Respiratory control and respiratory sensation in a patient with a ganglioglioma within the dorsocaudal brain stem

We encountered a young woman with severe central sleep apnea caused by a medullary glioma located slightly dorsal to and to the right of the midline, a region not generally associated with CO2 chemosensitivity. The patient had normal spirometric readings, lung volumes, diffusing capacity, maximal inspiratory pressure, and alveolar-arterial oxygen difference. While awake, she displayed marked irregularity in her breathing pattern; her end-tidal CO2 (FETCO2) ranged from 5.3 to 10.9%. During voluntary hyperpnea, she could quickly reduce her FETCO2 to 4.2%, but her PCO2 did not change after administration of acetazolamide or progesterone. Like patients with congenital central hypoventilation syndrome (CCHS), our patient had a relatively intact ventilatory response to exercise; her PCO2 was high at the start of exercise and increased slightly thereafter. In contrast to CCHS patients, however, our patient had an intact hypoxic ventilatory response (Delta VE/Delta Sa(O2) = -0.37 L/min/Sa(O2)). In further contrast to CCHS patients, our patient had a very short breathholding time and described a sensation of air hunger as the factor limiting her breathholding ability. Her heart rate and blood pressure responses to the Valsalva maneuver were normal.