140 Chapter 5 Table 1: Continued. Patients (n = 12) Controls (n = 11) P-value PLMI (mean, SD) 4.84 (7.50) - * One patient had a deficient hypocretin-1 level (138 pg/mL) slightly above the diagnostic threshold (< 110 pg/mL). This patient was still included given the clinically typical narcolepsy and still deficient hypocretin-1 level. EDS = excessive daytime sleepiness; ESS = Epworth sleepiness scale; HLA = human leukocyte antigen; IQ = intelligence quotient; IQR = interquartile range; MSLT = multi sleep latency test; PLMI = periodic leg movement index; SD = standard deviation; SOREM = sleep onset rapid eye movement; TST = total sleep time. Tract-based spatial statistics (I) Whole-brain microstructural WM differences were observed in people with narcolepsy in comparison to controls by means of overall significantly lower FA and higher RD (Figure 1). Most prominent differences were found in the bilateral ventral diencephalon (comprising i.e. hypothalamus), thalamus, midbrain, pons, (orbito-) frontal, anterior cingulate, primary motor and somatosensory WM, internal capsule and the corpus callosum. No differences between groups were seen in other contrasts and in the cerebellum altogether. No significant relationships between time since EDS onset and ESS score and FA were present. Randomly creating two new groups pooling evenly cases and controls to detect spurious results did not yield significant differences. Masking the FA results with the JHU white matter tractography atlas’ tracts showed highly significant clusters with lower FA widely spread throughout the brain (Figure 2); up to 68.1% of the left corticospinal tract voxels were significantly different. In contrast, only the parahippocampal cingulum WM showed a limited number of significantly different voxels [left: 2.1%, right: 3.3%].
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