Describe the dorsal-column–medial-lemniscus pathway and the spinothalamic tract in terms of modalities and crosses.

• A. Dorsal columns carry pain and temperature; cross in the brainstem to form the medial lemniscus; Spinothalamic carries fine touch, vibration, and proprioception; crosses in the spinal cord near entry.
• B. Dorsal columns carry crude touch; Spinothalamic carries proprioception; crosses in dorsal root.
• C. Dorsal columns carry fine touch, vibration, and proprioception; cross in medulla to form the medial lemniscus; Spinothalamic carries pain and temperature; crosses in the spinal cord near entry.
• D. Dorsal columns do not decussate; Spinothalamic pathways cross at the cortex.

Answer: (C)

Two main somatosensory highways differ in what they carry and where they cross. The dorsal column–medial lemniscus pathway handles fine touch, vibration, and proprioception. Its fibers run up the same side through the dorsal columns, then cross in the medulla to form the medial lemniscus, which carries the signal upward to the thalamus and then the cortex.

The spinothalamic tract carries pain and temperature. Its fibers enter the spinal cord and immediately cross to the opposite side at or near the level of entry (via the anterior white commissure), then ascend in the anterolateral system to the thalamus and onward to the cortex.