Ellen

K. Tabor,

MD

#{149} Hugh

D. Curtin,

Osteogenesls of the Temporal

tomographic findingS in the temporal bone of two patients with osteogenesis imperfecta tarda are described. One of the patients had bilateral facial nerve paresis, and both patients presented with hearing loss. terms:

21.1551

Nerves, CT, 21.1214

bone,

Bones,

#{149}

osteochondrodysplasias. 2123.99 #{149} Temporal #{149} Temporal bone, diseases,

facial,

21. 1551 Radiology

#{149} Barry

Imperfecta Bones

The computed

Index

MD

1990; 175:181-183

T

E. Hirsch,

MD

#{149} Mark

Tarda: at CT’

HERE arc two sis impenfecta

with

forms of osteogene(OI)-congenita

ostcogcncsis

impcrfccta

tarda (OIT) have a normal life expectancy. The syndrome that was oniginably described by van den Hocve and deKlejn included the classical triad of fragile bones, blue sclcra, and hearing loss. The hearing loss may be conductive, sensorineural, on mixed (1,2). Computed tomography (CT) of the temporal bones was performed on two patients with OIT and progressive hearing boss. The CT findings and the hearing boss in OIT can be identical to those in otoscbcrosis (3).

CASE

REPORTS

Case 1.-A 19-year-old woman had bilateral facial nerve paresis, greaten on the left than on the right, and mixed hearing loss. The hearing loss, progressive since early childhood, was thought to be due to otosclerosis. The diagnosis of OIT had not

previously been established. CT was performed in axial and coronal projections on a 9800 scanner (GE Medical Systems, Milwaukee). Thin (1.5-mm) 5cctions bone

were with

obtained intravenous

enhancement.

through the temporal contrast material

The bone

surrounding

the

cochlea, vestibule, and semicircular canals was markedly thickened and had much lower attenuation than the normal otic capsule. In some areas, the dysplastic bone was separated from the membranous labyrinth by residual dense bone of the otic capsule, while in other areas the undermineralized bone abutted the membranous labyrinth. The dysplastic bone

extended I From the Departments H.D.C.) and Otolaryngology

University of Pittsburgh 230 Lothrop St. Pittsburgh, October 19, 1989; revision 8; revision

received

cember 1 1 . Address ,c RSNA, 1990

of Radiology

November

reprint

(E.K.T.,

(B.E.H., MM.), School of Medicine, PA 15213. Received requested November 27;

requests

accepted

from

the promontory

the De-

to H.D.C.

(bone

covering the basal turn of the cochlea) along the lateral aspect of the horizontal semicircular canal to above the superior

semicircular canal bone significantly middle

malleus

laterally canal and

The

prolific

and

short

bone

proliferation

the aditus

struction

occluded

resulting

of the mastoid

normal stapes round

in ob-

antrum.

The ab-

bone completely enveloped the and covered the oval window. The window niche was filled with the

thickened The

apparently

ad antmum,

was masThe

and undenmineralized

labyminthinc

of the facial

and

nerve

bone.

tympanic

canal

segments

were

indistinct

and irregular bilaterally (Fig ic). The mastoid segment of the facial nerve canal was normal. The CT findings raised the possibility of OIT. A skeletal survey demonstrated multiple wormian bones in the skull, Osteoporosis of the axial skeleton, biconcave intervertebral spondylolisthesis

disk

spaces, at L5-Sl.

and The

grade patient

III

was noted to have blue-tinged sclera and abnormal dentition with obliteration of the pulp cavity. The clinical and radiologic findings were believed to be sufficient for the diagnosis of 01. Tnansmastoid, translabynmnthinc decompression of the facial nerve was performed. Operative findings included an enlarged and overgrown otic capsule with a pinkish hue. The ossicles were encroached upon by the dysplastic bone, and the tympanic facial nerve was cornpletely enveloped. The tympanic facial nerve was followed anteriorly and mcdially toward the labyninthine segment. The segment of the nerve arising from the internal auditory canal was stninglike. The facial nerve was markedly swollen proximal and distal to its constricted course within the bony labyrinth. Electnical stimulation of the nerve peripheral to the constriction resulted in facial musculan contraction; however, stimulation ccntral to the constriction did not. It was be-

lieved portion

it would

be

beneficial

of the nerve

and

bypass

to resect this the dys-

plastic process by putting in a nerve graft. A great auriculan nerve graft was placed from the internal auditory canal to the nation

vertical

of the

segment.

nesected

Pathologic

nerve

cxami-

revealed

bone

from the horizontal abutted the head of the

the body

the incus (Fig lb). The Prussak space clear, but the antrum and peripheral toid were opacified on the right side.

distal

(Fig la). The thickened narrowed the lumen of

can cavity.

extending semicircular

MD

Appearance

and tarda. Patients with osteogenesis impenfecta congenita (OIC) usually die in uteno on shortly after birth. Patients

May,

process

of

Abbreviations: OIC = osteogenesis =

osteogenesis

01

osteogenesis imperfecta

imperfecta

impenfecta. congenita.

OIT

tarda.

181

a.

b.

c.

Figure 1. Case 1. CT scans obtained with bone algorithm. (a) Coronal image. The otic capsule is markedly thickened and undermineralized (arrowheads). Prolific bone covers the oval window (arrow). SSC superior semicircular canal, P promontory. (b) Axial image. The dysplastic bone abuts the ossicles medially (wavy arrow), resulting in opacification of the right mastoid. 0 ossicles, C cochlea. (c) Axial image at a higher level. The labyrmnthine facial nerve canal is indistinct and irregular (arrow). HSC horizontal semicircular canal.

a.

b.

Figure 2. Case 2. mineralized bone Note the promontory.

marked

stapedial

pemineural

Axial (a) and coronal (b) CT scans obtained with bone algorithm. The findings are less severe in this patient. (arrowheads) surrounds the cochlea. On the left side the labyrinthine facial nerve canal is involved (straight prosthesis on the right (wavy arrow, b). C cochlea, FN facial nerve canal, HSC horizontal semicircular

and

endoneural

fibmo-

mineralized

were

sis-

dysplastic

Case 2.-A 32-year-old man with a known history of OIT had progressive lateral mixed hearing loss. The patient had

a past

history

of

multiple

bi-

fractures.

CT scans in axial

use trast

of a bone material

were and

obtained coronal

algorithm. was not

as 1.5-mm projections

Intravenous administered.

secwith conThe

bone of the otic capsule was thickened but had a much lower attenuation than normal. The undemmincralized bone summounded the cochlea but was separated from the lumen of the membranous labyninth by a small amount of more normally 182

#{149} Radiology

in

(Fig

the

findings

oval

window

on

chain

The

cus.

the oval the was

the

the

right

nerve

by the thickened, bone, giving an margin (Fig 2b). The patient tympanotomy adhesions

dle ear. Tissue bled readily.

tympanic

canal

segments

were

the

window

were

around Inspection

present

the

were

was

was over was

to and

performed. the then

stapes

be drill

inoval

obliterated out

by

of

the

graft

window,

positioned

was The

A vein oval

in-

Although

deficient.

noted

bone,

placed thesis

of the

cruma

and

immobile.

superstructure

tact,

malleus

P

foot-

was

and

a pros-

medial

the

to

incus.

of

DISCUSSION indistinct

exploratory At surgery,

left.

was

canal,

surrounded

undemmineralized irregular and

underwent on the

a mobile

stapes

dysplastic

in this case were severe, so than in case 1. The semiwere not involved. The and

facial

revealed

The

plate

findings less canals

labyrinthine

brous

The

bilaterally.

2a).

The although circular the

capsule.

symmetric

bone completely filled and extended down onto A stapedial prosthesis

window promontory. present

He had undergone surgery on his right ear 10 years earlier and wore a hearing aid in the right ear. This patient was descnibed previously (4). tions

otic

fairly

The underarrow, b).

oval of the

in

the

window ossicular

The

fimid-

of 01

diagnosis

tablishing

increased

associated

with

connective

abnormal combination

is made

by

fragility

involvement

tissues

dentition, (1,2).

such

of

as blue

hearing

es-

of bone other

sclera,

loss,

April

or a

1990

There is a controversy in the tune regarding the relationship otoscbenosis

ized sis

and

bone

01.

disease

There

temporal

would

protein

be considered

manifestation

bone. and

tempo-

opin-

otosclerosis and origin, in which

otosclerosis

a localized

in the

The

of 01

in the

concentration

various

enzymes

of are

dif-

ferent in bone affected by 0! and otoscienosis. The biochemical data suggest that the two diseases are enzymaticably different and therefore not determined by a common abnonmal gene (5). The onset of hearing loss is earlier in OIT patients, occurring most cornmonby

during

the

2nd

on 3rd

decade

of life. The audiometnic findings of otosclerosis and OIT can be indistinguishable. The hearing loss may be conductive, sensonineural, or a combination. OIT patients arc more likeby to have a mixed hearing loss (conductive and sensorineural). OIT patients may have a sensonineural hearing loss alone. This is present in approximately 10% of affected patients and may progress to a profound hearing boss (6). The sensonineural hearing loss is believed to result

from

microfractunes,

hemon-

rhage, and encroachment of nepanativc vascular and fibrous tissue in and about the cochlea (7). Pure sensorineunal hearing loss is a rare occurrence in otosclerosis. Differences encountered during the surgical treatment of OIT, as opposed to otosclcrosis, include thin Ossides and crura, which arc often deficient and fail to contact the footplate. Stapedial crunab fractures are considened a frequent contribution to the conductive hearing loss in OIT in addition

to fixation

of the

footplate.

Other observations include thin temnal auditory canal skin, brittle tum, hyperplastic mucosa in the die ear, and persistent bleeding. These findings are not observed ing

stapedectomy

for

treatment

cxscumiddunof

otosclerosis (8). Usually no major difficulties or serious complications arc encountered in OIT patients during stapcdectomy, in spite of the differ-

Volume

175

#{149} Number

1

ences. Both the immediate postoperative and the long-term hearing me-

round

and

oval

windows,

and

enve-

Radiologically, OIT of the temponab bones may be very similar to sevene otoscierosis. The abnormalities in OIT can be described as undermineralized, thickened bone involving

lope the stapes footplate. (c) The dysplastic bone may extend as high as the upper margin of the superior semicircular canal. (d) The facial nerve canal may also be involved in the dysplastic process, resulting in facial nerve paresis or paralysis. Facial paralysis is a rare manifestation

the

in 01,

suits are (9,10).

otoscleno-

arc different

ions as to whether 01 have a common

case

is a general-

while

is a localized

nab bone.

01

disorder,

literaof

otic

in general

capsule.

exceedingly

The

good

thickness

of the

prolific bone in OIT appears to be much greater than that described in otoscierosis. Also, the involvement of the bony labyrinth appears to be more extensive than is usually seen in otosclerosis (specifically involvemcnt of the otic capsule extending above

the

superior

semicircular

canal

in OIT). The middle ear cavity may be narrowed by the thickened bone extending from the labyrinth. The hypertrophic bone may obstruct the oval

window,

with

ra embedded (ii).

The

the

in the facial

stapedial

cru-

dysplastic

nerve

canal

was

volved.

One

other

case

of the

otoscienosis

and

In Paget

base

of the

petnous

The bone around the tory canal is involved medial internal auditory not involved in either tients. The ages of the also are not consistent disease. In summary, the CT OIT

are

as follows:

4.

internal audifirst (1 1). The canal was of our patwo patients with Paget findings

Barr

in is exten-

sive proliferation of undenminenalized bone involving all on part of the otic capsule. (b) The proliferation of the bony labyrinth may narrow the middle can cavity, obliterate the

depic-

5.

1987; Forfar

BJ.

6.

7.

8.

10.

12.

Imaging CE,

1344-1402.

imperfecta

J

Throat

of the

Endahl

Comparative

GC,

Edinburgh:

1978;

Nose

of bone

JO, Arneil

of paediatrics,

Ear

York:

Disorders

York: Thieme,

Holdsworth

and

1984;

temporal 1986; 164.

GL,

Soifer

biochemical

N,

study

et

of

otosclerosis and osteogenesis imperfecta. Arch Otolaryngol 1973; 98:336-339. Pedemsen U. Hearing loss in patients with osteogenesis imperfecta: a clinical and audiological study 201 patients. Scand Audio! 1984; 13:67-74. Shapiro JR. Pikus A, Weiss G, Rowe DW. Hearing and middle ear function in osteogenesis imperfecta. JAMA 1982; 247:21202126. Armstrong

BW.

with

Stapes

surgery

in

pa-

imperfecta. Ann Otol Rhino! Laryngol 1984; 93:634-636. Pedersen U, Elbrond 0. Stapedectomy in osteogenesis imperfecta. ORL J Otorhinolaryngol Relat Spec 1983; 45:330-337. Shea J, Postma DS. Findings and longterm surgical results in the hearing loss of osteogenesis imperfecta. Arch Otolaryn-

go! 1982; 11.

JO.

In: Forfar

loss.

New

tients

9.

New

Osteogenesis

63:283-288. Swartz JD.

of conHarri-

E, ed.

1680-1688.

Livingstone,

Cohen

a!.

disorders

In: Braunwald of medicine.

DGD,

bone.

pyramid.

(a) There

Heritable

textbook

hearing

disease,

the temporal bone involvement is usually accompanied by changes in the skull. The progression of undermineralization extends from the apex to the

tissues.

Churchill 3.

dis-

degree

extent.

DJ.

nective

and cartilage. eds. Textbook

stated, OIT may from diffuse for differences in

knowledge,

McGraw-Hill,

CT ap-

Paget

Prockop son’s

2.

ease. As previously be indistinguishable otosclerosis except and

1.

en-

pearance of the temporal bone in OIT has been reported (1 1 ). Our case 1 had bilateral facial paresis. The bilaterality and slow, progressive course help differentiate the facial panesis from idiopathic (Bell) palsy (i2). The two entities most closely mcsembling 01 of the temporal bone are advanced

to our

References

mass

veboped in the abnormal bone in both of our cases. The labyninthine and tympanic segments were in-

and

tion of involvement of the facial nerve canal by CT has not been previously described. Although OIT may be audiometnically and radiobogicaily indistinguishable from otosclerosis, several distinguishing features include earlier onset of hearing loss, higher association of sensorineural hearing loss, and greater severity of involvement. U

osteogenesis

108:467-470.

Jardin C, Ghenassia M, Vignaud J. Tomographic and CT features of the petrous bone in Lobstein’s disease. J Neuroradiol 1985; 12:317-326. May M. Differential diagnosis by history. physical

findings,

and

laboratory

In: May M. ed. The facial nerve. York:

Thieme,

1986;

results.

New

181-216.

Radiology

#{149} 183