1The Diagnostic Work-up — What to Order and When

FA symptom in search of a cause

Tinnitus is the conscious perception of sound without an external source. It is never a disease in its own right — it is the auditory system reporting that something, somewhere along the pathway from cochlea to cortex, has changed. The job of the work-up is therefore not to “measure the tinnitus” but to characterise the auditory system that is producing it and to exclude the small but important minority of cases with a serious or treatable structural cause [2014].

The great majority of patients have chronic, bilateral, non-pulsatile tinnitus accompanied by some degree of hearing loss. A focused, tiered work-up reassures these patients and guides rehabilitation, while reserving expensive or invasive tests for those whose presentation actually warrants them [2013].

TThe history is the test-selection engine

Before any instrument is switched on, the history has already narrowed the differential. Three features carry most of the diagnostic weight: laterality (unilateral or markedly asymmetric tinnitus raises the question of retrocochlear pathology), character (pulsatile tinnitus points toward a vascular or third-window cause), and associated symptoms (vertigo, aural fullness, otorrhoea, facial numbness or other cranial-nerve signs).

These features behave as branch-points. Symmetric, non-pulsatile tinnitus with symmetric hearing loss needs little beyond audiology; unilateral tinnitus with asymmetric sensorineural loss earns an MRI of the internal auditory canals; pulsatile tinnitus is routed toward temporal-bone CT and vascular imaging [2014]. The clinician who orders tests before taking this history almost always orders the wrong ones.

TAudiology first — always

A comprehensive audiometric assessment is the cornerstone of the tinnitus work-up and should precede every other instrumented test [2014]. There are three reasons. First, it is the highest-yield investigation: more than nine in ten tinnitus patients have measurable hearing loss, and the audiogram frequently reveals the cochlear lesion that is driving the percept [2005]. Second, it triages the rest of the algorithm — asymmetry on the audiogram, not the patient’s impression, is what justifies imaging. Third, the audiogram is the substrate for management: amplification and sound therapy are configured from it.

Audiology also documents a baseline. Because tinnitus is often progressive and medico-legally charged (noise exposure, ototoxic drugs), a dated, quantified record of hearing at presentation has lasting value.

FThe chapter map: a tiered, symptom-driven battery

The investigations in this chapter are best pictured as concentric tiers. The core tier is pure-tone and speech audiometry with tympanometry and acoustic reflexes — performed in essentially every patient. The cochlear/neural tier (otoacoustic emissions, ABR, electrocochleography, extended high-frequency audiometry) refines the picture when thresholds are normal or retrocochlear disease is suspected. The functional tier (psychoacoustic pitch and loudness matching, minimum masking level, residual inhibition, and patient-reported outcome measures) characterises the tinnitus itself and its impact.

Finally, the structural tier (labs and imaging) is invoked only on specific triggers. The art of the work-up is spending the most on the patients most likely to harbour a treatable lesion, and the least on the reassuringly typical majority [2013].