Case 41: What is the most likely diagnosis?
Right
Left 1 of 2
Facial Nerve Prolapse- giving rise to a Stapes Deficiency
Case 41: What is the most likely diagnosis?
In a congenitally malformed middle ear, a dehiscence of the bony fallopian canal may be discovered and the soft epineurium of the facial nerve may be exposed. A prolapsed facial nerve is defined as a nerve that is displaced inferiorly to cover a portion or the entire stapes footplate (red arrows), or an overhanging facial nerve. The facial nerve course is often anomalous in the presence of ossicular chain anomalies as the ossicles develop from the first and second branchial arches and the nerve develops from the second arch. Facial nerve prolapse may cover the stapes and oval window and cause degrees of hearing loss. The greatest consequence of this finding is its complication to surgery of the middle ear.
Right DDx: Dehiscent Facial Nerve
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Left
DDx
Case 42: What is the most likely diagnosis?
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Case 42: What is the most likely diagnosis?
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Congenital Incus Fixation
Case 42: What is the most likely diagnosis?
Numerous congenital disorders present with symptoms of ossicular fixation. Most commonly, the malleus fuses with the incus head to the epitympanic wall by a fibrous band or a bar of bone (red arrows) resulting in conductive hearing loss. Rarely, the malleus handle is fixed to the posterior tympanic wall by a bony bar. In Down’s syndrome, abnormal ossicle formation is also seen, most commonly in the stapes. Most ossicular ankyloses and abnormalities can be treated surgically. It is presumed that the mesenchyme behind the malleus handle is incompletely absorbed in development and this persistent mesenchymal tissue differentiates into osseous tissue. Fixation is often resultant of malformations during this process.
DDx: Ossicular Fixation 1. 2.
Tympanosclerosis Chronic Otitis Media
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DDx
Case 43: What is the most likely diagnosis?
1 of 3
Case 43: What is the most likely diagnosis?
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Bilateral Enlarged Trigeminal Cisterns
Case 43: What is the most likely diagnosis?
The trigeminal cistern, or Meckel’s Cave, is an anterior extension of the subarachnoid prepontine space containing CSF. The presence of CSF explains the normal hyperintensity on T2-weighted imaging. This contains the trigeminal nerve and trigeminal ganglion. Enlarged cisterns can be seen as CSF intensity structures extending posteriorly from the normal Trigeminal cistern to remodel the petrous apices. It is a normal variant.
DDx: Enlargement of the trigeminal cisterns 1. 2. 3. 4. 5.
Trigeminal schwannomas Arachnoid cyst Infection Trauma Hemorrhage
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DDx
Case 44: What is the most likely diagnosis?
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Bilateral Tegmen Tympani Dehiscence
Case 44: What is the most likely diagnosis?
The tegmen tympani is the the bony covering of the epitympanic space separating it from the middle cranial fossa. Pulsatile tinnitus in the absence of any vascular lesion may be due to the presence of meningoceles, either congenital or aquired. Temporal bone defects resulting in meningocele can present with conductive hearing loss, persistent middle-ear effusion, and persistent otorhhea. Meningoceles arising from defects in the tegmen can occur as a result of previous surgery, trauma, infection, or may be congenital. Cholesteatoma is a common cause for acquired dehiscence of the tegmen and this region should always be assessed. MR can be beneficial to better evaluate for possible meningoencephalocele.
DDx: Tegmen Tympani Dehiscence 1. 2. 3. 4.
Acquired Cholesteatoma Otitis Media Meningocele Encephalocele
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DDx
Case 45: What is the most likely diagnosis?
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Congenital Tegmen Tympani Dehiscence- Meningitis
Case 45: What is the most likely diagnosis?
Dehiscence of the tegmen tympani from what ever etiology can be a possible etiology for meningitis. Loss of the normal bony wall between the epitympanum and middle cranial fossa can expose the intracranial contents to possible infectious organisms in the middle ear. This region should always be assessed on temporal bone studies. Dehiscence with soft tissue in this region raises the possibility of a meningoencephalocele. This should be further evaluated by MRI. In addition to infection, CSF leaks and pulsatile tinnitus can be potential problems.
DDx: Tegmen Tympani Dehiscence 1. 2. 3. 4.
Acquired Cholesteatoma Otitis Media Meningocele Encephalocele
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DDx
Case 46: What is the most likely diagnosis?
1 of 3
Case 46: What is the most likely diagnosis?
2 of 3
Congenital Encephalocele through the Tegmen Tympani
Case 46: What is the most likely diagnosis?
Meningoencephaloceles (MECs)are often seen with bony dehiscences, and can be caused by various processes such as otologic infection, trauma, surgery, neoplasia, or may occur spontaneously. Chronic otitis media and middle ear surgery are considered the main causative factors of MECs. Spontaneous MEC is quite rare and are either congenital in origin or are otherwise idiopathic. Skull base defects are not ucommon and most often occur in the tegmen tympani or tegmen mastoideum. Normal dura is structurally capable of supporting brain, even over large defects; loss of structural dural integrity often participates in the formation of MECs. Patients often present with conductive hearing loss, otorrhea, and recurrent meningitis. On CT, absence of either a tympanic membrane perforation or ossicular chain erosion and presence of an intact scutum should make the diagnosis of otitis media or cholesteatoma less likely (red arrows). MRI should be obtined to better assess.
DDx: Encephalocele through Tegmen Tympani 1. 2. 3.
Acquired Cholesteatoma Chronic Otitis Media Otitis Media with Effusion
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DDx
DDx: Perilymphatic Fistula (Semicircular Canals) 1. 2. 3. 4.
Case 47: What is the most likely diagnosis?
Meniere’s Disease Syphilis Acquired Cholesteatoma Congenital Dehiscence
Perilymphatic Fistula (Lateral Semicircular Canal) A perilymph fistula is an abnormal connection between the air-filled middle ear and the fluid-filled inner ear. The oval and round windows are the weakest and therefore most common areas for an abnormal fistula to develop (oval window more common), but are also seen in the semicircular canals. A dehiscence or bony erosion of the semicircular canals (red arrows) makes the ear more sensitive to pressure and noise. Changes in air pressure can stimulate balance and hearing structures, and symptoms often include dizziness, vertigo, imbalance, nausea, vomiting, and an unsteadiness with increases in activity. Bony erosions of the semicircular canals can be caused by cholesteatoma, chronic mastoid inflammation, and fenestration surgery. Hearing loss with perilymphatic fistula is usually fluctuating SNHL, likely from intermittent leakage. Sudden hearing loss can be associated with PLF.
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DDx
Case 48: What is the most likely diagnosis?
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Case 48: What is the most likely diagnosis?
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Labyrinthitis Ossificans
Case 48: What is the most likely diagnosis?
Labyrinthitis ossificans is the pathological ossification of the membranous labyrinth spaces in response to processes which are destructive of the membranous labyrinth or the endosteum of the otic capsule. The most common causative agents are inflammation of the inner ear secondary to bacterial (pneumococcal) meningitis and subsequent purulent labyrinthitis. Temporal bone trauma, autoimmune disease, sequela of mumps or measles, and otitis media have also been reported in association with labyrinthitis ossificans. Ossification commonly occurs primarily at the basal turn of the cochlea, which is the insertion site of the electrodes of cochlear implant devices which may interfere with successful insertion. MRI is used to assess for early fibrosis prior to the formation of calcification. On CT, osseous obliteration is often seen of the visualized cochlea, vestibule, and the lateral semicircular canal (red arrows).
DDx: Labyrinthitis Ossificans 1. 2. 3.
Chronic Sclerosing Otomastoiditis Otosclerosis Michel Aplasia
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DDx
DDx: Otosclerosis 1. 2. 3. 4.
Case 49: What is the most likely diagnosis?
Osteogenesis Imperfecta Paget’s Disease Fibrous Dysplasia Hyperparathyroidism
Fenestral and Retro-Fenestral (Cochlear) Otosclerosis Fenestral otosclerosis usually occurs in young adults and is mostly (85%) a bilateral disease. Patients present with conductive hearing loss and tinnitus. Histologically, enchondral bone is replaced by a foci of spongy new bone, which later calcify into a dense, ossific plaque. The fixation of the stapedial footplate is responsible for the conductive hearing loss in fenestral otosclerosis. The most common CT finding for fenestral otosclerosis is a lucent area just anterior to the stapedial footplate (red arrows), the fissula ante fenestrum. Cochlear (retrofenestral) otosclerosis is less common, but is almost always associated with fenestal otosclerosis. Histologically, foci of spongy new bone extend around the cochlea and may involve the vestibule and semicircular canals. In cochlear otosclerosis, CT shows focal lucencies in the otic capsule, possibly extending ring-like around the cochlea (blue arrows).
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DDx
DDx: Otosclerosis 1. 2. 3. 4.
Case 50: What is the most likely diagnosis?
Osteogenesis Imperfecta Paget’s Disease Fibrous Dysplasia Hyperparathyroidism
Fenestral and Retro-Fenestral (Cochlear) Otosclerosis Fenestral otosclerosis usually occurs in young adults and is mostly (85%) a bilateral disease. Patients present with conductive hearing loss and tinnitus. Histologically, enchondral bone is replaced by a foci of spongy new bone, which later calcify into a dense, ossific plaque. The fixation of the stapedial footplate is responsible for the conductive hearing loss in fenestral otosclerosis. The most common CT finding for fenestral otosclerosis is a lucent area just anterior to the stapedial footplate (red arrows). Cochlear (retrofenestral) otosclerosis is less common, but is almost always associated with fenestal otosclerosis. Histologically, foci of spongy new bone extend around the cochlea. In cochlear otosclerosis, CT shows focal lucencies in the otic capsule, possibly extending ring-like around the cochlea (blue arrows).
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DDx