with
mature teratoma of the supramedial
cerebellum
Saura H, Beppu T, Matsuura H, Asahi S,
Uesugi N, Sasaki M, Ogasawara K
Departments of Neurosurgery
and Diagnostic Pathology and Division of
Ultrahigh Field MRI, Institute for Biomedical
Sciences Iwate Medical University, Morioka.
Japan
Yawning occurs in various conditions such as
hypoxia, epilepsy, and sleep disorders including
sleep apnea. Intractable yawning associated with
a brain tumor has been rarely reported. A
19-year-old woman presented with intractable
yawning. Magnetic resonance imaging showed a
tumor in the supramedial cerebellum that
compressed the dorsal side of the midbrain and
upper pons. After subtotal removal of the tumor,
the yawning completely disappeared.
Postoperative MRI showed resolution of
compression of the brainstem. The tumor was
histologically diagnosed as a mature teratoma.
The present case suggested that the intractable
yawning resulted from the tumor compressing the
dorsal side of the junction between the midbrain
and pons.
Yawning occurs in various conditions such as
hypoxia, epilepsy, and sleep disorders,
including sleep apnea. Neural networks among the
pons, hypothalamus, limbic System, and autonomie
nervous System may be associated with yawning.
However, intractable yawning associated with a
brain tumor has rarely been reported.
We report a rare case involving a patient
who had a mature teratoma in the supramedial
cerebellum and suf-fered from intractable
yawning. After subtotal removal of the tumor,
the yawning completely disappeared. Case Report
A 19-year-old woman with recurrent yawning
visited a local hospital, and an intracranial
mass was detected on MRI. The patient visited
our institution 4 weeks after symptom onset. The
yawning occurred 20 times per minute and
continued for approximately 60-90 minutes. Such
yawning attacks occurred 2 or 3 times per week.
Neurological examination demonstrated no
abnormal findings.
Magnetic résonance imaging depicted a
high-intensity mass in the supramedial
cerebellum on Tl- and T2-weighted images. The
tumor compressed the dorsal midbrain and upper
pons. Blood gas analysis findings, including
partial oxygen pressure, were within normal
limits during yawning. Blood counts and
biochemical data were also within normal limits.
Although the patient's score was 20/24 on the
Epworth Sleepiness Scale for detection of sleep
disorders (normal score < 11),
polysomnography showed no abnormality.
Electroencephalography also demonstrated no
abnormality. After improving her daily living
environment according to our advice, the
patient's Epworth Sleepiness scale score
declined to 9/24.
However, the yawning continued for 2 years
after the decrease in the Epworth Sleepiness
Scale score, and then diplopia developed.
Neurological examination demonstrated a right
trochlear nerve palsy. Magnetic resonance
imaging showed no change in the tumor.
Operation and Postoperative Course
The patient underwent removal of the tumor
through an occipital transtentorial approach
performed under general anesthesia. The tumor
was hard and contained yellowish fat tissue and
calcified components. During surgery, we found
that the tumor adhered to the dorsal side of the
midbrain and upper pons and involved the right
trochlear nerve and the right superior
cerebellar artery. Therefore, the tumor except
the part adhering to the dorsal midbrain was
removed. The surgical specimen was
histologically diagnosed as a mature teratoma
composed of fat, muscle, and nerve cells with
poor heteromorphism. The yawning completely
disappeared immediately after surgery and has
not recurred 7 months after surgery.
Postoperative MRI showed a residual tumor at the
dorsal midbrain and resolution of the brainstem
compression.
Discussion
Based on blood gas analysis, the Epworth
Sleepiness Scale score, and findings on
polysomnography and electroencephalography,
intractable yawning in this patient was likely
not caused by hypoxia, epilepsy, or a sleep
disorder such as sleep apnea. Furthermore, the
yawning disappeared immediately after surgery
and did not recur after surgery.
These findings suggested that the yawning
was associated with a tumor in the supramedial
cerebellum that compressed the dorsal midbrain
and upper pons. The parabrachial area is located
on the dorsal side of the junction of the
midbrain and pons and plays a role in unifying
the autonomic nervous system. In the human
brain, the parabrachial area is a
horseshoe-shaped band of gray matter composed of
the lateral parabrachial nucleus (PBN), the
Kölliker-Fuse nucleus, and the medial PBN.
These nuclei receive important afferent fibers
from the cardiovascular, respiratory, and
gustatory systems and project efferent fibers
toward superior centers.
On the other hand, the paraventricular
nucleus (PVN), which is located in the medial
hypothalamus, is a center of the autonomic
nervous system and neuroendocrine system, and it
is closely associated with yawning. An
experimental study in rats demonstrated the
occurrence of yawning upon electrical or
chemical stimulation of the PVN. Furthermore,
the PVN has reciprocal connections with
brainstem autonomic centers including the PBN.
In particular, the PVN transmits signals mainly
from the lateral PBN. In the present case, any
extraordinary stimulation from the lateral PBN
in the brainstem to the PVN in the hypothalamus
may have led to the development of pathological
yawning. In this case, MRI showed that the tumor
preoperatively compressed the dorsal
