Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society
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J Clin Neurophysiol · Oct 2002
Review Comparative StudyAnesthesia for intraoperative neurophysiologic monitoring of the spinal cord.
Intraoperative neurophysiologic monitoring (INM) using somatosensory and motor evoked potentials (MEPs) has become popular to reduce neural risk and to improve intraoperative surgical decision making. Intraoperative neurophysiologic monitoring is affected by the choice and management of the anesthetic agents chosen. Because inhalational and intravenous anesthetic agents have effects on neural synaptic and axonal functional activities, the anesthetic effect on any given response will depend on the pathway affected and the mechanism of action of the anesthetic agent (i.e., direct inhibition or indirect effects based on changes in the balance of inhibitory or excitatory inputs). ⋯ The management of the physiologic milieu is also important as central nervous system blood flow, intracranial pressure, blood rheology, temperature, and arterial carbon dioxide partial pressure produce alterations in the responses consistent with the support of neural functioning. Finally, the management of pharmacologic neuromuscular blockade is critical to myogenic MEP recording in which some blockade may be desirable for surgery but excessive blockade may eliminate responses. A close working relationship of the monitoring team, the anesthesiologist, and the surgeon is key to the successful conduct and interpretation of INM.
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Vagus nerve stimulation (VNS) is an accepted therapy for the treatment of refractory epilepsy and now even depression. More than 10,000 people have had the device implanted over a period of 12 years. Initial side effects in the early years such as lower facial weakness and electrode lead breaks have now been resolved. ⋯ These side effects tend to diminish with time. Cognitive side effects often seen with antiepileptic drug use are not reported. The side effect profile of VNS is positive, and this treatment option offers patients with refractory epilepsy prospects of good efficacy with only minor and often resolvable side effects.
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J Clin Neurophysiol · Sep 2000
ReviewThe role of evoked potentials in anoxic-ischemic coma and severe brain trauma.
The early recognition of comatose patients with a hopeless prognosis-regardless of how aggressively they are managed-is of utmost importance. Median somatosensory evoked potentials supplement and enhance neurologic examination findings in anoxic-ischemic coma and severe brain trauma, and are useful as an early guide to outcome. The key finding is that bilateral absence of cortical evoked potentials, generated by thalamocortical tracts, reliably predicts unfavorable outcome in comatose patients after cardiac arrest, and correlates strongly with death or persistent vegetative state in severe brain trauma. ⋯ The majority of patients with normal central conduction times had a good outcome, whereas a delay in central conduction times increased the likelihood of neurologic deficit or death. This report includes a systematic review of the literature concerning adults in anoxic-ischemic coma and severe brain trauma, in which somatosensory evoked potentials were used as an early guide to predict clinical outcome. Greater use of somatosensory evoked potentials in anoxic-ischemic coma and severe brain trauma would identify those patients unlikely to recover and would avoid costly medical care that is to no avail.
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With rapid advances in noninvasive technology, the need for chronic intracranial monitoring to define the epileptogenic region has diminished significantly. Its role in presurgical evaluation has come under scrutiny particularly in adults with lesional epilepsy. With the shift in surgical candidacy toward the younger age groups, however, invasive monitoring has regained its utility especially in children with normal imaging studies and cortical dysplasia. This review critically evaluates its continuing role, attempting to assess cost-benefit under specific clinical scenarios and proposes how the findings can be incorporated into the challenging task of surgical planning in intractable childhood epilepsy.
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J Clin Neurophysiol · Jul 1999
ReviewAssessing the outcomes in patients with nonconvulsive status epilepticus: nonconvulsive status epilepticus is underdiagnosed, potentially overtreated, and confounded by comorbidity.
Nonconvulsive status epilepticus (NCSE) is characterized by behavioral or cognitive change from baseline for at least 30 minutes with EEG evidence of seizures. Categorized into complex partial status epilepticus (with lateralized seizures), and generalized nonconvulsive status epilepticus (bilateral diffuse synchronous seizures), there is debate regarding the diagnosis and morbidity of NCSE. Because EEG is needed for diagnosis, only a high index of suspicion leads to a request for the study, whereas EEG is often unavailable after hours or on weekends. ⋯ Regarding treatment, comatose NCSE patients treated with benzodiazepines may worsen, whereas generalized nonconvulsive status epilepticus patients may suffer iatrogenically from aggressive treatment (hypotension and respiratory depression) necessitating balancing the potential neurologic morbidity of NCSE against the possible morbidity of IV antiepileptic drugs. A high index of suspicion is needed to initiate EEG studies. Better stratification of level of consciousness will be needed to distinguish among morbidity due to underlying conditions, treatment, and the effects of status epilepticus, proper.