Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 5, 2011, pp. 782-783

Neurology India, Vol. 59, No. 5, September-October, 2011, pp. 782-783

Letter to Editor

Central neurogenic hyperventilation due to pontine glioma

DJ Van Wamelen¹, A Dara Hama-Amin², HJ Gilhuis³, S. F. T. M. De Bruijn²

¹ Department of Neurology, Leiden University Medical Center, Leiden, Netherlands
² Department of Neurology, Haga Hospital, The Hague, Netherlands
³ Department of Neurology, Reinier de Graaf Hospital, Delft, Netherlands
Correspondence Address: H J Gilhuis, Department of Neurology, Reinier de Graaf Hospital, Delft, Netherlands, gilhuis@rdgg.nl

Date of Submission: 21-Jun-2011
Date of Decision: 22-Jun-2011
Date of Acceptance: 22-Jun-2011

Code Number: ni11240

PMID: 22019680

DOI: 10.4103/0028-3886.86573

Sir,

A 29-year-old otherwise healthy man presented with hyperventilation of at least 6 weeks duration. He also complained of weakness of right arm and leg and persistent occipital headache. The leg weakness used to worsen on walking. On examination, blood pressure was 130/80 mmHg, heart rate 75/min and respiratory rate 28 breaths/min and no dyspnea. Neurologic examination revealed mild right paresis and diminished touch sensation and right extensor plantar response. Gait was slightly wide-based. Arterial blood gas revealed a respiratory alkalosis with pH. 7.50, PCO ₂ 2.7 kPa (20.3 mmHg), HCO ₃ 16 mmol/L, PO ₂ 17.0 kPa (128 mmHg), and SaO ₂ 99%. Posteroanterior and lateral chest radiographies and an electrocardiogram, as well as routine blood tests, showed no abnormalities. T2-weighted and gadolinium-enhanced magnetic resonance imaging (MRI) showed a low-grade glioma of 3.2 × 2.6 × 1.8 cm in the ventrocaudal pons and rostral medulla oblongata [Figure - 1]a and b. With this clinical and laboratory findings the diagnosis of central neurogenic hyperventilation (CNH) was made.

CNH in conscious patients, defined as the presence of hyperventilation with low arterial PaCO ₂ , high arterial PaO ₂ , and high arterial pH, persisting during sleep and not due to drug-induced or metabolic causes, is a very rare disorder. ^[1] Nearly all cases are due to brainstem malignancies, but other causes include bilateral medial thalamic infarction and multiple sclerosis lesions in the brainstem. ^[2],[3] The mechanisms of CNH is thought to be due to disconnection between pontine and medullary respiratory centers leading to unopposed stimulation of the latter or from acidosis due to lactate production by the tumor mass, activating brainstem chemosensitive respiratory neurons. ^[1] Although a reduction in respiratory rate in CNH has been achieved by opioid and fentanyl administration, only aggressive treatment, such as radiation or excision of tumor mass, seems to bring about complete remission of CNH. ^[4],[5],[6]

Our patient was treated with dexamethasone 4 mg four times a day and cranial radiation in dose of 33 times 1.8 Gy, resulting in complete remission of neurologic deficits, including hyperventilation. An arterial blood gas performed after cranial radiation revealed a pH. of 7.47, PCO ₂ 4.7 kPa (35 mmHg), HCO ₃ 25 mmol/L, PO ₂ 11.3 mmol/L (85 mmHg), and SaO ₂ 98%, values within the normal range. Repeated cerebral MRI showed reduction of pontine tumor mass to 2.0 × 1.8 × 1.6 cm, without significant uptake of gadolinium. He has remained symptom-free during a follow-up at 3 months, after which he returned to his home country. In conclusion, we suggest in case of unexplained hyperventilation, the diagnosis of a brainstem malignancy should be considered.

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