IMMUNOTHERAPY-RESPONSIVE SEIZURE-LIKE EPISODES WITH POTASSIUM CHANNEL ANTIBODIES

Abstract

We describe three 69-year-old patients who developed subacute onset of frequent, unprovoked seizure-like episodes. The main attack phenotype took the form of uni- or bilateral arm posturing with facial grimacing (video). Highly stereotyped attacks occurred up to 70 times per day. Each episode lasted a few seconds without loss of consciousness. Attacks would cause them to drop objects within their grasp or to fall if legs were involved. All the patients experienced a few generalized tonic-clonic seizures during the course of their illness. Onset of attacks in patient 1 was associated with memory loss and hyponatremia (lowest sodium 114 mmol/L). Ictal EEG demonstrated background attenuation and high amplitude rhythmic activity. The T2-weighted brain MRI demonstrated high signal in the right caudate and putamen; CSF was normal. As high-dose antiepileptic drug (AED) therapy with phenytoin, levetiracetam, and phenobarbitone had minimal effect on episodes, IV immunoglobulin and steroids were commenced empirically. After 3 weeks of immunomodulatory therapy, voltage-gated potassium channel antibodies (VGKCAbs) were first measured at 238 pM (normal <100 pM), prompting a 5-day course of plasma exchange. Two weeks after this treatment, attack frequency decreased dramatically \***|(figure e-1 on the Neurology ® Web site at www.neurology.org). Over the next 12 months, the steroid dose was tapered and VGKCAbs became undetectable. This serologic improvement …