Abstracts

Rationale: Drug-induced movement disorders are most often produced by neuroleptics and antiparkinsonian drugs but can also rarely occur with certain antiepileptic medications, most notably phenytoin. Choreoathetosis is the most common reported dyskinesia related to phenytoin use, with dystonia and orofacial dyskinesia being less frequently encountered. To our knowledge, there are no previous reports of akathisia secondary to phenytoin.  Methods: A 55-year-old female was referred to the neurology clinic for gait disturbance. She had history of epilepsy since the age of 33, secondary to a left oligodendroglioma which was treated with surgical resection, chemotherapy and radiation. She had been on phenytoin since the diagnosis of epilepsy was made, with more than 20 years of seizure freedom. Her physical exam was remarkable for mild bilateral dysdiadokinesis, wide-based gait, positive Romberg test, and significant motor restlessness consistent with akathisia. When asked about her restlessness, the patient reported that she could not resist the urge to move and had been unable to sit still for “years,” possibly since the onset of her epilepsy. She reported this symptom was most bothersome while attending church. Magnetic resonance imaging (MRI) of the brain showed left frontal encephalomalacia and generalized cerebral and cerebellar atrophy, more than expected for age. Electroencephalography (EEG) was normal. Total and free phenytoin serum levels were 17.7 and 1.1 µg/mL, respectively. Results: Due to concerns phenytoin could be contributing to cerebellar atrophy and gait disturbance, a decision was made to start lacosamide and slowly taper off phenytoin. At a 4-month follow-up visit, the patient reported improvement in her gait. Physical exam revealed complete resolution of akathisia, but was otherwise unchanged. The patient reported her restlessness completely disappeared after she discontinued phenytoin. She commented that she was now able to sit still in church for the first time. Conclusions: Phenytoin-induced movement disorders are rare but well documented. Choreoathetosis, dystonia, orofacial dyskinesia, and ballism have previously been reported. Our case widens the symptomatological spectrum of phenytoin-related movement disorders to also include akathisia, the syndrome of motor restlessness. As illustrated in this case, akathisia is often overlooked despite the significant discomfort it can cause. Movement disorders induced by phenytoin, including akathisia, are reversible, and recognizing them may prevent unnecessary treatments. Funding: No funding was received.