A 58-year-old man undergoes operative repair of a descending thoracic aortic aneurysm. There are no intraoperative complications, but postoperatively the patient is found to have new-onset neurologic deficits. Imaging of the brain is normal, but MRI of the lower thoracic spinal cord reveals ischemic infarct of the areas shown in the exhibit below: Lower extremity examination of this patient is most likely to show which of the following neurologic findings?

Question

A 58-year-old man undergoes operative repair of a descending thoracic aortic aneurysm. There are no intraoperative complications, but postoperatively the patient is found to have new-onset neurologic deficits. Imaging of the brain is normal, but MRI of the lower thoracic spinal cord reveals ischemic infarct of the areas shown in the exhibit below:

Lower extremity examination of this patient is most likely to show which of the following neurologic findings?

Quizplus · Accepted Answer

11ec160b_35c7_cae6_9249_9301937ab1e8_MD0001_00 This patient's thoracic aortic aneurysm repair has been complicated by ischemic injury to the anterior two-thirds of the spinal cord (SC). This area is perfused by the anterior spinal artery, which receives blood flow from segmental arteries (eg, intercostal arteries) arising off the thoracic aorta. Disruption of circulation to this area classically results in anterior cord syndrome, characterized by the following bilateral tract lesions and clinical signs: Spinothalamic tract (STT): loss of pain/temperature (lateral spinothalamic) and crude touch (anterior spinothalamic) sensation 1-2 levels below the lesion Anterior horn (lower motor neuron): flaccid paralysis and muscle atrophy at the level of the lesion Lateral corticospinal tract (CST) (upper motor neuron): paralysis below the level of the lesion. Flaccid paralysis from spinal shock (ie, temporary loss of all distal SC function) occurs initially, but upper motor neuron signs (eg, spasticity, hyperreflexia) subsequently develop over days to weeks As in this patient, the dorsal columns are typically spared (due to intact circulation from the posterior spinal arteries), preserving proprioceptive, vibratory, and light touch sensation below the level of the lesion. (Choice B) Complete loss of all lower extremity sensation (due to injury of the STTs and dorsal columns) and motor function (due to injury of the CSTs) may be seen in complete SC injury, as can occur in SC transection. (Choices C and E) An isolated defect of crude touch sensation or pain/temperature sensation could occur only with isolated injury to the anterior or lateral STT, respectively. Because the anterior spinal artery also supplies the tracts (eg, CSTs) surrounding the STTs, it is extremely uncommon to have bilateral injury to only the anterior or lateral STT. (Choice D) Diminished proprioception and motor function can occur with simultaneous injury to the dorsal columns and CSTs. A classic cause is subacute combined degeneration of the dorsal and lateral SC white matter, which is seen in vitamin B₁₂ deficiency. (Choice F) Selective loss of proprioceptive (along with vibratory and light touch) sensation occurs with isolated injury of the bilateral dorsal columns. A classic example is tabes dorsalis, a form of tertiary neurosyphilis that causes damage to the dorsal columns and dorsal nerve roots. Educational objective: Ischemia of the anterior two-thirds of the spinal cord can occur with disruption of the anterior spinal artery blood supply. The resulting anterior cord syndrome causes bilateral distal loss of pain, temperature, and crude touch sensation (from injury to the spinothalamic tracts) and paralysis (from injury to the lateral corticospinal tracts). __________ References: Incomplete cord syndromes: clinical and imaging review. (http://www.ncbi.nlm.nih.gov/pubmed/29995620) Spinal cord injury following thoracic and thoracoabdominal repairs. (http://www.ncbi.nlm.nih.gov/pubmed/25178467)

A 58-Year-Old Man Undergoes Operative Repair of a Descending Thoracic