A Case of Neuronal Intranuclear Inclusion Disease Mimicking Acute Stroke

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disorder with diverse clinical manifestations, including encephalitis-like, stroke-like, and seizure episodes. We report a female patient who experienced recurrent stroke-like attacks with cerebrovascular changes resembling an embolism. At the ages of 65 and 71, she exhibited transient stenosis and hypoperfusion of the left middle cerebral artery, followed by hyperperfusion. Initial imaging lacked characteristic diffusion-weighted imaging (DWI) abnormalities, resulting in a misdiagnosis of infarction. The diagnosis of NIID was later confirmed by the appearance of characteristic corticomedullary junction (CMJ) hyperintensity on DWI and the identification of a GGC repeat expansion in NOTCH2NLC. A retrospective review of serial brain MRIs revealed that FLAIR hyperintensity in the paravermal region was present significantly earlier than CMJ hyperintensity on DWI. NIID should therefore be considered in cases of recurrent stroke-like episodes with reversible perfusion changes. Even in the absence of CMJ hyperintensity on DWI, paravermal hyperintensity on FLAIR imaging may serve as an important early diagnostic clue for NIID.