Temporal Evolution of Hypertrophic Olivary Degeneration in a Pediatric Patient: A Case Report and Review of Literature.

Hypertrophic olivary degeneration (HOD) is a rare type of neuronal degeneration seen after interruption of the dentato-rubro-olivary tract also known as the Guillain-Mollaret triangle (GMT). It is associated with hypertrophic changes of the inferior olive. Commonly reported in adults, this lesion presents with ataxia and oculopalatal myoclonus. Up to date, few cases have been published in the literature that refer to pediatric cases. This diagnosis is particularly important in the setting of brainstem tumor surgery as it should not be confused for tumor recurrence or metastasis, in turn avoiding unwarranted surgical intervention. We present the case of a 15-year-old male who underwent resection of a left superior cerebellar peduncle (SCP) pilocytic astrocytoma. On follow-up, magnetic resonance imaging (MRI) demonstrated evidence of mild residual tumor as well as progressive engorgement of the inferior olivary nucleus (ION). The patient was clinically asymptomatic and has since been observed expectantly without any issues. We were able to pinpoint the most probable location of injury in our patient's GMT. HOD remains a somewhat obscure entity. Its presentation may be early and not accompanied by significant neurologic findings, in contrast to what has been previously reported. Particularly in neoplastic cases, it may represent a diagnostic challenge and could be easily confused for tumor recurrence. A multidisciplinary approach for this entity, as with other pathologies, is of particular importance. Its proper recognition will result in the best outcomes for the patient.

Rasmussen Encephalitis: An Update.

Rasmussen encephalitis (RE) is a rare, devastating, progressive pediatric epilepsy. First described 60 years ago, RE continues to present challenges in diagnosis and management. RE causes a unilateral focal epilepsy in children that typically becomes medically refractory, results in significant hemiparesis, and causes progressive cognitive decline. The etiology is a cell-mediated immune attack on one cerebral hemisphere, though the inciting antigen remains unknown. While the underlying histopathology is unilateral and RE is described as "unihemispheric," studies have demonstrated (1) atrophy of the unaffected hemisphere, (2) electroencephalographic abnormalities (slowing and spikes) in the unaffected hemisphere, and (3) cognitive decline referable to the unaffected hemisphere. These secondary contralateral effects likely reflect the impact of uncontrolled epileptic activity (i.e., epileptic encephalopathy). Hemispheric disconnection (HD) renders 70 to 80% of patients seizure free. While it has the potential to limit the influence of seizures and abnormal electrical activity emanating from the pathological hemisphere, HD entails hemiparesis and hemianopia, as well as aphasia for patients with dominant HD. With the recent expansion of available immunomodulatory therapies, there has been interest in identifying an alternative to HD, though evidence for disease modification is limited to date. We review what is known and what remains unknown about RE.