Ratios of wrist to elbow and elbow to axilla segmental ulnar mixed nerve amplitudes were determined in 11 patients with ulnar neuropathy at the elbow. In 20 control subjects, the mean ratio was 1.06 +/- 0.25 (standard deviation). All patients had ratios less than two standard deviations of the control mean ratio. This method is a useful adjunct to conventional nerve conduction techniques in the localization of ulnar neuropathy at the elbow.

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

OBJECTIVES: To evaluate serial central motor conduction time in the Miller Fisher syndrome. METHOD: Three patients with classic Miller Fisher syndrome were evaluated clinically. They had serial central motor conduction times measured with transcranial magnetic stimulation and nerve conduction studies. Motor evoked potentials were recorded from the first dorsal interossei and abductor hallucis muscles. RESULTS: All three patients showed reduction in central motor conduction times in tandem with gradual clinical improvement at each review. CONCLUSIONS: There is electrophysiological evidence of a central reversible corticospinal tract conduction abnormality in the Miller Fisher syndrome.