Vasovagal syncope during sleep

Sleep vasovagal syncope is defined as loss of consciousness in a non-intoxicated adult occurring during the night (e. g. 10:00 pm to 7:00 am), in which the patient wakes up with pre-syncopal and abdominal symptoms (i.e. an urge to defecate) and losses consciousness in bed or immediately upon standing.
There is no tongue biting or post-ictal confusion. There is usually a history of daytime vasovagal syncope and there seems to be a more pronounced fear of blood and medical procedures than in other syncope patients [1]. Physical examination, ECG and EEG are within normal limits. The vasovagal reaction is thought to start while asleep [2][3], and continuing after waking up, hence the name. During syncope there may be a profound sinus-bradycardia [2]. Vasovagal sleep syncope occurs at all ages.

Differential Diagnosis

Sleep vasovagal syncope is diagnosed by excluding beyond reasonable doubt the hereafter mentioned disorders [3].
Epilepsy is the foremost alternative diagnosis to consider, but can often easily be ruled out on clinical grounds. Complex partial, generalized tonic-clonic and myoclonic epilepsy may occur during sleep and can imitate syncope when causing cause sinus-bradycardia [4].
There are a number of related conditions, including “abdominal epilepsy” and Panayiotopoulos syndrome (typically with vomiting) [5], in which the associated clinical features are abdominal pain and confusion.
Sleep paralysis and hypnogogic hallucinations occur in narcolepsy but also as isolated phenomena, mostly with other characteristic features in the history (e. g., daytime somnolence, in contrast to syncope there’s no amnesia.) and abnormal polysomnography, which can also be used to diagnose sleep apnoea and night terrors.
Occasionally cardiac disorders may cause cardiac arrhythmias during sleep. Most of these are unlikely if the 12-lead ECG is normal, and in some patients long-term ambulatory ECG monitoring is required [6].
Some patients with a diagnosis of defaecation syncope (see below) described abdominal and pre-syncopal symptoms that started simultaneously during sleep [7][8] there may be some overlap between this condition and sleep syncope [3].

References

1. Jardine DL, Krediet CT, Cortelli P, & Wieling W (2006b). Sleep syncope: clinical features and autonomic profiles. Clin Auton Res 16, 321-322.

2. Krediet CT, Jardine DL, Cortelli P, Visman AG, and Wieling W. Vasovagal syncope interrupting sleep?. Heart. 2004 May;90(5):e25. DOI:10.1136/hrt.2003.031294 |
4. Tinuper P, Bisulli F, Cerullo A, Carcangiu R, Marini C, Pierangeli G, and Cortelli P. Ictal bradycardia in partial epileptic seizures: Autonomic investigation in three cases and literature review. Brain. 2001 Dec;124(Pt 12):2361-71. DOI:10.1093/brain/124.12.2361 |
5. Covanis A. Panayiotopoulos syndrome: a benign childhood autonomic epilepsy frequently imitating encephalitis, syncope, migraine, sleep disorder, or gastroenteritis. Pediatrics. 2006 Oct;118(4):e1237-43. DOI:10.1542/peds.2006-0623 |
6. Brierley EJ, Jackson MJ, Clark RS, and Kenny RA. Alarming asystole. Lancet. 2001 Jun 30;357(9274):2100. DOI:10.1016/s0140-6736(00)05184-9 |
7. Pathy MS. Defaecation syncope. Age Ageing. 1978 Nov;7(4):233-6. DOI:10.1093/ageing/7.4.233 |
8. Fisher CM. Syncope of obscure nature. Can J Neurol Sci. 1979 Feb;6(1):7-20. DOI:10.1017/s0317167100119316 |