Sleep-state transition instability with recurrent multisystem activation: A case-based phenotypic framework.

The wake-to-sleep transition is a physiologically vulnerable period during which benign and pathologic motor phenomena may emerge. Current sleep nosology recognizes isolated hypnic jerks, propriospinal myoclonus at sleep onset, sleep-related rhythmic movement disorder, and other minor sleep-related motor activities, but these entities may not fully explain patients with persistent, repetitive motor activation recurring across successive attempts to fall asleep. We describe eight representative cases characterized by recurrent motor events centered on sleep onset or early sleep-state transitions, associated sensory and autonomic symptoms, clinically meaningful sleep fragmentation, and absence of a more satisfactory alternative diagnosis. On the basis of these observations, we introduce sleep-state transition instability with recurrent multisystem activation (SSTI-RMA) as a provisional, hypothesis-generating phenotypic construct rather than an established diagnostic entity. The recurring clinical pattern comprises recurrent motor activation during wake-to-sleep or early sleep transitions together with variable sensory, autonomic, cardiovascular, respiratory, or other non-motor manifestations, repetition or clustering of events, difficulty initiating or stabilizing sleep, clinically significant distress or impairment, and absence of a more satisfactory alternative explanation. We conceptualize the SSTI-RMA phenotype as a possible disorder of sleep-state instability rather than as an isolated motor phenomenon, potentially involving impaired coordination among neural, autonomic, and vascular processes during sleep entry. No validated polysomnographic signature, frequency threshold, biomarker, or prevalence estimate is currently available, and the relationship of this phenotype to severe or recurrent sleep starts remains unresolved. SSTI-RMA should therefore be regarded as a descriptive research framework intended to facilitate standardized phenotyping and prospective studies capable of determining whether it represents a distinct entity, part of a continuum of established sleep-onset phenomena, or a heterogeneous phenotype with multiple causes.