Abstracts

Rationale: Tiagabine, one of the ‘new’ anti-epileptic drugs (AEDs), inhibits y-aminobutyric acid (GABA) reuptake into neurons and glia. It is indicated as adjunctive therapy in partial seizures but is increasingly used ‘off-label’ as an anxiolytic agent and for sleep disorders. Its use may be associated with cognitive and neuropsychiatric adverse effects and rarely status epilepticus, both convulsive and non-convulsive. We report four patients with tiagabine-induced encephalopathy with significant clinical and electroencephalographic improvements after withdrawal of the medication.Methods: Four patients with new-onset of atypical behavior are described. Three of the patients received tiagabine in conjunction with other AEDs for epilepsy and one was prescribed tiagabine for anxiety. Common behavioral features included intermittent periods of psychomotor slowing, somnolence, confusion and language difficulties lasting from minutes to hours. Doses of tiagabine ranged from 12 to 40 mg/day. The electroencephalograms (EEGs) of all four patients captured during symptomatic episodes showed a characteristic pattern of generalized, irregular, frontal-predominant delta slowing, with multifocal sharps without consistent lateralizing features, demonstrated in Figure1. Results: The episodes of atypical behavior promptly and unequivocally resolved after gradual but complete withdrawal of tiagabine in all four patients. The EEGs of all patients returned to baseline (see Figure 2). In this patient series there was no correlation between the development of the encephalopathy and the dose of tiagabine or the duration of treatment.Conclusions: Although tiagabine is a valuable option as adjunctive therapy in partial seizures, clinicians need to be vigilant for the development of an encephalopathic state. This state, which may resemble an epileptic or metabolic encephalopathy, is fully reversible following withdrawal of the medication and therefore its recognition is important. The characteristic EEG pattern is a useful diagnostic tool. This case series illustrates that both patients and physicians should be aware of this clinical entity given the increasing use of tiagabine both in epilepsy and other ‘off-label’ indications.