Hemimegalencephaly as diferential diagnosis of Rasmussen encephalitis

*Correspondence: [e-mail].

Abstract

Case Presentation: KV, female, 5 years old, born in good vital conditions, presented about 4 generalized tonic-clonic seizures (GTC) per day after her 1st year of life and progressive global delay of neuropsychomotor development, especially in regard to her language. As she initially presented multifocal spikes on electroencephalogram (EEG). Phenobarbital and sodium valproate were prescribed but both with no response and with side effects. Valproic acid was changed later to Levetiracetam. KV evolved with progressive left hemiparesis, maintaining her language delay, besides periods of good and bad control of the seizures. Currently at 8 years old, she is on Phenobarbital, Clobazam, and Levetiracetam with partial control of the epilepsy and relative autonomy for daily life activity. EEG on 09/2021 with marked signs of dysfunction located in the right hemisphere. Brain Magnetic Resonance Imaging (MRI) performed on 01/2023 showed hemimegalencephaly of the right hemisphere and thinning of the corpus callosum with altered pattern of sulcus and gyration, and diffuse cortical thickening, especially in the frontal, parietal and temporal regions, with polymicrogyria, findings consistent with a diagnosis of Hemimegalencephaly (HME). The investigation will be complemented with exome sequencing.

Discussion: The HME is a rare congenital brain malformation characterized by hamartomatous overgrowth of a cerebral hemisphere. It occurs in isolation or as part of Hypomelanosis of Ito, Tuberous Sclerosis, Epidermal Nevus Syndrome or Klippel-Trenaunay Syndrome. It has a prevalence of 1 to 3 cases per 1,000 epileptic children, occurring in up to 14% of cortical developmental abnormalities. Clinically, HME is manifested by the triad composed of refractory epilepsy, cognitive decline, and progressive contralateral hemiparesis. Therefore, the possibility of Rasmussen's Encephalitis diagnosis was raised during the investigation.

Final Comments: Both diagnoses are based on clinical and imaging findings. The definitive diagnosis was only possible through MRI, a highly complex exam that is difficult to perform in the public health system. HME shows neither familial component nor gender preference. Somatic genetic variants in the PI3K-Akt-mTOR signaling pathway, such as AKT3, PIK3CA, MTOR and TSC2, have been reported.

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Artikel online veröffentlicht:
12. Mai 2025