Vertigo
Dizziness and vertigo account for over 8 million primary care visits in the US each year. Dizziness is the leading presenting complaint for seniors over age 75. (1,2) Disequilibrium may arise from one or multiple anatomical structures. "Central" origins include the brain stem, cerebellum, or other supratentorial structures (or the vasculature supplying those tissues). "Peripheral" origins include: the vestibular, visual, and spinal proprioceptive systems. (3)
The cervical spine plays a critical role in the maintenance of balance. (4-7) In fact, Guyton states that the cervical spine is the most essential contributor toward equilibrium. (7) The term "cervicogenic vertigo", first described in 1955 by Ryan and Cope, describes dizziness or disequilibrium originating from abnormal proprioceptive activity in the cervical spine. (9,10)
Although the exact mechanism of cervicogenic vertigo is debatable, most researchers ascribe to an altered "mechanoreceptive" theory. The upper cervical (C0-3) facet joints are highly innervated, supplying up to 50% of all cervical proprioceptive input. (11,83) The cervical spine muscles, particularly the suboccipital muscles, are extensively supplied with muscle spindles providing additional contributions. (12,81,82) Patients with cervicogenic vertigo frequently exhibit muscle hypertonicity, limited upper cervical ROM, and joint position errors. (84) The abnormal stimulation of the articular capsule and/ or muscular spindle mechanical receptors provides conflicting input with visual and vestibular afferents. This sensory mismatch between visual, vestibular, and cervical mechanoreceptive input "confuses" the brain into a temporary state of dizziness. (11,13-18,78)
Other hypothetical models for cerviogenic vertigo include vascular compression and vasomotor changes secondary to irritation of the cervical sympathetic chain (16,17), or stimulation of sympathetic nerve fibers within the ligamentum flavum. (85)
Cervical spine proprioception may be affected by conditions that alter mechanoreceptive input including: degeneration, inflammation, joint dysfunction, disc lesion, muscle hypertonicity or trauma. (9,14,19-21) Dizziness frequently accompanies whiplash injury (22-24). Research suggests that between 25 and 80% of patients who suffer a whiplash injury will experience late onset dizziness, vertigo, or disequilibrium. (22,25,27,28) There is generally a temporal relationship between cervical spine injury and the onset of vertigo, although symptoms may be delayed from days to months. (21,29) Stress and anxiety are thought to be compounding factors for dizziness, as these conditions may increase muscle tone and sympathetic firing rates. (30,31)