Phenytoin Induced Chorea: A Case Report

Movement disorders associated with antiseizure medications: A systematic review

New-onset movement disorders have been frequently reported in association with the use of antiseizure medications (ASMs). The frequency of specific motor manifestations and the spectrum of their semiology for various ASMs have not been well characterized. We carried out a systematic review of literature and conducted a search on CINAHL, Cochrane Library, EMBASE, MEDLINE, PsycINFO, and Scopus from inception to April 2021. We compiled the data for all currently available ASMs using the conventional terminology of movement disorders. Among 5123 manuscripts identified by the search, 437 met the inclusion criteria. The largest number of reports of abnormal movements were in association with phenobarbital, valproic acid, lacosamide, and perampanel, and predominantly included tremor and ataxia. The majority of attempted interventions for all agents were discontinuation of the offending drug or dose reduction which led to the resolution of symptoms in most patients. Familiarity with the movement disorder phenomenology previously encountered in relation with specific ASMs facilitates early recognition of adverse effects and timely institution of targeted interventions.

Paroxysmal Genetic Movement Disorders and Epilepsy

Paroxysmal movement disorders include paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, paroxysmal exercise-induced dyskinesia, and episodic ataxias. In recent years, there has been renewed interest and recognition of these disorders and their intersection with epilepsy, at the molecular and pathophysiological levels. In this review, we discuss how these distinct phenotypes were constructed from a historical perspective and discuss how they are currently coalescing into established genetic etiologies with extensive pleiotropy, emphasizing clinical phenotyping important for diagnosis and for interpreting results from genetic testing. We discuss insights on the pathophysiology of select disorders and describe shared mechanisms that overlap treatment principles in some of these disorders. In the near future, it is likely that a growing number of genes will be described associating movement disorders and epilepsy, in parallel with improved understanding of disease mechanisms leading to more effective treatments.

Phenytoin-induced choreoathetosis after serial seizures due to traumatic brain injury and chronic alcoholism

Intravenous phenytoin (PHT) for suspected seizures may trigger severe choreoathetosis. Discontinuation of PHT results in immediate and complete resolution of hyperkinesias. Co-medication with valproic acid, levetiracetam, tranquilisers, and anesthetics or alcohol presumably do not modify this adverse effect of PHT. Choreoathetosis can be easily misinterpreted as seizures.

Phenytoin Induced Chorea: A Rare Adverse Effect of the Drug

BACKGROUND

Dyskinetic neurological diseases are common presentations of adverse reaction to many therapeutic agents. Phenytoin, a widely used age-old antiepileptic drug has been reported to cause dyskinesias, a rare Adverse Drug Reaction (ADR) in adults with toxic therapeutic serum level. When the drug is used in combination with other drugs which augments free drug level of phenytoin or in patients of organic brain lesion, this side effect is very occasionally reported with even normal therapeutic drug level.

CLINICAL CASE

We report a case of young male presented with chorea after two months of starting phenytoin for primary generalised epilepsy with normal therapeutic serum drug level. After excluding other differentials, drug-induced chorea was the final diagnosis. Despite phenytoin level was in therapeutic range, we have a trial of stopping Phenytoin with complete disappearance of chorea in 3 days. On reintroduction of phenytoin in the same dose, there was the reappearance of chorea in onemonth re-emphasising the diagnosis as "phenytoin-induced chorea".

CONCLUSION

If any patient on phenytoin develops any new neurological feature including dyskinesias, it should be considered as an ADR despite drug serum level within the normal therapeutic range.