Persistent myoclonic jerks: a case of epilepsia partialis continua or myoclonic progressive epilepsy?

Introduction: Patients with myoclonic jerks and seizures represent a diagnostic and therapeutic challenge as they fall under the differential diagnosis of uncommon and often difficult to diagnose diseases. Progressive myoclonic epilepsies (PMEs) are a group of disorders which presentation is during late childhood or adolescence characterized by progressive neurologic disability, background slowing on EEG and refractory to antiepileptic drug therapy.1 The majority are genetic conditions related to specific mutations but a large proportion of patients with PMEs does not have a specific genetic cause.2 Epilepsia Partialis Continua (EPC) is characterized by frequent, repetitive jerks continuing over prolonged periods of time. Recently autoimmune processes have received considerable attention in EPC.3 Methods: Case report. Results: The patient had epilepsy onset in 2012 at 16 yo with frequent myoclonic jerks of the face and left arm. In 2014 the patient underwent a hospitalization for persistency of the seizures associated with episodes of left leg paresthesia. Brain MRI and muscle biopsy were negative, EEG showed right fronto-temporal paroxysmal activity, PET right fronto-parietal hypometabolism and MEG showed precentral and postcentral right gyrus epileptic activity. CSF analysis showed oligoclonal bands (OB), while paraneoplastic and anti-neuron antibodies dosing were negative. Steroids and Intravenous Immunoglobulin were administered with apparent resolution of seizures and a diagnosis of “EPC and sensitive seizures in immune-mediated encephalitis” was posed. In 2016 the patient was re-hospitalized for reappearance of the same seizures. Again OB were positive, low anti-GAD was found in blood and low anti GRUR3 antibodies were found in blood and CSF. Genetic testing was negative. Again the patient was treated with steroids and immunoglobulins with improvement of seizures and partial response to the therapy at that time but, again, he presented a recurrence of myoclonic jerks and seizures later on. Currently the patient is still drug-resistant experiencing frequent left arm myoclonic jerks, left leg paresthesia and focal-seizures clusters sometimes followed by loss of consciousness. He also complains of small-amplitude action myoclonus in the left hand, with impairment of motor tasks and of marked sleepiness, with initial but stationary verbal and visuospatial short-term memory impairment. Despite an apparent initial response to different pharmacological trials, the patient has always experienced a recurrence of seizures. Conclusions: The etiological definition of this case is still uncertain: negative genetic tests, absence of cognitive impairment and ataxia would exclude a progressive myoclonic encephalopathy; negative imaging, autoantibody-production fluctuation and not consistent immunotherapy-response would rule out autoimmune genesis. In conclusion, this case might represent on one hand a non-progressive chronic EPC, where partial immunotherapy response might be attributed to the role of inflammation in the exacerbation of seizures; on the other hand this case could represent a form of PME caused by an unknown genetic mutation, whit slow clinical progression, minor cognitive impairment and typical poor response to pharmacological therapy.