Presentation, diagnosis and treatment of bilateral Rasmussen's encephalitis in a 12-year-old female

Aim. To describe the clinical course and pathological diagnosis of a 12-year-old female who presented with an acute syndrome of right hemispheric epilepsy and cortical dysfunction and brain MRI demonstrating atrophy of the left cerebral and right cerebellar hemispheres. Results. The patient presented with occasional partial seizures consisting of a left calf sensation followed by left leg clonic jerking. Initial brain MRI showed left cerebral and right cerebellar atrophy with T2 hyperintensity in the left parietal region. After six months, the seizure frequency increased and semiology evolved to include frequent clonic movements of the left side of the face, arm and leg and epilepsia partialis continua (EPC) of the left arm and leg. There was progressive weakness of the left leg and, to a lesser extent, her left arm. MRI at this time demonstrated an additional T2 hyperintensity in the right frontal lobe. An extensive evaluation for paraneoplastic, mitochondrial, and genetic epilepsy syndromes was unrevealing. On biopsy evaluation, chronic T-cell mediated encephalitis was demonstrated within bilateral frontal lobes. Treatment with immunomodulatory therapy resulted in some improvement in her seizure frequency and motor function. Conclusion. Rasmussen's encephalitis can be a challenging diagnosis. The patient's clinical history, including EPC, with bilateral frontal lobe biopsies confirming a T-cell mediated encephalitis supports a diagnosis of bilateral Rasmussen encephalitis. This case highlights the diagnostic challenges and treatment dilemmas that arise in an adolescent presenting with bilateral inflammatory lesions of Rasmussen's encephalitis.