Hypothesis: the etiology of midcervical quadriplegia after operation with the patient in the sitting position.

A hypothesis of the pathophysiology of midcervical quadriplegia after posterior fossa operation with the patient in the sitting position under general anesthesia is presented. Observations and experimental evidence are presented to support the theory that stretch of the cervical spinal cord associated with neck flexion may be sufficient to impair the autoregulation of spinal cord blood flow enough so that the reduced, but otherwise acceptable, hemodynamic parameters associated with general anesthesia in the sitting position contribute to the risk of spinal cord infarction.