Use of neck torsion as a specific test of neck related postural instability.

BACKGROUND: Disturbed postural stability in neck pain (NP) is likely due to abnormal cervical afferent function. Several potential causes requires specific diagnostic tests. The neck torsion (head still body rotated) manoeuvre stimulates cervical but not vestibular receptors and identified abnormal cervical afferent input as the cause in patients with NP compared to healthy controls. Comparison between vestibular and NP subjects is now needed.

AIMS: To compare individuals with unilateral vestibular loss (UVL), persistent NP and asymptomatic controls. It was hypothesized that neck torsion will increase postural stability in NP compared to both the asymptomatic and UVL groups.

METHODS: Twenty UVL, 20 persistent NP and 20 asymptomatic control subjects underwent measurement of postural stability on a computerised force plate with eyes closed in comfortable stance under 5 conditions: neutral head, head rotated 45° (left and right) and neck torsion (left and right). Root mean square (rms) amplitude of sway was measured in the anterior posterior (AP) and medial lateral (ML) directions. Average torsion and torsion difference (average torsion - neutral neck) were calculated.

RESULTS: NP subjects had significantly greater (p < 0.05) AP sway with average torsion and torsion difference compared to both control and UVL. There were no significant differences between control and UVL and no between group differences for neutral neck, rotation or rotation difference.

CONCLUSION: The results of the study suggest that the torsion manouever may identify cervical afferent causes of disturbed postural stability. This is important for guiding assessment and management of balance disturbances in patients.