Introduction Yawning may trigger
cephalic, pharyngeal or upper cervical pain in
trigeminal, geniculate and glossopharyngeal
neuralgias, temporomandibular joint dysfunction
(TMJ) and Eagle syndrome (ES) (secondary yawning
pain). In primary yawning headache (PYH), no
underlying lesion or disorders are present,
therefore it represents an isolated, benign
condition of minor clinical significance. In PYH
the pain is cephalic in distribution. ES is
probably the form of secondary yawning pain less
recognized by neurologists. It is characterized
by neuralgic or steady pharyngeal pain radiating
to the ear, mimicking carotidynia and
glossopharyngeal neuralgia. Calcification or
elongation of the stylohyoid ligament causes ES.
Surgical resection of the elongated styloid
process is curative. Two patients are described
with yawning pain of extracephalic location. One
had an underlying lesion in the area where the
pain was perceived. Neither ofthe two had
evidence of ES.
Case reports
Case 1 A 45-year-old male reported
episodes characterize by recurrent, intense,
steady right shoulder and arm pain triggered by
yawning and associated with inability to breathe
spontaneously of abrupt onset. Symptoms
developed 2 years earlier. He had to take
voluntary control of his breathing during these
episodes. He had no numbness of the arms, chest
pain or palpitations during these episodes that
lasted a maximum of 2 min. He had no other
precipitants of the pain. Witnesses never saw
him change colours or act inappropriately. He
had history of gout and of an old sacral
radiculopathy. One uncle had Parkinson's
disease. He took allopurinol for his gout. His
general physical examination was normal. On
neurological examination he deviated
simultaneously his jaw to the same side of his
tongue when asked to wiggle his tongue
side-to-side (linguo-pterygoid synkinesis).
Facial gestures or wide opening of the mouth did
not reproduce the pain. Brain magnetic resonance
imaging (MRI) and electroencephalogram (EEG)
were normal. His cervical MRI showed mild
central disc bulging at C5 and C6 levels,
causing no root encroachments or spinal cord
impingement. Cranial nerve testing including
blink reflexes, mental and facial nerve
responses and electromyography (EMG) of the
facial muscles were normal. Palpation of the
tonsillar fossa and Panorex X-rays of the skull
were normal. He was reassured about the benign
nature of his condition and medication was not
prescribed.
Case 2 A 84-year-old retired female
nurse was referred for neurological evaluation
because of anterior cervical piercing pain,
precipitated by yawning, for the last 9 months.
She had history of migraine with visual aura,
right eye blindness, anti-phospholipid antibody
syndrome, hypothyroidism, arteriosclerotic heart
disease, deep venous thrombosis, ventricular
fibrillation, aortocoronary bypass, aortic valve
replacement and pacemaker insertion. Palpation
of the thyroid gland revealed a mobile painless
mass over the right upper pole of the thyroid.
She was totally blind on her right eye. Her
vital signs and neurological examination were
normal otherwise. Imitation of yawning or
forceful opening of the mouth did not cause any
neck pain. CT of the head showed silent lacunar
strokes and leukoaraiosis. Carotid Doppler
ultrasound of the neck revealed no stenotic
lesions. Panorex views of the skull showed no
elongation of the styloid. A thyroid ultrasound
demonstrated a 1.9*2.6*1.7 cm solid nodule over
the right upper pole. Aspiration of the nodule
was diagnostic of Hürthle cell carcinoma.
Conservative management was advised given her
age and lack of symptoms, other than yawning
pain.
Discussion Yawning is a normal
phenomenon in mammals signifying drowsiness,
fatigue, hunger or boredom. In male rodents, it
represents pre-coital behaviour that can be
precipitated by cortical spreading depression.
Yawning is under the complex control of several
neurotransmitters including dopamine, nitric
oxide, glutamate, GABA, serotonin, ACTH, MSH,
sexual hormones and opioid peptides. ,Dopamine
in particular, is of greater importance.
Dopamine increases oxytocin synthesis in the
paraventricular nucleus of the hypothalamus,
subsequently inducing yawning, by activating
cholinergic transmission in the hippocampus.
Ultimately, acetylcholine acts upon the
muscarinic receptors of the effectors. Of
clinical relevance is that compulsive yawning
may constitute a migraine prodrome and yawning
is readily induced in migraineurs after the
administration of sublingual apomorphine, a
dopamine agonist drug. This susceptibility to
dopamine seems to arise from the expression of
D2 receptor genes in those patients exhibiting
precephalgic yawning that results in central and
peripheral (lymphocyte) dopamine receptor
up-regulation and hypersensitivity. Also of
interest, is the association of migraine and
restless legs, as the latter is a condition
based on central dopaminergic dysfunction .
Conversely, levodopa alleviates pathological
yawning associated with periodic leg movements
of sleep.
The pathogenesis of yawning pain is unclear.
The first patient herein described had no
history of migraine to suggest underlying
dopaminergic dysfunction and, although the
second patient had history of migraine, her pain
localized to the area occupied by the thyroid
tumour only, and was not pre- or peri-cephalgic
in nature. Unfortunately, 18 Fdopa PET scan
could not be performed on these patients, in
order to assess the potential role of central
dopaminergic dysfunction on their symptoms, nor
were they tested for apomorphine
hypersensitivity. It can be speculated that a
reflex arch is formed between cranial and
capsular temporomandibular stretch receptors and
trigeminal nerve fibres, including those
travelling through the upper cervical nerves.
The pain experienced by these two patients,
however, included lower cervical dermatomes
outside the expected trigeminal zone of
innervation. In any event, a facilitatory
mediation by the cerebral hemispheres needs to
be postulated as the simple imitation of
yawning, normally activating stretch receptors,
did not reproduce their pain. Participation of
the medullary centres in the first patient is
suggested by his loss of spontaneous breathing,
immediately following yawning-induced pain.
The cause of the yawning-respiratory
synkineses experienced by the first patient is
also unknown. His pain was not reproduced by
eructation, as experienced by a previously
reported patient with primary yawning headache.
Its occurrence could have indicated the
involvement of C3, C4 and C5 spinal cord
segments innervating the diaphragm. Brainstem
lesion, demyelination and aberrant innervation
were ruled out by a normal brain MRI and cranial
nerve electrophysiological testing. Although
yawning may be an exceptional epileptic
manifestation, there is no justification to
support the diagnosis of partial reflex epilepsy
on this patient either, in the absence of
additional ictal symptoms and EEG abnormalities.
Cervical myelopathy or radiculopathy could not
be adduced as a mechanism for his right shoulder
pain. His cervical MRI showed only mild central
disc bulging without root encroachment and there
were no other clinical signs of
radiculopathy.
Of additional interest is that the cervical
pain reported by the second patient was
localized precisely to the area of the thyroid
tumour, even when the palpation of the tumour
did not elicit pain. She had no clinical
evidence of paraneoplastic peripheral neuropathy
or central nervous system metastatic lesions, in
order to postulate an explanatory mechanism on
those bases. Motor activity may result in
paroxysmal referred pain, experienced away from
the anatomic area engaged in the movements.
Rarely, this referred pain may serve to diagnose
an underlying lesion. I reported earlier, two
patients with pain during the act of
masturbation. When achieving orgasm, the first
patient had piercing (ice pick-like) pain in the
neck. His imaging studies revealed advanced
cervical spondylosis and spinal cord
compression. This second patient suffered pain
in the groin, testicle and rectal area. He had
an intraspinal lipoma and tethered cord.
Although probable stretching of the tumour
tissue occurred during yawning in the second
patient, it is unexplained why stretching of the
same tissular area with the imitation of yawning
or with palpation did not reproduce the
pain.
In conclusion, yawning pain may have
an extracephalic localization and similar to its
cephalic counterpart, it may have an underlying
cause (secondary yawning pain) or, as
exemplified by the first patient, have no
apparent cause (primary yawning pain). Following
the IHS classification, primary yawning pain (or
PYH) with and without extracephalic
manifestation, may be classified under
'miscellaneous headaches not associated with a
structural lesion, while secondary yawning pain
(i.e. ES) may be classified under 'headache or
facial pain associated with disorder of cranium,
neck, eyes, nose, sinuses, teeth, mouths or
other facial or cranial structures'.
Alternatively, both conditions could be listed
as 'headachenot classifiable'.
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