Case Report: A 22 year-old woman with a BMI of 22.4 kilograms/meter2 was initiated on tiagabine for pain secondary to Chronic Regional Pain Syndrome. Two years later, confusional spells began after dose escalation to 32 milligrams (mg) per day and continued despite decreasing the dose to 28 mg per day in three divided doses. Spells began gradually with poor concentration and a hot sensation, followed by one to 10 hours of confusion with impaired awareness. She could complete complex tasks but displayed atypical behavior, such as undressing. Approximately forty-percent of spells occurred one hour after ingesting tiagabine.
Prolonged video EEG monitoring for one day revealed intermittent generalized theta and delta slowing. Within one hour of challenging the patient with an escalated dose of tiagabine 12 mg, a typical six-hour spell of slowed responsiveness and word finding difficulty was recorded. EEG during the event demonstrated continuous, high amplitude, rhythmic, generalized monomorphic delta slowing. Following resolution of symptoms, EEG showed generalized, frontally dominant, atypical spike and wave and polyspike and wave discharges, which completely resolved in the final hours of the EEG recording.
The patient tapered tiagabine by four mg per week until off. Spells had not recurred at eight months follow-up, which supports the hypothesis of tiagabine-induced encephalopathy.