Can bone dehiscence along the petrous segment and cavernous segment of the internal carotid arteries (ICAs) cause abnormal sounds or pounding in the right ear?

Can Bone Dehiscence of the Internal Carotid Artery Cause Right Ear Pulsatile Tinnitus?

Yes, bone dehiscence along the petrous and cavernous segments of the internal carotid artery exposing the vessel into the sphenoid sinus and pneumatized petrous apex can cause pulsatile tinnitus in the right ear, though this is a rare anatomic variant that creates turbulent blood flow audible to the patient's auditory system. 1, 2

Understanding the Mechanism

The imaging findings describe bilateral ICA canal dehiscence with exposure of the artery into the sphenoid sinuses and left pneumatized petrous apex. This anatomic variant allows transmission of arterial pulsations and turbulent flow sounds directly to adjacent air-filled spaces and ultimately to the auditory system. 1, 2

• Dorsal (endocranial) petrous carotid canal dehiscence occurs in 83-89% of the general population, making this an extremely common anatomic finding that usually remains asymptomatic. 3
• Ventral (exocranial) dehiscence is less common (34-37%) and more likely to be clinically relevant when the artery is exposed into air-filled spaces like the sphenoid sinus or pneumatized petrous apex. 3
• The key distinction is whether the dehiscence exposes the artery into an air-filled cavity (like your patient's sphenoid sinus exposure), which creates an acoustic pathway for pulsatile sounds, versus simple thinning of bone without cavity communication. 1, 2

Why This Causes Pulsatile Tinnitus

• Turbulent arterial flow through the exposed ICA segment generates rhythmic sound synchronized with the cardiac cycle, which transmits through the air-filled sphenoid sinus and pneumatized petrous apex to reach the middle ear and cochlea. 4, 1
• The pneumatized left petrous apex noted on imaging creates an additional acoustic resonance chamber that can amplify these vascular sounds, though the patient's symptoms are right-sided. 1, 2
• This represents an arterial cause of pulsatile tinnitus, which the American College of Radiology recognizes as part of the differential diagnosis requiring systematic vascular evaluation. 4

Critical Diagnostic Considerations

The imaging already performed (angiographic protocol CT) is appropriate and has identified the anatomic cause. 5, 4 However, you must exclude other more dangerous causes of pulsatile tinnitus:

• Atherosclerotic carotid disease (17.5% of pulsatile tinnitus cases) should be evaluated with carotid duplex ultrasound if not already performed, as this is the most common cause overall. 4
• Dural arteriovenous fistula (8% of cases) is life-threatening and can lead to hemorrhagic stroke if missed—the angiographic protocol CT should have evaluated for this, but if clinical suspicion remains high and symptoms persist, catheter angiography may be needed. 5, 4
• Arterial dissection must be excluded as this is potentially life-threatening and can cause pulsatile tinnitus in 8-10% of dissection patients. 5, 4

Management Approach

Conservative management is the primary recommendation for ICA canal dehiscence, as this is typically a benign anatomic variant. 1, 2 However:

• If symptoms are unbearable and significantly impair quality of life, surgical correction through a middle cranial fossa approach with bone grafting over the dehiscent segment has been reported with successful resolution of pulsatile tinnitus. 1
• One case report describes complete resolution of pulsatile tinnitus immediately postoperatively with no recurrence at 9-month follow-up after surgical correction of ICA canal dehiscence into the tympanic cavity. 1
• Surgical intervention carries risks including ICA injury (3-5% in skull base procedures) and should only be considered for debilitating symptoms after excluding all other treatable causes. 3

Common Pitfalls to Avoid

• Do not assume the dehiscence is the cause without excluding more dangerous etiologies first—atherosclerotic disease, dural AVF, and arterial dissection must be ruled out as these are treatable and potentially life-threatening. 4
• The bilateral nature of the dehiscence on imaging but unilateral symptoms (right ear only) suggests the anatomic variant may be incidental—unilateral pulsatile tinnitus has higher likelihood of identifiable structural cause requiring further workup. 4
• Carotid duplex ultrasound should be performed to evaluate for atherosclerotic stenosis, which is the most common cause of pulsatile tinnitus and could coexist with the anatomic variant. 4, 6
• If the angiographic CT did not include delayed venous phase imaging, consider dedicated CT venography to exclude sigmoid sinus abnormalities, which are common causes of pulsatile tinnitus. 4

Next Steps

• Obtain carotid duplex ultrasound to exclude atherosclerotic disease as the primary cause. 4, 6
• Review the angiographic protocol images specifically for dural AVF, as these require high index of suspicion and may be subtle on CTA. 5, 4
• If all dangerous causes are excluded and symptoms are tolerable, reassure the patient that ICA canal dehiscence is a common anatomic variant (present in up to 89% of the population) that rarely requires intervention. 3
• Reserve surgical consultation for cases where symptoms are truly debilitating and all other causes have been definitively excluded. 1