A 52-year-old woman with a history of breast cancer presents with back pain. She has sensory loss below the nipple level, hyperreflexia, and weakness in the legs while arms are relatively normal. Where is the lesion?

• A. Thoracic spinal cord
• B. Lumbar spinal cord
• C. Cervical spinal cord
• D. Brainstem

Answer: (D)

A spinal cord problem at the thoracic level best fits this pattern. The nipple area corresponds to the T4 dermatome, so a sensory loss beginning below the nipple points to a lesion around T4. The legs show upper motor neuron signs (hyperreflexia and weakness) because the corticospinal tract is affected below the brain, while the arms are relatively normal since the cervical segments that control the arms are above or outside the lesion. A brainstem lesion would typically produce cranial nerve findings and a different distribution of deficits, not a clean sensory level at the trunk with sparing of the arms. In a patient with breast cancer and back pain, vertebral or epidural metastatic disease compressing the thoracic spinal cord is a common mechanism producing this exact pattern.