ABSTRACT
Tinnitus is a condition in which patients perceive sound without an external stimulus. It can be classified into either pulsatile or nonpulsatile tinnitus. This condition affects around 14% of the global population, and the severity of tinnitus can range from barely noticeable to devastating. In most cases, tinnitus is benign and nonpulsatile in nature. The diagnostic role of imaging is to detect treatable and specific pathology. Therefore, a comprehensive clinical assessment, which includes a meticulous examination for associated symptoms like hearing loss, vertigo, or headaches, along with a thorough physical examination, otoscopy, and audiologic testing, is imperative before considering any imaging studies as the choice of imaging will depend on various factors. Nonpulsatile or continuous tinnitus is most commonly associated with presbycusis but can also be caused by functional injuries due to ototoxic medications or exposure to loud noise and usually requires no imaging evaluation. Unlike nonpulsatile tinnitus, imaging patients with pulsatile tinnitus typically reveals perceptible findings. The cause of pulsatile tinnitus is usually a vascular tumor, vascular malformation, or vascular anomaly. Other causes of tinnitus include idiopathic intracranial hypertension, otosclerosis, Paget’s disease, and Meniere’s disease. One of the main challenges is that the underlying cause of tinnitus is often unknown. Another challenge is that tinnitus can have a significant effect on a person’s quality of life, yet the condition is not life-threatening and there is no cure. We present a clinical review of the most prevalent causes of tinnitus along with an emphasis on the diagnostic imaging workup and management of common presentations.
INTRODUCTION
Tinnitus is a medical condition in which patients perceive sound without an external stimulus. The patient may describe the sound as a buzzing, ringing, whistling, hissing, roaring, or whooshing sound.[1] Based on a comprehensive meta-analysis, the pooled prevalence of tinnitus in adults is estimated at 14.4%, with a range spanning from 4.1–37.2%, with 2.3% of adults experiencing a severe form of it.[2] This translates to affecting over 740 million adults worldwide. Furthermore, although the prevalence of tinnitus does not differ by sex, it rises significantly with advancing age.[2] The severity of tinnitus can range from barely noticeable to severely debilitating. In most cases, tinnitus is benign, nonpulsatile, and strongly associated with sensorineural hearing loss.[3] A comprehensive clinical assessment, which includes a meticulous examination for associated symptoms like hearing loss, vertigo, or headaches, along with a thorough physical examination, otoscopy, and audiologic testing, is imperative before considering any imaging studies as the choice of imaging will depend on various factors.
CLASSIFICATION OF TINNITUS
Tinnitus can be classified in several ways such as primary or secondary, subjective or objective, and pulsatile or nonpulsatile.[1] Pulsatile tinnitus is usually synchronous with the patient’s heartbeat and may be either subjective (heard only by the patient) or objective (heard by both the patient and an examiner listening with a stethoscope).[4] Primary tinnitus is idiopathic, whereas secondary tinnitus is typically linked to an underlying and identifiable factor. Subjective nonpulsatile tinnitus emerges as the most frequently observed form of tinnitus, affecting between 70% and 80% of patients with tinnitus.[5]
Nonpulsatile Tinnitus
Primary nonpulsatile tinnitus does not appear to have an established cause. However, it is most commonly accompanied by age-related hearing loss (presbycusis), and risk factors include hypertension, increasing age, and anxiety.[6] Secondary nonpulsatile tinnitus is a symptom of an underlying disorder, such as otosclerosis, middle ear disease, and vestibular schwannoma. Nonpulsatile or continuous tinnitus may also be associated with functional injuries such as medication toxicity or exposure to loud noise.[7]
Pulsatile Tinnitus
Pulsatile tinnitus, also known as pulse-synchronous tinnitus, is characterized by a rhythmic sound that aligns with the heartbeat. Patients can describe this phenomenon by tapping their finger in sync with the perceived rhythm.[8,9] It may manifest as either subjective, audible only to the patient, or objective, detectable by both the patient and the healthcare provider. In certain instances, the sound can even be discerned by the physician during auscultation at the area of interest. Imaging patients with pulsatile tinnitus yields a high diagnostic value, as pathology can be seen in 40–70% of cases.[5,10]
The literature regarding the causes of pulsatile tinnitus is diverse. The causes of pulsatile tinnitus can be classified into vascular tumors, vascular malformations, or vascular anomalies. The most common venous causes of pulsatile tinnitus are idiopathic intracranial hypertension (IIH) and sigmoid sinus wall abnormalities (e.g., dehiscence, diverticulum). The most commonly reported arterial causes are arterial stenosis (e.g., atherosclerosis) and dural arteriovenous (AV) fistulas and malformations.[1,5,9–12] If clinical suspicion of IIH is present (headaches, vision loss, elevated body mass index), the first diagnostic step involves conducting a computed tomography venogram (CTV) or magnetic resonance venogram (MRV) to visualize the venous system. This diagnostic tool helps identify potential dural venous sinus stenosis, which may contribute to pulsatile tinnitus.[11]
Vascular tumors such as paragangliomas can present typically close to the middle ear cavity and can sometimes be visualized on otoscopy. The best modality to diagnose paragangliomas at the skull base and temporal bone is magnetic resonance imaging (MRI) with contrast with CT correlation to look for a moth-eaten or permeative appearance. Vascular tumors can be often divided into three main entities: glomus tympanicum, glomus jugulare, and glomus jugulotympanicum. Both glomus jugulare and jugulotympanicum have a salt (T1) and pepper (T2)–like appearance on MRI.[13]
Vascular malformations can be classified into AV malformations and fistulas. An AV malformation is an abnormal communication between an artery and vein with a visible nidus, whereas an AV fistula is an abnormal communication between an artery and vein but without a nidus. A time-of-flight MR angiography will show a flow-related signal in the transverse sinus and jugular bulb, suggestive of venous shunting in AV fistulas.[7]Figure 1 displays images of a vascular malformation presenting in a 68-year-old female patient as objective pulsatile tinnitus.
A 68-year-old woman with left-sided objective pulsatile tinnitus. A. CT angiogram viewed on bone windows shows transosseous vascular channels in the left occipital bone (white arrows) as well as arterial filling in the dural venous sinuses (white stars). B. Digital subtraction angiography shows a selective injection of the left occipital artery, demonstrating fistulous connection with the left transverse venous sinus. CT: computed tomography.
A 68-year-old woman with left-sided objective pulsatile tinnitus. A. CT angiogram viewed on bone windows shows transosseous vascular channels in the left occipital bone (white arrows) as well as arterial filling in the dural venous sinuses (white stars). B. Digital subtraction angiography shows a selective injection of the left occipital artery, demonstrating fistulous connection with the left transverse venous sinus. CT: computed tomography.
Vascular anomalies may be an incidental observation completely unrelated to the cause of tinnitus, therefore even when discovered, the physician should keep searching for another, more plausible source of pathology. They can be broadly categorized into jugular bulb abnormalities, sigmoid sinus wall abnormalities (e.g., dehiscence, diverticulum), aberrant carotid artery, and persistent stapedial artery. The general approach to such anomalies is with bone algorithm CT scans, CT or MR angiography, and MR venography.[7]
Jugular bulb abnormalities include a high-riding jugular bulb above the level of the floor of the internal auditory canal or tympanic annulus. There can also be jugular bulb diverticulum or dehiscence, where the anterior osseous margin is missing, and this can sometimes be visible on direct otoscopy. Sigmoid plate dehiscence can also occur with or without diverticulum and is a commonly underrecognized cause of pulsatile tinnitus. Figure 2 illustrates pulsatile tinnitus in a 50-year-old man, attributed to a high-riding jugular bulb and a small diverticulum.
A 50-year-old man with pulsatile tinnitus underwent a CT temporal bone scan (coronal images displayed). A. A high-riding jugular bulb (white arrows). B. A small diverticulum (black arrow) arising from the jugular bulb. CT: computed tomography.
A 50-year-old man with pulsatile tinnitus underwent a CT temporal bone scan (coronal images displayed). A. A high-riding jugular bulb (white arrows). B. A small diverticulum (black arrow) arising from the jugular bulb. CT: computed tomography.
In the case of an aberrant carotid artery, a hypertrophied inferior tympanic artery (a branch of the external carotid artery) communicates with the caroticotympanic artery to reestablish the internal carotid. The aberrant course of the artery passes through the hypotympanum and under the cochlear promontory, causing symptoms. A persistent stapedial artery occurs in the setting of an absent foramen spinosum. The middle meningeal artery arises from a persistent stapedial artery instead of the maxillary artery.
Miscellaneous Causes of Tinnitus
Other causes of tinnitus include otosclerosis, Paget’s disease, and Meniere’s disease, which can all be well detected on CT of the temporal bones. Carotid stenosis and dissection are pathologies that are best seen on a CT angiogram, whereas other causes like hypertension and anemia should be investigated primarily with laboratory testing.
IMAGING APPROACH AND MANAGEMENT
The diagnostic role of imaging is to detect treatable and specific pathology. Although it is critical not to miss significant pathology, it is also important not to overscan people where substantial pathology is unlikely. Not only is this cost avoidable, but it may also be stressful and unpleasant for the patient and expose them to an unnecessary dose of ionizing radiation or risk of adverse effects from the contrast agent. Some individuals may become anxious while waiting for the scan results; the clinician can help minimize this anxiety by openly discussing the reasons for the scan, the benefits and risks of the scan, and the possible outcomes. In their Clinical Practice Guideline on Tinnitus, the American Academy of Otolaryngology makes a strong recommendation against pursuing imaging for patients with tinnitus alone.[14] Neuroimaging is only recommended for patients whose tinnitus is unilateral, pulsatile, associated with asymmetric hearing loss, or associated with additional neurologic deficits or a history of trauma.[1,3,4] Patients with pulsatile tinnitus would consider it desirable to have an investigation that would either indicate a condition to be treated or rule out any serious pathology.[15]
It is important to note that imaging is not recommended in the setting of bilateral nonpulsatile tinnitus without hearing loss.[16] However, if it is asymmetric, the imaging of choice is a contrast-enhanced MRI of the brain and internal auditory canals.[16] This imaging protocol is designed to detect a lesion in the internal auditory canal or cerebellopontine angle such as a vestibular schwannoma. Usually, however, most patients with nonpulsatile tinnitus do not have imaging abnormalities. Less common causes of continuous tinnitus include palatal or middle ear myoclonus, multiple sclerosis, Chiari malformations, and nonsteroidal anti-inflammatory drugs.[7] Tinnitus with asymmetric hearing loss should be evaluated with imaging. Conductive hearing loss suggests evaluation with CT of the temporal bones. For sensorineural hearing loss, MR imaging is recommended.
CLINICAL MANAGEMENT OF TINNITUS
The clinical assessment of tinnitus starts with a meticulous examination of the patient’s history and a thorough head and neck physical examination with otoscopy. Once the nature of tinnitus is characterized, distinguishing between subjective or objective and pulsatile or nonpulsatile is important. If a patient reports pulse-synchronous tinnitus that worsens with ipsilateral neck compression, there is a high likelihood of an arterial abnormality. Conversely, if the tinnitus improves with ipsilateral neck compression, there is a strong indication of an underlying venous abnormality.[5,12]
The presence of a vascular retrotympanic lesion on otoscopic examination in pulsatile tinnitus introduces a distinct set of differential diagnostic considerations that influences the decision-making process regarding which imaging studies to pursue and their sequential order.[1] The next crucial step involves a comprehensive hearing test. This step is pivotal in precisely determining the presence of associated hearing loss and discerning its type, whether conductive, sensorineural, or mixed. In addition to otoscopy, the Weber and Rinne tuning fork tests can offer insights into the type of hearing loss. Although these tuning fork tests can be informative, every patient undergoing tinnitus evaluation should undergo a comprehensive audiogram, providing a more detailed and accurate assessment of their auditory function.[17] The decision to undergo further imaging will depend on the findings of the history, physical examination, and audiologic testing. Figure 3 is an optimized imaging algorithm for tinnitus that can be used to guide the clinician, based on clinical manifestations seen on assessment of the patient.
Optimized imaging algorithm for tinnitus, based on clinical manifestations seen on assessment. CT: computed tomography; CTV: CT venography; MRV, magnetic resonance venography; IIH: idiopathic intracranial hypertension; MRI IAC: magnetic resonance imaging of the internal auditory canal.
Optimized imaging algorithm for tinnitus, based on clinical manifestations seen on assessment. CT: computed tomography; CTV: CT venography; MRV, magnetic resonance venography; IIH: idiopathic intracranial hypertension; MRI IAC: magnetic resonance imaging of the internal auditory canal.
Tinnitus can have a significant effect on a person’s quality of life, negatively affecting sleep, concentration, and overall well-being.[18] In cases associated with secondary causes of pulsatile tinnitus, treatment of the underlying pathology usually allows tinnitus to subside. If there is associated hearing loss, treating this hearing loss may lead to a reduction in tinnitus. Management options for hearing loss–associated tinnitus include hearing aids, sound therapy, and tinnitus retraining therapy. Hearing aids can help amplify external sounds, which can make tinnitus less noticeable. Sound therapy, which involves exposing the person to soothing sounds, can also be helpful. Tinnitus retraining therapy is a form of habituation therapy that aims to retrain the brain to ignore the tinnitus.[19] However, many people do not find relief from these treatments. Furthermore, the treatment response can be highly variable among individuals, making it difficult to predict which treatment will be effective for a specific person.
CONCLUSION
Tinnitus is a complex condition that can be difficult to treat. A key obstacle is that the root cause of tinnitus is often unknown, and that the known etiopathologic factors demonstrate a wide range of conditions. Before considering any imaging tests, a comprehensive approach involving a detailed patient history, a thorough physical examination encompassing otoscopy, and audiologic testing is essential to guide the clinician to the imaging modality of choice. In most cases, tinnitus manifests as benign and nonpulsatile, often closely linked with age-related hearing loss. It is important to refrain from ordering imaging tests for cases of nonpulsatile bilateral tinnitus without accompanying hearing loss, particularly in the absence of neurologic dysfunction or a history of trauma. For cases involving pulsatile tinnitus, normal otoscopy, and the absence of signs of IIH, the preferred imaging modality is a CT angiogram. This selective approach ensures a targeted investigation in cases where imaging is necessary to detect treatable and specific pathology.
References
Competing Interests
Source of Support: None. Conflict of Interest: None