SLEEP STARTS (HYPNIC JERKS)
On entering sleep, sudden jerks of the arms or legs commonly occur and are especially frequent when a conscious effort is made to remain awake, e.g. during a lecture. This is a physiological form of myoclonus.
Lesions which affect the structures in the floor of the third ventricle may produce excessive sleepiness, e.g. tumours or encephalitis, and are often associated with diabetes insipidus.
Systemic disease such as myxoedema may result in hypersomnia, as may conditions which produce hypercapnia - chronic bronchitis, or primary muscle disease, e.g. dystrophia myotonica.
Respiratory rate fluctuates during REM sleep with occasional short episodes of apnoea. These are normal physiological events and are brief and infrequent.
Prolonged sleep apnoea results from central reduction of respiratory drive, a mechanical obstruction of the airway or a mixture of both.
Central causes: Mechanical causes:
Brain stem medullary infarction or following Obesity. Tonsillar enlargement, cervical/foramen magnum surgery. Myxoedema. Acromegaly.
When breathing ceases, the resultant hypercapnia and hypoxia eventually stimulate respiration. Patients may present with daytime sleepiness, nocturnal insomnia and early morning headache. Snoring and restless movements are characteristic. In severe cases of sleep apnoea, hypertension may develop with right heart failure secondary to pulmonary arterial hypertension. Polycythaemia and left heart failure may ensue.
Evaluation requires sleep oximetry and video recording with low level illumination. Fall in oxygen saturation may be as much as 50%.
Treatment depends on aetiology. Mechanical airway obstruction should be relieved; drugs such as theophylline are occasionally helpful. Continuous positive airway pressure (CPAP) applied to the nose may help. Surgical reconstruction of palate and oropharynx is offered in extreme cases.
The Pickwickian syndrome: sleep apnoea associated with obesity, named after the Dickens' fat boy who repeatedly fell asleep.
The most common sleep disorder, difficult to evaluate and of multiple causation including psychiatric, alcohol, drug related or due to systemic illness. Treatment depends on cause e.g. antidepressant.
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