Neurologic and electroencephalographic correlates in glutethimide intoxication.

Neurologic and electroencephalographic (EEG) examinations were performed every two hours during a case of severe glutethimide intoxication resulting from the acute ingestion of at least 15 grams of glutethimide. Neurologic data were reduced to 10 measurements of brainstem function and plotted as an index that varied cyclically in amplitude during the clinical course. Electroencephalographic data were computer-processed by power spectral methods and related to the brainstem function index. Good positive correlation existed between the frequency and reactivity of EEG activity and the level of brainstem function as reflected in the index. The cyclic and, sometimes, unilateral nature of the clinical findings previously reported in glutethimide coma was confirmed and seen to be reflected in the EEG. The present case also indicates that, in the absence of cerebral ischemia or hypoxemia secondary to cardiopulmonary depression, complete clinical recovery from glutethimide-induced coma is possible no matter how severe the presenting neurologic and EEG signs.

EEG correlations with biochemical abnormalities in Reye syndrome.

A patient with Reye syndrome was studied throughout the course of the illness with continuous EEG monitoring, and these patterns were correlated with serial determinations of serum ammonia and short-chain fatty acid concentrations. There was high correlation between degree of EEG abnormality, clinical symptoms, and elevations of the short-chain fatty acids, while serum ammonia concentrations correlated poorly with the EEG and with the clinical state.

Prognostic value of brainstem auditory evoked potentials in neonates.

The clinical outcome in 74 children at risk for audiologic or neurologic sequelae of a variety of perinatal insults was correlated with brainstem auditory evoked potentials (BAEPs) in the newborn period. No constant relationship was found between BAEP findings and later hearing status in preterm infants or in infants with severe brain damage. However, persistent patterns of wave I abnormality correctly predicted the presence and type of hearing loss in other infants. Central BAEP abnormalities recorded in preterm infants or in infants who had just suffered anoxia had little predictive value. The abnormalities had greater prognostic value when there was a delay between acute injury and testing. Prognostic errors could be minimized in this population by obtaining repeated recordings at least one month post term and after injury from infants who showed BAEP abnormalities in the neonatal period.

Brain stem auditory-evoked responses in suspected central pontine myelinolysis.

Central pontine myelinolysis was suspected in two chronic alcoholics who developed and recovered from a progressive spastic paresis of all muscles, that derived innervation at and below the level of the pons. In both cases, short-latency auditory-evoked responses aided in the diagnosis by indicating a slowing of conduction in the pontine auditory pathway, which varied in degree with the severity of the clinical manifestations of pontine demyelination.

Brainstem auditory-evoked responses. Normal variation as a function of stimulus and subject characteristics.

Brainstem auditory-evoked responses (BAERs) were elicited from 64 neurologically and audiometrically normal adults and 77 normal, full-term neonates with broadband rarefaction or condensation clicks at sensation levels (hearing levels in neonates) of 30 to 70 dB and at rates of ten and 80 clicks per second. In addition to the known effects of rate, previously unrecognized effects of acoustic phase and stimulus intensity on BAER interpeak latencies (IPLs), and an interaction of all three stimulus parameters, were found. Stimulus characteristics, age, and sex can account for much of the inter- and intrasubject variability of BAER IPLs and morphology. The BAER effects of many of these variables and their interactions have not been appreciated in clinical applications of BAER. Recognition and control of such reducible, methodological sources of BAER variability will enhance the sensitivity and specificity of the test in neurologic diagnosis.

Brainstem auditory evoked potentials in 20 patients with palatal myoclonus.

Brainstem auditory evoked potentials (BAEPs) were obtained in 20 patients with palatal myoclonus. The group included 14 men and six women whose ages ranged from 19 to 82 years. Six of the patients had abnormal BAEPs: two with severe head trauma and one each with a brainstem infarct, tumor, demyelination, and an indeterminate inflammatory process. The 14 patients with normal BAEPs had palatal myoclonus secondary to head trauma (five patients), brainstem infarcts (four patients), cerebellar tumors (two patients), degenerative processes (two patients), and an Arnold-Chiari malformation (one patient). Since the auditory pathways are separate from the structures associated with palatal myoclonus, it is possible to have discrete lesions producing palatal myoclonus with sparing of the auditory structures, whereas diffuse or multifocal lesions of the brainstem are more likely to be associated with abnormal BAEPs.

Central pontine myelinolysis. A clinical reappraisal.

We discuss three patients with clinical findings of central pontine myelinolysis (CPM). Two patients survived with minimal neurological deficits, and one patient died from medical complications while recovering from his neurological deficit. Postmortem examination showed the typical lesion of CPM. Brain stem auditory evoked potential studies in two of our patients indicate that there was impairment of function in auditory pontine pathways that returned to normal as the patients improved clinically. We conclude that CPM can be diagnosed clinically and that patients may recover if intercurrent illnesses are vigorously treated.

Electroencephalographic findings in phencyclidine intoxication.

The first report of electroencephalographic findings in clinically encountered phencyclidine intoxication is presented. When first seen, the patient was in a coma, initially distinguished only by nystagmus, waxy rigidity of the extremities, and an EEG with a widespread, sinusoidal theta rhythm interrupted every few seconds by periodic slow-wave complexes. The similarity of the EEG to that of deep ketamine anesthesia suggested intoxication with a ketamine-related (phenylcyclohexylamine) drug. Phencyclidine, the prototype of the phenylcyclohexylamine compounds and a widely abused hallucinogen, was subsequently identified in the urine and blood.

Clinical and pathologic correlates of brain stem auditory response abnormalities.

Short-latency auditory evoked responses were recorded in over 100 neurologic patients. Abnormalities of each response component were correlated with postmortem or radiologic localization of different brain stem lesions. These findings suggested that waves I-VII largely reflect activity at the following levels of the auditory pathway: acoustic nerve (I), pontomedullary junction (II), caudal pons (III), rostral pons or midbrain (IV), midbrain (V), thalamus (VI), and thalamus or auditory radiation (VII). When this information was applied prospectively to the evaluation of brain stem dysfunction, response abnormalities proved useful in detecting and localizing certain lesions not revealed by other tests. Serial recordings provided information about the evolution of brain stem lesions and their response to therapy.

Detection and localization of occult lesions with brainstem auditory responses.

Seven vertex-positive potentials--the brainstem auditory response--can be recorded from the human scalp within 10 milliseconds of an appropriate acoustic stimulus. The first of these potentials is generated in the acoustic nerve, the third in the pons, and the fifth in the midbrain. Measurement of the relative latencies and amplitudes of these potentials allowed detection of subclinical lesions in 37 (53 percent) of 70 patients with suspected multiple sclerosis who had no signs or symptoms of brainstem involvement by the disease. Abnormalities in the brainstem auditory response provided the first evidence of the pressence of multiple lesions in 14 (35 percent) of 40 patients with suspected multiple sclerosis who had clinical evidence of only a single spinal or cerebral lesion. Response abnormalities also suggested the presence of tumors of the posterior fossa in three patients with nonspecific symptoms and normal neurologic examinations, the test indicated the need for contrast studies, which then led to the correct diagnosis of infratentorial neoplasm.

Clinically useful applications of evoked potentials in adult neurology.

Recent advances in the field of sensory evoked potentials (EPs) have allowed assessment of function in regions of the nervous system that were previously inaccessible to noninvasive electrophysiologic study. Pattern visual and brainstem auditory EPs, respectively, are more sensitive to certain optic nerve or posterior fossa lesions than either clinical or laboratory tests. Short-latency somatosensory EPs from the upper and lower extremities are sensitive to pathology at cervicomedullary and thoracolumbar levels of the neuraxis as well as to suprasegmental lesions. This article reviews the development of these tests as clinically useful tools and the applications in which they have contributed most to the practice of adult neurology.

Effects of hypothermia on the human brainstem auditory response.

Latency measurements between three potentials (waves I, III, and IV/V) of the human brainstem auditory response can allow early detection of certain posterior fossa lesions. The diagnostic use of these interwave latencies requires knowledge of what factors may prolong them in the absence of disease. Hypothermia appears to be one such factor--in 5 neurologically and audiometrically normal patients, mean esophageal temperatures as high as 34.5 degrees C resulted in prolongations of central auditory conduction time. Interwave latency prolongations that were abnormal relative to an age-matched normal population were seen at 32.1 degrees +/- 0.3 degrees C in patients with both spontaneous and induced hypothermia, and these abnormalities disappeared after rewarming to normothermia. Hypothermia often accompanies intoxication and coma and should therefore be considered when brainstem auditory response abnormalities are being interpreted in these two clinical conditions.

The effects of temperature and acute alcohol intoxication on brain stem auditory evoked potentials in the cat.

The effects of core temperature changes (less than 1 degree C) and acute ethanol intoxication (100-400 mg%) on brain stem auditory evoked potentials in cats were studied independently--then together--to distinguish between a putative direct pharmacological action of ethanol on brain stem auditory neurons, as reflected in reported BAEP latency changes, and in indirect action of ethanol mediated through slight changes in central temperatures. The results suggest that the reported BAEP latency effects are attributable, largely if not entirely, to the second mechanism above. No significant temperature-independent BAEP latency alterations occurred at any sublethal blood ethanol concentration or in one dosage that subsequently proved fatal. These findings do not exclude a direct ethanol effect on brain stem auditory neurons but provide no evidence for a temperature-independent effect. Knowledge of secondary BAEP temperature effects associated with drug administration is crucial to proper interpretation of BAEPs in both experimental and clinical applications.

Monitoring of cerebral perfusion during anesthesia by time-compressed Fourier analysis of the electroencephalogram.

Time-compressed Fourier analysis of the electroencephalogram has proven to be a useful analytical procedure during anesthesia and surgery which simplifies data interpretation by presenting the EEG in a time-compressed frequency domain rather than the conventional time domain. This method of data analysis graphically accentuates the electroencephalographic correlates of ischemia-induced cerebral dysfunction and other cerebral oxygen consumption abnormalities. The ability to accentuate trends in frequency and power is derived from sequential plotting of spectra to produce a graph with three dimensional axes of frequency, time, and power. In carotid endarterectomies the system has proven more useful than the conventional EEG in assessing the need for a vascular shunt to maintain internal carotid flow during endarterectomy. In open-heart surgery time-compressed EEG spectral analysis has allowed early recognition of cerebral ischemia resulting from arterial hypotension and venous hypertension. Five cases are presented which demonstrate the ability of our system to reflect developing cerebral ischemia.

Effects of acute and chronic paleocerebellar stimulation on experimental models of epilepsy in the cat: studies with enflurane, pentylenetetrazol, penicillin, and chloralose.

Effects of acute and chronic paleocerebellar stimulation were evaluated in four experimental models of epilepsy in 24 adult cats chronically implanted with bilaterally symmetric parasagittal electrocorticographic electrodes and anterior lobe cerebellar stimulation electrodes. Pentylenetetrazol was given intraveneously in 50-mg increments or 4% enflurane was inspired until grand mal seizures occurred spontaneously or were triggered by photic or auditory stimuli. Alpha-chloralose, 50 mg/kg, was injected intraperitoneally to produce a model of stimulus-sensitive myoclonus and sodium penicillin G, 350,000 units/kg, was injected intramuscularly to produce a model of petit mal epilepsy. One- to 250-Hz electrical stimulation of paleocerebellar cortical surfaces was performed with constant-voltage or constant-current stimulators at threshold and suprathreshold intensities with average intensities of 8 V and 2.5 mA, respectively. Acute or chronic, threshold or suprathreshold paleocerebellar stimulation did not predictably alter the electrographic or clinical manifestations in any of these four models.

Ectopic internal carotid artery seen initially as middle ear tumor.

An ectopic carotid artery is rare. Its first symptoms may be neurological and could bring the patient to the neurologist during the initial evaluation. However, more often, the neurologist examines a patient in whom serious neurological deficit has occurred after transtympanic exploration of an undiagnosed vascular mass. Because diagnosis can be definitively established by angiography and the consequences of injury to an aberrant carotid artery are serious, operative exploration of vascular middle ear masses probably should be deferred until an ectopic carotid artery has been excluded by angiography.