What is the clinical significance and recommended management of an incidentally identified high‑riding jugular bulb on CT scan?

High-Riding Jugular Bulb on CT Scan

A high-riding jugular bulb identified incidentally on CT scan is a benign anatomical variant that requires no intervention in asymptomatic patients, but warrants high-resolution temporal bone CT to assess for bony dehiscence when patients present with pulsatile tinnitus, conductive hearing loss, or vestibular symptoms. 1

Clinical Significance

Anatomical Context

• A high-riding jugular bulb represents an anatomical variant where the superior aspect of the jugular bulb extends above the floor of the hypotympanum, occurring in 3.5% to 6% of temporal bones 2
• The variant occurs more frequently on the right side 2
• Most individuals with this anatomical variation remain completely asymptomatic throughout life 2

Symptomatic Presentations

When symptoms do occur, they typically manifest as:

• Pulsatile tinnitus due to turbulent venous flow creating audible pulsations 1
• Conductive hearing loss when the jugular bulb erodes into the vestibular aqueduct (present in 5 of 11 symptomatic patients in one series) 3
• Vestibular symptoms from compression of adjacent vestibular structures or the vestibular aqueduct 1
• Dizziness from increased venous pressure effects 4

Critical Pathological Associations

• The high-riding jugular bulb can erode into the inner ear structures, specifically the vestibular aqueduct (most common) or posterior semicircular canal 3
• Erosion into the vestibular aqueduct is particularly associated with both pulsatile tinnitus and conductive hearing loss 3
• Bony dehiscence of the jugular bulb (loss of the bony wall separating it from the middle ear) increases the risk of surgical complications 1

Recommended Diagnostic Workup

Initial Imaging for Symptomatic Patients

High-resolution CT temporal bone without contrast is the critical next step for any symptomatic patient with a high-riding jugular bulb identified on standard CT. 1

This study must specifically evaluate:

• Jugular bulb dehiscence: whether the bony wall separating the jugular bulb from the middle ear or inner ear remains intact 1
• Erosion into inner ear structures: specifically the vestibular aqueduct and posterior semicircular canal 3
• Sigmoid sinus wall abnormalities: commonly associated with venous pulsatile tinnitus 1
• Round window accessibility: critical for surgical planning if cochlear implantation is considered 5

When Standard Temporal Bone CT Is Unrevealing

If high-resolution temporal bone CT does not explain the symptoms, proceed with CTA head and neck with IV contrast to evaluate for:

• Dural arteriovenous fistula 1
• Arteriovenous malformations 1
• Sigmoid sinus stenosis or transverse sinus abnormalities 1

Asymptomatic Incidental Findings

• No further imaging is required for truly asymptomatic patients with incidentally discovered high-riding jugular bulb 2
• Regular long-term follow-up is recommended to monitor for development of symptoms 2

Critical Clinical Pitfalls

Surgical Hazards

• Never perform otoscopic biopsy of a suspected vascular retrotympanic mass, as inadvertent biopsy of the high-riding jugular bulb can cause devastating hemorrhagic complications 1
• The high-riding jugular bulb may completely cover the round window, making cochlear implantation technically impossible or extremely hazardous 5
• Preoperative imaging is mandatory before any otologic surgery to identify this variant and prevent catastrophic intraoperative hemorrhage 2, 5

Diagnostic Errors

• Standard CT angiography alone is insufficient for evaluating high-riding jugular bulb because it lacks the high-resolution bone algorithm and small field-of-view needed to assess temporal bone microanatomy 1
• MRI/MRA should not be ordered as first-line imaging because it cannot adequately assess the temporal bone microanatomy needed to characterize high-riding jugular bulb and associated dehiscences 1
• Radiologists frequently identify the high-riding jugular bulb but commonly fail to report erosion into inner ear structures, requiring careful independent review by the clinician 3

Misdiagnosis Risk

• High-riding jugular bulb with dehiscence can be misdiagnosed as a glomus tumor on physical examination when a vascular retrotympanic mass is visible 6
• The key distinguishing feature is that high-resolution CT demonstrates direct venous connection to the jugular bulb rather than a separate vascular tumor 6

Management Approach

Asymptomatic Patients

• Observation with regular follow-up is the standard approach 2
• No surgical intervention is indicated 2
• Patient education about the benign nature of the finding 2

Symptomatic Patients with Pulsatile Tinnitus

• Jugular vein ligation has been reported to achieve good results in alleviating intractable pulsatile tinnitus 2
• This intervention should be reserved for severe, refractory cases after conservative management fails 2

Patients with Conductive Hearing Loss

• Exploratory tympanotomy is not recommended for patients with high-riding jugular bulb and conductive hearing loss due to high surgical risk 2
• The conductive hearing loss is typically due to erosion into the vestibular aqueduct rather than middle ear pathology amenable to surgical correction 3

Vestibular Symptoms

• Vestibular evoked myogenic potential (VEMP) testing can confirm inner ear dehiscence in patients with vestibular symptoms 3
• VEMP findings consistent with dehiscence were present in 3 of 6 tested patients with jugular bulb erosion into the inner ear 3

Pediatric Considerations

• High-riding jugular bulb typically develops after 2 years of age and is rare in younger children 5
• The earlier the high-riding jugular bulb forms, the larger it may grow over time, as demonstrated by longitudinal CT imaging showing progressive enlargement and protrusion into the tympanic cavity 5
• Serial imaging may be warranted in pediatric patients when surgical intervention (such as cochlear implantation) is planned for the future 5