Corticospinal pathway and exercise hyperpnea: lessons from a patient with Arnold Chiari malformation

Ventilatory response to exercise does not evidence electroencephalographical respiratory‐related activation of the cortical premotor circuitry in healthy humans

“…Our study adds to the observation made by Haouzi et al (2000) in a patient suffering from an Arnold Chiari malformation. This patient was able to mobilize her vital capacity normally and to achieve expected levels of voluntary hyperventilation but lacked chemosensitivity (Haouzi et al 2000).…”

“…A cortical mechanism has also been proposed to account for the increase in ventilation that occurs during anticipation of exercise and at its very onset (Tobin et al 1986), where ventilation exceeds the actual exercise-related ventilatory demand. In line with this, in a patient suffering from an Arnold Chiari malformation who completely lacked a ventilatory response to carbon dioxide, Haouzi et al (2000) observed that the ventilatory response to exercise was profoundly abnormal inspite of an apparently normal voluntary control of breathing. For example, Fink et al (1995) observed increases in regional blood flow during exercise in areas associated with volitional breathing.…”

“…This suggests that the rate at which CO 2 leaves the tissues and is exchanged at the lungs during exercise is a major determinant of exercise-related hyperpnea (Haouzi et al 2004) and that, in contrast, cortical commands play a minor role. In line with this, in a patient suffering from an Arnold Chiari malformation who completely lacked a ventilatory response to carbon dioxide, Haouzi et al (2000) observed that the ventilatory response to exercise was profoundly abnormal inspite of an apparently normal voluntary control of breathing. Although this observation contrasted with the persistence of a ventilatory response to aerobic exercise observed in patients with Ondine's curse also lacking chemosensitivity (Shea et al 1993), Haouzi et al (2000) concluded that the corticospinal respiratory pathway did not play a major role in exercise-related ventilatory adaptation.…”

“…This patient was able to mobilize her vital capacity normally and to achieve expected levels of voluntary hyperventilation but lacked chemosensitivity (Haouzi et al 2000). Her ventilatory response to exercise was profoundly abnor-mal, leading Haouzi et al (2000) to infer that the corticospinal pathway to the respiratory muscles was not adequate to ensure ventilatory adaptation. This observation is, however, not sufficient to rule out cooperative mechanisms involving a suprapontine control.…”

“…Cerebral imaging studies have lent support to this concept. Although this observation contrasted with the persistence of a ventilatory response to aerobic exercise observed in patients with Ondine's curse also lacking chemosensitivity (Shea et al 1993), Haouzi et al (2000) concluded that the corticospinal respiratory pathway did not play a major role in exercise-related ventilatory adaptation. During imagined exercise, Thornton et al (2001) also described activation in areas of the brain that relate to voluntary breathing during imagined exercise under hypnosis.…”