A 60-year-old man exhibits vigorous limb movements and vocalisation during sleep, acting out dream content. His bed partner reports he punched her. He has no memory of these events. This behaviour occurs during which sleep stage and is associated with future risk of which condition?
- A REM sleep; future risk of synucleinopathies (Parkinson's Disease, DLB, MSA) ✓
- B NREM Stage 3 (slow wave) sleep; future risk of sleepwalking
- C REM sleep; future risk of Alzheimer's Disease
- D NREM Stage 2; future risk of epilepsy
Explanation
REM Sleep Behaviour Disorder (RBD) occurs during REM sleep when the normal muscle atonia that accompanies REM is absent or incomplete, allowing the person to physically act out dream content. It is a polysomnography-confirmed diagnosis (REM without atonia). Idiopathic RBD is now recognised as a prodrome of alpha-synuclein pathology: longitudinal studies show that 80–90% of idiopathic RBD patients develop a synucleinopathy (Parkinson's Disease, Dementia with Lewy Bodies, or Multiple System Atrophy) within 10–15 years. This makes RBD a valuable early biomarker for these neurodegenerative conditions.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.