A patient with a spinal cord injury at C5 is examined 6 months later. The injury is complete (no motor or sensory function below C5). Which reflex would you EXPECT to be PRESENT below the level of the lesion?

• A Superficial abdominal reflex (T8–T12)
• B Knee jerk (patellar tendon reflex) — L3/L4 ✓
• C Cremasteric reflex (L1–L2)
• D Plantar flexion (normal) on plantar stimulation

Explanation

After spinal cord transection and resolution of spinal shock, deep tendon reflexes (DTRs) below the lesion are exaggerated (hyperreflexia) because the reflex arc is intact but is released from descending upper motor neuron inhibition. The knee jerk (L3/L4 arc) is below C5 and will be hyperreflexic. Superficial reflexes (abdominal, cremasteric) require intact corticospinal tracts and are ABSENT in UMN lesions. Plantar stimulation below a UMN lesion produces the Babinski sign (extension/dorsiflexion of the hallux), not normal plantar flexion.

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

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Written and medically reviewed by the StethoPrep medical team.