Clinical Reasoning: A 10-month-old boy with myoclonic status epilepticus

Abstract

A 10-month-old boy was transferred to our facility for workup and treatment of myoclonic status epilepticus. He was product of a healthy term pregnancy, born to nonconsanguineous parents, and was developmentally normal until the onset of myoclonic seizures at 8 months. Following this, developmental regression was noted. His myoclonic seizures were preceded by a febrile upper respiratory tract infection and involved the right upper and lower extremities for the first 5 weeks. However, all 4 extremities were eventually affected. His myoclonic seizures were reported to be resistant to IV lorazepam, levetiracetam, fosphenytoin, phenobarbital, IV immunoglobulin, a midazolam infusion, and pyridoxine. High-dose steroids (IV methylprednisolone for 4 days, followed by an oral prednisone taper) were subsequently initiated, with mild but unsustained attenuation of seizures. The ketogenic diet was also tried; this was discontinued secondary to intractable vomiting. On presentation to our facility, the patient was observed to have nearly continuous myoclonic jerks, predominantly involving the right upper extremity. EEG recording showed continuous generalized epileptiform discharges associated with body jerking, consistent with myoclonic status epilepticus. The myoclonic jerks persisted despite administration of prednisone, pyridoxal 5-phosphate, and lorazepam. The examination was limited due to medication effects; however, he was normocephalic and nondysmorphic. Funduscopic examination was normal. He was able to fixate and follow visually. Motor examination revealed diffuse hypotonia, although his reflexes were preserved and symmetric in all 4 extremities. General physical examination showed no skin findings and absence of hepatosplenomegaly. Family history was negative for neurologic disorders (including seizures). ### Questions for consideration: 1. What is a myoclonic seizure? 2. What tests would you order? 3. What is the differential diagnosis of myoclonic status epilepticus in an infant? Myoclonic seizures are defined as sudden, brief, involuntary jerking movements of the extremities arising secondary to a discharge from the brain. Our patient's history was …