A classification of congenital malformations of the inner ear
I. Malformations limited to the membranous labyrinth
A. Complete membranous labyrinthine dysplasia (Siebenmann-Bing)
B. Limited membranous labyrinthine dysplasia
1. Cochleosaccular dysplasia (Scheibe)
2. Cochlear basal turn dysplasia (Alexander)
II. Malformations of the osseous and membranous labyrinth
A. Complete labyrinthine aplasia (Michel)
B. Cochlear anomalies
1. Cochlear aplasia
2. Cochlear hypoplasia
3. Incomplete partition (Mondini)
4. Common cavity
C. Labyrinthine anomalies
1. Semicircular canal dysplasia
2. Semicircular canal aplasia
D. Aqueductal anomalies
1. Enlargement of the vestibular aqueduct
2. Enlargement of the cochlear aqueduct
E. Internal auditory canal abnormalities
1. Narrow internal auditory canal
2. Wide internal auditory canal.
Complete labyrinthine aplasia (Michel)
The severest deformity of the membranous and osseous labyrinth, complete
labyrinthine aplasia, was first described by Michel (1863). This malformation
is exceedingly rare. Presumably, a developmental arrest occurs before the
formation of an otic vesicle, resulting in a complete absence of inner ear
structures. Complete labyrinthine aplasia has been reported in association
with anencephaly and thalidomide exposure . A recent purported case of
Michel's dysplasia actually described a cystic inner ear of the common cavity
type. The incidence of complete labyrinthine aplasia is overestimated in the
radiographic literature because it is confused with labyrinthine ossification. In
the latter condition, which is usually acquired during life, a sizable and dense
otic capsule is present radiographically. In complete labyrinthine aplasia, the
otic capsule is entirely absent. Such ears are of course uniformly deaf.
HRCT: Show complete absence of inner ear with hypoplasia of the petrous bone
and narrow atretic ISC.
Absence of round and oval window.
Flattening of medial wall of middle ea cavity.
MRI: 8th cranial nerve not visualized on MR images associated wih skull base,
CVJ vascular anomalies.
Michel aplasia. The labyrinth is absent on the right (black arrow), whereas the left
cochlea is normal on computed tomography (white arrow). The right internal
auditory canal is narrow and contains only the facial nerve (thin white arrow). The
volume of the right petrous temporal bone is smaller than that of the left.
A deformed inner ear in which the cochlea and vestibule are confluent,
forming an ovoid cystic space without internal architecture, may be
explained by an arrest at the fourth week otocyst stage. Alternatively,
it may result from aberrant development at a later stage. An empty
ovoid space typically longer in its horizontal dimension is seen
adiographically. Although the size of the cyst may vary, it averages 7
mm vertically and 10 mm horizontally. It is quite easy to misdiagnose
a dysplastic lateral SCC as a common cavity deformity. The key to
differentiating between them is that a common cavity cochlea lies
predominantly anterior to the internal auditory canal (IAC) on axial
plane CT, and a dysplastic vestibular system lies posterior to it.
Histologically, an ovoid or spherical smooth-walled cystic cavity
containing a primordia of the membranous labyrinth has been
described. Sensory and supporting cells may be differentiated into
recognizable organs of Corti that are scattered peripherally around the
walls of the cyst. Neural population is usually sparse or absent. Hearing
is usually, but not invariably, poor.
Common cavity deformity on computed tomography (CT) (A) and fast imaging employing
steady-state acquisition (FIESTA) magnetic resonance imaging (MRI) (B). A septation
(thin white arrow—B) seen on FIESTA divides the primitive cochlea anteriorly (white
arrow—A,B) from the fused vestibule and semicircular canals posteriorly (black asterisk).
Note that a portion of the posterior semicircular canal has formed (black arrows). Note
the anomalous course of the common cochleovestibular nerve (white arrowheads) in the
internal auditory canal. Note the labyrinthine segment of the fallopian canal on CT (black
arrowhead—A) and the facial nerve in the internal auditory canal (black arrowhead—B).
In this deformity the cochlea is completely absent, presumably as a
result of an arrest in the development of the cochlear bud at the
fifth week. This morphologic pattern is rare.
Radiographically, only a vestibule and SCCs (usually deformed) are
present. To differentiate this anomaly from labyrinthine ossification
it is necessary to assess the amount of otic capsule bone anterior to
the internal auditory canal. In cochlear aplasia, the otic capsule is
absent, whereas in osseous obliteration it is dense and of normal
dimensions. Ears with cochlear aplasia are devoid of auditory
1- Absence of cochlea.
2- Dilatation of the vestibule.
3- Deformity of semicircular canal.
4- Dense otic bone.
Atresia of the cochlear foramen to the left and normal cochlear
foramen to the right and non-visualization of the left cochlear nerve.
An arrest during the sixth week results in a hypoplastic
cochlea consisting of a single turn or less. This deformity
comprises approximately 15% of all cochlear anomalies.
Radiographically, a small bud of variable length (usually 1 to
3 mm) protrudes from the vestibule as compared to normal
height of 12-13 mm. Abnormal small IAC. The vestibule is
frequently enlarged with accompanying semicircular
malformations in about half of faces. Small cochlear lacking
a modiolus or other internal architecture have been
described histologically . Hearing is variable in these ears
and may be remarkably good considering the minute size of
the cochlea. The variability of hearing presumably is
accounted for by degree of membranous labyrinthine
development within the truncated cochlear lumen.
Incomplete partition (Mondini)
Arrest at the seventh week stage yields a cochlea that has only 1.5 turns.
This is the most common type of cochlear malformation, accounting for
over 50% of all cochlear deformities. Radiographically, the cochlea is
smaller than normal and partially or completely lacks an interscalar
septum . Although the usual cochlea measures 8 to 10 mm vertically, it is
typically in the 5 to 6 mm range with incomplete partition deformity. Care
must be exercised in counting the number of cochlear turns
radiographically, as this may be difficult to determine even on high-
resolution CT scans. The radiographic diagnosis depends more on cochlear
size and the absence of a scalar septum than on the number of cochlear 8
turns perceived. Histologically, incomplete partition appears to be the
radiographic correlate of classical Mondini's dysplasia. In numerous
reported cases a small cochlea with 1.5 turns possessing an apical scala
communis due to deficiency in the osseous spiral lamina has been
described. Organ of Corti development is variable as is auditory neural
population. As might be expected, auditory function is also variable,
ranging from normal to profound deafness. The mean hearing threshold
(three tone average) in a group of 41 incomplete partition ears was 75 dB.
Classic Mondini malformation (incomplete partition type II.
Semicircular canal dysplasia
Dysplasia of the lateral SCC is a common type of inner ear
malformation. Approximately 40% of ears with a malformed
cochlea will have an accompanying dysplasia of the lateral
SCC. Occasionally, dysplasia of the lateral SCC exists as the sole
inner ear malformation. The lateral SCC is deformed more
often than the posterior or superior SCC, apparently because it
forms earlier in embryogenesis. The typical radiographic
appearance of SCC dysplasia is that of a short, broad cystic
space confluent with the vestibule.
Semicircular canal aplasia
SCC aplasia is only one-fourth as common as SCC dysplasia. It
is usually associated with cochlear anomalies. Presumably, it
arises from a failure in the development of the vestibular
anlage before the sixth week.
Axial CT image reveals fusion of the vestibule and LSC, forming a cystic lumen
on the left side (curved arrow). On the contralateral side, there is both a
narrow internal auditory canal and dysplastic vestibule-rudimentary LSC.
Enlarged vestibular aqueduct with modiolar dysplasia (Mondini malformation). Fast
imaging employing steady-state acquisition (FIESTA) magnetic resonance image
(MRI) of right inner ear (A) shows enlarged endolymphatic sac expanding the
vestibular aqueduct (thick white arrow) as compared with the normal posterior SCC
(arrowheads). The osseous spiral lamina and modiolus (thin white arrow) are
hypoplastic. Compare with the normal FIESTA MRI of the left inner ear (B). Note that
the vestibular aqueduct is typically only faintly visualized on FIESTA (thick black
arrow) and normal cochlea and modiolus (thin black arrow).
Developmental Anomalies of the Internal Auditory Canal
Narrow internal auditory canal:
A narrow IAC may indicate a failure of eighth nerve development.
When a patient has normal facial function and an IAC less than 3
mm in diameter, it is likely that the bony canal transmits only the
facial nerve. A narrow IAC may accompany inner ear malformations
or may be the sole radiographically detectable anomaly in a deaf
child. A narrow IAC has been considered a relative contraindication
to cochlear implantation.
Wide internal auditory canal: Unlike congenital narrowness
of the IAC, a congenitally large canal may be an incidental finding
in normal individuals. When a large IAC (> 10 mm in diameter)
accompanies a malformation of the inner ear, it does not, as an
independent variable, correlate with the level of hearing. The
importance of detecting enlargement of the IAC is its association
with spontaneous CSF leak and gusher during stapes surgery .
Narrow Internal Auditory Canal with Duplication in a
Patient with Congenital Sensorineural Hearing Loss
Narrowing of the left internal auditory canal with absence of left cochlear nerve.
Labyrinthitis. T1-weighted magnetic resonance image (T1W MRI) with (B)
and without (A) contrast shows dramatic enhancement of the cochlea
(black arrows) and vestibule (white arrows), indicating labyrinthitis.
Intralabyrinthine hemorrhage in a patient with endolymphatic sac tumor (not shown).
Hyperintense signal on noncontrast T1-weighted magnetic resonance image (T1W MRI)
fills the vestibule and a portion of the posterior SCC (white arrow—A). On fast-spin echo
T2-weighted magnetic resonance image (T2W MRI) (white arrow—B) the vestibule is
poorly visualized because of signal loss from blood. Note the normal appearance of the
cochlea on both the noncontrast T1W and T2W MRI (white arrowheads—A,B).
Petrous apicitis. MRI show fluid signal on T1-wi and T2-wi in right and left air cells
of PA & mastoid complex (arrows). Post-contrast T1-wi (with fat-sat) demonstrate
CE (arrowheads) on the right mastoid and extension into right cavernous sinus,
and skull base osteomyelitis (arrowheads), prevalent on the right side.
No apparent cause
Does not involve any other cranial nerves.
Pathogenesis: Secondary to swelling and edema
of the 7th nerve within the fascial nerve canal.
Bell's palsy is a form of facial paralysis resulting from a dysfunction
of the cranial nerve VII (the facial nerve) causing an inability to
control facial muscles on the affected side. Several conditions can
cause facial paralysis, e.g., brain tumor, stroke, myasthenia gravis,
and Lyme disease. However, if no specific cause can be identified, the
condition is known as Bell's palsy. Named after Scottish anatomist
Charles Bell, who first described it, Bell's palsy is the most common
acute mononeuropathy(disease involving only one nerve) and is the
most common cause of acute facial nerve paralysis (>80%). Bell's
palsy is defined as an idiopathic unilateral facial nerve paralysis,
usually self-limiting. The hallmark of this condition is a rapid onset of
partial or complete paralysis that often occurs overnight. In rare
cases (<1%), it can occur bilaterally resulting in total facial paralysis.
It is thought that an inflammatory condition leads to swelling of the
MRI show enhancement of the fascial nerve within the tympanic
portion of the fascial nerve canal which support the diagnosis.
Facial nerve schwannoma
A facial nerve schwannoma (FNS) (also known as facial nerve neuroma /
neurilemoma) a schwannoma that arises from the facial nerve. They are generally
uncommon, and when involving the temporal bone and make up less than 1% of
all temporal bone tumours.
As schwannomas elsewhere they originate from the surface of the nerve, and
displace and splay the nerve fibers over their eccentric growth (this compares
favorably to neurofibromas through which the axons are distributed). This allows
for potential resection of the tumour while sparing the nerve.
Similar to acoustic schwannomas, they may grow to a quite sizable extent and
exert positive mass effect with growth into the cerebellopontine angle.
They can present with a wide variety of symptoms. More frequently they present
with gradual, and often incomplete, facial nerve palsy. Rapid onset mimicking a
Bell's palsy is certainly also recognised. Mass effect on adjacent nerves may well
cause sensory neural hearing loss (SNHL) or even conductive hearing loss if growth
into the middle ear impairs the normal function of the ossicles. In a minority of
cases ( ~10%) the tumour is extra cranial, where it presents as an asymptomatic
Imaging characteristics of the tumour itself is the same as that of
schwannomas elsewhere : homogenous enhancement on both CT and MRI
when small; heterogenous when large. The best clue that a schwannoma is
of the facial nerve rather than the more common vestibulochoclear nerve
(CN VIII) is expansion extending along the facial nerve canal - especially
along the labyrinthine segment.
In all cases, hi resolution thin section bone CT of the temporal bone is
required to assess the otic capsule. Bony scalloping and remodeling may be
present. Failure to preoperatively diagnose bony erosion can lead to
postoperative fistula formation.
Signal characteristics include
T1 - typically iso- to hypo intense relative to gray matter
T2 - typically hyperintense ; large lesion may show heterogenous signal
T1 C+ (Gd) - usually demonstrate homogeneous enhancement with larger
lesions with cystic degeneration seen as focal intramural low signal
Right geniculate ganglion facial nerve schwannoma.
Left tympanic segment facial nerve schwannoma.
Facial nerve hemangioma
A facial nerve hemangioma is a benign vascular tumour of the facial nerve. This
and facial nerve schwannomas make up the majority of primary tumours of the
facial nerve, which are very rare entities(0.7%).
Location: It has a predilection for the region around the geniculate ganglion
(although even more rarely seen in the IAC), compared to schwannomas which
can occur anywhere along the nerve.
T1 - iso or slightly hypo intense
T2 - hyper intense
C+ Gd - intense contrast enhancement
Imaging differential considerations include
facial nerve schwannoma
facial nerve malignant schwannoma
facial nerve perineurioma
meningioma arising from the geniculate ganglion have been reported
facial nerve metastases, hematogenous and retrograde spread.
Hemangioma. Ax/Cor CT images show a poorly marginated mass of geniculate
fossa with typical amorphous “honeycomb” bone changes (arrows), post
gadolinium T1-wi demonstrate avid CE with foci of low signal (arrows).
Ménière's disease also called endolymphatic hydrops, is a
disorder of the inner ear that can affect hearing and balance
to a varying degree. It is characterized by episodes of
vertigo, low-pitched tinnitus, and hearing loss. The hearing
loss is for some time fluctuating rather than permanent,
meaning that it comes and goes, alternating between ears,
then becomes permanent with no return to normal function.
The condition affects people differently; it can range in
intensity from being a mild annoyance to a lifelong
1- Fluctuating hearing loss.
2- Episodic vertigo.
4- Sensation of fullness in the ears.
The role of imaging is controversial2, but improved spatial resolution
in CT and MRI is likely to show where endolymphatic flow is
MRI is used to exclude alternative diagnoses such as vestibular
schwannoma or other cerebellopontine angle lesions, and superior
canal dehiscence. High resolution MRI can show lack of a visible
endolymphatic duct and sac. The gadolinium successfully penetrate
the round window membrane, entering the perilymphatic space and
delineating the contrast enhanced perilymphatic and contrast-
negative endolymphatic spaces of the inner ear.
Reduced visualization of saccular duct and endolymphatic sinus are
features.6 At high-resolution temporal bone CT, the vestibular
aqueduct is either small or not visible at all, in contrast to the
congenital large vestibular aqueduct syndrome.
Grade 1 imaging findings in 61-year-old woman in nonacute phase of Meniere
disease with high-frequency hearing loss. A–D, Affected left ear. E–H,
Unaffected right ear. Bilateral endolymphatic sacs (arrows) are clearly visible.
Grade 2 imaging findings in 34-year-old woman in nonacute phase of Meniere
disease with high-frequency hearing loss. There is poor visibility of the contents of
the vestibular aqueduct in the affected left ear (A–D) as compared with the
unaffected right ear (E–H). Arrows show the endolymphatic duct and sac. Note
difference in visibility between the affected side and the unaffected side.
Grade 3 imaging findings in 28-year-old woman in
nonacute phase of Meniere disease. In the affected right
ear (A–E), the endolymphatic duct and sac are not
delineated. However, the endolymphatic duct and sac
(arrows) can be seen in the unaffected left ear (F–J).
Grade 3 imaging findings in 34-year-old woman in nonacute phase of
Meniere disease with flat hearing impairment. The affected left ear (A–D)
does not show the endolymphatic duct and sac; however, the endolymphatic
duct and sac are clearly visible in the unaffected right ear (E–H).
Grade 3 imaging findings in a 21-year-old man in the acute phase of Meniere disease. In
the affected right ear (A–D), the endolymphatic duct and sac are not delineated. However,
the endolymphatic duct and sac (arrows) can be seen in the unaffected left ear (F–I).
Endolymphatic sac tumour
Endolymphatic sac tumours (ELST) are very rare, locally invasive tumors of
endolymphatic sac. Early detection of ELST is very important, because early
surgical intervention may prevent further hearing loss.
Presentation of tumour is:
hearing loss : 95 %, acute in 43% and stepwise in second half
tinnitus : 92%
vertigo or disequilibrium : 62%
aural fullness : 29%
facial paresis : 8%
When visible, it gives a picture of bone erosion and the "moth-eaten" petrous
bone. ELSTs commonly enhance intensely on CT.
Signal characteristics include
T1: may show high-density
T1 C+ (Gd): typically show enhancement in the non-cystic component of the
T2: often of heterogenous signal.
Endolymphatic sac tumor. T1-weighted (T1W) precontrast (A) and postcontrast (B)
magnetic resonance image (MRI) show a hyperintense enhancing lesion (white arrow, B) in
the right petrous bone at the expected position of the endolymphatic sac. Note
hyperintensity (white arrows, A, D) on precontrast T1W (A) and T2-weighted (T2W) (D) MRI
caused by hemorrhagic and proteinaceous elements of the tumor. Computed tomography
demonstrates erosion of temporal bone (black arrow—C) adjacent to the vestibular
aqueduct (black arrowheads—C), which is characteristic of this tumor.
MRI T1 weighted images of the brain, showing a very large ELST of the left
temporal bone, in axial view on the left and coronal view on the right.
There has been complete erosion of the petrous temporal bone by the
tumor, with significant brainstem and cerebellar compression.
Tumour which has relation to the with inner ear.
Acoustic schwannoma is a relatively common type of tumour which arises
from the vestibulochoclear nerve (CN VIII). Bilateral acoustic
schwannomas are strongly suggestive of neurofibromatosis type 2 (NF2).
They account for 7-8% of all primary intracranial tumours and 75-90% of
cerebellopontine angle masses . Bilateral vestibular schwannomas are
highly suggestive of neurofibromatosis type 2 (NF2)), although bilateral
tumours are encountered in the familial form of acoustic schwannomas in
the absence of other stigmata of NF2.
Origin: Most from inferior vestibular nerve, at glial-schwann cell interface.
The typical presentation is with sensorineural hearing loss or tinnitus. In
some patients this goes unnoticed and presentation is delayed until the
lesion is much larger and presents with mass effect. Possibilities include
cerebellar and brainstem symptoms (e.g. other cranial nerve dysfunction),
or hydrocephalus due to effacement of the fourth ventricle.
May show erosion and widening of the internal acoustic meatus. The
density of these tumours on non-contrast imaging is variable, and often
they are hard to see, especially on account of beam hardening and streak
artefact form the adjacent petrous temporal bone.
Contrast enhancement is present, but can be underwhelming, especially in
larger lesions with cystic components.
Slightly hypo-intense c.f. adjacent brain – 63% iso intense c.f adjacent
brain – 37% may contain hypo intense cystic areas
Heterogeneously hyper intense c.f to adjacent brain cystic areas fluid
may have associated peri-tumoural arachnoid cysts .
T1 C+ (Gd)
Contrast enhancement is vivid but heterogeneous in larger tumours
Intralabyrinthine schwannoma. T1-weighted postcontrast magnetic resonance
image depicts an abnormally enhancing lesion within the left vestibule (white
arrow). Note that the imaging findings may be indistinguishable from labyrinthitis.
VIII cn schwannoma. Illustration from Diagnostic Imaging, head and neck
(Harnsberger et al.) When filling up the IAC schwannoma typically resembles an “ice
cream cone”. Signal intensity is low on T1-wi, heterogeneous but predominant high on
T2-wi. SSFP better demonstrate enlarging IAC mass. CE is marked and homogenous.
Bilateral vestibular schwannomas in a patient with neurofibromatosis 2 (NF2). (A,
B) Axial and coronal T1 weighted images with gadolinium enhancement are
shown. Note the presence of an associated trigeminal schwannoma (arrow). (C,
D) Significant enlargement has occurred over four years, with the left sided
vestibular schwannoma causing displacement of the brainstem.
IAC schwannoma and meningioma in patient with NF-2.
Meningiomas are a diverse set of tumors arising from the meninges ,
the membranous layers surrounding the central nervous system. They arise
from the arachnoid "cap" cells of the arachnoid villi in the meninges. These
tumors are usually benign in nature; however, a small percentage are
2nd most common CPA tumour(10%), usually arising from the meninges
covering posterior petrous bone, More common in female than male(3-1).
CT : 60% slightly hyperdense to normal brain, 20-30% have some
calcification , 72% brightly and homogenously contrast enhance, less
frequent in malignant or cystic variants.
MRI : Signal characteristics include:
T1 - isointense: 60-90%. somewhat hypointense: 10-40% compared to
T1 C+ (Gd) - usually intense and homogenous enhancement
T2 - isointense: 50%, hyperintense: 35-40%
DWI - atypical and malignant sub types may show greater than expected
restricted diffusion although recent work suggests that this is not useful in
prospectively predicting histological grade.
Meningioma. T1-weighted postcontrast magnetic resonance image demonstrates
a uniformly enhancing mass (black arrow) in the right cerebellopontine angle.
Note the broad-based dural attachment on the petrous bone and small dural tails.
Epidermoid. Magnetic resonance image shows enlargement of the left cerebellopontine
angle (CPA) (white arrows), with mass effect on the brainstem. Signal matches that of
cerebrospinal fluid (CSF) on T1-weighted (A) and T2-weighted (B) images. Hyperintensity
on diffusion-weighted imaging (C) and hypointensity on fast imaging employing steady-
state acquisition (FIESTA) (D) differentiates the epidermoid from an arachnoid cyst.
Internal auditory canal (IAC) lipoma. A hyperintense lesion (black arrow—
A) in the anterior aspect of the right IAC is seen on noncontrast T1-
weighted magnetic resonance image. FLAIR with fat saturation completely
suppresses signal from the lesion, confirming lipoma (white arrow—B).
Development of Solitary Plasmacytoma in the Internal Auditory Canal and Inner Ear
after Allogeneic Hematopoietic Stem Cell Transplantation for Plasma Cell Leukemia.
A glomus jugulare tumour is a paraganglioma of the
head and neck that is confined to the jugular fossa. While it
is a rare tumour, it is the most common of the jugular fossa
The lesion is arising from the 9th and 10th nerves and most
common of middle ear.
The unique names is according to the location:
Jugular bulb- Glomus jugulare.
Middle ear- Glomus tympanicum.
Carotid body- Carotid body tumour.
Vagus nerve- Glomus vagale.
Pulsating tinnitus with conductive hearing loss,,
Invasion of the cochlea, lead to sensorineural hearing loss.
Otoscopy shows blue tympanic membrane.
CT: CT is most useful at assessing the bony margins of the tumour, which are
typically irregularly eroded with a moth-eaten pattern. Eventually as the tumour
enlarges the jugular spine is eroded and the mass extends into the middle ear, as
well as inferiorly into the infratemporal fossa. CT is excellent at assessing the
integrity of the ossicles and bony labyrinth .
T1 - low signal
T2 - high signal
T1 C+ (Gd) - marked intense enhancement
Salt and pepper appearance is seen on both T1 and T2 weighted sequences; the
salt representing blood products from hemorrhage or slow flow and the pepper
representing flow voids due to high vascularity.
DSA - angiography
Angiography demonstrates an intense tumour blush, with the most common
feeding vessel being the ascending pharyngeal . Early draining veins are also
noted due to intra-tumoural shunting .
Indium-111 labelled octreotide accumulates in these tumours due to the presence
of receptors for somatostatin, best visualized with SPECT, but requires the tumour
to be greater than 1.5cm in diameter.
Glomus jugulare. A mass is present in the jugular foramen (black asterisks). It is hypointense on
T1-weighted magnetic resonance image (T1W MRI) (A), and hyperintense on T2-weighted
magnetic resonance image (T2W MRI) (B), and enhances dramatically on postcontrast T1W MRI
(C). Note the anterior displacement of the carotid flow void (white arrows) and a large flow void
posteriorly (black arrows) within the tumor. Axial computed tomography (D) shows irregular
bony erosion extending into the petrous portion of carotid artery canal (white arrowhead). Note
the vertical segment of the facial nerve just lateral to the tumor (black arrowhead).
Bony tumour related to the inner ear
Fibrous dysplasia of bone is a fibro-osseous tissue disease
which has unknown etiology and characterized by replacement
of normal bone by a variable amount of fibrous tissue and woven
bone. The disease may be unifocal, multifocal or as seen in
McCune Albright Syndrome. Fibrous dysplasia rarely involves
temporal bone and diagnosis is made with the displacement of
neighboring structures. The aim of treatment is cosmetic and
Osteochondroma: An abnormal, solitary, benign growth of
bone and cartilage, typically at the end of a long bone.
Osteochondromas are usually discovered in persons 15 to 25
years of age and are the most common benign bone tumor. An
osteochondroma is rarely occur at the ear.
Metastasis of the inner ear.
Metastasis of the inner ear is usually hematogenous dissemination
from mammary carcinoma, renal cell carcinoma and bronchogenic
carcinoma as being three most common tumours this embolic type
The second is direct invasion by nearby tumour such as those of the
epipharynx and the parotid gland via perineural spread.
Tumour cells occupy the internal auditory canal invading the V11th
and V111 nerve trunks.
Features of perineural spread:
1- Enlargement and enhancement of the involved nerve.
2- Obliteration of the fat surrounding neural foramina.
3- Atrophy of the muscles and replacement by fat of the
Esthesioneuroblastoma. A 39-year-
old man presented with 1 month
of decreased vision, left facial
numbness, and swelling. Physical
examination demonstrated left-
sided exophthalmos and blindness.
He was also unable to smell.
MRI demonstrated a large lesion
that originated in the paranasal
sinuses and extended through the
cribriform plate into the anterior
Perineural spread: facial nerve acinic cell carcinoma of left parotid gland. (A)
Preoperative MRI – acinic cell carcinoma (solid arrow) with cranial nerve VII perineural
spread (open arrow). (B) Postoperative MRI – skull base resection (open arrow),
postoperative changes (closed arrow). Patient underwent parotidectomy and temporal
bone resection. The proximal skull base surgical margin was clear but close (1 mm).
Metastasis. Ax T2WI(A) reveals area of inhomogeneous high signal
filling the right PA, post gadolinium Ax/CorT1WI (B;C) show diffuse CE.
Notice adjacent enhancing fat of the clivus and of VIII c.n (arrow in C).
Langerhans cell histiocytosis. Ax CT shows destructive bilateral PA masses with permeative
bone changes (A). After steroid treatment, 2 years later, notice the complete healing.