Yawning is a complex arousal defense
reflex generated in the reticular brainstem that
has a peripheral and central arc and is thought
to counteract brain hypoxemia Excessive or
pathological yawning, "chasm", is defined as
a compulsive, repetitive action which is not
trigered by "physiological" stimuli such as
fatigue or boredom.
A 44 year-old Irish woman was admitted
because of sudden onset of pathological yawning.
Her excessive pathological yawning caused her to
be socially extremely handicapped. She reported
sleeping well but felt tired again 2 h after
awakening and had several naps befor evening.
Snoring and apnea were denied; there was no
evidence of restless leg syndrome. There was a
history of hypertension for 5 years, which had
been treated with nifedipine. She neither drank
alcohol nor smoked. Physical examination showed
a mild left central hemiparesis, which had
escape the patient's notice, and moderate
obesity. The patient suffered excessive
repetitive, compulsive yawning that she was
unable to control for longer than 1 mn. Routine
blood tetst, EEG, and CSF findings were normal.
Cranial magnetic resonanceimaging showed some
small, presumbly ischemic lesions in the
frontal periventricular region on both
sides. There were no brainstem lesions.
All night polysomnography revealed disturbed
sleep structure with awakenings, poor cyclic
structure, and borderline fragmentation of
sleep. There were no apneas or hypoxemias.
Mainly in the first third of the night,
periodic leg movements appeared during
sleep stages 1 or 2, with typical arousals
including K-complexes and alpha activation.
During the rest of the night there was frequent
rhythmic activity of the facial muscles,
determined by chin muscle activity measured by
sub-mandibular electrodes (bruxism). Altogether,
116 movements were enregistred during 8 h of
sleep, most of them associated with arousals.
The movements of face and legs were not
synchronous. A diagnosis of periodoc leg
movements in sleep (PLMS) was made according to
criteria of the American Sleep Disorders
Association. The patient was put on long action
levodopa (100mg) at night.
Yawning disapperead promptly, and the patient
felt more alert and active during the day. The
effects of the treatment on yawning were
assessed by video-recording. After discharge the
patient increased the levodopa dose to 200 mg.
At follow up 4 weeks later, she was virtually
free of yawning and hypersomnia. However, the
were side effects from the levodopa, including
depreesed mood, nightmares, and sligt periods of
disorientation during awakenings in the night.
Polysomnographic findings were rather normal
now, with 55 movements registered and more
considered normal. A drug holyday precipited a
relapse of chasm and fatigue within a few days.
Polysomnography was not performed on that
occasion. After restitution of levodopa 100mg
the patient was almost free of symptoms and
without serious side effects. Another follow-up
after 4 weeks showed the patient in stable
condition. Six months later the patient
discontinued the medication and has suffered no
relaps since.
This is the first case of PLMS associated
with pathological yawning. Known causes of
pathological yawning include encephalitis,
seizures, tumors of the fourth ventricule
region, multiple sclerosis, progressive
supranuclear palsy, electroconvulsive therapy
and neuroleptic withdrawal. Valproate overdose,
dopamine agonists, imipramine, withdrawal from
morphine and estrogen substitution may also
induce pathological yawning.
Neuropharmacological experimental studies
show that dopaminergic, cholinergic, ACTHergic
and oxytocinergic systems are part of the
complex behavioral response of yawning. Studies
in man have stressed the importance of the
dopaminergic system in the generation of
yawning. Apomorphine in low doses induces
yawning (and penil erection) in man and rats.
This is probably due to a stimulation of
presynaptic D2 autoreceptors, which results in a
net reduction in dopamine releases. Dopamine
agonists at higher doses do not produce yawning
in rats, suggesting that reduced rather than
enhanced dopaminergic stimulation mediates
yawning reponse.
PLMS has also been linked to alterations in
dopaminergic neurotransmission. The therapy of
choice is levodopa or dopamine agonists. Here,
we treated pathological yawning and PMLS
successfully with levodopa. Since chasm was much
more prominent than the day-time hypersomnia, we
doubt that the remission of yawningwith levodopa
therapy simply resulted from the reduction of
hypersomnia after improvement in night sleep.
Thus the present case study raises the
possibility that chasm and PLMS reflect a common
disturbance of dopaminergic neurotransmission.
Transient withdrawal of levodopa precipited the
relapse of pathological yawning and thus
confirmed its therapeutic efficacy. Sudden onset
and delayed resolution of the symptom favor a
circumscribed ischemic lesion as a likely cause
of both PLMS and chasm in our patient. We
conclude that a therapeutic trial of levodopa
is justified in patients with pathological
yawning.
