[Reversible encephalopathy caused by valproic acid in an adolescent with idiopathic generalised epilepsy]

Encephalopathy due to valproic acid (VPA) is a rare complication leading to a disorder that affects the patient's mental status to a greater or lesser extent and which can be accompanied by a paradoxical worsening of the seizures. The diagnosis is obvious when it appears within the context of hyperammonemia or a liver pathology, but can be difficult to diagnose if it appears in isolation in patients who show no other signs of intoxication due to VPA.

We report the case of an adolescent who suffered idiopathic generalised epilepsy and presented sub-acute cognitive impairment and a worsening of his pattern of seizures some months after starting treatment with VPA. These manifestations were accompanied by a slowing of the baseline electroencephalogram (EEG) tracing; no biochemical signs of overdosage or toxicity that could be attributed to the drug or any other possible aetiology were observed. Withdrawing VPA resulted in a swift improvement in the patient's mental status and in the control of his seizures. Likewise, EEG recordings also returned to normal.

Encephalopathy due to VPA should be considered in patients who present a deterioration of their neurological status, whether associated to an aggravation of their seizures or not, despite the absence of any analytical signs suggestive of VPA toxicity or overdosage. If liver functioning is not affected, withdrawal of the drug will determine the disappearance of the symptoms and will also allow confirmation of the diagnosis.