Dizziness may mean true vertigo, which is a hallucination of movement of the patient or his environment, or lightheadedness, which is a feeling that one is going to faint (and sometimes does). The causes of lightheadedness are developed under the section on syncope (see page 418).
The diagnostic approach to dizziness or true vertigo uses anatomy, beginning with the external ear and working inwards toward the middle ear, labyrinth, auditory artery and nerve, and vesticular nuclei in the brainstem. Impacted wax or other foreign bodies in the external ear may cause vertigo. Otitis media, especially when it invades the mastoid or petrous bone, is the most important cause of vertigo in the middle ear. One should not forget serous otitis media from allergies or upper respiratory infections (URIs). If the drum is perforated, however, or if there is a perforation into the perilymph system, vertigo will occur, especially when water enters the ear.
|
|
|
Dilated pupils (mydriasis) |
|
|
|
Dizziness |
The inner ear is the site of two important causes of vertigo, acute labyrinthitis and Ménière disease. Acute labyrinthitis is more often toxic than infectious (viral) in nature. Drugs such as streptomycin and gentomycin are common causes, but aspirin and quinidine should be considered with a host of other drugs. This can be determined by a good history without looking up the long list of drugs. Perhaps more common and more important from a legal standpoint is traumatic labyrinthitis from head injuries. The cause of Ménière disease is not known, but swelling of the endolymphatic ducts is probably the major pathophysiologic mechanism. If the internal auditory artery is obstructed by spasm (as occurs in migraine), basilar artery insufficiency, or thrombosis, vertigo will result. Rarely, an aneurysm of this artery or the basilar artery at its branching may compress or hemorrhage into the vestibular nerve and cause vertigo.
Additional neurologic causes of vertigo are acoustic neuromas and other brainstem tumors, petrositis, and vestibular neuronitis, which may involve the vestibular nerve or nucleus. Finally, central vertigo may result from multiple sclerosis, concussion, epilepsy, and cerebral tumors.
Approach to the Diagnosis
The first step is to determine if the patient has true vertigo. True vertigo is the experience of subjective or objective rotation with respect to the environment. In other words, either the patient or his or her environment is turning. One other form of true vertigo is lateral pulsion. This is the feeling that one is moving sideways when that is not the case.
The patient who does not experience true vertigo should have a syncope workup (see page 418). Narrowing the differential diagnosis of true vertigo depends on the presence or absence of other symptoms and signs. If there are other cranial nerve or long tract signs on neurologic examination, the patient may have a space-occupying lesion of the brain or brainstem or a hemorrhage, thrombosis, or embolism in the vertebral–basilar artery distribution. A neurology consult should be obtained.
If there is true vertigo, tinnitis, and deafness, one would consider inner ear pathology such as Ménière disease, syphilis, petrositis, mastoiditis, and acoustic neuroma. If there is vertigo without tinnitus, deafness, or focal neurologic signs, the clinician should suspect acute labyrinthitis, vestibular neuronitis, benign positional vertigo, and drug toxicity. If there are rapid respirations during the attack of vertigo, one would consider hyperventilation syndrome. If there are significant findings on otoscopic examination, a diagnosis of otitis media, cholesteatoma, or mastoiditis should be considered.
The workup will depend on whether the patient has objective findings on otoscopic or neurologic examination. If local pathology is suspected, perhaps a tympanogram, x-ray of the mastoids and petrous bones, audiogram, or referral to an otolaryngologist are required. If there are neurologic findings, perhaps a CT scan or MRI of the brain and auditory canal is indicated along with a referral to a neurologist. It is wise to have a specialist on board before ordering an expensive workup.
Other Useful Tests
1. Thyroid profile (vertigo from thyroid disease)
2. Electronystagmogram (Ménière disease)
3. Brainstem evoked potentials (multiple sclerosis)
4. Caloric testing (Ménière disease)
5. Drug screen (drug abuse)
6. Hallpike maneuvers (benign positional vertigo)
7. VDRL or Fluorescent Treponemal Antibody Absorption (FTA-ABS) test (neurosyphilis)
Case Presentation #17
A 36-year-old black woman presents with acute dizziness, which she describes as a sensation of turning in relation to her environment.
Question #1. Given the methods provided above, what would be your list of possible causes?
Further history reveals that she has not been on any medication recently and denies fever or a recent URI. There is, however, a history of similar attacks in the past associated with numbness of the left side of the face and weakness of the extremities.
Question #2. What is your list of possibilities now?
