Insomnia Insomnia

Sleep State Misperception 95
marked discrepancy between objectively measured sleep and subjective reports.
Polysomnography is required because the distinguishing feature is normal SL and
continuity measures during polysomnographically measured sleep despite the
insomnia complaint. Primary sleep disorders such as sleep apnea syndrome and
periodic limb movement disorder may be associated with a perception of obtaining
virtually no sleep because the frequent arousals and awakenings in these disorders
may not allow normal perception of sleep. Unlike SSM, sleep continuity measures
in these patients are not normal, and other associated clinical symptoms usually
suggest the correct diagnosis.
DIAGNOSTIC WORKUP
As with other forms of insomnia, a thorough history and physical examination
are essential. The bedpartner should be interviewed if possible. Unlike other forms
of insomnia, however, polysomnography is essential for the diagnosis. The ICSD
(1) requires a PSG SL of less than 20 minutes, a minimum of 6.5 hours of sleep, and
a normal number of awakenings and arousals. Additionally, MSLT should show a
mean SL of greater than 10 minutes. The latter requirement is to assess for the
possibility that patients with idiopathic hypersomnia may interpret daytime sleepiness
as a consequence of inadequate sleep. However, because insomnia by nature
varies from night to night, occasionally bad sleepers can have a good night. Therefore,
the only way to diagnose SSM is if the individual states that he or she has not
slept well or not at all in the lab on a given night when the PSG shows normal sleep.
Although not required for diagnosis, actigraphy may be useful in establishing
the actual sleep patterns of these patients because, by definition, these indivduals
are unable to give accurate accounts of actual sleep time. Actigraphy is a recently
developed technique that records activity during waking and sleeping without
application of any electrodes. An actigraph is worn on the wrist and is about the
size of a watch. It consists of a movement detector and considerable memory, so it
can record movement and nonmovement data plotted against time for 1 or 2 weeks.
The patient can wear it continuously during sleep and as he or she performs routine
daily activities. Actigraphy is ideal for extended examination of the sleep–wake
cycle in the patient’s home environment. However, there may be a discrepancy in
some patients with SSM between actigraphy and polymsomnography, with wrist
actigraphy registering wakefulness, while the PSG shows sleep. Increased wrist
movements or similar events in these patients may be the reason they perceive themselves
as awake when they are actually asleep.
PREVENTION
Because the cause of SSM is poorly understood, effective prevention is not possible.
This disorder may share features with psychophysiological insomnia, thus, it
is possible that measures used for the prevention of psychophysiological insomnia
may also prevent SSM in some patients.