Differentials
Obstructive sleep apnoea
SIGNS / SYMPTOMS
Significant snoring, higher BMI, less sleep-maintenance insomnia, crowded oropharynx, and a short and thick neck are suggestive of obstructive sleep apnoea (OSA) but can also be seen in CSA.
OSA and CSA can and often do co-exist.[40]
INVESTIGATIONS
Polysomnography shows apnoeas accompanied by significant and paradoxical abdominal and chest wall movements not seen in central apnoeas.[1][36] In patients classified as New York Heart Association class II to IV, with heart failure and suspicion of sleep-disordered breathing or excessive daytime sleepiness, a formal sleep assessment is needed to distinguish OSA from CSA.[7][22]
Sleep-related hypoventilation/hypoxaemic syndromes
Depression
SIGNS / SYMPTOMS
Early morning awakening.
Overt sleepiness is quite uncommon, and observed breathing patterns (in patients without concurrent sleep-disordered breathing diagnosis) are normal.
Morning headaches are unusual.
Other symptoms of depression should be present, such as dysphoria, anhedonia, and altered appetite.
INVESTIGATIONS
Patients with depression most often have abnormal results on standardised depression scales, such as the Beck Depression Inventory or the Patient Health Questionnaire-9.
Paroxysmal nocturnal dyspnoea due to congestive heart failure
SIGNS / SYMPTOMS
Orthopnoea often accompanies poorly controlled congestive heart failure (CHF) with paroxysmal nocturnal dyspnoea.
INVESTIGATIONS
Medical management of CHF should be optimised. If symptoms remain, polysomnography may be necessary to determine the cause.
Restless legs syndrome
SIGNS / SYMPTOMS
A characteristic history of restless legs syndrome (RLS) may be obtained, including an unpleasant sensation in the legs, which almost demands movement (often difficult to describe, but occasionally described as creepy-crawly, cramping, or fidgety sensations), worse in the evening, worse during immobility, and transiently improved by movement of the affected limbs.
INVESTIGATIONS
RLS is diagnosed by a careful history.
Polysomnogram-associated features may include periodic limb movements, but polysomnography is not necessary to make the diagnosis in adults.
Insomnia due to medication effects
SIGNS / SYMPTOMS
Temporal relationship between onset of symptoms and initiation or increase in dose of candidate medications.
INVESTIGATIONS
Most helpful is a careful review of medications and their adverse-effect profile.
If a medication is strongly suspected, improvement in the symptom upon removal of the medication supports this diagnosis. However, this may not always be possible.
Hypersomnia due to inadequate sleep
SIGNS / SYMPTOMS
The sleep history will reveal marked restriction of sleep, such that even patients who are excellent sleepers experience chronic sleep deprivation.
INVESTIGATIONS
A careful sleep history is often adequate.
In more perplexing cases, a sleep diary kept by a spouse or carer, or even actigraphy, which continuously measures gross motor activity, may be required to obtain an accurate assessment of sleep time and pattern.
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