Pulsatile Tinnitus with High-Riding Jugular Bulb
The whooshing sound (pulsatile tinnitus), giddiness, and feeling of being "phased out" are most likely caused by the high-riding jugular bulb itself, which can create turbulent venous flow and potentially compress adjacent vestibular structures. 1
Understanding the Diagnosis
A high-riding jugular bulb (HRJB) is a well-recognized anatomical variant that can cause pulsatile tinnitus and vestibular symptoms. 1 The CT angiography showing an HRJB as the only abnormality strongly suggests this is the primary culprit, though additional evaluation is warranted to exclude other treatable causes.
Key Clinical Considerations
The combination of pulsatile tinnitus with vestibular symptoms (giddiness, feeling "phased out") in the setting of HRJB suggests possible:
- Direct mechanical compression of the vestibular aqueduct or inner ear structures 2
- Turbulent venous flow creating audible pulsations 1
- Potential jugular bulb dehiscence into the middle ear or vestibular structures 1
Recommended Diagnostic Workup
You need high-resolution CT temporal bone without contrast as the next critical step to fully characterize the jugular bulb anatomy and identify associated abnormalities. 1
What the Temporal Bone CT Should Evaluate:
- Jugular bulb dehiscence - whether the bony wall separating the jugular bulb from the middle ear or inner ear is intact 1
- Jugular bulb diverticulum - outpouching that may compress the vestibular aqueduct 1, 2
- Sigmoid sinus wall abnormalities (diverticulum or dehiscence) - commonly associated with venous pulsatile tinnitus 1
- Superior semicircular canal dehiscence (SSCD) - can cause both pulsatile tinnitus and vestibular symptoms 1
- Other temporal bone pathology - otosclerosis, Paget disease 1
Why CT Angiography Alone Is Insufficient:
The CT angiography of the brain provides excellent vascular detail but lacks the high-resolution bone algorithm and small field-of-view needed to assess temporal bone microanatomy. 1 IV contrast is not necessary for evaluating HRJB - the diagnosis relies on evaluating bone and air space contours. 1
Additional Imaging Considerations
If the high-resolution temporal bone CT is unrevealing, consider CTA head and neck with IV contrast to evaluate for:
- Dural arteriovenous fistula (dAVF) - sensitivity/specificity of 90% for this treatable cause 1
- Arteriovenous malformations 1
- Sigmoid sinus stenosis or transverse sinus abnormalities 1
- Vascular dissection or atherosclerotic disease 1
The ACR Appropriateness Criteria (2023) recommend CTA head and neck as first-line imaging for pulsatile tinnitus when vascular pathology is suspected, as it can detect both arterial and venous etiologies while providing bone detail from thin-section reconstructions. 1
Clinical Pitfalls to Avoid
Do not perform otoscopic examination looking for a retrotympanic mass - if one is visualized, it changes the diagnostic algorithm entirely, as inadvertent biopsy of vascular variants can cause devastating complications. 1
Do not dismiss the vestibular symptoms - while HRJB commonly causes pulsatile tinnitus alone, the presence of giddiness and altered consciousness ("phased out") suggests:
- Possible compression of the vestibular aqueduct 2
- Increased venous pressure effects (symptoms may worsen with Valsalva) 2
- Potential for other concurrent pathology requiring identification
Do not order MRI/MRA as first-line imaging - while useful for evaluating intracranial vascular malformations, MRI cannot adequately assess the temporal bone microanatomy needed to characterize HRJB and associated dehiscences. 1
Treatment Implications
If HRJB with dehiscence or diverticulum is confirmed and symptoms are disabling:
Endovascular treatment options exist including stent-assisted coil embolization of the jugular bulb, which has shown complete resolution of symptoms in case series. 2, 3 This minimally invasive approach may have a better benefit-to-risk ratio compared to open surgical resurfacing. 2, 4
Surgical resurfacing via transcanal endoscopic approach is another option for HRJB with dehiscence, providing direct visualization and less destruction than transmastoid approaches. 4
Natural History Context
HRJB prevalence increases with age - it can be identified in up to 42-50% of children by age 2 years and beyond, though it is rarely symptomatic. 5 The fact that your relative is symptomatic warrants thorough evaluation for associated anatomical abnormalities that may be treatable.