Subjects

The study was performed in the National Reference Centre for KLS in the Pitie-Salpêtrière University Hospital in Paris between December 2011 and March 2019. All patients referred for suspected KLS and their families underwent a long interview with the KLS physicians (including a neurologist and a psychiatrist, both sleep specialists), a cognitive assessment and blood sampling. The physicians examined previous medical information collected before referral, including medical history, brain morphological imagery, EEG, sleep studies, the results of the spinal tap if performed, as well as biological results (mostly autoantibodies and urine organic acid chromatography). To be included in the present study, patients had to meet the international KLS criteria,22 including the following: (i) experiencing at least two episodes of excessive sleepiness and sleep duration, each persisting for 2 days to 5 weeks; (ii) episodes recur usually more than once a year and at least once every 18 months; (iii) the patient has normal alertness, cognitive function, behaviour and mood between episodes; (iv) the patient must demonstrate at least one of the following during an episode: (1) Cognitive dysfunction; (2) Altered perception; (3) Eating disorder (anorexia or hyperphagia); (4) Disinhibited behaviour (such as hypersexuality); and (v) symptoms are not better explained by another sleep, medical, neurologic or psychiatric disorder (especially bipolar disorder), or use of drugs or medications. Patients with atypical or differential diagnoses, those with KLS secondary to other disorders and those with severe mental deficiency were excluded. Notably, this cohort of KLS patients was different from the 41 patients with KLS who benefitted from SPECT analysis between 2007 and 2011.13 For this analysis, patients who had the FDG-PET/CT during an episode were excluded, as well as those already treated for KLS at the time of the scan. All patients (including minor patients, in this case, in association with their parent-signed consent) signed an informed consent form for having their measures collected in the study. The research programme was approved by the ethics committee.