Automatic breathing is brainstem driven; voluntary breathing bypasses it through corticospinal tracts
Expansion
Breathing is driven by two anatomically distinct systems:
- Automatic: generated in the medulla, descending in the ventrolateral spinal cord
- Voluntary: from the motor cortex, descending in the corticospinal tracts
Because they are separate, one can fail while the other is intact.
Central hypoventilation (Ondine’s curse) is failure of the automatic system. Patients breathe adequately when awake, using cortical drive, but hypoventilate or become apnoeic when asleep, when cortical input is withdrawn.
Causes include the congenital form, associated with PHOX2B mutations and with Hirschsprung disease, and acquired damage to the medulla from stroke, surgery, syringobulbia or trauma.
The mirror image also exists: a high cervical cord lesion interrupting the corticospinal tracts but sparing the automatic pathway leaves a patient breathing automatically but unable to breathe or hold the breath voluntarily.
Management of central hypoventilation is nocturnal ventilatory support, or diaphragmatic pacing.