Which diagnostic tests best separate conductive (ETD-related) tinnitus from sensorineural or vascular causes in persistent unilateral tinnitus?
Executive summary
Persistent unilateral tinnitus demands a targeted diagnostic partitioning: simple bedside maneuvers and otoscopic exam first to detect conductive causes such as Eustachian tube dysfunction (ETD), formal audiometry and middle‑ear testing to distinguish conductive from sensorineural loss, and vascular/retrocochlear imaging when pulsatility, asymmetry, or red‑flag features are present [1] [2] [3]. Imaging—MRI with contrast for retrocochlear lesions and CT/angiographic studies for vascular etiologies—complements audiologic testing when clinical clues point beyond an isolated middle‑ear problem [4] [5] [6].
1. Clinical history and physical give the first split
A careful history (onset, pulsatility, change with posture or jugular compression, accompanying hearing loss or neurologic signs) and targeted head-and-neck exam including otoscopy and auscultation over the neck, mastoid and periauricular regions are essential because many conductive causes (cerumen, otitis media, ETD) are evident on exam and vascular tinnitus may be suppressed by jugular compression [1] [2] [6].
2. Bedside tuning‑fork and humming tests reliably distinguish conductive versus sensorineural causes
When a clinician must rapidly separate conductive from sensorineural tinnitus, the 512 Hz tuning‑fork tests—Weber (lateralization) and Rinne (air vs bone conduction)—remain useful if an interaural threshold difference is ≥20 dB, with conductive loss typically lateralizing to the affected ear and sensorineural loss to the better ear [7] [8]. In settings without a tuning fork, the humming test is a validated alternative with high sensitivity in small studies for detecting conductive pathology [9].
3. Formal audiologic testing defines the type and asymmetry of hearing loss
Comprehensive audiometry (pure‑tone and speech) is the cornerstone for distinguishing conductive, sensorineural, or mixed deficits and for documenting asymmetry that raises concern for retrocochlear disease; tympanometry and otoacoustic emissions further clarify middle‑ear function versus cochlear involvement [2] [3] [10]. Referral for audiology is recommended for chronic or unilateral tinnitus and should be performed promptly—guidelines suggest evaluation within weeks for unilateral symptoms [2].
4. Imaging selects the vascular versus retrocochlear pathway when indicated
Persistent unilateral tinnitus with asymmetric sensorineural loss, objective findings, or pulsatile quality warrants imaging: MRI with gadolinium is the preferred screen for vestibular schwannoma/retrocochlear lesions (having superseded ABR testing), while CT angiography, MR angiography/venography, or dedicated temporal‑bone CT are indicated for suspected arterial or venous vascular lesions, glomus tumors, or osseous causes [4] [5] [6].
5. Specific maneuvers and tests point to vascular causes
Pulsatile tinnitus that varies with carotid/jugular compression, is synchronous with the heartbeat, or produces an audible bruit on auscultation should prompt vascular imaging because many vascular lesions (dural arteriovenous fistula, sinus stenosis, paraganglioma) are identifiable on angiographic studies and account for a substantial fraction of pulsatile cases when properly investigated (approximately 70% yield with adequate workup) [1] [6].
6. Pragmatic diagnostic algorithm and known limitations
A pragmatic pathway begins with history/otoscopy and bedside tuning‑fork/humming tests, proceeds to formal audiology and tympanometry to confirm conductive ETD versus sensorineural loss, and reserves MRI or vascular imaging for unilateral asymmetric losses, objective/pulsatile tinnitus, or neurologic red flags; ABR may be of historical interest but MRI has largely supplanted it for vestibular schwannoma screening [4] [11] [2]. Sources emphasize that many tinnitus cases remain idiopathic and that laboratory testing has limited yield unless clinical suspicion for specific systemic disease exists [4].
Conclusion
To separate conductive (ETD-related) tinnitus from sensorineural or vascular causes in persistent unilateral tinnitus, start with otoscopy and focused physical maneuvers including auscultation and jugular compression, use tuning‑fork (Weber/Rinne) or humming tests as rapid discriminators, obtain comprehensive audiometry and middle‑ear testing to categorize the hearing loss, and escalate to MRI with contrast for retrocochlear concerns or CT/MR angiography/venography for suspected vascular etiologies; each step is supported by guideline and review literature but must be applied in the context of clinical red flags and limitations of each modality [1] [7] [2] [6] [5].