Audiological Testing for Typewriter Tinnitus
Yes, audiological testing can help diagnose typewriter tinnitus, specifically auditory brainstem response (ABR) testing, which detects the characteristic prolonged interpeak latency I-III (≥2.3 ms) that distinguishes this condition from other forms of tinnitus and can predict treatment response. 1
What Makes Typewriter Tinnitus Different
Typewriter tinnitus presents as paroxysmal attacks of staccato, clicking sounds—often described as Morse code, popcorn, or machine-gun sounds—caused by neurovascular compression of the cochlear nerve. 2, 3 This is fundamentally different from the continuous high-pitched ringing typically associated with noise-induced tinnitus from occupational exposure. 4
Specific Audiological Tests That Help
Auditory Brainstem Response (ABR) - The Key Diagnostic Test
- ABR testing reveals prolonged interpeak latency (IPL) I-III in typewriter tinnitus, with affected ears showing IPL I-III ≥2.3 ms compared to the unaffected side and controls. 1
- ABR also demonstrates longer wave III and V latencies in the affected ear. 1
- This test has diagnostic value because it objectively identifies the neurovascular compression affecting the cochlear nerve pathway. 1
Comprehensive Audiological Evaluation
- Pure tone audiometry, speech audiometry, and acoustic reflex testing should be performed for any persistent or unilateral tinnitus, as recommended by the American Academy of Otolaryngology. 5
- Standard audiometry in typewriter tinnitus patients often shows symmetric hearing consistent with age, unlike typical noise-induced hearing loss which shows asymmetric high-frequency loss. 6
Prognostic Value of ABR Testing
ABR testing predicts which patients will relapse after stopping carbamazepine treatment:
- Patients with IPL I-III >2.4 ms have 100% sensitivity for predicting relapse after medication cessation. 1
- Those with longer IPL I-III, older age, and poorer hearing are significantly more likely to experience symptom recurrence. 1
- This information guides decisions about long-term medication management versus considering surgical decompression. 1
Critical Distinction from Occupational Noise-Induced Tinnitus
Your occupational noise exposure history is less relevant for typewriter tinnitus specifically:
- Occupational noise-induced tinnitus develops gradually over many years of exposure and presents as continuous high-pitched tonal sounds. 4, 7
- Typewriter tinnitus has sudden onset (ages 39-87 years in case series), is unilateral, and has a staccato quality completely distinct from noise-induced tinnitus. 6
- The mechanism is neurovascular compression, not cochlear hair cell damage from noise. 2, 3
Imaging Recommendations
Beyond audiological testing, the American College of Radiology recommends:
- MRI with heavily T2-weighted thin-section sequences to detect neurovascular loops in contact with cranial nerve VIII, which is the definitive diagnostic imaging for typewriter tinnitus. 2, 3
- This imaging can visualize the vascular compression causing your symptoms and guide treatment decisions. 2
Treatment Implications
The diagnosis matters because typewriter tinnitus responds remarkably well to carbamazepine, with alternative options including oxcarbazepine or gabapentin. 3, 1 This is completely different from the limited treatment options for noise-induced tinnitus. 4
Common Pitfall to Avoid
Do not assume your tinnitus is simply noise-induced based on occupational history if it has the staccato, intermittent quality of typewriter tinnitus—this would delay appropriate diagnosis and highly effective treatment. 6