Imaging in pulsatile tinnitus: Diagnostic pearls and potential pitfalls

Transcription

1 Imaging in pulsatile tinnitus: Diagnostic pearls and potential pitfalls Poster No.: C-1114 Congress: ECR 2014 Type: Educational Exhibit Authors: B. S. Purohit, R. Hermans, K. Op de beeck ; SINGAPORE/SG, Leuven/BE Keywords: Education and training, Diagnostic procedure, MR-Angiography, MR, CT-High Resolution, Head and neck DOI: /ecr2014/C-1114 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 30

2 Learning objectives Aims and objectives: 1. To describe the more common causes of pulsatile tinnitus (PT) with a pictorial review. 2. To describe certain diagnostic pearls and potential imaging pitfalls in each of the cases. 3. To describe an imaging flowchart for the evaluation of PT. Background Assessment of PT is a common indication for radiological evaluation of the temporal bone in adults. PT refers to the perception of rhythmic sound in the ear which is pulse-synchronous. PT may be cassified into arterial or venous subtypes. Arterial PT rises in systole and is not affected by pressure on the ipsilateral internal jugular vein (IJV). Venous PT is a continuous hum perceived in the ear and abolished by compression of the ipsilateral IJV. PT may be subjective or objective in nature. It may or may not be associated with a vascular tympanic membrane (TM). PT suggests a vascular neoplasm, vascular anomaly or vascular malformation of the temporal bone or adjacent skull base. A detailed medical examination and otological examination should precede imaging studies. The diagnosis of PT may often lie with the radiologist because it may be impossible for the clinician to distinguish between these entities on otoscopy. Misidentification of normal vascular variants or 'touch me not lesions' as pathology may be hazardous if biopsied (for eg: misdiagnosing an aberrant internal carotid artery [ICA] as glomus tumour). Findings and procedure details Materials and methods: Page 2 of 30

3 We retrospectively reviewed CT and MR studies and digital substraction angiographies (DSA) performed for the evaluation of PT at the University Hospitals, Leuven from This pictorial review illustrates the imaging findings in some of the commonly encountered causes of PT. Common causes of PT: 1. Acquired vascular lesions: Atherosclerotic carotid artery stenosis ICA dissection Dural arteriovenous fistula (DAVF) 2. Vascular variants: Aberrant ICA Dehiscent jugular bulb (DJB) 3. Vascular tumours: Glomus tympanicum Glomus jugulare Glomus jugulotympanicum (GJT) Meningioma 4. Miscellaneous causes: Inflammatory diseases of the middle ear cavity (MEC) Otosclerosis 5. Systemic causes: Benign intracranial hypertension Thyrotoxicosis Anaemia Imaging approach to PT: Radiological evaluation can be simplified if the type of PT and appearance of TM are known. Also, it is necessary to assess for associated conductive hearing loss (CHL). Page 3 of 30

4 If associated with CHL and/or vascular TM, non-contrast high resolution CT (HRCT) of the temporal bones is performed, with additional MR if needed, typically for GJT. Otherwise, MRI including MR angiography (MRA) is the study of choice. In cases of objective PT with negative MR, DSA helps to exclude with more certainty a potentially treatable vascular abnormality like a DAVF. In patients with PT and risk factors for carotid pathology (age above 50 years, cardiovascular risk factors, carotid bruit), US, CT angioggraph (CTA) or MRA of the carotid vessels is indicated [1-6]. Fig. 1 References: Bela Purohit Fig. 1: Imaging flowchart for the evaluation of PT. Etiology: 1. Acquired vascular lesions Page 4 of 30

5 Stenotic lesions and dissections of the ICA: Clinical presentation: Patient (often with cardiovascular risk factors, carotid bruit) presents with objective PT and normal otoscopy findings. History of trauma with severe posterior neck pain/ Horner's syndrome in a young patient may be the presenting feature of ICA dissection. Pathology: Severe atherosclerotic carotid artery stenosis or craniocervical ICA dissection leads to arterial turbulence and jetting of blood near the temporal bone and thereby causes PT. Diagnostic pearls and potential pitfalls: CTA and MRA both can be used to demonstrate carotid stenosis. The window levels in CTA must be set so as to distinguish between calcification and arterial enhancement. ICA dissections typically begin about 2-3 cm above the carotid bifurcation and usually stop before the petrous ICA. CTA may show a spectrum of imaging findings in dissection which include mural thickening and/or irregularity, intimal flap with double lumen formation, complete luminal occlusion or pseudoaneurysm formation. MRI is the modality of the evaluation of suspected ICA dissection. Fatsaturated axial T1W MR images elegantly demonstrate the crescentric high signal intensity mural haematoma narrowing the signal void of the vessel (Fig. 2, 3) [1-4, 7, 8]. Page 5 of 30

6 Fig. 2 References: Department of Radiology, University Hospitals, Leuven Fig. 2: Coronal T1W MR image in a patient with neck trauma followed by severe leftsided neck pain and PT. The high signal intensity mural haematoma (arrow) adjacent to the left ICA lumen confirms the diagnosis of dissection. Page 6 of 30

7 Fig. 3 References: Department of Radiology, University Hospitals, Leuven Fig. 3: Axial T1W MR image in the same patient as in Fig. 2. The cresentric high signal intensity mural haematoma (arrow) narrows the left ICA flow void. DVAF: Clinical presentation: Patient often presents with objective PT and normal otoscopy findings. There may be neurological findings like headache and ischaemic events/ intracranial haemorrhage (ICH). Pathology: DVAFs commonly arise due to recanalisation of thrombosed venous sinuses with the transverse and sigmoid sinus being the most frequent locations. Branches of the external carotid artery (ECA) are the most common feeders. The dilated vasculature leads to increased blood Page 7 of 30

8 flow near the temporal bone and causes PT. DVAFs which drain exclusively into cortical veins are associated with increased risk of ICH. Diagnostic pearls and potential pitfalls: Non-enhanced CT (NECT) may be normal in cases which present without ICH. Contrast-enhanced CT (CECT) may show enlarged tortuous draining veins in an aggressive DVAF. Bone window images may show transosseous collaterals in the occpito-mastoid region. Conventional MR studies may demonstrate dilated dural venous sinus, high T1W signal in venous sinsues, large dilated cortical veins, adjacent perfusion anomalies in the brain or may be completely normal. Venous collateral flow in dural sinus thrombosis may be very prominent and may mimic a DVAF. Although MRA is sensitive for detection of DVAF (Fig. 4), it may miss very small lesions. DSA is the gold standard for the evaluation of DVAF. It helps to detect small/ obscure DVAFs which are not seen on CECT/MRI/MRA (Fig. 5). To ensure complete evaluation in cases of ICH, it is important that both the anterior (ICA and ECA) and posterior circulations (vertebral artery) are assessed. Identification of associated venous varix is important on DSA as it is associated with increased risk of ICH [1-8]. Page 8 of 30

9 Fig. 4 References: Diagnostic Imaging, National University Hospital, National University Hospital - SINGAPORE/SG Fig. 4: Axial MRA source image in a patient with left-sided objective PT, normal otoscopy and normal findings on conventional MR sequences. MRA shows a leash of nodular and seripiginous vessels (arrows) in the region of the left jugular bulb in keeping with a DVAF. Page 9 of 30

10 Fig. 5 References: Diagnostic Imaging, National University Hospital, National University Hospital - SINGAPORE/SG Fig. 5: Lateral DSA image in the same patient as in Fig. 4 confirms the presence of a DVAF in the region of the left sigmoid sinus/jugular bulb. 2. Vascular variants Aberrant ICA: Clinical presentation: Patient commonly presents with objective PT and vascular TM on otoscopy. There may be associated CHL. Sometimes, an aberrant ICA may be detetced incidentally on imaging studies. Page 10 of 30

11 Embryology: An aberrant ICA occurs due to failure of formation of the proximal ICA and replacement by the inferior tympanic artery which enters the skull base lateral to the expected course of the vertical portion of the carotid canal (which is absent). This aberrant artery enters the MEC through an enlarged inferior tympanic canaliculus. It then crossses the mesotympanum and exits anteromedially to become the horizontal portion of the carotid canal (Fig. 6, 7). Stenosis may occur at this point with resultant turbulence and PT. Diagnostic pearls and potential pitfalls: Axial HRCT images are often diagnostic showing a tubular soft tissue density structure in the MEC, which enters posterolateral to the cochlea, crosses over the promontory and exits anteromedially to continue as the horizontal portion of ICA (Fig. 8). An aberrant ICA may mimic a glomus tumour sitting on the promontory on a single coronal HRCT image or on CECT images. Tubular appearance of the vessel on NECT images and an enlarged inferior tympanic canaliculus are diagnostic (Fig. 9). Aberrant ICA is a 'touch me not' lesion of the temporal bone. Misdiagnosis of an aberrant ICA as glomus tumour can be catastrophic as it may lead to a biopsy. Coventional MR images do not pick up the aberrant vessel in the MEC. The source MRA images must be carefully scrutinised so as not to miss the diagnosis. Source MRA images show the aberrant vessel in the MEC (coursing more laterally than normal) and forming of a "7" or "reversed-7" configuration (Fig. 10). A laterally displaced ICA (lies anteromedial to MEC, with dehiscent lateral wall of petrous ICA genu) should not be confused with an aberrant ICA [1-5, 7, 8]. Page 11 of 30

12 Fig. 6 References: Bela Purohit Fig. 6: Graphic representation of course of the normal adult cervical and intrapetrous ICA. Page 12 of 30

13 Fig. 7 References: Bela Purohit Fig. 7: Graphic representation of connections that constitute the aberrant ICA. Page 13 of 30

14 Fig. 8 References: Department of Radiology, University Hospitals, Leuven Fig. 8: Axial HRCT of the temporal bone in a patient with right-sided arterial PT and vascular TM. An aberrant ICA (arrow) is seen coursing through the right MEC and becoming continuous with the horizontal portion of the carotid canal. Page 14 of 30

15 Fig. 9 References: Department of Radiology, University Hospitals, Leuven Fig. 9: Coronal HRCT image in the same patient as in Fig. 8. The aberrant ICA is seen to enter the right MEC through the enlarged inferior tympanic canaliculus (arrow). Page 15 of 30

16 Fig. 10 References: Department of Radiology, University Hospitals, Leuven Fig. 10: Axial MRA source image of the same patient as in Fig. 8, 9. The right-sided aberrant ICA (arrow) is seen traversing the right MEC. Dehiscent jugular bulb/djb : Clinical presentation: Patient may present with venous hum in the ear and a bluish TM on otoscopy. Patholohy: DJB is a venous variant where the jugular bulb enters the MEC through its dehiscent floor. It must be differentiated from a high-riding jugular Page 16 of 30

17 bulb and jugular bulb diverticulum both of which show intact floor of the MEC. Diagnostic pearls and potential pitfalls: HRCT is often diagnostic showing a soft tissue density structure in continuity with the jugular bulb protruding through the deficient floor of the MEC (Fig. 11, 12). On CECT, the protruding mass enhances to the same extent as the jugular bulb. DJB may show variable signal intensity on both T1W and T2W sequences. Contrast-enhanced MRI (CEMRI) shows an avidly enhancing MEC mass connecting to an avidly enhancing jugular bulb. DJB may be a clinical and imaging mimic for any vascular retrotympanic lesion. DJB is a 'touch me not' lesion of the temporal bone. The smooth bony margins of the jugular foramen help to exclude more aggressive lesions like a glomus jugulare or jugular foramen meningioma. The surgeon must be warned about the presence of DJB if MEC surgery is contemplated for any indication [1-4, 7, 8]. Page 17 of 30

18 Fig. 11 References: Department of Radiology, University Hospitals, Leuven Fig. 11: Coronal HRCT of the temporal bone in a patient with right sided venous PT and bluish appearance of the right TM on otoscopy. The right jugular bulb (asterisk) is seen protruding superiorly through the deficient bony floor (arrow) of the right MEC. Page 18 of 30

19 Fig. 12 References: Department of Radiology, University Hospitals, Leuven Fig. 12: Axial HRCT of the temporal bone in the same patient as in Fig. 11. The right DJB (asterisk) is seen protruding through the deficient bony floor (arrow) of the right MEC. 3. Vascular tumours: Glomus tumours: Clinical presentation: Patients with glomus tympanicum tumours present with PT, vascular TM, with or without CHL. Patients with glomus jugulare Page 19 of 30

20 tumours present with PT, vascular TM and CHL (if mass extends into the MEC) and sometimes with lower cranial neuropathy. Pathology: Glomus tumours are benign, locally aggressive tumours which arise from chemoreceptor cells. Glomus tympanicum arises from the Jacobsen's nerve over the cochlear promontory and glomus jugulare arises from the adventitia of the jugular bulb. When a glomus jugulare extends into the MEC, it is called GJT. The highly vascular nature of these tumours results in PT. Multiple glomus tumours are seen in 10% patients. Diagnostic pearls and potential pitfalls: On HRCT, glomus tympanicum is seen as a well-circumscribed, soft tissue density mass with its base over the cochlear promontory (Fig. 13). The inferior wall of the MEC is intact. Avid post contrast enhancement is seen on CECT and CEMRI (Fig 14). On HRCT, GJT is seen as a mass extending from the jugular bulb to the MEC (with erosion of its bony floor) and permeative erosion of the bony walls of the jugular foramen (Fig. 15). On T1W MR images, larger GJT tumours show 'salt and pepper' appearance due to foci of haemorhage and vascular flow voids within the tumour (Fig. 16). GJT shows avid post contrast enhancement (Fig. 17). The radiologist must look out for multicentric glomus tumours. DSA may be performed prior to tumour embolisation. Enlarged feeding arteries, intense tumour blush and early draining veins are noted. Jugular foramen schwannoma and jugular foramen meningioma may mimic GJT. Schwannomas show smooth scalloping of the walls of the jugular foramen on HRCT and absence of flow voids on T1W/T2W MR sequences. Also, they are less vascular compared to glomus tumours. Jugular foramen meningiomas may show associated bony hyperostosis and enhancing dural tail [1-5, 7, 8]. Page 20 of 30

21 Fig. 13 References: Department of Radiology, University Hospitals, Leuven Fig. 13: Axial HRCT image in a patient with left-sided PT, CHL and vascular TM. The wellcircumscribed, soft tissue density lesion (arrow) sitting over the left cochlear promontory is in keeping with glomus tympanicum. Page 21 of 30

22 Fig. 14 References: Department of Radiology, University Hospitals, Leuven Fig. 14: Axial CEMRI image in the same patient as in Fig. 13. The glomus tympanicum (arrow) shows intense post contrast enhancement. Page 22 of 30

23 Fig. 15 References: Department of Radiology, University Hospitals, Leuven Fig. 15: Coronal HRCT of the temporal bone in a patient with right- sided PT, CHL and vacular TM. A mass is seen centered in the right jugular foramen (black asterisk) with extension into the right middle ear cavity (white asterisk) and associated bony destruction (white arrows). Findings are suggestive of GJT. Page 23 of 30

24 Fig. 16 References: Department of Radiology, University Hospitals, Leuven Fig. 16: Axial T1W MR image in the same patient as in Fig. 15. The right jugular foramen mass (asterisk) shows hyperintense foci on T1W images in keeping with haemorrhage within the lesion. Page 24 of 30

25 Fig. 17 References: Department of Radiology, University Hospitals, Leuven Fig. 17: Axial CEMRI image in the same patient as in Fig. 15, 16. Intense post contrast enhancement in the right jugular foramen mass (asterisk) confirms the diagnosis of GJT. 4. Miscellaneous conditions: Otosclerosis: Page 25 of 30

26 Clinical Presentation: Patient presents with CHL or mixed hearing loss and sometimes with PT. The disease is bilateral in about 80% cases. Pathology: Otosccerosis is an otodystrophy of the otic capsule characterised by replacement of the normal ivory-like enchondral bone by spongy vascular new bone. The increased vascularity in the lytic phase is considered to be responsible for PT. Otosclerosis is categorised into two types, fenestral and retrofenestral/ cochlear. Diagnostic pearls and potential pitfalls: HRCT of the temporal bone is the modality of choice for the evaluation of otosclerotic plaques. These plaques (as small as 1 mm) are seen as hypodense foci in the region anterior to the oval window and in the peri-cochlear region (Fig. 18). MRI may be performed prior to CT for assessing the cause of hearing loss. A ring of pericochlear post gadolinium enhancement may be seen in cochlear otosclerosis, more so in the active phase. Paget's disease is also an otodystrophy which may affect the otic capsule and rarely present with PT in the lytic phase. Although it mimics the HRCT appearance of cochlear otosclerosis, the diffuse involvement of the skull base and other bones indicates the true etiology (Fig. 19) [1-3, 7, 8]. Page 26 of 30

27 Fig. 18 References: Department of Radiology, University Hospitals, Leuven Fig. 18: Axial HRCT of the temporal bone in a patient with right-sided mixed hearing loss and PT. Hypodense demineralised otosclerotic plaques are seen in the right fenestral region (white arrow) and pericochlear region (black arrow). Page 27 of 30

28 Fig. 19 References: Diagnostic Imaging, National University Hospital, National University Hospital - SINGAPORE/SG Fig. 19: Axial NECT of the skull base in a patient with right-sided PT and known Paget's disease. The hypodense appearance of bilateral otic capsules may mimic otosclerosis, however the diffuse lytic-sclerotic appearance of the skull base indicates the true pathology. Conclusion Take home points: PT indicates a vascular lesion of the temporal bone or the adjacent skull base. Page 28 of 30

29 The role of the radiologist is to identify all treatable causes of PT. It is necessary to be aware of the pertinent imaging findings and potential imaging pitfalls of the common etiologies of PT. A thorough clinical and otological examination is imperative prior to imaging. The imaging algorithm for PT depends on the type of PT and vascularity of the TM as seen on otoscopy. MRI including MRA is the study of choice for the evaluation of PT. However, if PT is associated with CHL and/or vascular TM, HRCT of the temporal bones is performed, with additional MR if needed, typically for glomus tumours. In patients with PT and risk factors for carotid pathology, US, CTA or MRA of the carotid vessels is indicated. In cases of objective PT with negative MR, conventional angiography helps to exclude an obscure dural AVF. Personal information Dr. Bela Purohit, MD, DNB, FRCR. Singapore. purohitbela@yahoo.co.in Prof. Dr. Robert Hermans, MD, Ph.D. Leuven, Belgium. robert.hermans@uzleuven.be Dr. Katya Op de beeck, MD. Leuven, Belgium. katya.opdebeeck@uzleuven.be References Page 29 of 30

30 1. Moonis G, Kim A, Bigelow D, Loevner LA (2009). Temporal Bone Vascular Anatomy, Anomalies, and Disease, with an Emphasis on Pulsatile Tinnitus. In Swartz JD, Loevner LA. Imaging of the Temporal Bone. 4th edition. New York, NY: Thieme: Harnsberger HR et al (2011). Diagnostic Imaging. Head and Neck. 2nd edition. Manitoba, Canada: Amirsys. 3. Weissman JL, Hirsch BE (2000). Imaging in Tinnitus: A Review. Radiology 216: Remley KB, Coit WE, Harnsberger HR, Smoker WRK, Jacobs JM, McIff EB (1990) Pulsatile Tinnitus and the Vascular Tympanic Membrane: CT, MR, and Angiographic Findings. Radiology 174: Shweel M, Handy B (2013). Diagnostic utility of magnetic resonance imaging and magnetic resonance angiography in the radiological evaluation of pulsatile tinnitus. Am J Otolaryngol34: Shin EJ, Lalwani AK, Dowd CF (2000). Role of Angiography in the Evaluation of Patients With Pulsatile Tinnitus. The Laryngoscope 110: Vattoth S, Shah R, Cure JK. A Compartment-Based Approach for the Imaging Evaluation of Tinnitus. AJNR Am J Neuradiol 31: Madani G, Connor SEJ (2009). Imaging in pulsatile tinnitus. Clin Radiol 64: Page 30 of 30