Tinnitus

Tinnitus is the perception of sound — ringing, buzzing, hissing, whooshing, clicking, or pulsing — in the absence of an external sound source. It may affect one or both ears and may be continuous or intermittent. Tinnitus is one of the most prevalent sensory symptoms, common in the general population, though in most cases mild and non-disabling. A smaller proportion of individuals experience tinnitus severe enough to interfere with sleep, concentration, and daily life. In the clinical context of skull base and cranial nerve disease, tinnitus — particularly when it is unilateral, pulsatile, or accompanied by hearing loss or balance disturbance — is an important early warning symptom that should prompt investigation

Tinnitus can be broadly categorized as non-pulsatile (a continuous or intermittent tone or noise) or pulsatile (a rhythmic sound synchronized with the heartbeat). Relevant causes in the brain tumor and skull base context include:

• Vestibular schwannoma (acoustic neuroma) — a common cause of unilateral non-pulsatile tinnitus, typically high-pitched and occurring in the same ear as progressive hearing loss.
• Glomus tumors (paragangliomas) — vascular tumors of the skull base that are the classic cause of pulsatile tinnitus; the pulsation reflects transmission of blood flow through the tumor's rich vascular network.
• Skull base tumors — any lesion involving the petrous bone, internal auditory canal, or jugular foramen can produce tinnitus by directly irritating cochlear or vestibular nerve fibers.
• Post-traumatic tinnitus — following temporal bone fracture or labyrinthine concussion from head injury; one of the most common sequelae of head trauma involving the ear region.
• Noise-induced and age-related hearing loss — the most common causes of bilateral tinnitus in the general population, reflecting damage to outer hair cells in the cochlea.

Medications — including aspirin in high doses, certain antibiotics (aminoglycosides), and loop diuretics — can cause or worsen tinnitus and should be reviewed in any patient presenting with new tinnitus.

Most cases of intermittent, bilateral, mild tinnitus in the setting of noise exposure or aging do not require specialist investigation. The following circumstances warrant prompt evaluation:

• Unilateral tinnitus — one-sided tinnitus, particularly when new and persistent, should always be investigated with audiometry and MRI of the internal auditory canals to exclude vestibular schwannoma.
• Pulsatile tinnitus — a rhythmic whooshing or thumping sound synchronized with the pulse, which may indicate a vascular tumor (paraganglioma), arteriovenous fistula, or venous sinus pathology.
• Tinnitus combined with hearing loss, dizziness, or ear fullness — particularly when ipsilateral, a combination that raises the probability of a structural or labyrinthine lesion.
• Sudden-onset tinnitus, particularly if accompanied by sudden hearing loss — which constitutes a medical urgency requiring rapid evaluation and treatment.
• Tinnitus following head injury — which may indicate temporal bone injury or labyrinthine concussion.