"Why Do I Hear a Heartbeat in My Ear?"
November 1, 2006 4 minutes read
"Why Do I Hear a Heartbeat in My Ear?"
Abstracts & Commentary
By Dara G. Jamieson, MD, Associate Professor, Clinical Neurology Director, Weill Medical College, Cornell University. Dr. Jamieson is a consultant for Boehringer Ingelheim and Merck, and is on the speaker's bureau for Boehringer Ingelheim, Merck, Ortho-McNeil, and Pfizer.
Synopsis: Pulsatile tinnitus is usually due to an ipsilateral venous anomaly that can be diagnosed with CT angiography and venography in most cases.
Sources: Krishnan A, et al. CT arteriography and venography in pulsatile tinnitus: Preliminary results. AJNR Am J Neuroradiol. 2006;27:1635-1638; Doshi J, et al. Objective pulsatile tinnitus: A video clip demonstration of the condition. Laryngoscope. 2006;116:1926.
Tinnitus is a common, annoying condition that can be pulsatile or non-pulsatile. While most tinnitus has a benign etiology, pulsatile tinnitus, due to vibrations of turbulent flow reaching the cochlea, may indicate a potentially concerning vascular lesion. Non-vascular causes are rare, and include idiopathic intracranial hypertension, skull base meningoceles, and medication. Multiple imaging modalities are often needed to distinguish between benign vascular etiologies such as an audible intracranial bruit and a more concerning condition such as a vascular malformation. Four vessel catheter angiography is the most sensitive modality to diagnose a dural arteriovenous malformation producing subjective auditory symptoms. Magnetic resonance studies, magnetic resonance imaging, magnetic resonance angiography, and magnetic resonance venography are used to look for carotid artery disease, cerebral venous disease, and idiopathic intracranial hypertension. A patient with pulsatile tinnitus and a retrotympanic mass may be screened with a CT scan of the temporal bone, looking for a cholesteatoma or glomus tumor. Ideally, imaging would involve a single study.
In the paper by Krishnan and colleagues, CT angiography and venography (CTA/V) was used prospectively to evaluate pulsatile tinnitus in 16 patients who had normal otological examinations and no middle ear mass. Arterial or venous localization was predicted using ipsilateral carotid artery or jugular vein compression. Both arterial and venous phases were obtained with a single acquisition after injection of non-ionic contrast, followed by imaging using a CT scanner, with sections from the vertex to C6 level. All images were reconstructed using standard bone reconstruction algorithms. Coronal reformations through the temporal bone, as well as coronal and sagittal reformations through the carotid artery bifurcations and posterior fossa venous sinuses, were generated.
The study included 9 women and 7 men ranging in age from 27 to 73 years. Only one had tinnitus that could be heard on auscultation. Six patients had presumed venous origin of the tinnitus based on neck compression, and 2 had obliteration of tinnitus on internal carotid artery compression. Five patients had entirely normal CTA/V studies. Six patients had strongly dominant venous systems, with all but one of these patients reporting tinnitus on the side of the dominant transverse and sigmoid sinus. An extremely thin sigmoid plate between the dominant transverse sinus and the ipsilateral mastoid complex was seen in 3 of these 6 patients. One patient, with a decade of tinnitus, noted resolution of symptoms after surgical repair of a diverticulum of the right transverse sinus extending into the mastoid complex. Other findings which lateralized to the side of the tinnitus were a dominant venous system, with a high-riding jugular bulb in one patient and external carotid stenosis in another patient. Mastoid air cell opacification was noted contralateral to the tinnitus in one patient.
Different CT settings can be used to evaluate pulsatile tinnitus. Bone window settings can be used to assess the temporal bone and middle ear on axial images and coronal reformations. An aberrant internal carotid artery can be diagnosed, with a vascular window setting to evaluate carotid stenosis, looking for a small patent luminal diameter on axial images. This same window setting can be used to evaluate for an empty sella and small ventricles, as found in idiopathic intracranial hypertension. The vascular window can be formatted to evaluate the venous system, including the dural venous sinuses. While dural arteriovenous fistula may be detected on CTA/V, the technique is not as sensitive as conventional angiography.
All the patients in this series who had lesions that could potentially account for tinnitus symptoms had venous etiologies, such as venous sinus dominance, transverse sinus stenosis, and venous diverticulum. The significance of the dominance of the venous sinus system in pulsatile tinnitus is unclear, as approximately 59% of the population has a dominant right venous system. Krishnan et al are conducting a study on the use of CTA/V in asymptomatic individuals, compared to patients with pulsatile tinnitus.
Krishnan et al conclude that the single CTA/V study of the middle and inner ear and of the vascular structures may replace multiple other imaging modalities used to evaluate a patient with pulsatile tinnitus. But, when a dural arterial venous malformation is suspected, CTA/V may not replace conventional angiography.
Doshi and colleagues report on a 72-year-old woman who sustained a small dural venous tear during the resection of a petrous meningioma. Two months later, she developed ipsilateral pulsatile tinnitus, with otoscopic evaluation revealing a tympanic membrane pulsating synchronously with her arterial pulse. CT showed opacified mastoid air cells, and surgical exploration found an iatrogenic communication between the upper end of the craniotomy and the mastoid air cells. The pulsatile tinnitus completely resolved with bio-glue repair of the defect. Doshi et al present a real time visual demonstration of the pulsating tympanic membrane through a non-pneumatic otoscopy at www.laryngoscope.com.
Pulsatile tinnitus is usually due to an ipsilateral venous anomaly that can be diagnosed with CT angiography and venography in most cases.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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