Investigations
1st investigations to order
sleep diary
Test
Used when a patient presents with difficulties initiating or maintaining sleep, difficulties waking up in the morning, hypersomnolence, or parasomnias. Important to keep on a daily basis, and should not be filled out while seated in the waiting room before the appointment.
Children and teenagers may be involved, but the responsibility for filling out the diaries should rest with a parent.
Result
may show erratic sleep schedule, disordered circadian rhythm, insufficient sleep, association of certain phenomena with triggers (parasomnias with insufficient sleep)
polysomnogram (PSG)
Test
Attended PSG is considered the diagnostic test of choice for obstructive sleep apnoea (OSA), although lack of agreement on how obstructive events should be scored results in different studies using different metrics to define obstruction, with significant obstruction defined as apnoea hypopnoea index ranging 1 to 5.[81][82]
Using the PSG as a stand-alone test to determine significance of obstruction has come under question with a proposal to score a patient based upon major and minor criteria in order to determine degree of risk.[83]
Distinguishes OSA from central sleep apnoea, periodic breathing, periodic limb movement disorder, abnormal electroencephalogram activity, cardiac arrhythmia, early REM onset, REM behaviour disorder, and medication effect on sleep architecture through number of obstructive events.
Also helps validate the accuracy of the multiple sleep latency test (MSLT) in diagnosing narcolepsy.
While the use of unattended PSG has been gaining attention for adults, its use in children is not recommended.[71][72]
Result
if OSA is suspected, PSG is the first test to order over sleep diary, distinguishing it from other disorders such as parasomnias, atypical seizures, REM behaviour disorder, hypoventilation, central sleep apnoea
multiple sleep latency test
Test
The diagnostic test for narcolepsy, and useful for evaluating other causes of hypersomnolence. Should be conducted in accordance with standard protocol, ideally following a full night polysomnogram documenting at least 7 hours of total sleep time, and off medications that can adversely affect sleep patterns, such as those that suppress REM.[78][79] If other causes of hypersomnolence are present, treatment of these are recommended prior to MSLT, with clinical judgement.[79]
Not indicated as part of routine evaluation of obstructive sleep apnoea, response to continuous positive airway pressure, insomnia, or circadian rhythm disorders.[78]
Result
reduced sleep latency (actual values change with Tanner sexual maturity scores) and 2 or more sleep-onset REM periods in 5 naps in narcolepsy
Investigations to consider
lateral neck films
Test
Often obtained to assess for adenotonsillar hypertrophy although they have low sensitivity. A normal neck film does not exclude obstructive sleep apnoea (OSA).
Result
enlarged adenoids and/or tonsils occluding the upper airway in OSA
nasal endoscopy
Test
Often done by otolaryngologist. Enlarged adenoids can cause significant obstruction.[34]
Result
enlarged adenoids, tonsils occluding the upper airway in obstructive sleep apnoea
overnight oximetry
Test
Can be utilised as a tool to gauge severity and plan perioperative care for children with obstructive sleep apnoea (OSA), but a normal test does not exclude OSA.[74] Many children with OSA do not have significant desaturations with obstruction, because their baseline PaO2 is high, and the drop in the PaO2 necessary to reduce the pulse oximeter oxygen saturation (SpO2) is large at those levels.
Result
significant desaturations in PaO2 in OSA
actigraphy
Test
Often used when there is discrepancy between the complaints or the amount of sleep as reported by the patient or carers. Activity variation may be due to erratic sleep schedule, disordered circadian rhythm, or insufficient sleep.
Result
erratic activity may be registered
audiovisual recording
Test
Helpful when dealing with complaints that are unusual or infrequent, and thus unlikely to be captured on a polysomnogram.
Result
may show evidence of obstructive sleep apnoea, parasomnias, movement disorders of sleep (such as jactatio capitis or rhythmic movement of the head, REM behaviour disorder), atypical seizure activity
HLA typing
Test
Sensitive, but not specific for narcolepsy. While certain human leukocyte antigen (HLA) types (HLA-DQB1*0602, HLA-DR2, and HLA-DQ1) are prevalent in patients with narcolepsy, they are also present in the general population in high percentages, and so their clinical utility is limited.[5]
Result
positive for HLA-DQB1*0602, HLA-DR2, HLA-DQ1 in narcolepsy
Emerging tests
pneumogram
Test
A limited, unattended polysomnogram, which offers much less information than a standard polysomnogram (PSG).
Not as sensitive as PSG.
Result
apnoea associated with desaturation, gastro-oesophageal reflux, bradycardia, or tachycardia in obstructive sleep apnoea
cerebrospinal fluid hypocretin levels
Test
Cerebrospinal fluid hypocretin levels are not routinely measured, but they are often low in patients with narcolepsy. Result is 110 picograms/mL or less or one third of normal control.
Result
low
Use of this content is subject to our disclaimer