For a patient with dizziness, should a computed tomography (CT) scan of the head be performed with or without contrast?

CT Scan Without Contrast is Recommended for Initial Imaging in Patients with Dizziness

For patients presenting with dizziness, a non-contrast CT scan of the head is recommended as the initial imaging study if imaging is deemed necessary.

Rationale for Non-Contrast CT in Dizziness

• Non-contrast head CT is the standard initial neuroimaging study for patients with dizziness when imaging is indicated, as it can quickly rule out life-threatening conditions such as hemorrhage 1.

• The diagnostic yield of CT in isolated dizziness is very low (<1%), but it has a high negative predictive value of approximately 90% for detecting serious pathology 1.

• CT without contrast is particularly useful for evaluating acute hemorrhage, which is a critical exclusion in patients with dizziness symptoms 2, 3.

Limitations of CT with Contrast for Dizziness

• There is no relevant literature supporting the use of CT head with IV contrast in the evaluation of isolated dizziness 1.

• CT with contrast does not provide significant additional diagnostic information over non-contrast CT in the setting of isolated dizziness 1.

• CTA (CT angiography, which uses contrast) has been shown to have a low overall diagnostic yield of approximately 3% in isolated dizziness and did not contribute additional information beyond non-contrast CT 1.

MRI Considerations

• MRI without contrast is more sensitive than CT for detecting posterior fossa lesions (which commonly cause dizziness) and has a slightly higher diagnostic yield (approximately 4%) 1.

• MRI is particularly valuable when there are abnormal neurological findings or when a central cause of vertigo is suspected 1, 4.

• However, MRI has longer scanning times and may not be as readily available in emergency settings 5.

Clinical Decision-Making Algorithm

1. For isolated dizziness without other neurological symptoms:

   • Non-contrast CT is appropriate as an initial imaging study if imaging is deemed necessary 1.
   • Be aware that the diagnostic yield is low (<1%) 1.

2. For dizziness with abnormal neurological examination:

   • Non-contrast CT can be performed initially to rule out hemorrhage 1, 2.
   • Consider following with MRI without contrast if CT is negative but clinical suspicion for central pathology remains high 1, 4.

3. For chronic recurrent vertigo:

   • MRI may be more appropriate than CT, particularly when evaluating for posterior fossa pathology 1, 6.

Important Caveats

• CT has limited sensitivity (20-40%) for detecting causative etiology of dizziness, particularly for posterior fossa lesions 1, 4.

• Intracerebral hemorrhage rarely presents with isolated dizziness without other neurological findings 2.

• Clinical assessment, including HINTS examination (when available), is crucial in determining the need for imaging in patients with dizziness 1, 6.

• For patients with high vascular risk factors or when a trained HINTS practitioner is not available, imaging may be more strongly indicated 1.