Diagnosis: Sigmoid Sinus Diverticulum and Migraine
Tinnitus is a common complaint among patients who consult an audiologist or otolaryngologist. Clinicians may commonly assume that the complaint is about a tonal or hissing tinnitus. However, clinicians must always ask patients what exactly the tinnitus sounds like and if it is a pulsatile or a constant sound. Many patients with pulsatile tinnitus will say that they have a whooshing tinnitus. A constant whooshing sound is usually due to a narrow- or broadband high-frequency tinnitus. However, pulsatile tinnitus is usually a vascular phenomenon. The workup for tonal unilateral tinnitus can be completed via a single-imaging modality of an MRI of the internal auditory canal (IAC) without gadolinium. This imaging modality includes a thinly sliced (1 mm cut) sequence called CISS, 3DMPR, or FIESTA (depending on the manufacturer of the MRI device). This 1 mm sequence allows the clinician or radiologist to rule out a mass down to 2 mm in size in the IAC. This sequence, also called Magnetization Prepared Rapid Gradient Echo (MPRAGE), can be performed as a T1 or T2 sequence. The T2 variety is performed as part of an MRI of the IAC without gadolinium. The T1 variety is performed post-gadolinium as part of a post-contrast IAC MRI.
An MRI of the brain, commonly ordered in a primary care setting, is of little value to the evaluation of pulsatile tinnitus. For this condition, the best primary imaging modality is an MRI of the IAC with and without contrast. This allows the clinician or radiologist to evaluate the vascular spaces. The normal 3 mm slice images of the post-gadolinium MRI are performed slowly. This causes the vascular spaces (e.g., the sigmoid sinus) to appear dark since the moving blood cells within the sigmoid will have moved by the time the image is taken. The resulting image will cause the sigmoid sinus and carotid artery to appear black (Fig. 1). With the MPRAGE T1 post-gadolinium sequence, thin (1 mm slices) images can be rapidly obtained. This allows for much better resolution of the sigmoid sinus with contrast within the sigmoid, where the sigmoid sinus will appear white (Fig. 2).
The best imaging technique to visualize the venous anatomy of the sigmoid sinus without the use of radiation is magnetic resonance venography (MRV). Direct venography using a catheter placed through the groin (femoral artery) or CT angiography with venography images can provide higher-resolution images than those via MRV. However, both latter techniques require the patient to be significantly exposed to radiation. MRV involves two sets of images. The first set is the time-of-flight sequence (TOF), which relies on detecting slow motion of blood in the venous system (Fig. 3). The second is a composite of all the bright segments that represents a two-dimensional reconstruction of the three-dimensional data (Fig. 4), allowing the composite image to be spun around (watch Video 3 online: bit.ly/CaseVideos) in different directions.
Once the MRV shows a sigmoid sinus diverticulum and no other venous abnormalities, a CT can be obtained to start surgical planning. CT imaging of this patient showed a rather extensive sigmoid sinus diverticulum that involved the subcutaneous tissues after it broke through the lateral mastoid cortex (Fig. 5).
It must be noted that the patient's sigmoid sinus diverticulum had most likely been present for several years. This was consistent with her 10-year history of pulsatile tinnitus. The question remained as to why the patient had intermittent increase in the volume of the tinnitus. In our experience and that of others, migraines play a significant role in the exacerbation and development of pulsatile tinnitus (Otol Neurotol. 2016 Mar;37(3):244-7). Intermittent activation of the migraine process can make the brain more sensitive, which leads to an increase in the volume of tinnitus.
Because of the common nature of pulsatile tinnitus in migraines, patients with pulsatile tinnitus are commonly given a migraine regimen. This includes making lifestyle and dietary changes such as taking vitamin B2 (riboflavin), magnesium supplements, and prophylactic medication. While the medication is tapered off slowly, the workup is performed with an MRI of the IAC with and without gadolinium, followed by an MRV and a consultation with a neuro-ophthalmologist. Pulsatile tinnitus can be a sign of idiopathic intracranial hypertension. Sigmoid sinus diverticulum is frequently associated with intracranial hypertension, so the presence of intracranial hypertension needs to be ruled out, usually via a lumbar puncture. Due to the invasive nature of this procedure and subsequent possible issues, the patient should consult with a neuro-ophthalmologist to get the best visualization of the optic nerve and the head to determine if intracranial hypertension is present.
In this case, the patient's atypical migraine, which was likely causing the exacerbated tinnitus, was treated with a gradually increasing course of verapamil, starting with 120 mg that was sustained-release for over 24 hours. After two weeks, the dosage was increased to 180 mg and eventually to 240 mg. On follow-up, the patient reported that the pulsatile tinnitus had returned to its baseline. Surgical repair of the sigmoid sinus diverticulum was also discussed with the patient. However, she chose not to undergo surgery, and instead chose to regularly check with a neuro-ophthalmologist to monitor the development of any intracranial hypertension.
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. Axial (horizontal) T1 post-gadolinium 3 mm cut MRI does not show the contrast within the sigmoid sinus due to fast-flowing and thick imaging slices.
- Video 2. Coronal (parallel to face) time-of-flight (TOF) sequence MRI showing the sigmoid sinus anatomy and the intracranial venous system.
- Video 3. Magnetic resonance venography (MRV) threedimensional reconstruction of the TOF sequence turning in the axial plane.
- Video 4. Axial (horizontal) T1 MPRAGE post-gadolinium 1 mm cut MRI showing the sigmoid sinus diverticulum.
- Video 5. Axial (horizontal) CT temporal bones showing the extension of the diverticulum into the subcutaneous tissues.
- Video 6. Coronal (parallel to the face) CT temporal bones showing the relationship between the sigmoid sinus and skull base.
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.