Diagnosis: Transverse Sinus Stenosis
Clinicians should investigate any patient complaint of pulsatile tinnitus. While there is no universally accepted method of workup for these patients, some form of imaging must be obtained to rule out a tumor. Some clinicians recommend performing a CT of the temporal bone with CT angiography of the head, while others perform an MRI of the temporal bone and internal auditory canal, MR angiography, or MRV as part of the workup. In many cases clinicians do not find any cause for a patient's complaints. In our practice, we usually obtain an MRI of the internal auditory canals with contrast to help rule out a skull base tumor such as glomus jugulare, intracochlear schwannoma, or vestibular schwannoma. If the results come out normal, an MRV is obtained. The patient is also referred to a neuro-ophthalmologist to get an evaluation for intracranial hypertension.
While the differential diagnosis of pulsatile tinnitus is long and includes tumors of the temporal bone or skull base, some non-tumor entities such as migraine can be the cause. While migraine can be suspected, a full workup is done during the treatment of a possible migraine etiology. When sudden unilateral pulsatile tinnitus occurs, a complete head and neck exam and audiogram are warranted. Attention should be given to the patient's microscopic ear exam, and all debris should be removed from the tympanic membrane prior to the exam. Debris on the tympanic membrane can hide underlying pathology such as a cholesteatoma. In a patient with a very hairy ear canal, visualizing the tympanic membrane using a large (e.g., 5 mm) speculum is difficult as hairs usually get hairs get caught in the speculum and interfere with visualization. In this case, even if the patient has a large ear canal, a smaller speculum (2.5 or 3 mm) should be used to pass through the hairs and reach the bony canal. In addition to a thorough ear exam, auscultation of the neck and the mastoid is a useful adjunct. While very rare, significant carotid stenosis or arteriovenous malformations can be heard when using a stethoscope to listen to the neck or the mastoid. Pulsatile sound in the neck would prompt a carotid ultrasound, while a pulsatile sound on the mastoid would warrant a magnetic resonance arteriography. If clinical suspicion is high, an evaluation of thyroid function, hemoglobin, and a pregnancy test may be needed.
Many patients have reported that the pulsatile tinnitus can be reduced or stopped by gently pressing the neck or turning the neck. This generally indicates that the sound is venous in origin. The jugular vein is a thin-walled venous vessel that can easily be compressed by pressing the fingers on the neck or turning the neck, thereby stretching the jugular vein. Magnetic resonance arteriography or formal angiography are then most likely unnecessary. If imaging of the blood vessels is to be obtained, MRV is the best choice for patients who can reduce the sound with gentle pressure on the neck or turning the neck. Formal angiography is rarely necessary and primarily indicated to rule out a dural arteriovenous fistula.
This patient's MRV showed a stenosis of the transverse sinus on the left side (Fig. 1), which is likely the cause of the pulsatile tinnitus. This occurs when blood flowing through a narrow segment becomes more turbulent, creating a sound that can be heard. A retrospective view of the patient's MRIs from 2019, 2018, and 2010 (Figs. 2-5) shows that the transverse sinus was narrow on all the imaging. It appears to have worsened from 2010. At present, experts still debate on whether transverse sinus stenosis (TSS) is caused by intracranial hypertension or if it's the other way around. High intracranial pressure compresses venous sinuses, most commonly the transverse sinus, and causes TSS. On the other hand, stenosis of venous sinuses, such as the transverse sinus, can cause a back-up of venous blood in the brain and thus intracranial hypertension. Patients with intracranial hypertension usually experience headaches, as well as back and shoulder discomforts. Symptoms of intracranial hypertension may overlap with those seen in migraine, thereby delaying proper diagnosis. The most concerning complication of untreated intracranial hypertension is visual loss. As such, transverse sinus stenosis and associated intracranial hypertension must be diagnosed as early as possible.
Several brain MRI findings have been found to be associated with intracranial hypertension. These include: the finding of an empty sella (>50% fluid in the sella [location of the pituitary gland]), optic nerve sheath dilation, Meckel's cave diverticula, vascular distension and protrusion of the optic papillae, “slit ventricles,” and hyperintensity at the optic nerve head on diffusion-weighted imaging. MRV sequence can show over 50 percent of bilateral transverse sinus stenosis in 93 percent of patients with intracranial hypertension. In a substantial number of patients with intracranial hypertension, only a brain or internal auditory canal MRI is obtained. In these cases, the diagnosis is likely to be missed. To get an early diagnosis, patients must consult with a neuro-ophthalmologist to evaluate for signs of intracranial hypertension and obtain an MRV.
Treatment of intracranial hypertension includes medication, weight reduction, and sometimes surgical shunting. Transverse sinus stenosis can be treated with interventional radiology techniques of stenting the transverse sinus. In some cases, reducing intracranial pressure with medication can restore the transverse sinus flow and eliminate the need for stenting.
BONUS ONLINE VIDEOS: VISUAL DIAGNOSIS
Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself.
- Video 1. Rotating images of the MRV in a lateral direction.
- Video 2. Axial T1 post gadolinium MRI of the brain obtained for the MRV showing detailed axial view of the transverse and sigmoid sinuses.
- Video 3. Coronal T1 post gadolinium MRI of the brain obtained for the MRV demonstrating the coronal view of the transverse and sigmoid sinuses.
- Video 4. Axial T2 MRI showing normal internal auditory canals and cochleae.
- Video 5. Axial T1 post gadolinium MRI of the brain obtained in 2010 showing a detailed axial view of the transverse and sigmoid sinuses and the narrowed areas.
- Video 6. Coronal T1 post gadolinium MRI of the brain obtained in 2010 showing the coronal view of the transverse and sigmoid sinuses and corresponding narrowing on the left.
Watch the patient videos online at thehearingjournal.com https://journals.lww.com/thehearingjournal/Pages/collectiondetails.aspx?TopicalCollectionId=23.Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.