Characterization of sleep in six patients with pantothenate kinase-associated neurodegeneration

Abstract

Background: Pantothenate kinase-associated neurodegeneration (PKAN) is a rare neurologic disorder included in the group of neurodegeneration with brain iron accumulation diseases (NBIA). Information regarding sleep in patients with PKAN is limited.

Objectives: To describe the clinical and polysomnographic characteristics of sleep in six patients with genetically confirmed PKAN.

Methods: The evaluation included a clinical interview, sleep questionnaires -Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI) and Hospital Anxiety and Depression Scale (HADS)- and a video-polysomnography (VPSG). In addition to standard sleep measures we manually quantified sleep spindle density in stage N2 and rapid eye movements in REM sleep comparing the results with matched controls. Quantification of EMG activity in REM sleep was performed following standard criteria.

Results: All the patients reported at least one sleep complaint, most commonly sleep fragmentation (4/6) and sleep onset insomnia (3/6). ESS and PSQI were abnormal in 3/6 and 4/6, respectively. VPSG showed in 4/6 decreased ocular movements during REM sleep, an increase in sleep spindles in 3/6 (all of them with deep brain pallidal stimulation), an absence of slow wave sleep in 2 and undifferentiated NREM sleep and delayed sleep phase in one. Three patients had an abnormal sleep apnea/hypopnea index, and 2 periodic limb movements of sleep. REM sleep muscular atonia was preserved in all.

Conclusions: Sleep disorders are common in patients with PKAN. Although our sample is small and heterogeneous, with different symptomatic treatments possibly influencing the results, it suggests that evaluation of sleep should be considered in their management.

Keywords: PKAN; Pantothenate kinase-associated neurodegeneration; Polysomnography; Rapid eye movements; Sleep; Sleep spindles.