Episodic coma due to acute basilar artery migraine: correlation of EEG and brainstem auditory evoked potential patterns

Our patient presented with three episodes of deep coma in 5 weeks, followed by a complete recovery. The neuroradiological tests and spinal fluid analysis excluded structural lesions, including subarachnoid hemorrhage, from the diagnosis. A nonconvulsive status was excluded by 24-hour EEG monitoring. The EEGs and brainstem auditory evoked responses were abnormal during ictus, but they reversed to normal with the clinical recovery. Timely neurophysiological tests helped in the diagnosis of basilar artery migraine.

Bilateral occipital lobe infarction in acute migraine: clinical, neurophysiological, and neuroradiological study

A woman having common migraine attacks coincident with an asymmetrical bilateral occipital lobe infarction that spared the brainstem and cerebellum underwent these studies: serial electroencephalography, brainstem auditory, visual and somatosensory evoked potentials, magnetic resonance imaging of the brain and cerebral arteriography. The patient's vision improved greatly during a one-year follow-up. The absence of risk factors for stroke suggested that migraine caused the infarction in the posterior circulation network. The pathophysiological mechanisms of stroke in migraine remains speculative.

Angelman's (happy puppet) syndrome: clinical, CT scan and serial electroencephalographic study

Of four patients having Angelman's syndrome admitted to a state mental facility who were clinically and electroencephalographically evaluated, 2 patients had CT scan studies of the brain. The most impressive and striking features that help in the diagnosis are the mental and physical retardation, nondevelopment of speech despite adequate visual and auditory function, various types of seizures, and episodic uncontrollable laughter. The CT scans of the brain did not offer any clue as to the pathogenesis. The EEGs appeared to fall into two groups: in one an arrest of electrical maturation occurred between ages 1 and 3 and in the other a slow but progressive maturation was evident.

Sydenham's chorea: clinical, EEG, CT scan, and evoked potential studies

An 8-year-old child developed acute mental confusion, and choreoathetosis without a preceding history of acute rheumatic fever. Serial EEGs showed focal suppression of sleep spindle activity over the right cerebral hemisphere along with high-amplitude polymorphic slow-wave complexes. CT scan studies on 4 occasions and MRI scan failed to show focal lesions corresponding to the clinical manifestations. Results of brainstem auditory evoked potential studies were normal. The short- and long-latency somatosensory evoked potential patterns were abnormal during the acute phase of illness as well as during the follow-up, when the patient was clinically intact. The persistent EEG and evoked potential abnormalities in the presence of clinical recovery from chorea raised questions as to the existence of a subclinical disease process.

Somatosensory and brainstem auditory evoked potential studies in nontraumatic coma

We believe that somatosensory and brainstem auditory evoked response studies help in the understanding of the dysfunction of the ascending sensory pathyways at various levels. In some patients where EEGs showed a significant contamination of muscle and background noise, the SEP studies helped to identify the level of dysfunction. The severity of the clinical condition (GCS score) correlated significantly (p = 0.003) with the prolongation of the CCT. Asymmetries in CCTs were more frequent in the stroke group than in the other groups. The presence of asymmetries in CCT in diffuse encephalopathies indicated a variable degree of dysfunction in the ascending sensory pathways, which clinically were not easily identifiable. This fact raised the possibility of either pre-existing lesion(s) or recent insult(s) such as ischemia. The presence or absence of N20 appeared to influence the duration of survival in subgroups. Some degree of difference in duration of survival was noted among the metabolic group with and without N20 potential. The subset of patients with N20 potential survived relatively longer than the group without it. A suggestion of influence was seen in the stroke group, but caution must be exercised because the absence of N20 was compatible with survival. The hypoxic group did not show any difference. A combination of prolonged interpeak EP-N13 and N13-N20 indicated a poor prognosis. A distinct absence of Wave I in BAER limited its usefulness on some occasions. A combination of abnormal interpeak III-V and abnormal CCT seemed to suggest a poor prognosis. Although death generally occurred earlier in the stroke group, age did not seem to influence the mortality in the first 10 days. Similarly, the cause of death also did not seem to influence the course in those 10 days. None of the adult patients survived.

Hypsarhythmia-infantile spasms in near-drowning: clinical, EEG, CT scan and evoked potential studies

A 13-month-old child developed hypsarhythmia-infantile spasms after nearly drowning. Serial EEG, multimodality evoked potential, and CT scan of the brain revealed hypsarhythmia, disruption of ascending and descending tracts rostral to the mesencephalon, and a fairly severe degree of dilation of the ventricular system and subarachnoid space. We speculate that deafferentiation of the cerebral cortex is critical in the genesis of the hypsarhythmic pattern.

Alpha-coma: clinical and evoked potential studies

Simultaneous brainstem auditory and somatosensory evoked potential studies to median nerve stimulation were performed in two comatose patients, having diffuse alpha-pattern in their EEGs. CT scan of the brain in both cases did not reveal any mass lesion. In Case 1, the clinical and evoked potential studies suggested a brain stem lesion, and in Case 2 there was diffuse encephalopathy, with asymmetric dysfunction of the brainstem as seen in the evoked potential patterns. The suggested separation of alpha-pattern into two distinct groups, based on the reactivity and the presence or absence of sleep activities, into brainstem and diffuse cortical lesions could not be supported by our evoked potential studies. Our study, based on the observations of the evoked potential studies, indicated that the reactivity to sensory stimulation and intermittent attenuation of diffuse alpha-like activity relate to the integrity of the ascending sensory inputs to the thalamus. In the absence of evoked potential data, the localization of lesion(s) in alpha-coma pattern may be imprecise. Moreover, the circadian sleep rhythms and the presence or absence of "sleep spindles" appeared to depend on the inputs of the ascending sensory pathways to the structures generating the sleep activities. The specific neuronal structures generating the alpha-pattern still remain unidentified; however, this pattern seems to be originating from the structures rostral to the mesencephalon, possibly in the thalamic-thalamocortical circuits.

Tuberous sclerosis: long-term follow-up and longitudinal electroencephalographic study

We analyzed 320 electroencephalograms done on 60 patients having tuberous sclerosis. The main features in EEGs were diffuse slowing in the background activity, slow spike-wave discharges, focal and multifocal spike discharges, and amplitude asymmetries. No significant changes occurred in EEGs during the follow-up. No characteristic pattern was identified for diagnosing TS. Severe abnormalities were seen in patients who had infantile spasms and frequent seizures, and who were mentally retarded. Slow spike-wave abnormality was less frequent in patients who had mild mental retardation and few seizures. The pathological findings did not offer any clue to the frequently recorded EEG abnormalities.

Neuropsychological impairment after carotid endarterectomy correlates with intraoperative ischemia

Detailed neuropsychological assessments were performed before and shortly after carotid endarterectomy in thirty-four patients. The degree of intraoperative ischemia was assessed by monitoring the somatosensory evoked cortical potential change upon carotid clamping. Changed neuropsychological performance was found to be related to intraoperative ischemia most clearly in patients with a history of previous stroke and in those with more severe vascular disease. In such patients greater SSEP change was correlated with greater neuropsychological change postoperatively.

Neuropsychological performance one week after carotid endarterectomy reflects intra-operative ischemia

Fourteen patients with severe bilateral carotid artery stenosis underwent carotid endarterectomy. Intra-operative ischemia was monitored by somatosensory evoked potentials (SSEP) bilaterally. Neuropsychological evaluations were completed within two days before operation and 4-9 days after operation. Complete loss of N1-P1 or P1-N2 components of the SSEP (seen in 4 patients) was associated with a worsening of neuropsychological abilities (p less than .01). Two of these patients subsequently had strokes (7 and 35 days after operation). No other patients in the series have had strokes. Patients whose N1-P1 or P1-N2 amplitudes decreased by 50% or more performed worse after operation than patients with less severe reductions in these amplitudes (p less than .02). Time since first ischemic symptoms, age, education, clamp time, pre-operative stroke, and interval from surgery to assessment were not statistically related to changes in neuropsychological abilities. Patients with ischemic events in the week prior to surgery tended to improve in neuropsychological abilities 4-9 days after operation (p less than .05). Recentness of ischemic episode, however, was not related to intra-operative SSEP change. Results suggest the potential utility of intra-operative SSEP monitoring and early post-operative neuropsychological assessments both for clinical and research purposes.

Changes in short-latency somatosensory evoked potentials during hemodialysis in chronic renal failure

Short-latency SEPs were monitored in eight patients undergoing hemodialysis for end-stage renal disease. The peak latencies of EP,N13, and N20 were significantly delayed compared with those of the control group. Because the interpeak latency of N13 - N20 (central conduction time) was not significantly prolonged, there could be no possible subclinical involvement of the ascending sensory fibers in the brainstem. The dialysis did alter the peak latencies of EP,N20, and interpeak latencies of EP-N13 and EP-N20; these changes, however, were not highly significant. The evoked potential changes did not correlate with the routine biochemical data. Monitoring short-latency SEP may lead to early recognition of pathologic involvement of the peripheral nervous system.

Long-latency somatosensory evoked potentials during carotid endarterectomy

Scalp recorded somatosensory evoked cortical responses (SSEP) may be measured under general anesthesia to assess the electrical responsiveness of the brain. Such potentials were measured in 25 patients undergoing carotid endarterectomy without shunt. Electrical unresponsiveness occurred bilaterally in one patient and unilaterally in one patient. The patient with unilateral electrical silence developed a perioperative stroke, the only stroke in this series. Analysis of the SSEPs recorded from these patients suggests that profound ischemia produces electrical silence: that intermediate degrees of ischemia produce prolonged interpeak latencies and decreasing amplitudes in the SSEP. This modality seems to offer promise as an intraoperative monitor during cerebrovascular surgery.

Cognitive improvement after extracranial reconstruction for the low flow--endangered brain

Twelve patients with multiple occlusive neck vessel lesions were thought to possess low flow-endangered brains. These patients were studied before and after carotid reconstruction with a battery of neuropsychologic tests emphasizing memory and mental agility. A closely matched control group was selected from patients undergoing endarterectomy for hemodynamically insignificant lesions. The patients with low flow-endangered brains showed significantly greater improvements in memory and mental abilities than did the control group. Reconstruction of neck vessels may reverse such global neurologic deficits in carefully selected patients.