CT as first diagnostic approach in non-traumatic conditions of temporal bone

Transcription

1 CT as first diagnostic approach in non-traumatic conditions of temporal bone Award: Certificate of Merit Poster No.: C-1408 Congress: ECR 2016 Type: Educational Exhibit Authors: M. Bernabéu Rodríguez, B. Gutierrez Martinez, I. Herrera, M. E. Capilla, M. T. Fernández Taranilla, R. G. G. Gonzalez, J. M. Garcia Benassi; Toledo/ES Keywords: Pathology, Education, Diagnostic procedure, Decision analysis, CT, Head and neck, Ear / Nose / Throat DOI: /ecr2016/C-1408 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 76

2 Learning objectives To understand basic temporal bone anatomy in order to identify the pathological CT findings. To perform a correct differential diagnosis with the help of CT semiology. To know the limitations of CT and to create an algorithm of additional imaging tests. Page 2 of 76

3 Background CT is an essential imaging test for the initial evaluation of temporal bone, as a result of its high resolution for bone assessment. In many cases, we will be able to reach a diagnosis or, at least, to reduce the range of pathological possibilities, taking into account certain imaging signs. CT has its limitations, but we should obtain all the information it can provide. Page 3 of 76

4 Findings and procedure details PROCEDURE DETAILS This exhibit is illustrated with cases taken from our Radiology Department database. The studies were performed with a 16 or 64-slice CT. To make the temporal bone evaluation easier, we use an space-specific approach. To help to identify the pathology we will show the temporal bone with the pathological condition and the normal contralateral side in the majority of cases. In the text, we will use the next abbreviations: EAC: External auditory canal IAC: Internal auditory canal CT: Computed Tomography CECT: Contrast-enhanced computed tomography MRI: Magnetic Resonance Imaging FINDINGS EXTERNAL AUDITORY CANAL A) ANATOMY: S-shaped. 2 parts: 1) Lateral one-third = fibrocartilaginous; 2) Medial two-thirds = osseous. Santorini fissures = small gaps in the inferior EAC cartilaginous wall, that permit spread of infection and malignancy inferiorly towards suprahyoid deep neck spaces. First-order lymphatic drainage: parotid lymph nodes. B) PATHOLOGY * CONGENITAL: EAC ATRESIA Fig. 1 on page 32 1/ births. 1/3 bilateral. Page 4 of 76

5 The auricle is usually malformed (microtia). The EAC/middle ear and inner ear have different embryologic origins so it is uncommon to have both EAC/middle ear and inner ear abnormalities. CT plays a central role in evaluating surgical candidates and planning the surgical procedure. Imaging checkpoints: Atretic oval and/or round window, facial nerve course, small ear cavity, poor neumatization of temporal bone and ossicles dysplasia. * EAC LESIONS WITH NO BONY EROSION 1.- OSSEOUS PROLIFERATION Fig. 2 on page EXOSTOSIS (SURFER'S EAR) Circumferential bony overgrowth. Normal soft tissues. Bilateral. Most common symptom: conductive hearing loss. Cause: chronic cold water exposure OSTEOMA Unilateral, pedunculated, bony overgrowth of EAC without aggressive features. Most common site: Bony-cartilaginous junction of EAC. Normal soft tissues. If large, conductive hearing loss. 2.- SOFT TISSUE PROLIFERATION KERATOSIS OBTURANS < 40 years old. Keratin plugs. Associations: sinusitis and bronquiectasis. Usually bilateral. Symptoms: Severe pain and conductive hearing loss; otorrhea relatively rare. Page 5 of 76

6 CT: Soft tissue filling EAC and mild diffuse bony enlargement possible without bony erosion or periostitis. Imaging is usually not required for diagnosis EAC MEDIAL CANAL FIBROSIS Post-inflammatory. It is considered a sequela of chronic otitis externa or media and ear surgery. Formation of fibrous tissue. Symptoms: Conductive hearing loss, and otorrhea. CT: soft tissue in the medial portion of EAC. Imaging is usually not required for diagnosis LESS AGRESSIVE MALIGNANCIES SUCH AS BASAL CELL CARCINOMA Fig. 3 on page 33 * LESIONS WITH BONY EROSION 1.- EAC CHOLESTEATOMA Fig. 4 on page 34 Middle age patients. Causes: trauma, surgery, radiation, EAC estenosis, idiopathic. Symptoms: Otorrhea, sometimes dull otalgia, hearing loss. Otoscopic examination: White flakes in the EAC= keratin debris = "squames". Clinically, presence of "squames" is diagnostic of a cholesteatoma. Most common unilaterally. Slowly progressing chronic disease. CT: Soft-tissue mass + osseous erosion. Typical location: at the bone-cartilaginous junction of the canal. It is usually eccentric, involving inferior or posterior wall or both. Anterior wall involvement 40%. 50% osseous fragments within the mass (can be helpful for distinguising cholesteatoma from squamous cell carcinoma). Page 6 of 76

7 It is important to evaluate possible extension into the middle ear and/or facial nerve. Contrast-enhanced CT: there is no enhancement. CT classification (Shin et al): I: EAC only. II: invasion of the tympanic membrane and the middle ear. III: involvement of the mastoid air cells. IV: lesions beyond the temporal bone. MRI: cholesteatomas shows restriction on diffusion. 2.- SQUAMOUS CELL CARCINOMA 5º - 6º decade of life Symptoms: otorrhea, otalgia, hearing loss and bleeding. Diagnosis is usually delayed: symptoms are similar to other benign otological diseases such as chronic suppurative otitis media. Lymph node: Parotid nodes: the first echelon nodes. Pre- and post-auricular lymphadenopathies are also common. Advanced disease. The purpose of imaging evaluation is to assess the degree of deep extension and regional spread of disease, because the prognosis depends on the local invasion and the extent of disease. And for this purpose, it is necessary to perform a CECT or MRI. 3.- NECROTIZING/MALIGNANT EXTERNAL OTITIS Fig. 5 on page 35 Invasive infection of the external auditory canal and skull base. Elderly diabetic or immunocompromised patients. Most common pathogen: Pseudomonas aeruginosa. Less commonly: Aspergillus fumigatus. High mortality rate. Page 7 of 76

8 Symptoms: severe otalgia that worsens at night and otorrhea. The pain often extends to the temporomandibular joint and is aggravated by chewing. Otoscopic findings: granulation tissue at the bony-cartilaginous junction of the EAC. It should be considered in patients at risk who have a prolonged course of otitis externa or severe symptoms disproportionate to physical findings. Fast-spreading and agressive. Spread towards every direction (superior, inferior, lateral, medial). Complications: Cranial nerves involvement: VII (inferior spread of infection); IX-XII (extension to jugular foramen, hypoglossal canal or carotid space); V and VI (petrous apex extension) Meningitis Brain abscess Deep sinus venous thrombosis CT: Thickened mucosa of the external auditory canal and auricle, enhancing after contrast medium administration. Bony destruction (early sign: subtle cortical erosions). Cellulitis or abscess of surrounding soft tissues (Early sign: infiltration of the temporomandibular fat pad) Diagnosis: Elderly diabetic patient, severe otalgia, otorrea + CT bony destruction. It is difficult to differenciate between malignant otitis externa, cholesteatoma and squamous cell carcinoma in terms of bony destruction pattern. If malignant otitis externa is suspected, it is necessary to initiate antibiotic treatment. Consider malignancy or cholesteatoma when there is no good response to treatment. Soft tissue changes are better marker of treatment response than erosive bony changes, therefore, contrast-enhanced CT or MRI are required as imaging follow-up. Bare in mind intracranial complications. 4.- OSTEORADIONECROSIS Page 8 of 76

9 Delayed complication following radiotherapy. Diffuse permeative demineralization of the skull base. EAC KEY POINTS: EAC is easily accesible to direct inspection and biopsy, therefore, clinical diagnosis is common and imaging has a major role in extension of disease. Primary EAC malignancies are not common, they are usually secondary to the extension of a regional primary tumor, such as an auricle tumor. Squamous cell carcinoma > basal cell carcinoma > adenoid cystic carcinoma. MRI is better than CECT in evaluating: Soft tissue involvement, specially perineural spread. Intracranial involvement of malignancies, intracanial complications of inflammatory/infection diseases. CHOLESTEATOMA MALIGNANT OTITIS EXTERNA SQUAMOUS CELL CARCINOMA Progression Slow Rapid Slow Patient Middle age Elderly, diabetic year old CT Osseous erosion Osseous erosion Osseous erosion Yes Yes Osseous fragments within the mass 50% Contrast enhancement No MRI Restricted diffusion EAC ALGORITHM Page 9 of 76

10 Fig. 6: EAC ALGORITHM References: - Toledo/ES Page 10 of 76

11 Fig. 7: EAC ALGORITHM References: - Toledo/ES MIDDLE EAR - MASTOID A) ANATOMY Fig. 8 on page 38 Middle ear can be divided into: 1) Epitympanum Fig. 9 on page 39 # above tympanic membrane. Prussak's space = space lateral to ossicles Tegmen tympani = bony separation between middle ear and cranial fossa. Aditus ad antrum = connection between epitympanum and mastoid antrum. 2) Mesotympanum # space between epi and hypotympanum. Page 11 of 76

12 Posterior wall: Fig. 10 on page 40 Facial nerve recess. Piramidal eminence. Sinus tympani. Medial wall: Fig. 11 on page 41 Oval and round windows. Cochlear promontory. 3) Hypotympanum # below tympanic membrane. Tympanic membrane: Pars flaccida: upper one third Pars tensa: rest of tympanic membrane. Ossicular evaluation AXIAL Fig. 12 on page 42 : * "Ice cream cone" (epitympanum) Anterior ice cream = malleus head Posterior cone = incus body and short process * "Two parallel lines" (mesotympanum) Anterior line = malleus handle Posterior line = incus long process * "Two dots" (mesotympanum - incudostapedial joint) Lateral dot = lenticular process Medial dot = stapes head CORONAL: * "Right angle" Vertical = Incus long process Horizontal = Incus lenticular process B) PATHOLOGY Page 12 of 76

13 MIDDLE EAR ABNORMALITIES CLASSIFICATION - INFECTIOUS/INFLAMMATORY: Otitis media and complications. - VASCULAR: Aberrant internal carotid artery. Lateralized internal carotid artery. Dehiscent jugular bulb (no osseous wall separating hypotympanum and jugular bulb) High riding jugular bulb (Most upper portion of jugular bulb extends superior to inferior wall of IAC and/or at level of basal turn of cochlea. Jugular bulb diverticulum. - BENIGN NEOPLASTIC: paragangliomas, schwannomas, meningiomas. - MALIGNANT NEOPLASTIC: osseous metastases. OTOSCOPIC MIDDLE EAR LESION CLASSIFICATION White lesion Cholesteatoma Middle ear schwannoma Red lesion Glomus tympanicum paraganglioma Glomus jugulare paraganglioma Aberrant internal carotid artery Blue lesion Middle ear cholesterol granuloma Chronic otitis media with hemorrhage Dehiscent jugular bulb 1.- OTITIS MEDIA More common in children because hypertrophied adenoida tissue and the horizontal course of the Eustachian tube lead to increased retention of secretions. CLASSIFICATION Page 13 of 76

14 *ACUTE: - With acute signs of illness and signs/symptoms of middle ear inflammation. - It ussually affects children aged under 2 year old. - Imaging is not neccesary unless standard treatment fails and complications are suspected. - Acute otitis media complications: Extracranial Coalescent mastoiditis: destruction of mastoid septations +/- cortex. Subperiosteal abscess (post-auricular). Bezold abscess: Superior neck abscess deep to the sternocleidomastoid muscle caused by extension of infection through the mastoid tip. Petrous apicitis. Facial nerve paralysis. Labyrinthitis Intracranial Meningitis Intracranial abscess (epidural, subdural o intraparenchymal) Deep venous sinus thrombosis. *CHRONIC: SEROUS OTITIS MEDIA OR OTITIS MEDIA WITH EFFUSION: middle-ear effusion without acute signs of infection. - It typically affects children between 3 and 7 year old. - The commonest reported symptom is hearing loss. - It frequently resolves spontaneoously. - It has a lower prevalence in adults and it is associated with other underlying diagnoses: 65% Paranasal sinus disease. 20 % Smoking-induced nasopharyngeal lymphoid hiperplasia and adult onset adenoidal hypertrophy. 5 % Head and neck tumors (mainly nasopharyngeal carcinomas) 2 % No cause identified Page 14 of 76

15 - Imaging has a role in diagnosing the underlying cause in adults or failure of treatment. SUPPURATIVE OTITIS MEDIA: Tympanic membrane perforation # otorrhea. Perforation: Central Marginal. This kind lead to cholesteatoma. POSSIBLE IMAGING FINDINGS IN EVOLUTION OF CHRONIC OTITIS MEDIA Fig. 13 on page 43 : Mastoid trabeculae thickening, sclerosis, and mastoid cell obliteration. Tympanic membrane thickening and retraction. CHRONIC OTITIS MEDIA SEQUELAE / RELATED LESIONS: - Post-inflammatory ossicular fixation: Tympanosclerosis. With fibrous tissue (usually in the niche of oval window, forming a "peristapedial tent"). New bone formation. - Acquired cholesteatoma. - Cholesterol granuloma of the middle ear. - Granulation tissue. TYMPANOSCLEROSIS Fig. 13 on page 43 - Calcific plaque deposition within the tympanic cavity % of chronic otitis media. - Asymptomatic or conductive hearing loss. - CT: Unifocal or multifocal, punctate or diffuse calcified densities in the middle ear cavity, on the tympanic membrane, along ligaments and tendons, or in direct apposition to the ossicular chain. Page 15 of 76

16 Punctate or web-like calcific densities, "extra ossicles", that can extend to the tympanic membrane. Involvement of the stapes = "too well seen" stapes. Sole tympanic membrane involvement = myringosclerosis. ACQUIRED CHOLESTEATOMA - "Skin in the wrong place". Benign, non-neoplastic but proliferating lesion, characterized by keratin debris accumulation within a sac of stratified squamous epithelium. - Soft tissue mass + bony erosion. - Acquired (98%) or congenital. Fig. 14: ACQUIRED CHOLESTEATOMA CLASSIFICATION References: - Toledo/ES Fig. 15 on page 46 Cholesteatoma checkpoints: - Ossicle erosion and displacement. - Involvement of: Tegmen tympani Lateral semicircular canal Facial nerve canal Mastoid Page 16 of 76

17 - Extension towards sinus tympani (a blind spot for surgeons). - Involvement of oval window niche. Complications of cholesteatoma (The same as acute otitis media complications) Fig. 17 on page 46 ; Fig. 18 on page 47 : - Labyrinthine fistula (dehiscence of semicircular canal). - Facial nerve paralysis. - Deep venous sinus thrombosis. - Meningitis, encephalitis, abscess. - Petrous apex syndrome (Gradenigo syndrome). CHOLESTEROL GRANULOMA Fig. 19 on page 48; Fig. 46 on page 49 CT: Tympanic soft-tissue lesion. Larger lesions smooth expansile scalloping of the surrounding bone and/ or ossicular displacement or erosion. GRANULATION TISSUE CT: Opacification of the middle ear and mastoid Without erosive changes. No mass effect Tympanic membrane contour is not altered or retracted. OTITIS MEDIA IMAGING KEY POINTS: a) Imaging techniques have a role related to otitis media in the following situations: 1) Acute otitis media and cholesteatoma complications. CT: can detect subtle bony erosion. Contrast-enhanced CT: a) Rim enhancement (abscess) or phlegmonous inflammatory changes; b) Dural venous sinus thrombosis. Contrast- enhanced MRI: Laberynthitis inner ear contrast-enhancement. Page 17 of 76

18 When intracranial complications are suspected, MRI is the examination of choice: a) Dural venous sinus thrombosis filling defects; b) Extraor intracranial abscess rim-enhancing collection; c) Meningitis leptomeningeal enhancement. 2) Chronic otitis media: CT indication: Long-standing inflammation, unresponsive to medical treatment. Evaluation of posible causes of conductive hearing loss (ossicle erosion or fixation). Clinical suspicion of cholesteatoma. Suspected intratemporal and intracranial complications. b) Causes of middle ear opacification that cannot be differenciated by CT attenuation values, but can be differenciated by MRI : Effusion. Cholesteatoma. Cholesterol granuloma Fig. 19 on page 48, Fig. 46 on page 49. Granulation tissue. Scar tissue. Encephalocele Fig. 20 on page 50; Fig. 21 on page 51. Fig. 22: CHRONIC OTITIS MEDIA MRI DIFFERENTIAL DIAGNOSIS References: - Toledo/ES c) Bony erosion and otitis media: Page 18 of 76

19 Osseous erosion is not specific for cholesteatoma, since noncholesteatomatous-chronic otitis media can also show bony erosion. The absence of bony erosion does not exclude cholesteatoma. d) Cholesteatoma diagnosis and evaluation If clinical suspicion of cholesteatoma and typical location and osseous erosion are present, the diagnosis can be made with CT. CT is usually enough for evaluating the extension of cholesteatoma. MRI have a role in confirming cholesteatoma diagnosis when no typical features are present and in intracranial complications. Fig. 23: CHOLESTEATOMA - MRI INDICATIONS References: - Toledo/ES 2.- CONGENITAL CHOLESTEATOMA Fig. 24 on page 53 Conductive hearing loss in child with no history of middle ear inflammatory disease. Page 19 of 76

20 Otoscopy: intact tympanic membrane. The usual site for a congenital cholesteatoma is the middle ear: adjacent to the eustachian tube, in the peristapedial region or in the anterior epitympanum (may involve the facial nerve canal). The differentiating features which suggest congenital cholesteatoma instead of acquired cholesteatoma are: Intact tympanic membrane. Well pneumatised mastoid. Origin clearly in the middle ear cavity. 3.- PARAGANGLIOMAS Highly vascular tumour arising from the extra-adrenal neuroendrocrine system. Head and neck paragangliomas arise from glomus bodies along the cochlear promontory (glomus tympanicum) and jugular bulb (glomus jugular). A glomus jugulotympanicum is a glomus jugulare with middle ear extension. Pulsatile tinnitus, hearing loss, vertigo. Red middle ear lesion on otoscopy. Cranial nerve can be compromised: a) Jugular foramen involvement # 9º, 10º, 11º; b) Hipoglosal canal involvement # 12º. CT: Glomus tympanicum: Fig. 25 on page 54 Nodular mass lesion anteriorly in the hypotympanum against the promontory. The mass can extend into the middle ear cavity. The ossicles are generally spared. Bone erosion is not common. Floor of middle ear cavity is intact. If clinical suspicion and typical CT appearance MRI is not required. Glomus jugulare/jugulotympanicum: Fig. 33 on page 62 Erosive masses centered within the jugular foramen Page 20 of 76

21 Moth-eaten erosive aspect of the jugular foramen, with extension of the soft tissue mass to the middle ear. More agressive pattern of growth. Contrast-enhancing lesion (It can be difficult to distinguish in glomus tympanicum). MRI: Lesions > 2 cm "salt and pepper" appearance. - Hyperintense T1 - salt = haemorrhage, slow flow. - Hypointense T1 - pepper = hypointense arterial flow voids. 4.- SCHWANNOMAS PRESENTING AS MIDDLE EAR SPACE MASSES They may originate a) From the tympanic cavity = Primary schwannoma Tympanic segment of cranial nerve VII sharply defined bony canal enlargement Chorda tympani, Jacobson nerve or Arnold's nerve (##frequency) b) By extension from outside the middle ear space = Secondary schwannoma: IAC schwannoma (vestibulocochlear nerve) inner ear middle ear (usually through the round window). Jugular foramen schwannomas (IX, X, XI cranial nerves), through lateral margins of the jugular foramen. Primary inner ear schwannomas. A MRI is needed to assess lesion extension. Facial nerve schwannoma differential diagnosis # hemangioma: Amorphous honeycomb bone changes on CT in larger lesions. 5.- TEMPORAL BONE MENINGIOMAS 3 types, according to the origin: a) Tegmen tympani # spread into the middle ear. b) Jugular foramen # spread into the middle ear. c) Internal auditory canal # invade the inner ear. CT findings: Page 21 of 76

22 Permeative - sclerotic or hyperostotic changes. May underestimate extent of tumor. Uniform enhancement with contrast CT. Ossicles encased. Intratumoral calcification common. MR finding: Avidly enhancing mass involving temporal bone Dural based morphology. Absence of flow voids. If dural "tail" present, helps to make diagnosis. MRI is needed to determine tumor extension. INNER EAR A) ANATOMY 1.- BONY LABYRINTH Cochlea Vestibule Semicircular canals Vestibular aqueduct 2.- MEMBRANOUS LABYRINTH (it contains endolymph) Scala media (within cochlea) Utricle and saccule (within vestibule) Semicircular ducts (within semicircular canals) Endolymphatic duct and sac (within vestibular aqueduct) 3.- PERILYMPHATIC LABYRINTH (it contains perilymph) Space between bony and membranous labyrinth. CT can only assess bony labyrinth. B) PATHOLOGY Page 22 of 76

23 1.- Congenital * Enlarged vestibular aqueduct sydrome Fig. 26 on page 55, Fig. 27 on page 56 - Sensorineural hearing loss. - Most common abnormality found in pediatric sensorineural hearing loss. - Bilateral more common. - It can be associated with other abnormalities of the inner ear. Deficient/absent modiolus. Asymmetric scalar chambers. Deficient septation between apical and middle turns of cochlea. Vestibular aqueduct caliber > 1,5 mm = enlarged. Vestibular aqueduct caliber > semicircular canal caliber = enlarged. CT: MRI is also needed to confirm diagnosis and look for other inner ear abnormalities. * Other (Lateral semicircular canal dysplasia Fig. 28 on page 57 ) 2.- Otosclerosis Fig. 29 on page 58 - Young adult. - 2 types: Fenestral and cochlear. Normal 0 21 false false false ES-TRAD JA X-NONE Fenestral Cochlear Fissula ante fenestram involvement = Surrounding cochlea region anterior to oval window. May extend around vestibule, semicircular canal and IAC. Conductive hearing loss. Sensorineural hearing loss. Page 23 of 76

24 - 2 phases: Early: lytic radiolucency. Late: bone formation. - CT is sufficient for diagnosis. 3.- Labyrinthitis ossificans Fig. 30 on page 59 - Labyrinthitis can be secondary to infection, inflammation, trauma or surgery. - Labyrinthitis has 3 radiological phases: Acute. Fibrous. Labyrinthitis ossificans. - Labyrinthitis ossificans = Healing process. CT is diagnostic for labyrinthitis ossificans: osseous formation within membranous labyrinthine. However, earlier phases of labyrinthitis cannot be detected with CT. 4.- Endolymphatic sac tumor (rare) Fig. 31 on page 60 CT: Posterior temporal bone. Permeative bone destruction. Intratumoral spiculated bone. Avid enhancement after contrast medium administration. Help with diagnosis and extension of disease. Heterogeneous in appearance on T1 and T2. Heterogeneous enhancement. MRI Other: Schwannoma, IAC meningioma. Page 24 of 76

25 JUGULAR FORAMEN A) ANATOMY Fig. 32: JUGULAR FORAMEN ANATOMY References: - Toledo/ES B) PATHOLOGY Page 25 of 76

26 Fig. 36: JUGULAR FORAMEN DIFFERENTIAL DIAGNOSIS References: - Toledo/ES Fig. 33 on page 62, Fig. 34 on page 63 NOTES: - Lesions frequency: Paraganglioma > Schwannoma > Meningioma. - Glomus jugulare: preoperative angiography and embolization needed. - Jugular foramen metastases: Show permeative bone destruction as glomus jugulare. Heterogeneously enhancing. - Other differential diagnosis: asymetrically enlarged jugular fossa, high-riding Fig. 35 on page 64 or dehiscent jugular bulb. - If a jugular foramen lesion is found with CT, a MRI should be also performed. - Presurgical angiography and embolization should be performed in case of paraganglioma. Page 26 of 76

27 INTERNAL AUDITORY CANAL - CEREBELLOPONTINE ANGLE MASSES The most common masses at this location are vestibular schwannoma and meningioma. They have the following differenciating characteristics. Fig. 39: VESTIBULAR SCHWANNOMA VS MENINGIOMA References: - Toledo/ES Fig. 37 on page 66, Fig. 38 on page 67 NOTES: A facial nerve schwannoma can be difficult to differenciate from vestibular schwannoma # look for labyrinthine segment tail. Take into account vertebrobasilar aneurysms Fig. 40 on page 69 in the differential diagnosis of vestibular schwannomas. They appear as well-defined round or oval lesions that can extend into the IAC, with homogeneous or heterogenous enhancement depending on aneurysm thrombosis. Page 27 of 76

28 When an unusual aggressive schwannoma-like mass is found, keep metastases in mind, specially from lung and breast. Other lesions similar to meningioma: tuberculosis and melanocytic neoplasms. Lipomas are possible CPA masses, but they have the characteristic fat attenuation. IAC hemangioma CT: punctate calcifications in IAC mass. Cystic lesions: a) Only cystic component: aracnoid cyst and epidermoid cyst # No MRI is necessary. Fig. 41: CEREBELLOPONTINE ANGLE CYST LESIONS References: - Toledo/ES b) With solid component: cystic tumour, including acoustic schwannoma (solid enhancing component). PROPOSED CEREBELLOPONTINE ANGLE IMAGING ALGORITHM Page 28 of 76

29 Fig. 42: IAC - CEREBELLOPONTINE ANGLE MASS IMAGING PROPOSED PROTOCOL References: - Toledo/ES PETROUS APEX Important anatomical relationships: - Lacerum segment of internal carotid artery. - Trigeminal nerve (V) - Abducens nerve (VI) Differential diagnosis Fig. 43 on page 71 Page 29 of 76

30 - Petrous apex trapped fluid - Petrous apex mucocele - Petrous apex cholesterol granuloma - Petrous apex congenital cholesteatoma - Neoplasms Fig. 44: PETROUS APEX DIFFERENTIAL DIAGNOSIS References: - Toledo/ES *Expansile lesion shows trabecular breakdown + cortical thinning. NOTES: Neoplasms show whole lesion enhancement. Page 30 of 76

31 It is necessary to take into account asymmetric petrous apex pneumatization within cholesterol granuloma differential diagnosis. Fatty bone marrow appears hyperintense on T1 as cholesterol granuloma, however, cholesterol granulomas will remain hyperintense after fat suppresion. PETROUS APEX IMAGING ALGORITHM Fig. 45: PETROUS APEX PATHOLOGY ALGORITHM References: - Toledo/ES Page 31 of 76

32 Images for this section: Fig. 1: EAC ATRESIA. Page 32 of 76

33 Fig. 2: EAC OSTEOMA VS EXOSTOSES Page 33 of 76

34 Fig. 3: EAC BASAL CELL CARCINOMA Page 34 of 76

35 Fig. 4: EAC CHOLESTEATOMA Page 35 of 76

36 Fig. 5: MALIGNANT OTITIS EXTERNA Page 36 of 76

37 Fig. 6: EAC ALGORITHM Page 37 of 76

38 Fig. 7: EAC ALGORITHM Page 38 of 76

39 Fig. 8: MIDDLE EAR ANATOMY Page 39 of 76

40 Fig. 9: EPITYMPANUM ANATOMY Page 40 of 76

41 Fig. 10: MESOTYMPANUM Page 41 of 76

42 Fig. 11: MESOTYMPANUM (2) Page 42 of 76

43 Fig. 12: OSSICLES EVALUATION (AXIAL) Page 43 of 76

44 Fig. 13: CHRONIC OTITIS + TYMPANOSCLEROSIS Page 44 of 76

45 Fig. 16: CHOLESTEATOMA Fig. 14: ACQUIRED CHOLESTEATOMA CLASSIFICATION Page 45 of 76

46 Fig. 15: TYPICAL LOCATION OF CHOLESTEATOMAS Page 46 of 76

47 Fig. 17: CHOLESTEATOMA COMPLICATIONS Page 47 of 76

48 Fig. 18: RECURRENT CHOLESTEATOMA COMPLICATION Page 48 of 76

49 Fig. 19: CHOLESTEROL GRANULOMA Page 49 of 76

50 Fig. 46: CHOLESTEROL GRANULOMA MRI Page 50 of 76

51 Fig. 20: DEHISCENT TEGMENT TYMPANI + ENCEPHALOCELE Page 51 of 76

52 Fig. 21: DEHISCENT TEGMENT TYMPANI + ENCEPHALOCELE (2) Fig. 22: CHRONIC OTITIS MEDIA MRI DIFFERENTIAL DIAGNOSIS Page 52 of 76

53 Fig. 23: CHOLESTEATOMA - MRI INDICATIONS Page 53 of 76

54 Fig. 24: CONGENITAL CHOLESTEATOMA Page 54 of 76

55 Fig. 25: GLOMUS TYMPANICUM Page 55 of 76

56 Fig. 26: BILATERAL ENLARGED VESTIBULAR AQUEDUCT Page 56 of 76

57 Fig. 27: ENLARGED VETIBULAR AQUEDUCT SYNDROME (2) Page 57 of 76

58 Fig. 28: SEMICIRCULAR CANAL DYSPLASIA Page 58 of 76

59 Fig. 29: OTOSCLEROSIS Page 59 of 76

60 Fig. 30: LABYRINTHITIS OSSIFICANS Page 60 of 76

61 Fig. 31: ENDOLYMPHATIC SAC TUMOR (CT) Page 61 of 76

62 Fig. 32: JUGULAR FORAMEN ANATOMY Page 62 of 76

63 Fig. 33: JUGULAR PARAGANGLIOMA Page 63 of 76

64 Fig. 34: JUGULAR SCHWANNOMA Page 64 of 76

65 Fig. 35: HIGH JUGULAR BULB Page 65 of 76

66 Fig. 36: JUGULAR FORAMEN DIFFERENTIAL DIAGNOSIS Page 66 of 76

67 Fig. 37: VESTIBULAR SCHWANNOMA Page 67 of 76

68 Fig. 38: VESTIBULAR SCHWANNOMA (2º CASE) Page 68 of 76

69 Fig. 39: VESTIBULAR SCHWANNOMA VS MENINGIOMA Fig. 40: BASILAR ARTERY ANEURYSM Page 69 of 76

70 Fig. 41: CEREBELLOPONTINE ANGLE CYST LESIONS Page 70 of 76

71 Fig. 42: IAC - CEREBELLOPONTINE ANGLE MASS IMAGING PROPOSED PROTOCOL Fig. 43: PETROUS APEX TRAPPED FLUID Page 71 of 76

72 Fig. 44: PETROUS APEX DIFFERENTIAL DIAGNOSIS Page 72 of 76

73 Fig. 45: PETROUS APEX PATHOLOGY ALGORITHM Page 73 of 76

74 Conclusion CT is the imaging modality of choice as the first approach to pathological entities of the temporal bone. It is a matter of great import to leverage the full capacity of this technique as well as to know its limits, to be able to decide when it is neccesary to perform other imaging tests to reach an accurate diagnosis. Page 74 of 76

75 References Hansberger et al. Diagnostic Imaging - Head and Neck. Part I: Temporal bone and skull base. 1º ed. Amyrsys; Gassner EM, Mallouhi A, Jaschke WR. Preoperative evaluation of external auditory canal atresia on high resolution CT. AJR Am J Roentgenol May;182(5): Ong CK, Pua U, Chong VF. Imaging of carcinoma of the external auditory canal: a pictorial essay. Cancer Imaging Oct 20;8:191-8 Rubin Grandis J, Branstetter BF 4th, Yu VL. The changing face of malignant(necrotising) external otitis: clinical, radiological, and anatomic correlations. Lancet Infect Dis Jan;4(1):34-9. Abele TA, Wiggins RH 3rd. Imaging of the temporal bone. Radiol Clin North Am Jan;53(1):15-36 Lo AC, Nemec SF. Opacification of the middle ear and mastoid: imaging findings and clues to differential diagnosis. Clin Radiol May;70(5):e1-e13 Mohan S, Hoeffner E, Bigelow DC, Loevner LA. Applications of magnetic resonance imaging in adult temporal bone disorders. Magn Reson Imaging Clin N Am Aug;20(3): Lemmerling MM, De Foer B, VandeVyver V, Vercruysse JP, Verstraete KL. Imaging of the opacified middle ear. Eur J Radiol Jun;66(3): Más-Estellés F, Mateos-Fernández M, Carrascosa-Bisquert B, Facal de Castro F, Puchades-Román I, Morera-Pérez C. Contemporary non-echo-planar diffusion-weighted imaging of middle ear cholesteatomas. Radiographics Jul-Aug;32(4): Juliano AF, Ginat DT, Moonis G. Imaging review of the temporal bone: part I. Page 75 of 76

76 Anatomy and inflammatory and neoplastic processes. Radiology Oct;269(1):17-33 Baráth K, Huber AM, Stämpfli P, Varga Z, Kollias S. Neuroradiology of cholesteatomas. AJNR Am J Neuroradiol Feb;32(2):221-9 Ong CK, Fook-Hin Chong V. Imaging of jugular foramen. Neuroimaging Clin N Am Aug;19(3): Qureishi A, Lee Y, Belfield K, Birchall JP, Daniel M. Update on otitis media prevention and treatment. Infect Drug Resist Jan 10;7:15-24 Schmalfuss IM. Petrous apex. Neuroimaging Clin N Am Aug;19(3): Page 76 of 76