Oculomotor disorders, such as ophthalmoplegia with diplopia, may be a source of spatial disorientation and brief sensations of vertigo, mild nausea, and staggering. These symptoms are maximal when the patient looks in the direction of action of the paralyzed muscle; it is attributable to the receipt of two conflicting visual images. Some normal persons may experience such symptoms for brief periods when first adjusting to bifocal glasses.
In a peculiar symptom called the Tullio phenomenon, a loud sound, or yawning, produces a brief sensation of vertigo or tilting of the environment. Some patients with this symptom are found to have an absence or thinning of the bony roof of the superior semicircular canal, which can be detected by thin (1 mm) slice CT. This disorder (Llyod Minor syndrome) is a form of perilymphatic fistula caused by a spontaneous or traumatic dehiscence of the bone of the superior canal. Occasionally, patients with Ménière disease report this symptom.
Other causes of dizziness are more difficult for the physician and patient to define. In severe anemic states, particularly pernicious anemia, and in aortic stenosis, easy fatigability and languor may be attended by light-headedness, related particularly to postural change and exertion. In the emphysematous patient, physical effort may be associated with weakness and peculiar cephalic sensations, and violent paroxysms of coughing may lead to giddiness and even fainting (tussive syncope) because of impaired venous return to the heart. The dizziness that often accompanies acute hypertension is difficult to evaluate; sometimes it is an expression of anxiety, or it may conceivably be the result of an unstable adjustment of cerebral blood flow. It is doubtful that chronic hypertension causes dizziness, although many of the medications for its treatment certainly can cause the symptom.
Postural nonvertiginous dizziness is another state in which inadequate vasomotor reflexes prevent a constant cerebral circulation; it is notably frequent in persons with orthostatic hypotension of any cause, for example, in those taking antihypertensive drugs, as well as in patients with a polyneuropathy that has an autonomic component. Such persons, on rising abruptly from a recumbent or sitting position, experience a swaying type of dizziness, dimming of vision, and spots before the eyes that last for several seconds. The patient is forced to stand still and steady himself by holding onto a nearby object. Occasionally, a syncopal attack may occur at this time (see Chap. 18). Hypoglycemia gives rise to yet another form of dizziness, marked by a sense of hunger and attended by trembling, sweating, and other autonomic symptoms. Drug intoxication—particularly with alcohol, sedatives, and antiepileptic drugs—may induce a nonspecific dizziness and, at advanced stages of intoxication, true vertigo.
In practice, it may nonetheless be difficult to separate these types of dizziness from vertigo, for there may, or may not be, feelings of rotation, impulsion, up-and-down movement, oscillopsia, or other disturbance of motion. The ancillary symptoms of true vertigo—namely, nausea, vomiting, tinnitus and deafness, staggering, and the relief obtained by sitting or lying still—are also absent. Furthermore, it is not an uncommon circumstance to find more than one type of dizziness in an individual who is carefully tested.
The Neurologic and Otologic Causes of Vertigo