From the Guidelines
There is significant value in adding MR angiogram (MRA) of the brain in the evaluation of pulsatile tinnitus, as it can help identify vascular abnormalities that may be causing the condition, such as arteriovenous malformations, dural arteriovenous fistulas, vascular stenosis, or vascular tumors like paragangliomas or glomus tumors, as highlighted in the most recent guidelines 1. The use of MRA in pulsatile tinnitus is supported by the fact that vascular causes account for a significant percentage of cases, and identifying them is crucial for appropriate management. Key points to consider when using MRA for pulsatile tinnitus include:
- The importance of combining MRA with standard MRI of the brain and temporal bones for a comprehensive evaluation of both vascular and non-vascular structures 1.
- The use of non-contrast time-of-flight MRA technique, which is often sufficient, though contrast-enhanced MRA may provide additional information in some cases.
- The need for both arterial and venous phase imaging to capture venous abnormalities, such as sigmoid sinus diverticulum or dehiscence, which are common causes of pulsatile tinnitus that might be missed with arterial imaging alone 1. Given the potential of MRA to identify treatable causes of pulsatile tinnitus and improve patient outcomes, its inclusion in the diagnostic workup is recommended, particularly when guided by a detailed history and clinical evaluation, as emphasized in the latest guidelines 1.
From the Research
Value of MR Angiogram Brain in Pulsatile Tinnitus
- The addition of MR angiogram to the evaluation of pulsatile tinnitus has been shown to be beneficial in identifying the underlying cause of the condition 2.
- A study published in 1994 found that MR angiography, in conjunction with spin-echo imaging, markedly enhances the ability of MR to diagnose the lesions responsible for pulsatile tinnitus, with 46% of lesions seen best and 36% seen only on MRA 2.
- More recent studies have also highlighted the importance of non-invasive imaging modalities, including MRI and MR angiography, in diagnosing pulsatile tinnitus, with MRI protocols such as time-of-flight, magnetic resonance angiography, and diffusion-weighted imaging able to identify serious causes, including vascular shunting lesions, venous sinus stenosis, and tumors 3, 4.
- The use of MR angiography has been shown to be particularly useful in identifying vascular etiologies of pulsatile tinnitus, with a diagnostic rate comparable to that of CT-based imaging 5.
Diagnostic Yield of MR Angiogram
- The diagnostic yield of MR angiogram in pulsatile tinnitus has been reported to be high, with one study finding that MRA identified patients with vascular etiologies of PT, including arteriovenous malformations, fistulas, and stenosis 2, 5.
- Another study found that MR-based imaging, including MRA, was equally efficacious as CT-based imaging in identifying the etiology of PT, with MR-based imaging preferred for neoplasms and CT-based imaging preferred for semicircular canal dehiscence 5.
- A focused, physiology-based protocol for MRI and MR angiography evaluation of pulsatile tinnitus has been proposed, which includes dedicated sequences such as time-of-flight magnetic resonance angiography and arterial spin labeling 4.
Clinical Implications
- The use of MR angiogram in the evaluation of pulsatile tinnitus has important clinical implications, as it can help identify underlying causes of the condition that may be amenable to treatment 2, 3, 4.
- A comprehensive and targeted radiographic imaging protocol, including MR angiography, can help ensure that patients with pulsatile tinnitus receive an accurate diagnosis and appropriate treatment 4.