Altered afferent input from the cervical spine is associated with impairment on which test?

• A. Gaze stabilization
• B. Saccadic eye movement test
• C. Smooth pursuit neck torsion test
• D. Balance test

Answer: (C)

Altered signals from the cervical spine disrupt how neck proprioception is integrated with visual and vestibular input to guide eye movements. The smooth pursuit neck torsion test specifically challenges this cervico-ocular coupling by having you track a moving target while the neck is rotated. When cervical afferents are altered, smooth pursuit becomes unstable during neck torsion—pursuit gain drops and corrective saccades appear—revealing the impact of neck input on eye tracking. Gaze stabilization mainly reflects the vestibulo-ocular reflex with head movement, not the neck proprioceptive contribution tested here. Saccadic eye movements rely on rapid shifts driven by brainstem and cortical control, not on ongoing cervical input. A balance test assesses postural control and multisensory integration at the level of stance rather than oculomotor tracking influenced by neck afferents. So this test best detects impairment from altered cervical afferent input.