Neuroscience Clerkship

 

 

DIFFERENTIATING BETWEEN DIFFERENT TYPES OF DIZZINESS

 

Often, a patient will present to an ER or outpatient clinic complaining of “dizziness.” It is imperative in this situation for the clinician to define what exactly is meant by “dizziness” as the differential diagnosis, diagnostic workup and subsequent treatment are markedly different.

The term “dizziness” is derived from the Old English word “dysig” which literally means “stupid;” The Merriam-Webster dictionary defines “dizziness” in three different ways:

Having a whirling sensation in the head with a tendency to fall

Mentally confused

• Causing giddiness.

The term “dizziness” may be also be used by a patient to describe any of the following symptoms:

“Blurry vision, bouncing, disorientation, falling, fainting, floating, imbalance, lightheadedness, listing, moving, oscillating, passing out, poor equilibrium, rocking, rolling, spinning, swaggering, swaying, swimming, tilting, twisting, unsteadiness, vertigo, weaving.”  

From the above examples, we can see that “dizziness” is an ill-defined term that needs further defining into the appropriate clinical category.

The main types of “dizziness” fall into one of the following three categories:


 

VERTIGO

Vertigo is a feeling of perceived motion, usually spinning or rotation of the environment or self when there actually is no motion. There is often associated intense nausea and vomiting, with nystagmus found on clinical examination. Vertigo results from false signals triggering the vestibular system.  Thus, patients will true vertigo have a disorder of one of the following locations:

Inner ear (semicircular canals and the utricle/saccule)

Vestibulocochlear nerve (cranial nerve VIII)

Vestibular nuclei in the brainstem

Cerebellum (or its connection with the vestibular nuclei)

Among the otologic causes of vertigo, the most common are benign paroxysmal positional vertigo, vestibular neuronitis, and Meniere's disease. Among neurologic causes, the most important are posterior circulation (verebrobasiliar) TIA/stroke, cerebellar or brainstem pathology (e.g., multiple sclerosis) and cranial nerve VIII abnormalities (e.g., schwannoma). Once the determination of vertigo is made, the next important step is to determine whether it is peripheral or central in origin, as this will guide the subsequent diagnostic evaluation.


 

PRESYNCOPE

As the name implies, presyncope is a syndrome that occurs before syncope. In some cases, it is followed by syncope; in others, it does not. It is a feeling like one may pass out or faint. In general, presyncope does not have a neurologic origin. The causes of presyncope are numerous and are mostly related to diffuse hypoperfusion of the brain from systemic hypotension. Symptoms of presyncope may include blurry vision, graying of vision, lightheadedness, confusion, sweating, flushing and abdominal discomfort. Symptoms of presyncope occur more frequently when standing or sitting than when lying flat. In patients presenting with presyncope, a careful physical examination should be done, including orthostatic blood pressures (checking BPs in lying, sitting and standing position), EKG to assess for arrhythmias including bradycardia or AV blocks, and telemetry or Holter monitoring. Tilt table testing is often helpful in confirming vasovagal syncope, one of the more common etiologies of presyncope/syncope. Systemic causes of presyncope are much more common than direct neurologic disease. Rarely, a TIA, seizure or migraine may mimic presyncope/syncope.
 

Causes of Syncope

From Kapoor, Review article: Syncope, NEJM Volume 343:1856-1862, Dec 2000.

 

DYSEQUILIBRIUM

Dysequilibrium is a sensation of loss of balance, or a feeling of falling. Some people describe this as feeling like they are on a boat or drunk. Dysequilibrium results from dysfunction of the vestibulocerebellum and/or its connections. These connections include the following fibers types:

• Vestibular

• Visual

• Proprioceptive

For vestibular lesions, either central or peripheral, dysequilibrium may precede frank vertigo. Loss of visual acuity, loss of depth perception or diplopia may result in a sensation of dysequilibrium. Proprioceptive fibers originate in the peripheral nerves and travel in the spinal cord in the posterior columns. Thus, some peripheral neuropathies and other spinal cord disorders (e.g., B12 deficiency, multiple sclerosis) may result in dysequilibrium.

Lastly, dysequilibrium frequently results from metabolic or toxic causes. Many drugs, especially sedatives, anti-histamines, and narcotics may result in dysequilibrium.