A 56-year-old man with a prolonged history of hypertension and medication nonadherence comes to the emergency department with abrupt-onset, severe, tearing back pain. Blood pressure is 240/130 mm Hg, and CT angiography reveals descending aortic dissection originating at the left subclavian artery takeoff and extending to the iliac arteries. Intravenous infusion of labetalol and nitroprusside are initiated, and the patient is admitted for further management. In the intensive care unit, the patient states that the pain has improved, but he is unable to move the lower extremities. Blood pressure is now 110/60 mm Hg, and pulse is 56/min. Physical examination shows normal heart and lung sounds and a distended urinary bladder. Neurological examination shows normal cranial nerves and upper extremity examination. There is weakness of bilateral lower extremities with decreased deep tendon reflexes. The patient is unable to sense crude touch and pain in the lower extremities, but vibration sensation is intact. Which of the following is the most likely cause of this patient's current neurological findings?

Question

A 56-year-old man with a prolonged history of hypertension and medication nonadherence comes to the emergency department with abrupt-onset, severe, tearing back pain.  Blood pressure is 240/130 mm Hg, and CT angiography reveals descending aortic dissection originating at the left subclavian artery takeoff and extending to the iliac arteries.  Intravenous infusion of labetalol and nitroprusside are initiated, and the patient is admitted for further management.  In the intensive care unit, the patient states that the pain has improved, but he is unable to move the lower extremities.  Blood pressure is now 110/60 mm Hg, and pulse is 56/min.  Physical examination shows normal heart and lung sounds and a distended urinary bladder.  Neurological examination shows normal cranial nerves and upper extremity examination.  There is weakness of bilateral lower extremities with decreased deep tendon reflexes.  The patient is unable to sense crude touch and pain in the lower extremities, but vibration sensation is intact.  Which of the following is the most likely cause of this patient's current neurological findings?

Quizplus · Accepted Answer

11ec25c8_d535_ea67_bc81_e3920fab5984_MD0003_00 This patient with abrupt-onset, severe, tearing chest pain has a descending aortic dissection (type B) extending from the subclavian to the iliac vessels. He subsequently developed urinary retention and lower extremity paresis, crude touch/pain sensation loss, and diminished reflexes, raising strong suspicion for thoracic spinal cord ischemia, a rare (2%-3%) complication of aortic dissection due to interruption of the intercostal and/or lumbar arteries (off the aorta) that feed the anterior spinal cord. Risk of anterior spinal cord ischemia is greatest at the T10-T12 levels, where blood flow is lowest. Patients generally develop bladder paresis (eg, urinary retention), motor paresis of the lower extremities, loss of crude touch/pain sensation (carried in anterior/lateral spinothalamic tracts), and diminished reflexes (reflexes are increased after days or weeks but are diminished initially). Because the posterior spinal cord receives some blood flow from the intact posterior spinal arteries (arising off the vertebral/posterior inferior cerebellar artery), the dorsal column of the spinal cord (eg, vibration sensation, proprioception) is generally preserved. In addition, spinal levels above the thoracic lesion (eg, upper extremities) will be intact. (Choice A) Carotid artery occlusion generally presents with acute stroke; patients usually have unilateral (not bilateral) motor symptoms, and bladder dysfunction would be atypical. (Choice B) Compressive lumbar myelopathy can occur as a consequence of lumbar stenosis and generally presents with back pain and lower extremity weakness and sensory loss that is exacerbated by activity and relieved with rest (pseudoclaudication). This patient's lower extremity neurologic symptoms shortly after descending aortic dissection make thoracic ischemia far more likely. (Choice C) Global cerebral hypoperfusion causes confusion, loss of vision, and diffuse/nonfocal neurologic manifestations (eg, in both the upper and lower extremities). (Choice E) Aortic dissections involving the ascending aorta (type A) can result in vertebral artery dissection, which usually causes neck pain, ischemic stroke, and headache. Patients can also develop posterior spinal cord ischemia, which usually presents with loss of proprioception/vibration sensation below the level of the lesion and mild/minimal weakness. type A Educational objective: Descending (type B) aortic dissections can be associated with interruption of blood flow to the anterior spinal cord, leading to anterior spinal cord ischemia (particularly in the lower thoracic levels). Patients generally develop acute bladder paralysis, lower extremity paresis, crude touch/pain sensation loss, and diminished reflexes (initially). Vibrioception and deep touch sensation are generally preserved because these are carried in the posterior columns and receive some blood flow from the intact posterior spinal arteries.

A 56-Year-Old Man with a Prolonged History of Hypertension and Medication