5Psychoacoustic and Temporal Subtypes

FListening to the description

Tinnitus is invisible, so the patient’s own description is the first investigation. Beyond the subjective/objective and functional/structural axes, clinicians subtype tinnitus by its psychoacoustic and temporal characteristics — the qualities the patient reports about the sound itself [2013]. Four pairs do most of the diagnostic work: continuous vs intermittent, pulsatile vs non-pulsatile, tonal vs noise-like, and unilateral vs bilateral.

None of these descriptors is a diagnosis on its own. Their power is in combination: each one shifts the probabilities, and together they steer the choice of investigation long before any equipment is switched on [2013].

TPulsatile vs non-pulsatile: the highest-yield split

Of all the descriptors, pulsatility is the most consequential. Tinnitus that beats in time with the heart points toward a vascular generator — turbulent or transmitted blood flow — and is the descriptor most likely to be objective and structural [2013]. Causes include arteriovenous fistulas, sigmoid-sinus or jugular-bulb anomalies, carotid atherosclerosis and idiopathic intracranial hypertension.

Because a pulsatile complaint can flag a treatable or even dangerous lesion, it has its own work-up: auscultation of the ear, neck and orbit, then dedicated vascular imaging such as CT or MR angiography and venography [2008]. Non-pulsatile (continuous-tone) tinnitus, by contrast, is the everyday neural-network type and almost never needs angiography [2013].

TTonal, noise-like, continuous, intermittent

The remaining descriptors refine the picture. Tonal tinnitus — a pure whistle or ring — is the commonest form in noise- and age-related cochlear damage, typically pitched in the region of the audiometric loss. Noise-like tinnitus (hissing, buzzing) is also common and similarly maps to sensorineural injury [2013].

Temporal pattern adds prognostic and mechanistic colour: continuous tinnitus is the chronic, habituation-target form, whereas intermittent or clicking tinnitus — especially if rhythmic and not heartbeat-synchronous — raises middle-ear or palatal myoclonus, a muscular (often objective) cause distinct from the vascular pulsatile group [2013]. A clicking that the patient can sometimes trigger by jaw or neck movement also hints at a somatosensory contribution.

CUnilateral vs bilateral: when laterality mandates MRI

Laterality is the descriptor with the clearest action attached. Most functional, cochlear tinnitus is bilateral and symmetrical, tracking a symmetrical audiogram. A unilateral percept — particularly with asymmetric sensorineural hearing loss — is the cardinal red flag for a retrocochlear lesion such as a vestibular schwannoma, and it mandates contrast MRI of the internal auditory canals [2014].

Putting the descriptors together yields a working differential before any scan: pulsatile drives a vascular work-up; unilateral with asymmetric loss drives an MRI; rhythmic clicking drives a search for myoclonus; and bilateral, non-pulsatile, tonal tinnitus with a symmetrical loss is reassuringly functional [2013]. This is why a careful history of the sound is the single most cost-effective step in tinnitus assessment.