Sleep results from activity in certain sleep producing areas of the brain rather than from reduced sensory input to the cerebral cortex. Stimulation of these areas produces sleep; damage results in states of persistent wakefulness.
Two states of sleep are recognised:
Pontine Medullary reticular formation raphe nuclei reticular formation raphe nuclei
1. Rapid eye movement (REM) sleep
Characterised by: - Rapid conjugate eye movement
- Fluctuation of temperature, BP, heart rate and respiration
- Muscle twitching
- Presence of dreams
Originates in: - Pontine reticular formation Mediated by: - Noradrenaline
2. Non-rapid eye movement (non-REM) sleep
- Absence of eye movement
- Stability of temperature,
BP, heart rate and respiration
- Absence of muscle twitching
- Absence of dreams
- Midline pontine and medullary nuclei (raphe nuclei)
The electroencephalogram shows characteristic patterns which correspond to the type and depth of sleep.
REM sleep __——a low voltage record with mixed frequencies, dominated by fast activity.
a relatively low voltage record with slow rhythms, interrupted by alpha rhythm, sharp waves evident in vertex leads (V waves).
a high voltage record dominated by slow wave activity.
The sleep pattern
In adults non-REM and REM sleep alternate throughout the night.
m n f 60-90 min 10-15 min Retiring
The proportion of REM to non-REM varies with age. In view of the important role of serotonin and noradrenaline in sleep, it is understandable that drugs may affect the duration and/or content of sleep.
DISORDERS OF SLEEP
NARCOLEPSY AND CATAPLEXY Narcolepsy
NARCOLEPSY AND CATAPLEXY Narcolepsy
The narcolepsy/cataplexy tetrad
Only 10% of patients manifest the complete tetrad
Males are affected more than females. Prevalence 1:2000.
Onset is in adolescence/early adult life. The disorder is life long, but becomes less troublesome with age. It may have a familial incidence, or may occur after head injury, with multiple sclerosis, or with hypothalamic tumours. The cause remains unknown, though the increased incidence of certain histocompatibility antigens (DR2) in sufferers does suggest an immunological basis. Diagnosis
The diagnosis is dependent upon the clinical history. The electroencephalogram may help, showing a REM pattern within 10 mins of sleep onset (normal - 90 minutes) Treatment
Drugs which inhibit REM sleep may benefit: - amphetamines and their derivatives, e.g.
dexamphetamine sulphate, methylphenidate hydrochloride. - other drugs are preferable but have a selective effect: mazindol & pemoline for narcolepsy; clomipramine for cataplexy.
OTHER SLEEP DISORDERS (PARASOMN1AS) NIGHT TERRORS (pavor nocturnus)
These occur in children, shortly after falling asleep and during deep to intermediate non-REM sleep. The child awakes in a state of fright with a marked tachycardia, yet in the morning cannot recollect the attack. Such attacks arc not associated with psychological disturbance, are self limiting and if necessary will respond to diazepam. NIGHTMARES
These occur during REM sleep. Drug or alcohol withdrawal promotes REM sleep and is often associated with vivid dreams.
SOMNAMBULISM (sleep walking)
Sleep walking varies from just sitting up in bed to walking around the house with the eyes open, performing complex major tasks. Episodes occur during intermediate or deep non-REM sleep. In childhood, somnambulism is associated with night terrors and bed wetting, but not with psychological disturbance. In adults, there is an increased incidence of psychoneurosis. Prevention of injury is important. 103
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