E. Lee Murray, MD
Dizziness and vertigo can have central or peripheral generators. The most common etiologies seen by hospital neurologists are complaints due to:
•Benign paroxysmal positional vertigo
•Toxic/metabolic, especially ethanol and medications.
Specific disorders are discussed in detail in Chapter 32 unless otherwise indicated.
TERMINOLOGY
Patients may report “dizziness” or “vertigo,” but the specific meaning may be uncertain. Most of these patients are referring to one of the following symptoms:
•Gait ataxia: Unsteadiness of stance and/or gait
•Limb ataxia: Appendicular ataxia affecting any or all extremities
•Syncope: Loss of consciousness due to cerebral hypoperfusion.
•Confusion: Cognitive dysfunction.
Vertigo
Vertigo is a sensation of movement of either the patient or the environment when none has occurred. Vertigo is central or peripheral. Peripheral vertigo is most common, but the central causes must not missed on clinical evaluation.
Peripheral vertigo includes the follow disorders:
•Benign paroxysmal positional vertigo (BPPV)
Central vertigo includes the following disorders:
•Other cerebellopontine tumors
Differentiating causes of vertigo depends on character and associated symptoms. Post-traumatic vertigo is considered by many to be a form of BPPV; it is not always paroxysmal, although it is usually positional.
Gait Ataxia
Gait ataxia presents with a propensity to stumble or fall and is sometimes described as “dizziness” even in the absence of true vertigo.
Differential diagnosis of gait ataxia is broad and is narrowed depending on acuity and associated features. Some of the possibilities include:
•Toxicity: Common examples are ethanol and phenytoin, but a host of medications and toxins can produce gait ataxia.
•Stroke: Ischemic and hemorrhagic stroke especially in the posterior circulation distribution can produce ataxia, but this is almost always associated with other neurologic deficits which localize the lesion.
•Multiple sclerosis (MS): Can present with ataxia and sometimes vertigo, but with MS, the ataxia is more severe than can be explained by vertigo alone.
•Tumor: Rarely, tumor in the brainstem or cerebellum can present as predominant gait ataxia. There are usually other findings related to cranial nerve involvement, mass effect, or hydrocephalus.
•Parkinson disease and related conditions: Certain diseases result in ataxia plus other motor symptoms depending on the precise disorder.
•Paraneoplastic syndrome: Paraneoplastic cerebellar degeneration presents with ataxia often with other brainstem signs.
•Sensory ataxia: Neuropathy with a prominent sensory component; Romberg is positive.
Limb Ataxia
Limb ataxia is only rarely referred to as dizziness by the patient. Limb ataxia is never due to peripheral vestibulopathy. Limb ataxia in the absence of weakness is usually due to a cerebellar lesion. Weakness with ataxia can be a lesion anywhere from brainstem to cerebral cortex.
Important etiologies of limb ataxia are:
•Multiple sclerosis and other immune-mediated conditions
•Parkinsonism and related movement disorders
One of the most unusual disorders with abnormal limb movements is corticobasal syndrome, discussed in Chapter 23.
Presyncope
Regional terminology sometimes reports presyncope or syncope as “dizziness”. Patients report that they feel as if they are going to faint. The common physiological effect is reduction in cerebral blood flow. Possible causes include:
◦Neurocardiogenic (i.e., vasovagal)
◦Vertebrobasilar insufficiency
◦From blood loss or hematologic disorder.
For some of these etiologies, presyncope may be the presenting complaint. We have seen this especially for anemia, GI bleed, pregnancy, and cardiac outflow impairment. Isolated presyncope due to cerebrovascular disease is rare.
Syncope
Syncope is sometimes used as a generic term for transient loss of consciousness (TLOC) but, strictly speaking, loss of consciousness develops because of cerebral hypoperfusion. The complaint of “dizziness” may sometimes precede TLOC or falls. Evaluation of TLOC and syncope is discussed in detail in Chapter 5.
Clonic syncope is shaking of the body in association with syncope. This is due to neuronal hypoxia. Clonic syncope is often mistaken for seizure. Presentation is with TLOC associated with jerking, which can be single or repetitive for a few seconds. Jerking lasting longer than this is unlikely to be clonic syncope.
Confusion
Confusion due to developing dementia usually is not described as “dizziness”, but the term is sometimes used for transient cognitive disturbance (e.g., transient disorientation).
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