The cohort included 28 men and 59 women, with a mean age of symptom onset of 60 ± 9.8 years (range: 21–78). The average expanded GGC repeat size was 113.8 ± 26.7 (range: 66–223). Skin biopsies from five patients revealed eosinophilic, p62-positive intranuclear inclusions. Initial clinical presentations included cognitive decline (30.2%), acute encephalitis-like episodes (3.9%), tremor/bradykinesia/ataxia (25.6%), and peripheral neuropathy (9.3%). Prior to genetic confirmation, 63 patients (72.4%) were diagnosed with NIID and 24 patients (27.6%) had alternative diagnoses, including cerebral small vessel disease (7 patients), Parkinson's disease (5 patients), Charcot-Marie-Tooth disease (3 patients), cerebellar ataxia (3 patients), ALS (1 patient), and mitochondrial disease (1 patient). MRI showed subcortical and periventricular white matter hyperintensities (WMH) in 87.2% of patients. WMH of the paravermis was observed in 53.5%, and middle cerebellar peduncle involvement was noted in 23.3%. Diffusion-weighted imaging (DWI) revealed curvilinear hyperintensities at the corticomedullary junction in 72.4% of patients.