*From the Departments of Pediatrics (Dr. Hui), Psychiatry (Dr. Wing), Surgery (Dr. Poon), Diagnostic Imaging (Dr. Chan), and Anaesthesia (Dr. Buckley), The Chinese University of Hong Kong, Hong Kong.
Correspondence to: Y. K. Wing, MD, Department of Psychiatry, The Chinese University of Hong Kong, 11th Floor Clinical Science Building, Prince of Wales Hospital, Shatin, Hong Kong; e-mail: email@example.com
A 3-year-old boy presented with brainstem astrocytoma and central
alveolar hypoventilation syndrome. Contrast MRI of the brain showed
that the tumor involved the cerebellum, with compression of brainstem,
and resolved after surgical resection. Polysomnography performed before
and after total tumor resection showed significant improvement in
nocturnal respiratory rate, respiratory disturbance index, and oxygen
desaturation. It is apparent that central alveolar hypoventilation
syndrome secondary to brainstem tumor may improve after surgical
resection for those with favorable anatomic location and histology.
Serial polysomnography and MRI scans are useful for diagnosis and in
the management plan, and to monitor progress.
hypoventilation syndrome (CHS) in children is an uncommon but
serious condition.1Central alveolar hypoventilation
caused by brainstem tumor is even rarer. There are only few case
reports, and all cases were fatal.2–4 Herein we describe
a child with CHS caused by brainstem astrocytoma with subsequent
improvement in ventilation status after tumor resection. The
improvement in ventilation status was demonstrated on serial
A 3-year-old boy presented with chronic cough, hoarseness of
voice, and left vocal cord paralysis. Contrast MRI of the brain
revealed a 4-cm cystic mass in the posterior fossa. The mass filled up
most of the fourth ventricle, extending to the inferior vermis
posteriorly and to the medulla anteriorly, with compression of the
dorsum of the pons and pontomedullary junction (Fig 1
, top). Posterior fossa craniectomy was attempted, but only a
small part of the tumor was removed. Histology showed pilocytic
astrocytoma. The child later developed bulbar palsy and left facial
nerve palsy. A tracheostomy was performed.
For the next 2 months, the child became oxygen dependent. When the
child was awake, arterial blood gas measurement showed elevated
CO2 level at a partial pressure of 48.6 mm Hg and
normal alveolar arterial oxygen gradient. He was drowsy in the
daytime and had recurrent apneic spells necessitating resuscitation. A
second craniectomy was carried out 3 months later, and the bulk of
residual tumor was removed. A left ventriculoperitoneal shunt was
inserted for hydrocephalus. The child had also developed left-sided
hemiparesis. A repeat arterial blood gas measurement, performed when
the child was awake, showed persistent CO2
retention at a partial pressure of 49.4 mm Hg. End-tidal
CO2 level during sleep was elevated up to 84 mm
Overnight polysomnographic evaluations were performed, using
an Oxford Medilog 9200 (Oxford Instruments; Oxon, England),
before the second operation and at 6 and 14 months after the second
operation. The airflow sensor was placed at the tracheostomy site in
all the studies. Central apnea was defined as cessation of airflow with
no respiratory effort for >10 s. The initial study had total
sleep time of 447.5 min, with sleep efficiency of 93.4%. The child’s
respiratory rate was 12 breaths/min during relaxed wakefulness, and it
further declined to 6 to 8 breaths/min during sleep (Fig 2
, top). There were multiple apneic episodes of central
origin, with a respiratory disturbance index (RDI) of 83.8/h. The
longest apneic episode was 30 s. The lowest arterial oxygen
saturation was 72%. There were 383 episodes of oxygen desaturation<4%, with 155 events of desaturation <90%.
The second study had total sleep time of 466 min, with sleep efficiency
of 79.3%. Respiration was more regular, with respiratory rate of 20
breaths/min. There was marked reduction in RDI to 9.9/h, and the
longest apneic episode was 38 s. The number of episodes of oxygen
desaturation <4% was reduced to 49, with 46 events of desaturations<90%. The third study had total sleep time of 391 min, with sleep
efficiency of 45%. There was continuing improvement in the regularity
and amplitude of breathing during sleep (Fig 2, bottom). The
RDI was 3.4/h. The longest apneic episode was 14 s. The lowest
arterial oxygen saturation was 83%. The number of episodes of oxygen
desaturation <4% was further decreased to eight, with two events of
Contrast MRI scan of the brain was repeated 22 months after surgery
(Fig 1, bottom). There was no evidence of enhancing tumor in
the posterior fossa, and compression was relieved. The child has
survived up to 3 years since initial presentation and has been
discharged home. He has residual bulbar and left facial palsy and left
hemiparesis. He does not receive ventilation in the daytime, but
receives home ventilation at night. We plan to reduce his ventilation
setting further, although previous attempts in taking him off night
ventilation have resulted in retained secretions, atelectasis, and
Brainstem tumor resulting in CHS has been rarely reported. The
prognosis of brainstem tumor in children is poor, with a 5-year
survival rate of 30%. Most reported cases of brainstem tumor with CHS
were invariably fatal.2–4 Our patient is unique, in that
not only did he survive after tumor resection, but also there was
improvement in his CHS. The tumor was a low-grade pilocytic
astrocytoma, with an anatomic growth pattern similar to that of a
dorsally exophytic and cervicomedullary tumor, which has a better
prognosis.5 One of the presenting features in our case was
bradypnea, which improved after tumor resection. Irregular respiratory
pattern in a patient with a brainstem tumor had been reported
The detailed mechanism of CHS is largely unclear. For secondary causes
such as brainstem tumor, the extent of involvement of various
respiratory centers would be important in determining the
outcome. Our studies of cases of brainstem infarct suggest that
unilateral involvement of pontomedullary reticular formation and
nucleus ambiguous can result in loss of automatic respiration, and that
associated lesion of the nucleus tractus solitarus may lead to more
severe respiratory failure, involving both automatic and voluntary
responses.6 In our patient, the tumor compressed the
dorsum of upper medulla and the distal pons up to its mid-upper
portion. The reticular formation and the pneumotaxic center are usually
located just ventral to the floor of the fourth ventricle and may have
been affected. Surgical resection of the tumor resulted in
relief of compression.
Although there was significant improvement in his central alveolar
hypoventilation, as shown on polysomnography, we were unable to wean
this child off night ventilation. This could be a result of respiratory
muscle weakness and abnormal ciliary function due to his neurologic
complications. Another possible explanation is that although there was
significant improvement in his central hypoventilation, the recovery
was not complete.
In conclusion, we presented a unique case of brainstem pilocytic
astrocytoma with improvement in CHS following surgical debulking.
However, the long-term prognosis of this patient awaits further
follow-up. A more invasive method for long-term ventilation, with the
use of diaphragmatic pacing, is not without complications and should be
reserved for future consideration.
Abbreviations: CHS = central hypoventilation
syndrome; RDI = respiratory disturbance index
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