Paediatric sleep investigations: polysomnography, sleep-study interpretation and MSLT — formative SAQs

SAQ 1 — Reading the polysomnogram of a snoring preschooler (10 marks, 15 minutes)

A four-year-old girl snores nightly with witnessed pauses and gasping, sleeps restlessly and is inattentive at kindergarten. She has large tonsils and her weight is on the tenth centile. An attended overnight polysomnogram reports an obstructive apnoea-hypopnoea index of 9 events per hour, a central apnoea index of 0.3, an oxygen saturation nadir of 84 per cent, and a peak carbon dioxide of 46 mmHg, with adequate total sleep and rapid-eye-movement sleep. [1]

a) Interpret this report: classify the predominant event type and grade the severity, stating why paediatric rather than adult thresholds are used. (4 marks) [6] [2]

b) What single channel distinguishes an obstructive from a central event, and how does it do so? (3 marks) [7]

c) What is your first-line treatment and what follow-up would you plan? (3 marks) [1] [2]

SAQ 2 — The sleepy adolescent and the nap test (10 marks, 15 minutes)

A fifteen-year-old boy has months of severe daytime sleepiness with sudden sleep attacks and episodes of knee-buckling when he laughs. His overnight polysomnogram is normal for breathing. He is referred for a multiple sleep latency test. [9]

a) What must be confirmed and prepared in the two weeks before the multiple sleep latency test, and why does each matter? (4 marks) [5] [8]

b) What result on the multiple sleep latency test supports a diagnosis of narcolepsy? (3 marks) [5] [9]

c) List three commoner causes of daytime sleepiness that must be excluded before the test is interpreted. (3 marks) [9] [8]