Abstracts

Rationale: Discuss the effects of valproate encephalopathy in a patient with juvenile myoclonic epilepsy (JME) and its differential diagnosis. Methods: This 22 year old patient presented with myoclonic jerks at 10 years of age. Ate the age of 12 years she started having generalized tonic clonic (GTC) seizures. An EEG at the time showed the presence of generalized 4Hz spike and wave discharges recorded with generalized distribution and bilateral synchrony, in addition to a normal background activity. These findings confirmed the clinical suspicion of JME. Seizures were initially well controlled on lamotrigine. However after 6 years she started having breakthrough seizures. At that point valproate was added. Her seizure frequency was not changed initially, therefore valproate dosage was gradually increased. Concomitantly, she started showing cognitive decline, reflected by poor school performance. She had to stop school due to the frequency of seizures (myoclonic and GTC) and the severity of cognitive decline. At the age of 20 she was admitted to the Epilepsy Monitoring Unit (EMU) for diagnostic reevaluation. Continuous video-EEG recordings revealed the presence of myoclonic seizures, generalized tonic clonic seizures with prolonged duration and generalized as well as multifocal interictal epileptiform discharges (IEDs). Interestingly, some of the GTC seizures would appear to stop but a focal (usually right posterior quadrant) ictal discharge would then appear at the end of the clonic phase, and this focal activity would last for several minutes before the seizure came to a complete stop. The background activity was abnormal, usually in the low theta frequency range. This admission to the EMU led to a new diagnosis of progressive myoclonus epilepsy (PME). No mutations were identified in the EPM1 (unverricht-Ludborg), EPM2A, EPM2B (Lafora disease), or EFHC1 (juvenile myoclonic epilepsy) genes. Valproate was substituted for lacosamide. Seizures immediately stopped. The patient has been on lacosamide for 18 months now. She continues seizure-free and her cognitive dysfunction disappeared. She is back to school and is able to obtain good grades. Results: This case illustrates a severe encephalopathy in response to valproate. Interestingly, it showed that focal onset seizures and IEDs could be generated during this period of encephalopathy. Valproate-induced encephalopathy is not new. However, to the best of the author's knowledge it has not been associated with new, focal ictal or interictal abnormalities in patients with a previous diagnosis of JME, mimicking PME. Conclusions: Worsening of symptoms in patients previously diagnosed with JME can be seen in early stages of PME. However, this case shows that valproate encephalopathy is an important cause of worsening of symptoms, mimicking the often fatal teenage onset PMEs. In that valproate is commonly used both for JME and PMEs, it is important to consider toxicity to this drug and in some cases a trial off valproate may prove useful.