The tectospinal tract arises from the superior colliculus and mediates reflex head and neck movements in response to visual and auditory stimuli. At which precise anatomical point does this tract decussate?

• A Superior cerebellar peduncle decussation at the level of the inferior colliculus
• B Ventral tegmental decussation at the level of the red nucleus
• C Pyramidal decussation at the spinomedullary junction
• D Dorsal tegmental decussation in the midbrain, just inferior to the inferior colliculus ✓

Explanation

The tectospinal tract decussates in the dorsal tegmental decussation (of Meeter) in the midbrain, just inferior to the inferior colliculus, then descends in the contralateral medial longitudinal fasciculus and ventral funiculus to terminate at cervical spinal levels. Option C is the pyramidal (corticospinal) decussation and is the strongest distractor as both are descending motor tracts. The superior cerebellar peduncle decussation (option A) carries dentatorubral and dentatothalamic fibres, not tectospinal fibres.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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