Differences in diffusion tensor imaging changes between narcolepsy with and without cataplexy

The distinctive clinical finding of Type 1 narcolepsy compared to Type 2 is the presence of cataplexy. Several neuroimaging studies have also reported abnormalities in narcolepsy patients with or without cataplexy. However, there are conflicting results to differentiate them. In this study, we aimed to clarify the white matter changes in narcolepsy patients both with and without cataplexy and compared them with healthy adults to evaluate microstructural differences in the brain.

Eleven narcolepsy patients with cataplexy (NC), 12 narcolepsy patients without cataplexy (NOC) and healthy age- and gender-matched controls (N = 16) were studied. Whole-brain diffusion tensor imaging (DTI) was obtained and tract-based spatial statistics were used to localize white matter abnormalities.

Compared with the healthy controls, both NC and NOC patients exhibited significant fractional anisotropy (FA) decreases in the bilateral cerebellar hemispheres, bilateral thalami, the corpus callosum and left anterior-medial temporal white matter. Compared with the controls, the NC patients' FA values were also decreased in the midbrain. No significant correlations were found between FA values and clinical-polysomnographic variables.

This DTI study has demonstrated white matter abnormalities in the midbrain-brainstem regions as a distinctive finding of narcolepsy patients with cataplexy. Involvement of bilateral temporal lobes with greater changes on the left lobe is also a supporting finding of patients with cataplexy. DTI changes in the midbrain-brainstem and bilateral temporal lobes can be signs of different pathological mechanisms in these patients.