Diagnostic indicators for adult-onset neuronal intranuclear inclusion disease

Adult-onset neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disorder. Abnormally high signals of diffusion-weighted image (DWI) along the corticomedullary junction are a useful diagnostic indicator for patients with adult-onset NIID. However, the DWI abnormalities usually were observed in the late stage of disease; further study might be helpful to elucidate some clinical indicators regarding the early awareness of NIID. In this study, we summarized 9 patients with NIID from multiple centers. The mean age was 60.0 ± 6.2 years. The mean duration of disease was 4.4 ± 3.2 years. The most common symptoms included cognitive impairment, episodic encephalopathy, and bladder dysfunction. Among the 6 patients with bladder dysfunction, 3 patients had the symptom prior to the development of other neurological symptoms; 5 patients needed permanent cystostomy. Isolated high DWI signals on the splenium of corpus callosum were observed in 2 patients at the early stage. The characteristic intranuclear inclusions in the skin were identified in all patients and confirmed by electron microscopy. Episodic encephalopathy or bladder dysfunction prior to other neurological symptoms were valuable diagnostic indicators for adult-onset NIID. High DWI signals on the splenium of corpus callosum might be an early indicator for the diagnosis of NIID. The immunostain of anti-ubiquitin or anti-p62 antibody was a convenient and sensitive biomarker for NIID with the background of typical phenotype with cognitive impairment and autonomic dysfunctions.