Is a CT scan done in the ER for stroke protocol the same as a CT of the temporal bone for evaluating unilateral pulsatile tinnitus and potential idiopathic intracranial hypertension (IIH)-like symptoms?

No, a CT for stroke protocol is NOT the same as a CT temporal bone

A stroke protocol CT head is fundamentally different from a dedicated high-resolution CT temporal bone and cannot adequately evaluate the causes of unilateral pulsatile tinnitus. You need a separate, specialized temporal bone CT ordered specifically for this purpose.

Why These Are Different Studies

Stroke Protocol CT Limitations

• Stroke protocol CT uses thick slices (typically 5mm), large field-of-view, and soft tissue algorithms designed to detect hemorrhage and large vessel occlusions 1
• The temporal bone structures require submillimeter resolution that stroke CT simply cannot provide 2
• Stroke CT has extremely low sensitivity (~10%) even for detecting posterior circulation strokes, let alone the microanatomy of the temporal bone 1

What You Actually Need

• The American College of Radiology recommends high-resolution CT temporal bone without contrast as the essential imaging study for evaluating pulsatile tinnitus 2, 3
• This specialized study uses:
  • Ultra-thin slices (0.5-0.6mm or thinner) 4, 5
  • Small field-of-view focused on the temporal bones 2, 3
  • Bone algorithm reconstruction (not soft tissue) 2
  • High-resolution matrix (512×512 or 1024) 4

What the Temporal Bone CT Will Evaluate

For your unilateral pulsatile tinnitus with possible IIH, the temporal bone CT specifically assesses:

• Sigmoid sinus wall dehiscence - the most critical finding in IIH-related pulsatile tinnitus, where bone separating the sigmoid sinus from the middle ear is absent 3, 6
• Sigmoid sinus diverticulum - outpouchings that commonly accompany dehiscence in IIH patients with pulsatile tinnitus 3, 6
• High-riding jugular bulb - can cause pulsatile tinnitus and requires assessment of whether the bony wall is intact 3
• Superior semicircular canal dehiscence 2
• Vascular variants like aberrant internal carotid artery or persistent stapedial artery 2
• Glomus tumors (paragangliomas) 2

Research shows that in IIH patients with unilateral pulsatile tinnitus, sigmoid sinus wall dehiscence is significantly more prevalent on the symptomatic side, and when present with diverticula, strongly correlates with the tinnitus 6.

Who Orders and Reads This Study

• An otolaryngologist (ENT), neuroradiologist, or neurologist typically orders the temporal bone CT 3
• A neuroradiologist with expertise in temporal bone imaging should interpret it, as the anatomy is complex and requires specialized knowledge 4, 5
• Your primary care provider or emergency physician would not typically order this specialized study 1

Additional Imaging You May Need

If the temporal bone CT doesn't reveal the cause, the American College of Radiology recommends CTA head and neck with IV contrast as the next step 2, 3:

• Evaluates for dural arteriovenous fistulas (90% sensitivity) 2
• Detects arteriovenous malformations 2
• Assesses for transverse/sigmoid sinus stenosis common in IIH 3, 6
• Identifies venous outflow dominance patterns 6

Critical Pitfall to Avoid

Do not assume your stroke CT already evaluated the temporal bones adequately - the resolution, field-of-view, and reconstruction algorithms are completely different 2, 1, 3. The microstructures that cause pulsatile tinnitus (dehiscences measuring <1mm) are invisible on standard stroke protocol imaging 4, 5.