Samuel L. Bridgers

The clinical utility of ambulatory cassette EEG

We obtained ambulatory EEG monitoring (A/EEG) before intensive monitoring in 33 patients newly referred to an epilepsy center. The A/EEG yield of evidence to support a diagnosis of epilepsy was 83% of that of intensive monitoring and 2.5 times that of routine EEG. Accuracy of A/EEG analysis was confirmed by two blind reviews for each tape, with only three misreadings among 99 interpretations rendered. Among 25 patients with specifically diagnostic referrals, A/EEG served the purpose of admission as well as intensive monitoring in 60%. Episodes not accompanied by A/EEG change required behavioral observation for correct identification.

Incidence of seizures with phenytoin toxicity

We reviewed ambulatory cassette EEG (A/EEG) records of 500 patients. Epileptiform abnormalities, seizures, or both were detected in 87 patients (17.4%), including 22 who were not taking anticonvulsant drugs. Epileptiform abnormalities were found in 1.5% of patients with syncope and in none without a clear history of episodic complaints. Abnormalities were found in 5.1% of patients referred by nonneurologic physicians. Some clinical seizures were not accompanied by A/EEG change and some episodes were not seizures, despite detection of epileptiform abnormalities.

EEG outside the hairline: Detection of epileptiform abnormalities

We have assessed the reliability in 25 epileptic patients of EEG recording using disposable self-adhesive electrodes and a seven-channel extra-hairline montage, through comparison to simultaneous standard cable telemetry. Epileptiform abnormalities were detected in all patients on blind interpretation of data acquired using the novel technique. On comparison of specific epileptiform abnormalities identified blindly, a false positive rate of 10% and a false negative rate of 8% were encountered. Posterior temporal complexes accounted for most false negatives, and most false positives did not represent failings of the recording technique. We conclude that EEG recording outside the hairline with disposable electrodes represents a reliable means to acquire, quickly and simply, EEG evidence of epilepsy. As such, it may prove useful in the acute evaluation of patients presenting with apparent seizures.

Direct comparison of 3‐ and 8‐channel ambulatory cassette EEG with intensive inpatient monitoring

During the intensive monitoring of 30 patients by means of cable telemetry EEG, simultaneous 3- and 8-channel ambulatory EEG recordings were also obtained. Blinded interpretations of the cassette tapes were compared with those of the cable telemetry records. Both 3- and 8-channel ambulatory EEG reviews correctly identified 93% of the records as either normal or epileptiform. Lateralization of abnormalities was equally good with either cassette system, but more detailed characterization was achieved with 8-channel ambulatory EEG. Although 100% of seizures were detected on both systems, there were more false-positive errors when only three data channels were available. Better ability to differentiate real abnormalities from artifacts was the most significant advantage of 8-channel over 3- to 4-channel ambulatory EEG.

Predictors of success for drug discontinuation following neonatal seizures

Guidelines for the discontinuation of antiepileptic drugs in neonatal seizures are not well defined. Some studies suggested possible criteria for antiepileptic drug discontinuation but no precise criteria have emerged. We performed a retrospective analysis of 58 infants with neonatal seizures during a 3 year period. Antiepileptic drugs were discontinued when patients were seizure-free for 3 months, had normal electroencephalography initially or at subsequent examination, and had a nonfocal examination. Normal initial electroencephalography was demonstrated to be a reliable predictor for discontinuing antiepileptic drugs successfully in 18 of 22 term infants; normal subsequent electroencephalography was a reliable predictor of successful discontinuation of antiepileptic drugs in 9 of 10 premature infants.

Supervision of ambulatory cassette EEG screening: a strategy based on the temporal distribution of epileptiform abnormalities.

The interposition of screening personnel in the analysis of extended cassette EEG recordings requires a method for supervision by the responsible electroencephalographer. To this end, analysis was undertaken of the temporal distribution of epileptiform abnormalities and seizures on cassette EEG in 40 epilepsy unit inpatients for whom these abnormalities were confirmed by simultaneous cable telemetry. Epileptiform abnormalities were noted in the hour following sleep onset in 38 patients (92%). Seizures occurred primarily in wakefulness. One hundred cassette EEG tapes obtained for clinical purposes and previously found to contain evidence of epilepsy were then subjected to an abbreviated review. Eighty-seven contained epileptiform abnormalities in the first hour of sleep, and 7 additional tapes contained only EEG seizure activity coincident with reported clinical events. Considering that fewer than 20% of cassette recordings obtained in unrestricted clinical use are likely to harbor epileptiform abnormalities or seizures, correct identification of about 99% of tapes as normal or abnormal can be anticipated with an abbreviated review consisting of analysis of the first hour of sleep; and analysis of reported clinical events if no abnormalities are noted in the first hour of sleep. Such a review is sufficiently accurate to serve as a supervisory analysis of cassette EEG tapes that have been previously screened and reported to lack evidence of epilepsy.

Absence of Hydrocephalus despite Disproportionately Increasing Head Size after the Neonatal Period in Preterm Infants with Known Intraventricular Hemorrhage

Of a group of 20 infants weighing less than 1,250 g at birth and surviving with intraventricular hemorrhage (IVH) documented by computed tomography, 6 exhibited excessive head growth between 6 and 14 weeks after birth with no evidence of neurologic deterioration. Repeat computed tomography was normal in all 6 infants. Rapid head growth after the immediate neonatal period can be expected in some infants with a history of lesser degrees of IVH and is not in itself indicative of posthemorrhagic hydrocephalus.

Cassette electroencephalographic recording of neonates with apneic episodes.

To evaluate the practical importance of seizures as a cause of neonatal apnea, we obtained extended cassette electroencephalographic recording for periods as long as 24 hours from 50 neonates experiencing apneic episodes unassociated with clinical seizure activity. Electroencephalographic recording through definite apneic episodes was obtained in 37 neonates; a total of 153 episodes were detected. None was associated with electroencephalographic seizure activity, although one term neonate without documented apneic episodes had seizure activity detected by cassette electroencephalography and may have had apneic seizures. The episodic apnea and bradycardia commonly encountered in preterm neonates is unlikely to be a manifestation of seizure activity, and extended electroencephlographic monitoring of such patients is of low yield.

Brief reportNeuropsychological signs of asymptomatic carotid stenosis

Several investigators have reported cognitive deficits associated with symptomatic carotid artery disease. This paper reports the findings of a study investigating cognitive deficits associated with asymptomatic carotid stenosis. Experimental subjects consisted of six patients who, in the course of routine physical examinations, showed carotid bruits and, on carotid ultrasound studies, showed 70% or greater stenosis in one or both arteries. No clinical symptoms had been associated with that stenosis. Six control subjects who were group-matched in terms of age and years of education were drawn from a control group evaluated previously for comparison with a transient ischemie attack (TIA) sample. All patients received a battery of tests consisting of a Wechsler Adult Intelligence Scale-Revised, abbreviated Halstead-Reitan Neuropsychological Battery, Revised Wechsler Memory Scale, and a written word fluency measure. Findings were converted to Rating Equivalents according to standard guidelines and an average Impairment Index was computed for each subject. ANOVA revealed that the two groups were significantly different in terms of the average Impairment Index. The clinical significance of these findings is discussed and implications for future research are reviewed.