Recurrent hypersomnia following traumatic brain injury

BackgroundRecurrent hypersomnia (RH) following a traumatic brain injury (TBI) is a rare form of RH. According to the International Classification of Sleep Disorders, 2nd edition (ICSD-2), RH must be considered in the differential diagnosis as secondary to an organic insult of the central nervous system and not as the clinical subtype of RH, Kleine-Levin syndrome (KLS). The aim of our study was to investigate if cases of RH following TBI should be considered in the differential diagnosis of RH as indicated by the International Classification of Sleep Disorders, 2nd edition or as genuine, or indicated by ICSD-2, RH must cases of KLS.MethodsTwelve cases of RH developed after TBI were collected and analyzed for circumstance at onset, severity of TBI, delay between TBI and occurrence of first episode of RH, symptoms of RH, duration and cycle length of episodes of hypersomnia, physical signs, and brain morphological imaging at the time of hypersomnia episodes.ResultsFactors such as the delay between TBI and the first episode of RH, the presence of other triggering factors and potential genetic factors, the degree of the severity of TBI, the presence or absence of any consistent brain imaging abnormality, provided the following results: (1) two of the cases could be considered as symptomatic of the underlying pathological brain process, (2) eight of the cases could be considered as simply triggered by TBI in patients at risk for KLS, and (3) two cases could be considered neither symptomatic nor triggered by TBI, due to the long delay between TBI and occurrence of symptoms.ConclusionCases of RH following TBI do not present under a single mechanism. Clinical assessment and laboratory tests are necessary to correctly classify them.