A 69-year-old man is evaluated shortly after undergoing elective surgical repair of a descending thoracic aortic aneurysm. He has weakness in both lower extremities and urinary retention, which were not present before the procedure. The surgery was complicated by significant blood loss requiring multiple transfusions. The patient has a history of osteoarthritis, hypertension, hyperlipidemia, type 2 diabetes mellitus, and coronary artery disease. He also has 70% stenosis of his right carotid artery. Neurologic examination shows flaccid paralysis and loss of pain sensation in the lower extremities; vibratory sensation is intact. Upper extremity examination reveals no abnormalities. Which of the following is the most likely cause of this patient's neurologic dysfunction?

Question

A 69-year-old man is evaluated shortly after undergoing elective surgical repair of a descending thoracic aortic aneurysm.  He has weakness in both lower extremities and urinary retention, which were not present before the procedure.  The surgery was complicated by significant blood loss requiring multiple transfusions.  The patient has a history of osteoarthritis, hypertension, hyperlipidemia, type 2 diabetes mellitus, and coronary artery disease.  He also has 70% stenosis of his right carotid artery.  Neurologic examination shows flaccid paralysis and loss of pain sensation in the lower extremities; vibratory sensation is intact.  Upper extremity examination reveals no abnormalities.  Which of the following is the most likely cause of this patient's neurologic dysfunction?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d591_032b_bc81_8bcfa0e3a0b3_MD0003_00 Spinal cord (SC) ischemia is a devastating but not uncommon (~5%-15%) complication of thoracic aortic aneurysm (TAA) repair. TAA repair can disrupt SC blood flow: Aortic cross-clamping causes temporary SC hypoperfusion, and vascular graft placement (to recreate the luminal wall) can disrupt segmental arteries arising from the aorta. Because the anterior spinal artery relies on blood supply from these segmental arteries, the SC territory that it supplies-the anterior two-thirds of the SC-is particularly susceptible to ischemic infarct. segmental arteries Infarction of the anterior SC results in anterior cord syndrome, with the following findings distal to the lesion: Bilateral paralysis from damage to the lateral corticospinal tracts and anterior horn cells Loss of pain/temperature and crude touch sensation from damage to the lateral and anterior spinothalamic tracts Urinary retention from damage to the descending autonomic tracts involved in bladder control In contrast, the posterior spinal arteries, which arise off the vertebral/posterior inferior cerebellar artery, are intact and maintain perfusion to the posterior SC. Therefore, vibratory, proprioceptive, and light touch sensation (conveyed by the dorsal columns) are typically preserved. Although flaccid paralysis due to spinal shock (ie, temporary loss of all distal SC function) occurs initially, upper motor neuron signs such as spasticity and hyperreflexia subsequently develop over days to weeks. (Choice A) Neck hyperextension (eg, during intubation) in the setting of cervical spondylosis (ie, degenerative changes in the spine) classically causes central cord syndrome, characterized by disproportionately greater motor impairment in the upper extremities compared with the lower extremities. central cord syndrome (Choice B) SC compression from a spinal epidural hematoma can cause lower extremity motor and sensory deficits. However, epidural hematomas more commonly complicate procedures involving puncture of the spinal dura and are not a common complication of TAA repair. (Choice C) Intraoperative hypoperfusion in the setting of right carotid artery atherosclerosis can cause a cortical stroke. However, this typically presents with unilateral, contralateral neurologic deficits rather than bilateral deficits. (Choice D) Lumbar plexopathy, a peripheral neuropathy involving multiple adjacent nerve roots, can cause lower extremity weakness and diminished sensation. However, findings are typically asymmetric and focal (eg, unilateral footdrop) rather than symmetric and diffuse (eg, bilateral flaccid paralysis), and both pain/temperature and vibratory/proprioceptive sensation are affected. Educational objective: Thoracic aortic aneurysm repair can cause spinal cord ischemia, especially of the anterior cord. Anterior cord syndrome typically presents with distal, bilateral flaccid paralysis; loss of pain/temperature and crude touch sensation; and urinary retention. References: Spinal cord injury following thoracic and thoracoabdominal aortic repairs. (http://www.ncbi.nlm.nih.gov/pubmed/25178467) Incomplete cord syndromes: clinical and imaging review. (http://www.ncbi.nlm.nih.gov/pubmed/29995620)

A 69-Year-Old Man Is Evaluated Shortly After Undergoing Elective Surgical