Vertigo is the false sensation of spinning or motion when a person is standing or sitting still. This symptom is not a diagnosis, but a sign of an underlying issue affecting the balance system. A Computed Tomography (CT) scan cannot detect the sensation of vertigo itself. Imaging is used instead to identify the structural cause behind the symptom when a serious condition is suspected. Determining vertigo’s origin relies primarily on a thorough clinical examination and medical history, not on an immediate scan.
Understanding Vertigo: Peripheral vs. Central Causes
The origin of the spinning sensation determines whether imaging is needed, as vertigo is categorized by its anatomical source. Peripheral vertigo is the most common form, arising from the inner ear or the vestibular nerve. Common causes include Benign Paroxysmal Positional Vertigo (BPPV), caused by dislodged calcium crystals, and labyrinthitis, which is inner ear inflammation.
These peripheral issues are generally not life-threatening and account for the vast majority of cases. They are frequently accompanied by hearing loss or tinnitus. Central vertigo is less frequent but far more serious, originating from a problem in the brain, typically the brainstem or the cerebellum.
Potential central causes include stroke, tumors, multiple sclerosis, or certain types of migraine. Distinguishing between these two sources is the physician’s most important step, as it dictates the urgency and necessity of imaging tests.
The Role and Limitations of CT Scans in Diagnosis
A CT scan uses X-rays to create cross-sectional images and performs well at visualizing dense structures like bone. For vertigo, a CT scan can clearly show structural problems in the inner ear’s bony labyrinth or detect acute issues such as a skull fracture. The scan is also the fastest tool available to identify acute hemorrhage, or bleeding, within the brain.
However, the technology is poor at visualizing soft tissues, including the brainstem and cerebellum, where many central vertigo causes originate. The CT scan’s sensitivity for detecting an early ischemic stroke, particularly in the posterior fossa, is very low. This limitation means a CT scan can provide a false sense of reassurance by missing a subtle but serious central cause.
For common peripheral causes, like BPPV or vestibular neuritis, a CT scan provides no diagnostic value because these are functional or inflammatory issues, not structural abnormalities. Consequently, for isolated vertigo without other concerning symptoms, the diagnostic yield of a head CT is extremely low. When imaging is necessary for soft tissue evaluation, Magnetic Resonance Imaging (MRI) is the superior tool.
Identifying “Red Flags” that Require Immediate Imaging
Imaging is only ordered when a physician suspects a central cause, indicated by accompanying symptoms known as “red flags.” These signs suggest a problem beyond the inner ear and point to possible involvement of the brainstem or cerebellum. Highly concerning symptoms include:
- A new, severe headache
- Double vision
- Slurred speech (dysarthria)
- Difficulty swallowing (dysphagia)
- Acute limb weakness
- An inability to stand or walk independently (truncal ataxia)
These neurological deficits mandate immediate neuroimaging to rule out conditions like stroke or intracranial hemorrhage.
In emergency settings, a CT scan is often performed first due to its speed and availability, allowing for the rapid exclusion of life-threatening acute hemorrhage. If the CT scan is negative but central symptoms persist, an MRI is then required. MRI offers much greater detail for detecting subtle ischemic strokes or other soft tissue lesions in the posterior brain.