Somatosensory evoked potentials in the assessment of peripheral neuropathies: Commented results of a survey among French-speaking practitioners and recommendations for practice.

BACKGROUND: Somatosensory evoked potentials (SSEPs) are increasingly performed for the assessment of peripheral neuropathies, but no practical guidelines have yet been established in this specific application. STUDY AIM: To determine the relevant indication criteria and optimal technical parameters for SSEP recording in peripheral neuropathy investigation. METHODS: A survey was conducted among the French-speaking practitioners with experience of SSEP recording in the context of peripheral neuropathies. The results of the survey were analyzed and discussed to provide recommendations for practice. RESULTS: SSEPs appear to be a second-line test when electroneuromyographic investigation is not sufficiently conclusive, providing complementary and valuable information on central and proximal peripheral conduction in the somatosensory pathways. CONCLUSIONS: Guidelines for a standardized recording protocol, including the various parameters to be measured, are proposed. CLINICAL RELEVANCE: We hope that these proposals will help to recognize the value of this technique in peripheral neuropathy assessment in clinical practice.

Restless legs syndrome is frequently overlooked in patients being evaluated for polyneuropathies.

Restless legs syndrome (RLS) often presents with paresthesias and dysesthesisas. We have investigated the prevalence and clinical features of RLS in a cohort of patients referred for clinical suspicion of peripheral neuropathy (PN). Sixty-four patients with sensory symptoms, and 101 age-matched controls were prospectively evaluated for RLS, PN and causes of both conditions. In the 64 patients (60 +/- 14 years), none were referred with a suspicion of RLS. Forty-one had a sensori-motor PN of which 22 had a definite RLS (54%). When excluding other causes of RLS, 8 of 41 patients had a RLS associated with a neuropathy (20%). The proportion of RLS in the healthy controls was 10%, lower than in the cohort of patients. In patients without PN, 57% had a RLS, and 55% in the whole cohort, a higher proportion than in the healthy controls (P < 0.0001). Patients with PN and RLS had more sleep disorders (P < 0.04), and legs and calves symptoms (P = 0.09) than patients with PN without RLS. Toes symptoms were more frequently observed in patients with PN but without RLS (P < 0.02). We conclude that RLS frequently presents with symptoms suggestive of peripheral neuropathy, and therefore, is often overlooked.

[The predominance of myopathy as a cause of intensive-care-unit-acquired paralysis: the diagnostic value of direct muscle stimulation]. / Prédominance des atteintes myopathiques à l'origine des parésies acquises en réanimation. Intérêt de la technique de stimulation musculaire directe.

INTRODUCTION: In the intensive care unit (ICU) patients sometimes develop diffuse neuromuscular deficit resulting in flaccid tetraparesia with a more or less severe prognosis. STATE OF THE ART: ICU-acquired neuromuscular disorders have various possible origins, including necrotic or catabolic myopathies and sensori-motor axonal neuropathies. Electrophysiological testing determines these pathophysiological mechanisms better than clinical examination. The technique of direct muscle stimulation has been proposed, in addition to conventional electroneuromyographic methods, to improve the reliability of electrodiagnosis in ICU, but has been rarely studied. Using this technique, we recently showed that a majority of ICU-acquired pareses are of myopathic origin. PERSPECTIVES: The technique of direct muscle stimulation could be fruitfully associated with usual electroneuromyographic methods to differentiate myopathic from neuropathic involvement at the origin of any severe weakness in ICU. CONCLUSION: The contribution of myopathic processes in ICU-acquired paresis is probably underestimated. Direct muscle stimulation enables better understanding of the mechanisms underlying acquired motor deficit in ICU patients. However, it remains to be determined whether this refinement could have a significant impact on prognosis and treatment.

[Neurogenic electromyographic activity in a patient with non-paraneoplasic Lambert-Eaton syndrome]. / Activité électromyographique neurogène dans un cas de syndrome de Lambert-Eaton non-paranéoplasique.

INTRODUCTION: Lambert-Eaton myasthenic syndrome (LEMS) is a rare presynaptic disorder of the neuromuscular junction. Electrodiagnosis is characterized by compound muscle action potentials of small amplitude at rest, normalizing immediately after brief exercise or high-rate nerve stimulation. Needle electromyographic (EMG) activity is classically described as normal or myogenic. CASE: We report the case of a young patient with a non-paraneoplastic LEMS in whom the initial electroneuromyographic examination showed neurogenic changes in needle EMG concomitant with typical features of presynaptic neuromuscular junction disorder at single and repetitive nerve stimulation. DISCUSSION: Neurogenic EMG abnormalities were not previously described in patients with LEMS and could result from "functional" reversible denervation, depending on the presence of anti-calcium channel antibodies at axon terminals. CONCLUSION: Neurogenic features in needle EMG examination in case of subacute motor deficiency should not eliminate the possibility of a presynaptic neuromuscular junction disorder, such as LEMS.

Origin of ICU acquired paresis determined by direct muscle stimulation.

BACKGROUND: Acquired diffuse paresis in an intensive care unit (ICU) can result from critical illness myopathy or polyneuropathy. Clinical examination and conventional neurophysiological techniques may not distinguish between these entities. OBJECTIVE: To assess the value of direct muscle stimulation (DMS) to differentiate myopathic from neuropathic process in critically ill patients with diffuse severe muscle weakness. METHODS: 30 consecutive patients with ICU acquired diffuse motor weakness were studied. Responses of the right deltoid and tibialis anterior muscles to DMS and to motor nerve stimulation (MNS) were studied and compared with results of conventional nerve conduction studies and concentric needle electromyography (EMG). An original algorithm was used for differential diagnosis, taking into account first the amplitude of the responses to DMS, then the MNS to DMS amplitude ratio, and finally the amplitude of the sensory nerve action potentials recorded at the lower limbs. RESULTS: Evidence of neuropathy and myopathy was found in 57% and 83% of the patients, respectively. Pure or predominant myopathy was found in 19 patients. Other results were consistent with neuromyopathy (n = 5) and pure or predominant neuropathy (n = 2). Four patients had normal results with stimulation techniques, but spontaneous EMG activity and raised plasma creatine kinase suggesting necrotic myopathy. CONCLUSIONS: A neurophysiological approach combining DMS and conventional techniques revealed myopathic processes in a majority of ICU patients. Reduced muscle fibre excitability may be a leading cause for this. The diagnosis of myopathy in ICU acquired paralysis can be established by a combination of DMS, needle EMG, and plasma creatine kinase.