In a patient with pulsatile tinnitus who refuses CT angiography and contrast, what non‑contrast imaging and evaluation steps should be taken?

Proceed with High-Resolution CT Temporal Bone Without Contrast

In a patient with pulsatile tinnitus who refuses CTA and contrast, obtain a high-resolution CT temporal bone without IV contrast as your primary imaging modality. This non-contrast study can diagnose many critical causes of pulsatile tinnitus and is explicitly supported as appropriate first-line imaging by the 2023 ACR guidelines 111.

What CT Temporal Bone Without Contrast Can Detect

This study effectively identifies numerous treatable and important causes of pulsatile tinnitus:

Vascular variants that could cause catastrophic complications if biopsied:

• Aberrant or lateralized internal carotid artery
• Persistent stapedial artery
• Dehiscent jugular foramen
• High-riding jugular bulb

Temporal bone pathology:

• Superior semicircular canal dehiscence (SSCD) - a known cause of PT
• Sigmoid sinus wall abnormalities (SSWA) - may be the most common identifiable cause in this group 11
• Sigmoid sinus diverticulum and dehiscence
• Glomus tympanicum (small paragangliomas)
• Otospongiosis and Paget disease
• Jugular bulb diverticulum

The key diagnostic principle: Changes in the contour of bone and air spaces in the temporal bone are sufficient to diagnose these conditions - contrast is not necessary 11.

Critical Limitations You Must Understand

CT temporal bone without contrast CANNOT detect:

• Dural arteriovenous fistulas (dAVF) - potentially dangerous lesions with 2-27% prevalence in PT patients 11
• Arteriovenous malformations (AVM)
• Arterial dissections (carotid or vertebral) - present in 8-10% of PT patients 11
• Transverse/sigmoid sinus stenosis
• Intracranial vascular abnormalities
• Cervical arterial pathology

Alternative Non-Contrast Approach: MRI/MRA

If the patient will accept MRI (which also doesn't require iodinated contrast), consider MRI head and MRA head without IV contrast as an alternative strategy 2. Recent literature suggests MRI is increasingly preferred as first-line screening for PT due to its ability to identify vascular shunting lesions, venous sinus stenosis, and tumors without radiation 23.

MRI/MRA advantages:

• Can detect dAVFs and other vascular causes that CT temporal bone misses
• No ionizing radiation
• Can identify venous sinus pathology
• Time-of-flight MRA sequences don't require gadolinium contrast

MRI/MRA limitations:

• Less optimal for fine temporal bone detail compared to high-resolution CT
• May miss small glomus tympanicum
• Cannot assess bony dehiscences as well as CT

Clinical Algorithm When Contrast is Refused

Step 1: Perform otoscopy

• If vascular retrotympanic lesion seen → CT temporal bone without contrast is appropriate first-line 11
• If no retrotympanic lesion → consider MRI/MRA without contrast to screen for vascular causes

Step 2: Based on CT temporal bone results:

• If diagnostic finding identified (SSCD, SSWA, vascular variant, etc.) → proceed to appropriate management
• If negative or non-diagnostic → strongly counsel patient about limitations and need for vascular imaging

Step 3: If CT temporal bone is negative:

• Revisit discussion about vascular imaging necessity
• Explain that dangerous causes (dAVF, AVM, dissection) cannot be excluded without vascular imaging
• Consider MRI/MRA without gadolinium as compromise
• If patient continues to refuse all vascular imaging, document thoroughly and consider DSA if clinical suspicion remains high for vascular etiology 11

Critical Pitfall to Avoid

Do not assume the workup is complete with only CT temporal bone without contrast. While this study diagnoses many causes of PT, it systematically misses vascular pathologies that can lead to hemorrhagic or ischemic stroke 4. The 2023 ACR guidelines clearly state that CTA head and neck with contrast is the preferred first-choice imaging when vascular pathology is suspected because it captures both arterial and venous causes plus temporal bone detail 11.

Document extensively that the patient was counseled about the limitations of non-contrast imaging and the potential for missing life-threatening vascular causes. More than 70% of PT cases have an identifiable cause with thorough evaluation 4, but this requires appropriate vascular imaging in most cases.