A 58-year-old man reports unsteadiness walking in dim light. Examination shows impaired vibration and joint position sense in the feet, absent ankle jerks, and a positive Romberg sign that worsens when the eyes close. Hemoglobin is low with an MCV of 108 fL. The gait abnormality results from involvement of:
- A Dorsal columns of the cervical and thoracic cord ✓
- B Spinocerebellar tracts bilaterally
- C Lateral spinothalamic tracts bilaterally
- D Ventral horns of the lumbar cord
Correct answer: A. Dorsal columns of the cervical and thoracic cord
Explanation
The macrocytic anemia points to vitamin A12 deficiency causing subacute combined degeneration, which damages the dorsal columns and lateral corticospinal tracts. Loss of conscious proprioception produces a sensory ataxia that is compensated by vision and exposed when the eyes close, giving the positive Romberg sign. The spinothalamic tracts carry pain and temperature and are spared, and the pattern is not primarily cerebellar.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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