Differential Diagnosis of Vascular Causes of Unilateral Pulsatile Tinnitus
The vascular differential diagnosis of unilateral pulsatile tinnitus is systematically divided into arterial causes (carotid atherosclerosis, dissection, fibromuscular dysplasia), arteriovenous shunts (dural arteriovenous fistulas, arteriovenous malformations, carotid-cavernous fistulas), venous causes (transverse sinus stenosis, sigmoid sinus abnormalities, jugular bulb variants), and vascular tumors (paragangliomas/glomus tumors). 1, 2
Arterial Causes
Carotid atherosclerosis is the most common vascular cause, accounting for 17.5% of pulsatile tinnitus cases, resulting from turbulent flow through stenotic vessels. 2 This can be detected with carotid duplex ultrasound when a neck bruit is present, though CT angiography provides more comprehensive evaluation. 1
Arterial dissection (carotid or vertebral) causes pulsatile tinnitus in 8-10% of patients and represents a life-threatening emergency requiring urgent identification. 1, 2, 3 This diagnosis is critical because delayed recognition can lead to catastrophic stroke. 2, 4
Fibromuscular dysplasia of the carotid arteries creates abnormal arterial flow patterns that generate pulsatile tinnitus. 1, 3 This is best visualized on CT angiography or MR angiography. 1
Arteriovenous Shunts
Dural arteriovenous fistulas (dAVF) account for 8% of pulsatile tinnitus cases and represent the most dangerous missed diagnosis, as they can cause hemorrhagic or ischemic stroke if untreated. 2, 4, 5 These lesions require high clinical suspicion because they may present with isolated pulsatile tinnitus before catastrophic hemorrhage. 2 Digital subtraction angiography has higher sensitivity than CTA or MRA for detecting dAVFs, particularly when noninvasive imaging is negative but clinical suspicion remains high. 1
Arteriovenous malformations (AVMs) are high-flow vascular lesions that can cause pulsatile tinnitus through abnormal arteriovenous shunting. 1, 2, 3
Carotid-cavernous sinus fistulas create abnormal connections between the carotid artery and cavernous sinus, producing pulsatile tinnitus. 1, 3
Venous Causes
Idiopathic intracranial hypertension (IIH) with transverse sinus stenosis is the second most common cause of pulsatile tinnitus overall. 2 This diagnosis is particularly important in young, overweight women with headaches, as missing it can lead to vision loss. 2 The mechanism involves elevated intracranial pressure causing venous sinus stenosis. 1, 3
Sigmoid sinus wall abnormalities (SSWA), including sigmoid sinus diverticulum and sigmoid sinus wall dehiscence, are increasingly recognized causes of pulsatile tinnitus and are commonly associated with intracranial hypertension. 1, 2, 3 These can be identified on high-resolution temporal bone CT. 1
Jugular bulb abnormalities, including high-riding jugular bulb or dehiscence of the sigmoid plate, allow transmission of vascular sounds into the middle ear. 2, 3 These are anatomic variants best seen on temporal bone CT. 1
Aberrant venous anatomy, including persistent petrosquamosal sinus and prominent mastoid or condylar emissary veins, can cause pulsatile tinnitus through abnormal venous drainage patterns. 1, 2, 3
Vascular Tumors
Paragangliomas (glomus tympanicum/glomus jugulare) are highly vascularized skull base tumors accounting for 16% of pulsatile tinnitus cases. 2, 3 These appear as vascular retrotympanic masses on otoscopic examination, making otoscopy a critical part of the evaluation. 1, 2 High-resolution temporal bone CT without contrast is the first-line imaging modality when a retrotympanic mass is visualized. 1, 2
Critical Clinical Distinctions
Objective pulsatile tinnitus (audible to the examiner with a stethoscope) is rare but strongly suggests vascular pathology requiring immediate workup, while subjective pulsatile tinnitus (audible only to the patient) still warrants comprehensive imaging in nearly all cases. 2
Tinnitus relieved by carotid or jugular compression suggests either venous etiology (sigmoid sinus abnormalities, jugular bulb variants) or arterial dissection, helping narrow the differential diagnosis. 2
Common Diagnostic Pitfalls
Missing dural AVF is the most dangerous error, as this life-threatening cause can present with isolated pulsatile tinnitus before catastrophic hemorrhage. 2, 4 If initial CTA/MRA is negative but clinical suspicion remains high, proceed to digital subtraction angiography. 1
Dismissing pulsatile tinnitus as benign is inappropriate, as identifiable causes are found in 70-91% of cases with proper workup. 1, 2, 6, 7 Unilateral pulsatile tinnitus has particularly high likelihood of structural or vascular pathology. 2
Inadequate otoscopic examination can lead to delayed diagnosis of paragangliomas and inappropriate imaging selection. 2 Always perform otoscopy before ordering imaging to determine whether a retrotympanic mass is present, as this fundamentally changes the imaging approach. 1
Overlooking intracranial hypertension in young, overweight women with headaches can result in permanent vision loss if the diagnosis is missed. 2