Chapter 022. Dizziness and Vertigo (Part 4) doc

Chapter 022. Dizziness and Vertigo
(Part 4)

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In Ménière's disease, the direction of the fast phase is variableVertigo may
be a manifestation of a migraine aura (Chap. 15), but some patients with migraine
have episodes of vertigo unassociated with their headaches. Antimigrainous
treatment should be considered in such patients with otherwise enigmatic
vertiginous episodes.
Vestibular epilepsy, vertigo secondary to temporal lobe epileptic activity, is
rare and almost always intermixed with other epileptic
manifestations.Psychogenic Vertigo
This is sometimes called phobic postural vertigo and is usually a
concomitant of panic attacks (Chap. 386) or agoraphobia (fear of large open
spaces, crowds, or leaving the safety of home).
It should be suspected in patients so "incapacitated" by their symptoms that
they adopt a prolonged housebound status. Most patients with organic vertigo
attempt to function despite their discomfort. Organic vertigo is accompanied by
nystagmus; a psychogenic etiology is almost certain when nystagmus is absent
during a vertiginous episode. The symptoms often develop after an episode of
acute labyrinthine dysfunction.

Miscellaneous Head Sensations
This designation is used, primarily for purposes of initial classification, to
describe dizziness that is neither faintness nor vertigo. Cephalic ischemia or
vestibular dysfunction may be of such low intensity that the usual
symptomatology is not clearly identified.
For example, a small decrease in blood pressure or a slight vestibular
imbalance may cause sensations different from distinct faintness or vertigo but
that may be identified properly by provocative testing techniques (see below).
Other causes of dizziness in this category are hyperventilation syndrome,

hypoglycemia, and the somatic symptoms of a clinical depression; these patients
should all have normal neurologic examinations and vestibular function tests.
Depressed patients often insist that the depression is "secondary" to the dizziness.


Approach to the Patient: Dizziness and Vertigo

The most important diagnostic tool is a detailed history focused on the
meaning of "dizziness" to the patient. Is it faintness (presyncope)? Is there a
sensation of spinning?
If either of these is affirmed and the neurologic examination is normal,
appropriate investigations for the multiple causes of cephalic ischemia, presyncope
(Chap. 21), or vestibular dysfunction are undertaken.
When the meaning of "dizziness" is uncertain, provocative tests may be
helpful. These office procedures simulate either cephalic ischemia or vestibular
dysfunction.
Cephalic ischemia is obvious if the dizziness is duplicated during
maneuvers that produce orthostatic hypotension. Further provocation involves the
Valsalva maneuver, which decreases cerebral blood flow and should reproduce
ischemic symptoms.
Hyperventilation is the cause of dizziness in many anxious individuals;
tingling of the hands and face may be absent. Forced hyperventilation for 1 min is
indicated for patients with enigmatic dizziness and normal neurologic
examinations.
The simplest provocative test for vestibular dysfunction is rapid rotation
and abrupt cessation of movement in a swivel chair. This always induces vertigo
that the patients can compare with their symptomatic dizziness.
The intense induced vertigo may be unlike the spontaneous symptoms, but
shortly thereafter, when the vertigo has all but subsided, a lightheadedness
supervenes that may be identified as "my dizziness."

When this occurs, the dizzy patient, originally classified as suffering from
"miscellaneous head sensations," is now properly diagnosed as having mild
vertigo secondary to a vestibulopathy.
Patients with symptoms of positional vertigo should be appropriately tested
(Table 22-1). A final provocative and diagnostic vestibular test, requiring the use
of Frenzel eyeglasses (self-illuminated goggles with convex lenses that blur out
the patient's vision, but allow the examiner to see the eyes greatly magnified), is
vigorous head shaking in the horizontal plane for about 10 s.
If nystagmus develops after the shaking stops, even in the absence of
vertigo, vestibular dysfunction is demonstrated. The maneuver can then be
repeated in the vertical plane. If the provocative tests establish the dizziness as a
vestibular symptom, an evaluation of vestibular vertigo is undertaken.