OBJECTIVE The phenomenon of delayed neurological deficit after thoracoabdominal aortic aneurysm repair was first reported in the late 1980s. The mechanism may be reduced collateral circulation during periods of hypotension, cord edema, or reperfusion injury. Few patients with delayed-onset neurological deficit have recovered from this devastating complication. The experience with six patients treated with lumbar cerebrospinal fluid (CSF) drainage is reported. METHODS Five patients underwent thoracoabdominal aortic aneurysm repair. Before and immediately after the operation, the patients exhibited no abnormalities in motor or sensory function. Patients presented between 12 and 40 hours postoperatively with rapid motor and sensory loss in their lower extremities. Hypotensive events immediately preceded the onset of deficit in five patients. The sixth patient experienced an acute onset of back pain and was found to have thrombus without evidence of dissection in the descending aorta. RESULTS Patients were treated with volume expansion and vasoactive drugs to achieve a mean arterial pressure of more than 70 mm Hg. Lumbar CSF drainage was instituted promptly in four patients; all displayed marked neurological improvement. Two patients underwent CSF drainage several hours after the onset of symptoms and did not improve. The duration of CSF drainage ranged from 15 to 72 hours, with a goal of maintaining the lumbar CSF pressure at less than 10 mm Hg. CONCLUSIONS The efficacy of CSF drainage may relate to reducing CSF pressure, which may increase spinal cord perfusion. Rapid initiation of CSF drainage with aggressive support of blood pressure may result in neurological improvement in some patients.