The spinothalamic tract (anterolateral system) carries pain and temperature. A patient reports loss of pain sensation in the left arm and right leg simultaneously. Where is the most likely lesion?

• A Central spinal cord lesion at the cervical level damaging decussating spinothalamic fibers bilaterally ✓
• B Right anterolateral spinal cord (Brown-Séquard variant with bilateral pattern suggesting central cord)
• C Left thalamus (VPL nucleus) affecting crossed spinothalamic input
• D Left posterior column affecting the medial lemniscus

Explanation

Spinothalamic fibers cross within 1–2 segments of entry in the anterior commissure of the spinal cord. A central cord lesion (e.g., syringomyelia at the cervical level) destroys these crossing fibers bilaterally, producing a cape-like or suspended pattern of bilateral pain/temperature loss affecting cervical dermatomal levels (arms), while sparing fibers already crossed at thoracic/lumbar levels (legs may be less affected). This crossed bilateral deficit at the same level is the hallmark of central cord pathology.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.