Biemond and DeJong described a kind of nystagmus and vertigo originating in the upper cervical roots and the muscles and ligaments that they innervate (so-called cervical vertigo). Spasm of the cervical muscles, trauma to the neck, and irritation of the upper cervical sensory roots were said to produce asymmetrical spinovestibular stimulation and thus to evoke nystagmus, prolonged vertigo, and disequilibrium. Toole and Tucker demonstrated a reduced flow through these vessels (in cadavers) when the head was rotated or hyperextended. In our view, the existence of “cervical vertigo,” or at least these interpretations of it, is open to question. However, we acknowledge having encountered patients with cervical dystonia who describe something akin to vertigo, and this may speak to a relationship between cervical proprioceptors and vertigo.
Causes of vertigo other than Ménière disease that originate in the vestibular nerve are discussed further on.
In summary, for all practical purposes, vertigo indicates a disorder of the vestibular end organs, the vestibular division of the eighth nerve, or the vestibular nuclei in the brainstem and their immediate connections, including the inferior cerebellum. Although lesions of the cerebral cortex, eyes, and perhaps the cervical muscles may give rise to vertigo, they are not common sources of the symptom, and vertigo is rarely the dominant manifestation of disease in these structures. The clinical problem resolves by deciding which portion of the labyrinthine–vestibular apparatus is involved. Usually this determination can be made on the basis of the form of the vertiginous attack, the nature of the ancillary symptoms and signs, and tests of labyrinthine function. These tests are described below, followed by a description of the common labyrinthine– vestibular syndromes.
Tests of Labyrinthine Function
The most rudimentary test of labyrinthine function is simply to have the patient shake his head from side-to-side in an attempt to elicit symptoms that simulate the dizziness that has been described and to observe the degree of postural instability during this maneuver. Falling and marked intensification of the dizziness is almost always an indication of labyrinthine disease. Also, nystagmus may be evoked, indicating a vestibular instability. More informative in identifying a diseased labyrinth is the “rapid head impulse” test, which is conducted by asking the patient to fixate on a target and then for the examiner to rotate the patient’s head quickly by 10 degrees (an explanation must be given to encourage the patient to relax the neck muscles and remain focused on the fixation point). The eyes are observed for a slippage from the target; this is most evident by a quick saccadic return to the point of focus. Ocular instability is observed when the patient turns his head toward the side of the affected labyrinth. This use of the vestibuloocular reflex is said by Halmagyi and Crener to be among the most dependable bedside tests of labyrinthine function.
Maneuvers designed to elicit positional vertigo by rapidly changing from a seated to a supine position with the head turned to one side bring about vertigo in a number of conditions but are specifically intended to detect benign positional vertigo and are described further on.
A number of other interesting but less well validated tests that bring out instabilities in station and gait may be used to supplement the conventional tests for vestibular dysfunction. The Unterberger-Fukuda maneuver requires the patient to march in place with eyes closed and arms outstretched. Normally, less than 15 degrees or so of rotation is displayed; asymmetry of labyrinthine function is manifest as excessive rotation away from the diseased side. A related test involves having the patient walk around a chair with eyes closed; an increasing or decreasing radius is indicative of an imbalance between the two sides of the labyrinthine apparatus. Both of these tests, however, often show abnormalities with cerebellar disease as well, in which the patient veers to the affected side. The sensitivity of maneuvers such as these has been questioned. We can only comment that they seem in our experience to demonstrate vestibulocerebellar lesions.