Dizziness is a common complaint ranging from momentary unsteadiness to a debilitating sensation of spinning. While many causes are benign, dizziness can signal a serious underlying issue, such as the narrowing of a vital body passage. Stenosis refers to this abnormal narrowing, which becomes a concern when it restricts blood flow to the brain’s complex balance system. This restriction can lead directly to various forms of dizziness, indicating a disruption in the body’s vascular network.
Defining Stenosis and Dizziness
Stenosis describes the abnormal narrowing of any tubular structure or passageway within the body. This narrowing often affects major blood vessels, heart valves, or the spinal canal. In arteries, stenosis is most commonly caused by the buildup of plaque in the walls, a process called atherosclerosis. When this occurs in arteries supplying the head, it reduces the volume of blood and oxygen delivered to the brain.
Dizziness is an imprecise term encompassing three distinct sensations: lightheadedness, vertigo, and disequilibrium. Lightheadedness (presyncope) is the feeling of being faint or about to lose consciousness. Vertigo is the distinct sensation of spinning or movement of oneself or the surrounding environment. Disequilibrium is characterized by unsteadiness or a loss of balance, particularly when walking.
For stenosis to cause dizziness, the narrowing must be located in arteries that supply the brain’s balance control centers. These centers include the vestibular system in the inner ear and processing areas in the brainstem and cerebellum. A reduction in blood flow (ischemia) to these regions causes them to malfunction. This sends confused signals to the brain, resulting in the sensation of movement or unsteadiness.
Arterial Narrowing: The Direct Cause of Dizziness
The arteries supplying the brain are divided into anterior and posterior circulation, and the location of stenosis dictates the type of dizziness experienced. Stenosis in the carotid arteries, which form the anterior circulation, is a frequent finding. However, it is generally an uncommon cause of isolated dizziness. Carotid arteries supply the front two-thirds of the brain, and severe narrowing often leads to non-specific lightheadedness or symptoms of a transient ischemic attack (TIA).
When carotid artery stenosis (CAS) causes dizziness, it manifests as lightheadedness or a feeling of being faint (presyncope). This is often related to a temporary, overall drop in cerebral blood flow, particularly in older patients. The primary danger of CAS is not isolated dizziness but the risk of plaque breaking off and traveling to the brain, causing a stroke.
Stenosis in the vertebral arteries, which form the posterior circulation, is a more direct cause of severe dizziness. These arteries merge to form the basilar artery, supplying the brainstem, cerebellum, and inner ear structures responsible for balance. Narrowing in this system leads to vertebrobasilar insufficiency (VBI), which reduces blood supply to the balance centers.
The resulting lack of oxygen to the vestibular nuclei and the cerebellum disrupts the body’s ability to process spatial orientation, leading to vertigo. Since the posterior circulation is closely linked to balance, even a temporary interruption of blood flow from vertebral artery stenosis can result in spinning and disequilibrium.
Symptom Presentation: Types of Dizziness and Warning Signs
The nature of the dizziness often points toward the area of the brain affected by the stenosis. Dizziness described as vertigo—a rotational or spinning sensation—suggests insufficient blood flow to the posterior circulation. This vertigo is often accompanied by nausea and vomiting due to brainstem involvement.
Lightheadedness or presyncope, a feeling of wooziness or impending faintness, is more often linked to general systemic issues or severe carotid artery stenosis. This feeling is not a spinning sensation but a sense of weakness and reduced awareness. Disequilibrium, or unsteadiness while walking, indicates a coordination problem, often localized to the cerebellum.
Rotational Vertebral Artery Syndrome, sometimes called Bow Hunter syndrome, is a specific presentation. This occurs when the vertebral artery is mechanically compressed by head movement, such as turning the head quickly or extending the neck. This compression temporarily occludes blood flow, instantly triggering vertigo, syncope, or other neurological symptoms.
Stenosis-related dizziness, particularly when caused by a Transient Ischemic Attack (TIA), is usually not an isolated event and is accompanied by other neurological symptoms. These signs serve as critical warning signs and include the sudden onset of one-sided numbness or weakness in the face or limbs, slurred speech, or difficulty finding words. Other concerning symptoms are double vision, sudden vision loss in one eye, or severe loss of coordination (ataxia).