P. Ratnagopal

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.

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. Muscle Nerve 27: 494–496, 2003

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 neuropthy. 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.

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.

EFFECT OF EXERCISE ON REPETITIVE NERVE STIMULATION STUDIES: NEW APPRAISAL OF AN OLD TECHNIQUE

Repetitive nerve stimulation (RNS) is a simple and rapid method for evaluation of neuromuscular transmission defects. Although the effect of exercise in conjunction with RNS is well recognized, it has not been standardized in actual patient and control groups. In a prospective study over a period of 1 year, the authors evaluated the effect of exercise in conjunction with RNS in comparison with conventional 3-Hz RNS at rest in the clinical setting. Fifty-four patients who were referred for possible neuromuscular transmission disorders, in addition to 35 healthy control subjects, were studied. Amplitude and area decremental responses with RNS at rest and after 20 seconds of maximal exercise at 1-minute intervals up to 3 minutes were evaluated. The use of RNS with exercise resulted in additional diagnostic yield of up to 36.4% compared with conventional 3-Hz RNS at rest. The standardized use of exercise with RNS is advocated for increasing its diagnostic yield in the neurophysiologic laboratory.

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.

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.

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.

Zolpidem and its effects on hypoxic encephalopathy

drivers of disease clusters such as Western Pacific amyotrophic lateral sclerosis and parkinsonism-dementia complex, a disappearing prototypical neurodegenerative disorder found in Guam, West Papua, and Japan; Nodding syndrome, a fatal seizure disorder among children in Sudan and Tanzania; Strachan’s syndrome in Cuba; and konzo, a form of epidemic primary lateral sclerosis in sub-Saharan populations dependent for food on cassava. That these central nervous system conditions are unfamiliar to many readers makes the point that the burden of neurological diseases in developing regions cannot be assessed only with a yardstick that measures conditions prevalent in affluent populations. Of major importance for the poor of low-income countries are the neurological and developmental disorders associated with malnutrition, parasitism, and infection, including but certainly not restricted to human immunodeficiency virus and tuberculosis. Add to these the neurological effects of medications both native and synthetic, substance abuse, pesticides and other workplace chemicals, food and water contaminants, envenomation, and especially trauma and stress. Johnston and Hauser’s proposed cadre of bright young investigators who can make the case for the importance of global issues in neurology will need additional transdisciplinary training in global environmental health (environment in this context refers to all external stressors, whether chemical, physical, or other), clinical and research experience in low-income countries, and an audience that listens to and is willing to fund creative new proposals that tackle seemingly exotic conditions with strange names. Global understanding of neurological disease will thereby be enhanced, local communities will benefit from education that leads to primary prevention, and new treatments will become available for those who have succumbed to the neglected neurological conditions of the Third World. Placement of environmental neurological disease together with other top contenders for the proposed new global research and training agenda would address reality for many populations in low-income countries.

Segmental mixed nerve conduction studies in ulnar neuropathy at the elbow

Summary 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.