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Phasic motor activity reduction occurring with horizontal rapid eye movements during REM sleep is disturbed in
J Kohyama1, Y Ohsawa, M Shimohira
1Department of Pediatrics, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
Insights
Infantile spasms (IS) patients show reduced REM sleep but an elevated phasic inhibition index (PII). This PII may help predict prognosis and understand IS pathophysiology.
Area of Science:
- Neurology
- Sleep Medicine
- Pediatric Neurology
Background:
- Infantile spasms (IS) are a severe epilepsy syndrome in infants.
- Understanding the neurophysiological underpinnings of IS during sleep is crucial for prognosis.
Purpose of the Study:
- To investigate polysomnographic sleep features during REM sleep in infants with IS.
- To identify sleep parameters that correlate with IS prognosis.
Main Methods:
- Single polysomnography was conducted before treatment in 17 IS patients and 22 age-matched controls.
- REM sleep components, including tonic muscle atonia, REM sleep duration, gross movements, phasic chin muscle activity, and rapid eye movements, were analyzed.
- The phasic inhibition index (PII) was calculated as the rate of simultaneous phasic chin muscle activity and bursts of horizontal rapid eye movements.
Main Results:
- IS patients had significantly less REM sleep compared to controls.
- Incidences of gross movements, phasic chin muscle activity, and rapid eye movements were similar between groups.
- The phasic inhibition index (PII) was significantly higher in IS patients than in controls.
Conclusions:
- Elevated PII in IS patients may indicate impaired phasic motor activity reduction during REM sleep, potentially linked to rostral pontine tegmentum dysfunction.
- PII emerged as the sole REM sleep parameter reflecting patient prognosis.
- PII is proposed as a valuable tool for assessing IS prognosis and understanding its pathophysiology.
Abstract:
Single polysomnography was performed before treatment in 17 patients with infantile spasms (IS) (13 with a cryptogenic type and 4 with a symptomatic one). Their sleep components during rapid eye movement (REM) sleep were compared with those in 22 age-matched controls. The tonic muscle atonia during REM sleep was observed in all IS patients as in controls. The amount of REM sleep in IS patients was significantly lower, while the incidences of gross movements, phasic chin muscle activity, and bursts of horizontal rapid eye movements were identical with those in controls. The phasic inhibition index (PII), i.e., the rate of simultaneous occurrence of phasic chin muscle activity and bursts of horizontal rapid eye movements, was significantly higher in IS than in controls. The PII value was the only parameter that reflected our patients' prognosis among the obtained REM sleep parameters. We presume that the elevated PII in IS reflects the weakness of the phasic motor activity reduction occurring with horizontal rapid eye movements, and attribute this disturbance to a functional instability of the rostral pontine tegmentum. We propose that PII is a useful parameter for assessing the prognosis of IS. Considering the neural basis for elevated PII in IS, this index is expected to provide a clue for explaining the pathophysiology of IS.