Not only is pulsatile tinnitus a common, irritating (or worse) condition that three-fourths of adults will experience in their lifetimes, but it also is the canary in the coal mine for many potentially serious underlying conditions. 

For some, the persistent "whooshing" sound that is rhythmic and synchronous with the patient's heartbeat will be nothing more than a mild nuisance, but tinnitus can affect cognition, decrease quality of life, contribute to stress, depression, and anxiety, and even lead to suicide when severe and persistent. More than 75% of patients experiencing pulsatile tinnitus will have positive and often subtle findings on imaging that will identify a wide gamut of pathologic conditions that in some cases could lead to serious harm if not diagnosed and treated. However, the optimal diagnostic paradigm is based on a thorough physical examination with relevant clinical context to inform the appropriate choice of imaging modality and technique.

A Common but Serious Condition

With the literature changing rapidly due to improved imaging techniques and novel minimally invasive treatments, Suehyb Alkhatib, MD—an neurointerventional radiologist (NIR) with member practice Radiology Associates of Richmond—and colleagues undertook a literature review focusing on pathophysiologic mechanisms, diagnostic pathways, imaging findings, and management strategies.

"I really enjoy high-resolution imaging," said lead author Dr. Alkhatib. "I came into neuroradiology and NIR because of 3D T2 internal auditory canal (IAC) imaging, where we can literally see individual nerves, and 3D time-of-flight imaging of the Circle of Willis. A temporal bone CT has similar high resolution detailed anatomy but was always intimidating to interpret. I spent a lot of time trying to get more comfortable with temporal bone and IAC imaging while also learning neurointervention and that kind of formed the basis for the start of a lot of this work."

When in fellowship at the University of Pennsylvania, Dr. Alkhatib started to develop an interest in idiopathic intracranial hypertension (IIH) as a disease process and the role of imaging in its diagnosis.  He read a temporal bone CT for a patient with pulsatile tinnitus, and questioned an area of sigmoid wall thinning, one of the causes of pulsatile tinnitus.

Dr. Alkhatib (center) and two of his co-authors, Sandeep Kandregula, MD, and Kelley Flesher, MD

"The patient had a prior CT several years old that was interpreted as normal," he recalled. "I subsequently met her in preparation for a diagnostic cerebral angiogram and ultimately participated in her venous sinus stenting. She was tearful after the procedure because it was the first time in years she didn't hear the tinnitus, after seeing multiple physicians and having repeat imaging all read as normal. That experience really gave me a new appreciation for how impactful we can be and started the journey for wanting to start compiling the patient's imaging into an article that can be used as a reference for this challenging condition."

The resulting paper published recently in Radiographics yielded a structured framework that will be quite useful for community and academic radiologists and their referents with good potential for improving patient lives as many patients can be cured or experience meaningful improvement in symptoms. The authors also share common imaging findings, normal variants, and common misses, misinterpretations and artifacts, in a review article that is fully illustrated with clinical images, useful tables, and a diagnostic algorithm.

Why History Matters

A thorough exam including auscultation of the neck, ear, and surrounding structures is a must in patients with pulsatile tinnitus. Because of the high incidence of positive findings, the authors urge the radiologist to make an effort to obtain the clinical scenario and access the patient's symptoms in the medical record.

For instance, the pitch of the tinnitus will help differentiate a venous from an arterial cause: high-pitched tinnitus with objective components such as an audible bruit is more likely due to an arterial or arteriovenous junction cause. Tinnitus due to a venous cause will likely be low pitched. Pulsatile tinnitus that is altered with head positioning, standing, or lying down supports a venous cause; likewise, alteration of pulsatile tinnitus with jugular vein compression.

Hypercoagulability may suggest a venous cause, while trauma or neck manipulation would support a possible arterial cause (e.g .an internal carotid or vertebral artery dissection). Conductive hearing loss can lead to pulsatile tinnitus; this is more common with bony structural and neoplastic causes or middle ear masses.

"These are all details that can help clue the radiologist into possible causes and can help guide the radiologist's eye to the underlying pathologic condition, which can sometimes be subtle," Dr. Alkhatib et al wrote. The authors created an algorithm for diagnostic purposes (see Figure), a helpful table that lists vascular imaging and search patterns based on clinical history.

Once the history is clarified, appropriate imaging can be recommended, and the imaging findings can be reviewed systematically to evaluate for potential underlying treatable disease. Careful review of the history and physical examination results will improve the diagnostic yield of imaging.

Imaging Pulsatile Tinnitus

Pulsatile tinnitus can be attributed to any cause of altered conduction or blood flow within the temporal bone, either from altered arterial or venous vascular flow, an abnormal arteriovenous connection, a hypervascular mass in the temporal bone, thinning of the temporal bone cortex, or loss of normal ossicular conduction.

When there is no conductive hearing loss, the initial workup should include MR angiography or MR venography to assess for venous or arterial causes, depending on the supporting clinical feature. Other options are CT angiography or CT venography, but MR— angiography or venography—is the most appropriate initial test for patients presenting with pulsatile tinnitus and an audible bruit or alteration of tinnitus with head position or internal jugular vein compression.

In the presence of conductive hearing loss, bone CT is the study of choice. Other imaging modalities and techniques, including arterial spin labeling, digital subtraction angiography, duplex ultrasound,  and lumbar puncture should be considered based on supporting clinical features.

"If a vascular cause is suspected, invasive diagnostic angiography may allow confirmation of the suspected finding and provide insight into potential treatment options and remains the standard of reference," the authors wrote.

Venous Causes. Most often, pulsatile tinnitus is caused by alterations in venous flow, with lesions located from the transverse sinus to any place in the internal jugular vein through the mediastinum. The most common cause is venous sinus stenosis, often seen in combination with IIH, but not always. Jugular bulb anomalies are another common cause but also are seen often with venous sinus stenosis. 

Arteriovenous Junction Causes. Up to one-fifth of patients undergoing workup for pulsatile tinnitus may have a dural arteriovenous fistula (an acquired abnormal connection between a dural arterial supply and adjacent vein frequently in the setting of a preceding trauma). As previously stated, this is the lesion of greatest clinical concern. "All cases of pulsatile tinnitus should have a high index of suspicion for arteriovenous junction entities, as these can represent dangerous lesions that are at risk for rupture, resulting in significant morbidity and even in death," wrote Alkhatib et al.

Arterial Causes. The authors enumerated common and uncommon arterial causes of pulsatile tinnitus and urged careful evaluation of the arterial vascular tree for aneurysms, particularly intradural aneurysms, which can rupture and cause significant patient harm.

Clues in the patient history include atherosclerotic disease, hypertension, dyslipidemia, and smoking.

Osseous Causes. CT of the temporal bone is the most appropriate study for evaluating the inner ear structures, middle ear and mastoid portion of the temporal bone in patients with pulsatile tinnitus and conductive hearing loss, although vascular imaging may still be required to rule out dural arteriovenous fistula or arteriovenous malformation. Any pathology that alters the bony structures of the middle or inner ear, the tegmen, or the bone covering the blood vessels running through the area of the mastoid can contribute to pulsatile tinnitus. The most common osseous defect causing pulsatile tinnitus is an abnormality of the sigmoid plate; thinning of the sigmoid sinus wall is an imaging finding that is easily missed.

Neoplasms and Other Masses. Hypervascular masses involving the petrous, mastoid, or tympanic part of the temporal bone can manifest with pulsatile tinnitus; parapanglioma is the most common middle ear mass causing pulsatile tinnitus. Other less common neoplastic causes include any vascular tumor of the petrous bone, skull-base or petrous meningiomas, skull base low-flow venous malformations, and skull base and inner ear schwannomas. Depending on the suspected mass, temporal bone CT and MRI are used; in head and neck paraganglioma, gallium 68 tetraazacyclododecane tetraacetic acid–octreotate (DOTATATE) or copper 64–DOTATATE scanning can help with staging and provide increased sensitivity for detecting additional sites of involvement. 

The authors also included a review of treatment options for the myriad clinical findings. Click here for access to "Imaging of Pulsatile Tinnitus"  published online Sept. 5, 2024, by Radiographics.  "Shared decision making regarding the extent of imaging workup and treatment options should be undertaken with the patient, considering the patient's perceived disability, the risk features of the specific underlying pathologic condition, and the patient's broader health picture," Dr. Alkhatib et al recommended.

Conclusion

The authors conclude that imaging findings can be subtle, but most patients with pulsatile tinnitus will have an identifiable and often treatable cause of tinnitus at imaging. Given the high incidence of positive findings, care should be taken to access relevant patient history to guide both imaging modality and protocol selection and interpretation.

Having undertaken this literature review with colleagues, Dr. Alkhatib gained a greater appreciation for the importance of the entire care team in arriving at an efficient and accurate diagnosis. "A good history is very important in evaluating imaging performed for pulsatile tinnitus, at the very least knowing whether the tinnitus is pulsatile or not and the side of tinnitus," he said, adding that he has reached into the ENT community in Radiology Associates of Richmond practice-area and visited several clinics. "I've made an effort to reach out to our regional ENT physicians and let them know I'm interested in this condition."

Access the full article in Radiographics here.