Phenytoin Increases the Severity of Cortical Hemiplegia in Rats

Authors:

• Simon Brailowsky

• Robert T. Knight

• Robert Efron

Date: 1986

PubMed: 3719374

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Abstract:

The effects of systemic phenytoin administration on the motor deficit resulting from a cortical lesion were studied in rats trained to walk coordinately on a narrow beam. The somatomotor cortex lesion was produced by an indwelling cannula through which saline or GABA were infused chronically via an osmotic minipump. Phenytoin (50 mg/kg i.p.) administered between days 3 and 5 after the intracortical catheter implantation produced a significant increase in the severity of the resulting hemiplegic syndrome. This DPH effect was more noticeable in those animals also receiving intracortical GABA infusions. The anticonvulsant at the dose used had no effect on motor performance when administered preoperatively or when given to the animals 14 days after surgical intervention when their hemiplegic syndrome had cleared. These findings suggest that phenytoin administration to brain-damaged individuals in the initial postlesion stage may be deleterious.

Status Epilepticus Manifesting as Reversible Wernicke's Aphasia

ABSTRACT

Ictal aphasia in adults is a rare phenomenon, with the majority of reported cases showing a nonfluent Broca's or mixed aphasic speech pattern associated with disturbances of level of consciousness. There is usually only one prolonged episode of aphasia with evidence of lateralized neurological findings and structural pathology on CAT scan. We describe a patient with intermittent episodes over a 10‐year period of a fluent Wernicke's aphasia associated with paroxysmal posterior temporoparietal spike‐wave activity on the EEG. Interictally, the patient was clear of neurologic signs and symptoms. These episodes were repeatedly misdiagnosed as psychotic breaks and treated with antipsychotic medication and psychiatric hospitalization. Unless language performance is assessed, these cases of focal epilepsy may be diagnosed as schizophrenic “word‐salad,” leading to delay of appropriate treatment.

AUTHORS

• Robert T. Knight

• Joanna Cooper

Date: 1986

DOI: 10.1111/j.1528-1157.1986.tb03543.x

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Electrophysiologic evidence of increased distractibility after dorsolateral prefrontal lesions

Authors:

• David L. Woods

• Robert T. Knight

Date: 1986

PubMed: 3945393

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Abstract:

Patients with left prefrontal lesions and control subjects showed enhanced event-related potentials (ERPs) to attended tone sequences presented in a dichotic attention task. ERP enhancements were comparable at short and long interstimulus intervals (ISIs), and did not depend upon whether attended stimuli were preceded by other attended stimuli or by distracting stimuli in the opposite ear. In contrast, patients with right prefrontal lesions showed absent ERP attention effects to contralateral (left ear) tones at all ISIs, and reduced attention effects to ipsilateral tones at long ISIs and when these were preceded by distracting sounds. The results are consistent with an asymmetric organization of dorsolateral prefrontal cortex, and indicate that increased distractibility may contribute to the attention disorders that follow prefrontal lesions.

Gamma-Aminobutyric Acid-Induced Potentiation of Cortical Hemiplegia

Authors:

• Simon Brailowsky

• Robert T. Knight

• Katherine Blood

• Donatella Scabini

Date: 1986

PubMed: 3942881

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Abstract:

A novel model of hemiplegia in young and aged rats is described. Osmotic minipumps were used to deliver a chronic (7 days), localized application of gamma-aminobutyric acid (GABA) (100 micrograms/microliter/h), to the somatomotor cortex of unrestrained rats. This resulted in an easily quantifiable, contralateral and reversible motor syndrome in both young and aged animals. In the young group, the motor deficit cleared over 5-day period, while in the aged animals it persisted for at least a 2-week period. Control animals treated with saline-filled minipumps did not develop a long-lasting motor deficit. The GABA-induced facilitation of hemiplegia due to small motor cortex lesions and the age effects on behavioral recovery of function are discussed. Cortical inhibitory mechanisms may play a role in debilitating syndromes such as stroke or post-epileptic paralysis.