Abstract |
- Narcolepsy is a complex of physiological and behavioral
symptoms. The most striking of these are: excessive daytime
sleepiness, extremely short latency to rapid eye movement (REM)
sleep, hypnogogic hallucinations; sleep paralysis, and cataplexy,
which is loss of skeletal muscle tonus in response to intense
emotions such as surprise, anger, laughter, competition, or sexual
intercourse. What unifies these symptoms is that they are
components of the REM phenomenon and narcolepsy has come to be
known as REM disorder.
The cause(s) of narcolepsy is unknown. A genetic aspect is
possibly involved (Carskadon, 1 982; Guilleminault, 1989) and,
historically, the pandemic encephalitis lethargica resulted in many
reported cases of narcolepsy. Typically, onset of symptoms appear
in teenage years although diagnosis usually takes place many years
after the actual onset (Navelet, 1 976). There are over 200,000
diagonosed cases in the U.S. (Dement, 1979). Studies using lesions
and microelectrode recordings followed by definitive immunohistochemical staining methods have located structures
that are possibly involved in the generation of REM components.
Pharmacological studies complement the neuroanatomical data by
the exogenous induction and suppression of REM and suggest that
the cholinergic and catecholaminergic neurotransmitter systems
are involved. These same systems are implicated in cognitive
behavioral functions of alerting and attention.
Narcoleptics have not been extensively studied with cognitive
testing, despite the fact that their catecholaminergic and
cholinergic systems are impaired as evidenced by the mechanisms
of their effective therapies (Mitler, 1986; Soldatos, 1983; Phillips,
1983) and animal studies of receptor number and serum levels of
neurotransmitter metabolites (Baker and Dement, 1 985; Kilduff et
al., 1986; Faull et a]., 1986). A case study presented in this thesis
attempts to assess the ability of a narcoleptic individual to shift
covert attention, respond to a warning cue and perform an
increasingly difficult response. These tests were given on two
different days. On the first day, the subject was using
protriptyline, a tn-cyclic antidepressant which potentiates the
monoamines and controls cataplexy in the narcoleptic. The second
day of testing took place two months after the subject had taken a
drug holiday from protriptyline. The results may indicate this
individual displays a left hemispheric effect that manifests in
difficulty in disengagement, longer reaction times to contralateral
targets, and slower motor responses. This case study, suggests
future study of cognitive function in the narcolpetic population.
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