Hand dominance shift during sleep in sexsomnia: a clue to pathophysiology?

Study objectives: To elucidate whether awake handedness in sexsomnia is retained during sleep to uncover potential clues about the underlying neurophysiologic mechanisms.

Methods: Participants' and observers' self-reported handedness during sexsomnia events.

Results: Case 1: A 22 y/o right-handed female with an eight-year history of nocturnal sleep-related masturbatory behavior (SMB) involving the left hand (LH) exclusively. Case 2: A 30 y/o ambidextrous male with SMB involving both hands, but most prominently the LH. Case 3: A 33 y/o right-handed female with exclusively LH SMB in the setting of acute multiple sclerosis exacerbation with cervical spinal cord and brainstem involvement. Case 4: A 44 y/o right-handed (RH) male with bilateral dream enactment behavior (DEB) and LH-predominant SMB noted by the bed partner (BP). Case 5: A 59 y/o RH female with a history of multiple system atrophy (MSA) and REM sleep behavior disorder (RBD) developed a new SMB, noted by the BP involving exclusively the LH. Case 6: A 37y/o RH man with inappropriate sexual behaviors involving the non-dominant LH without retention of memory for the events. Case 7: A 17 y/o RH male with polysomnographic evidence of genital manipulation using both hands but predominantly involving the non-dominant hand.

Conclusions: We speculate that sexsomnias originate from CPG in the brainstem and spinal cord, as opposed to the cerebral cortex. The lack of involvement of cerebral motor control is further substantiated by amnesia for sexsomnia events. The implications of this data provide fundamental new clues about the mechanism of sexsomnias with critical forensic implications.