Review Question - QID 106882

The patient has injured his left corticospinal tract (left-sided motor function sense), left dorsal columns (left-sided vibration and position sense), and left spinothalamic tract (right-sided pain and temperature loss), consistent with a left-sided Brown-Sequard syndrome.

Knowing where different sensory and motor tracts cross the midline is important for localization of different spinal cord lesions. The corticospinal tract, which carries efferent motor nerves from the brain, crosses in the pyramidal decussation in the caudal medulla. Therefore, a corticospinal tract lesion distal to the decussation will yield ipsilateral weakness. The afferent nerves in the dorsal columns also cross in the medulla, and therefore a lesion below the brainstem will cause ipsilateral loss of vibration and position below the lesion. In contrast, afferent nerves from the spinothalamic tract cross within 1-2 spinal cord levels and travel to the cortex on the contralateral side. Therefore, a lesion below the brainstem causes contralateral loss of pain and temperature.

Illustration A depicts spinal cord cross-sections in central cord syndrome (syringomelia), anterior cord syndrome, and a left-sided Brown-Sequard Syndrome. Illustration B is a chart of causes and symptoms of different spinal cord syndromes. Illustration C is an MRI of a patient with a syrinx, likely to cause central cord syndrome.

Incorrect Answer:
Answer 2: This lesion would produce right-sided weakness and loss of vibration and position sensation, and left sided loss of pain and temperature sensation.
Answer 3: This lesion would produce bilateral motor weakness and loss of pain and temperature sensation, with preserved vibration and position sensation.
Answer 4: This lesion would produce isolated, bilateral loss of vibration and position sense.
Answer 5: This lesion produces bilateral weakness (upper extremities > lower extremities), with possible associated loss of vibration and position sensation, but typically spares the dorsal columns.