Vascular and Bony Causes of Audible Bruit Behind the Ear

Vascular Causes

• Arterial dissection can cause abnormal blood flow, leading to pulsatile tinnitus, as reported by the American College of Radiology 1, 2
• Fibromuscular dysplasia of the carotids is a vascular anomaly that can cause pulsatile tinnitus, according to the American College of Radiology 3
• Dural arteriovenous fistulas (dAVF) are abnormal connections between arteries and veins that can cause pulsatile tinnitus, as noted by the American College of Radiology 1, 2
• Arteriovenous malformations (AVM) can cause pulsatile tinnitus due to abnormal blood flow, as reported by the American College of Radiology 3
• Carotid cavernous sinus fistulas can cause pulsatile tinnitus due to abnormal blood flow, according to the American College of Radiology 3
• Transverse sinus stenosis is often associated with idiopathic intracranial hypertension and can cause pulsatile tinnitus, as noted by the American College of Radiology 3
• Sigmoid sinus diverticulum can cause pulsatile tinnitus due to abnormal blood flow, as reported by the American College of Radiology 1, 2
• Persistent petrosquamosal sinus can cause pulsatile tinnitus due to abnormal blood flow, according to the American College of Radiology 1, 2
• Prominent mastoid or condylar emissary veins can cause pulsatile tinnitus due to abnormal blood flow, as noted by the American College of Radiology 3
• Paragangliomas (glomus tumors) are highly vascular tumors that can occur in the middle ear and cause pulsatile tinnitus, as reported by the American College of Radiology 1, 4
• Vascular middle ear tumors can cause pulsatile tinnitus due to abnormal blood flow, according to the American College of Radiology 1, 4

Bony Abnormalities

• Superior semicircular canal dehiscence is an abnormal opening in the bone overlying the superior semicircular canal that can cause pulsatile tinnitus, as noted by the American College of Radiology 2, 3
• Sigmoid sinus wall dehiscence can cause pulsatile tinnitus due to abnormal blood flow, according to the American College of Radiology 3
• High jugular bulb is an abnormally high position of the jugular bulb that can cause pulsatile tinnitus, as reported by the American College of Radiology 1, 3
• Paget disease is a bone disorder that can affect the temporal bone and cause pulsatile tinnitus, as noted by the American College of Radiology 3

Clinical Approach

• The American College of Radiology recommends determining if the tinnitus is pulsatile or non-pulsatile, and checking if the sound is objective or subjective, as part of the initial assessment 1
• Otoscopic examination should be performed to identify any vascular retrotympanic mass, as noted by the American College of Radiology 1, 4
• For pulsatile tinnitus without visible retrotympanic lesion, CT angiography (CTA) of the head and neck is recommended as a first-line imaging modality, according to the American College of Radiology 1, 2
• Dedicated temporal bone CT can identify bony abnormalities and vascular variants, as reported by the American College of Radiology 1, 4
• MRI and MR angiography (MRA) are comparable to catheter angiography in detecting vascular abnormalities, as noted by the American College of Radiology 2
• Carotid duplex or Doppler ultrasound is helpful when carotid stenosis is suspected, according to the American College of Radiology 2
• For pulsatile tinnitus with visible retrotympanic lesion, high-resolution temporal bone CT without IV contrast is recommended as first-line imaging, as reported by the American College of Radiology 5

Imaging Evaluation of Jugular Bulb Lateral Diverticulum

Preferred Initial Modality

• High‑resolution temporal bone CT without contrast is recommended as the first‑line imaging technique to characterize jugular bulb diverticula and associated bony dehiscence in adults. (American College of Radiology) 6, 7

Additional Cross‑Sectional Techniques

• CT angiography with bone algorithms can be employed to assess dehiscence of the sigmoid plate or jugular bulb when detailed bony anatomy is required. (American College of Radiology) 6, 7
• MRI/MRA may be added when soft‑tissue characterization is needed or to exclude alternative causes of pulsatile tinnitus or hearing loss. (American College of Radiology) 6, 7

Role of CT in Differential Diagnosis

• High‑resolution CT reliably distinguishes jugular bulb diverticulum from mimicking lesions such as glomus tumors, vascular middle‑ear masses, and other causes of pulsatile tinnitus by demonstrating the venous origin and direct connection to the jugular bulb. (American College of Radiology) 6, 7
• Temporal bone CT effectively differentiates vascular and bony abnormalities—including sigmoid sinus diverticulum, high jugular bulb, and superior semicircular canal dehiscence—when evaluating patients with pulsatile tinnitus or retrotympanic masses. (American College of Radiology) 6, 7