What is the differential diagnosis for a patient presenting with tinnitus, considering potential causes such as exposure to loud noises, earwax buildup, certain medications (e.g. aspirin), and underlying medical conditions (e.g. hypertension, thyroid disorders)?

Differential Diagnosis for Tinnitus

Critical First Distinction: Pulsatile vs. Non-Pulsatile

The most important initial step is determining whether the tinnitus is pulsatile (synchronous with heartbeat) or non-pulsatile, as this fundamentally changes the differential diagnosis and urgency of evaluation. 1, 2

Pulsatile Tinnitus Differential (Requires Urgent Imaging)

Pulsatile tinnitus has an identifiable structural or vascular cause in over 70% of cases and can represent life-threatening pathology. 1

Arterial Causes:

• Atherosclerotic carotid artery disease (most common cause, 17.5% of pulsatile tinnitus cases) 1
• Arterial dissection (potentially life-threatening, requires urgent identification) 1
• Fibromuscular dysplasia of carotid arteries 3

Arteriovenous Causes:

• Dural arteriovenous fistulas (8% of cases, can lead to hemorrhagic or ischemic stroke if untreated) 1
• Arteriovenous malformations (high-flow vascular lesions) 1
• Carotid cavernous sinus fistulas 3

Venous Causes:

• Idiopathic intracranial hypertension (second most common cause of pulsatile tinnitus, particularly in young overweight women) 1
• Sigmoid sinus diverticulum or dehiscence 1
• Jugular bulb abnormalities (high-riding jugular bulb or dehiscence of sigmoid plate) 1
• Transverse sinus stenosis 3
• Aberrant venous anatomy (persistent petrosquamosal sinus, abnormal condylar and mastoid emissary veins) 1

Vascular Tumors:

• Paragangliomas (glomus tympanicum/jugulare) (16% of pulsatile tinnitus cases, appear as vascular retrotympanic masses on otoscopy) 1
• Adenomatous middle ear tumors 1

Bony/Structural Abnormalities:

• Superior semicircular canal dehiscence (allows transmission of vascular sounds) 1
• Sigmoid sinus wall dehiscence 3
• Paget disease affecting temporal bone 3

Non-Pulsatile Tinnitus Differential

Primary Otologic Causes:

• Sensorineural hearing loss (most common underlying cause of non-pulsatile tinnitus) 3, 2, 4, 5
• Presbycusis (age-related hearing loss, most common in older adults) 3
• Noise exposure (occupational or recreational) 3, 2
• Sudden sensorineural hearing loss 3, 2
• Cochlear synaptopathy ("hidden hearing loss") 3
• Cerumen impaction 6
• External ear infection 6
• Middle ear effusion 6
• Otosclerosis (conductive hearing loss) 3, 2
• Menière's disease 3, 4, 7
• Eustachian tube dysfunction 2

Neurologic Causes:

• Vestibular schwannoma (acoustic neuroma) - particularly with unilateral tinnitus and asymmetric hearing loss 1, 4, 7
• Neurodegeneration 3
• Spontaneous intracranial hypotension 3

Pharmacologic Causes:

• Ototoxic medications (e.g., aspirin, aminoglycosides, loop diuretics, chemotherapy agents) 3, 2, 7

Other Causes:

• Temporomandibular joint dysfunction 2
• Trauma 7

Psychogenic Factors:

• Anxiety and depression (can be both cause and consequence) 1, 3

Red Flags Requiring Urgent Evaluation

Immediate imaging and specialist referral indicated for: 1, 2, 5

• Pulsatile tinnitus (any presentation)
• Unilateral or asymmetric tinnitus
• Focal neurological abnormalities
• Asymmetric hearing loss
• Sudden onset unilateral tinnitus with hearing loss
• Objective tinnitus (audible to examiner - strongly suggests vascular pathology)
• Severe anxiety or depression (increased suicide risk requires prompt intervention) 1, 3

Common Clinical Pitfalls

• Dismissing pulsatile tinnitus as benign without imaging - treatable and life-threatening causes are common 1
• Missing dural arteriovenous fistula - can present with isolated pulsatile tinnitus before catastrophic hemorrhage 1
• Inadequate otoscopic examination - can miss vascular retrotympanic masses (paragangliomas) 1
• Overlooking intracranial hypertension in young overweight women with headaches - can lead to vision loss 1
• Ordering imaging for bilateral, symmetric, non-pulsatile tinnitus without localizing features - represents inappropriate resource utilization with no benefit 1, 2