Characteristics of ocular findings of patients with neuronal intranuclear inclusion disease

This study aimed to explore the ocular characteristics of neuronal intranuclear inclusion disease (NIID), caused by GGC repeat expansion in the NOTCH2NLC gene, combined with the systemic clinical manifestations, and propose early diagnostic features of NIID.

Six patients (12 eyes) were enrolled in this study. In vivo corneal confocal microscopy (IVCCM), fundus photography, fundus autofluorescence (FAF) imaging, optical coherence tomography (OCT), full-field electroretinography (ERG), and electromyography were performed.

The average corneal nerve fiber density (CNFD) was 6.83 ± 4.96 number/mm², and the corneal nerve fiber length (CNFL) was 6.76 ± 1.96 mm/mm². The nerves were looser and more curved in affected individuals. Dendritic cells were observed in patients with NIID. Chorioretinal atrophy, hyper-AF spots, and outer retinal abnormalities were observed during FAF imaging and OCT examinations. In full-field ERGs, the amplitudes of the a-wave and b-wave reduced or extinguished over time. The compound muscle action potential and motor nerve conduction velocity of the left common peroneal nerve decreased substantially.

The findings of IVCCM and retinal changes should be included in the diagnostic criteria for NIID. Corneal confocal characteristics may precede the systemic neurological manifestations and provide a clinical basis for the early treatment and staging of the disease. ClincalTrials.gov. Identifier: ChiCTR21000500227.