Neurophysiologie clinique = Clinical neurophysiology
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Review
[Monitoring the neurogenic mixed evoked potentials during surgery of the spine: a good solution?].
Spinal deformity surgery carries a risk of rare but dramatic neurological complications. Intraoperative spinal cord monitoring has been initially performed using somatosensory evoked potentials (SEP). However, false-negative cases have been reported and neurophysiologists supplement SEPs with concurrent motor evoked potentials. ⋯ They are recorded from a peripheral nerve after spinal cord stimulation. NMEPs have been experimentally and clinically shown to be sensible for detecting spinal cord injury. They are easily and rapidly recorded, and NMEP monitoring may be continuously performed during the critical steps of surgery.
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Clinical Trial
Evaluation of early motor and sensory evoked potentials in cervical spinal cord injury.
To determine the efficacy of motor evoked potentials (MEP) and sensory evoked potentials (SEP) in the assessment of severe cervical injury, 17 subjects with severe cervical injury were studied. During the 1st week post-injury and post-surgical treatment, all subjects were submitted to electromyogram (EMG) recordings, dermatomal somatosensory evoked potentials (D. SEP), posterior tibial nerve somatosensory evoked potentials (PTN. ⋯ A good correlation was found between the severity of the spinal cord injury and SEP grading. For MEP, the presence or absence of intercostal responses (C4) to cervical and cortical stimulation was the best prognostic indicator. The combined electrophysiological exploration of MEP and SEP proved to be a useful tool for monitoring patients with severe spinal cord injury.
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EEG is a major tool in convulsive status epilepticus. Several techniques may be used, including conventional or digitized EEG using 4, 8, 10 or 16 channels, continuous monitoring with or without simultaneous video recording, and cerebral function monitor. ⋯ However, rapid control of seizure at this phase is the primary goal, and optimization of EEG availabilities may lead to more systematic indications. After adequate control of seizures, EEG is mandatory in the following situations: i) a difficult-to-control convulsive status epilepticus, with a high risk of subsequent evolution towards subtle status epilepticus; ii) a resistant status epilepticus which needed high dose of sedatives drugs and/or curarization, to evaluate the level of anaesthesia and to watch for recurrence of epileptiform abnormalities; iii) a permanent, unexplained impairment of consciousness which followed an apparently successful treatment, to detect non convulsive status epilepticus; 4. a doubtful clinical diagnosis, to confirm pseudo-status epilepticus.
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Rare distal compressions of lower limb nerves include tarsal tunnel syndrome, entrapment of the first branch of the lateral plantar and medial calcaneal nerves, interdigital neuroma, compression of the deep peroneal nerve on the dorsum of the foot, entrapment of the superficial peroneal and sural nerves. Nerve conduction and electromyographic studies are essential to evaluate these peripheral nerve injuries in order to differentiate focal lower extremity nerve entrapments from ischemic mononeuropathies, lumbar radiculopathies or plexopathies, and generalized peripheral neuropathies. This review summarizes the clinical and electrophysiological findings for each of these rare entrapment syndromes and provides the necessary clues to obtain a correct differential diagnosis with other more common causes of foot and ankle pain and paresthesias.
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The first results concerning the role of event related potentials (P300) in assessing a prognosis in comatose patients reported in the literature have been encouraging. The cause of the coma is an important prognostic factor by itself, especially when traumatic and anoxic comas are compared, with a less favorable prognosis in anoxic coma. In our study, only anoxic patients have been investigated using somatosensory evoked potentials, brainstem auditory evoked potentials P300 auditory event-related potentials. ⋯ In twenty patients studied, six had a positive P300 and three of them awake. Out of the 14 patients without a P300 only one awoke (5%), 12 patients died and one is in deep coma. Despite the small number of patients in this study, the first results confirm the interest of auditory P300, in addition to clinical evaluation and evoked potential testing.