In syringomyelia, the syrinx cavity expands within the central spinal cord, first destroying which fiber type, producing the characteristic clinical pattern?

• A Dorsal column fibers → bilateral loss of proprioception and vibration
• B Corticospinal tract fibers → bilateral spastic paraparesis
• C Anterior horn cells → bilateral flaccid weakness of upper and lower limbs simultaneously
• D Pain and temperature fibers decussating in the anterior white commissure → bilateral cape distribution hemianalgesia with preserved proprioception ✓

Explanation

The syrinx cavity begins centrally, first disrupting the decussating spinothalamic (pain and temperature) fibers crossing through the anterior white commissure. Since these fibers cross 1–2 segments above entry and span multiple cord segments, their bilateral destruction produces a cape-like (suspended) pattern of bilateral loss of pain and temperature over the upper back, shoulders, and arms, while dorsal column proprioception is initially spared — this dissociated sensory loss is the hallmark. As the cavity enlarges, it later involves anterior horn cells (wasting), corticospinal tracts (spasticity), and eventually all modalities. Dorsal column loss would not be the first finding.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.