Allen

D. Elster,

MD

Elias

G. Theros,

#{149}

Cranial Imaging Osteopetrosis Part

and

The authors reviewed cranial imaging studies (radiographs, computed tomographic scans, and magnetic resonance [MR] images) in 13 infants and children with the autosomal recessive form of osteopetrosis to characterize

of skull

patterns

base,

and cranial nerve involvement sentation and with progression disease. Marked sclerosis and tion

of osteopetrotic

bone

brain, at preof deposi-

was noted

along the anterior (but not posterior) occipitomastoid suture (n = 8), at the basioccipital-exoccipital synchondrosis (n 9), and along the sphenooccipital synchondrosis (n = 8). Endobones, presumably representing unresorbed primitive ossification centers, were seen in the sphenoidal body and basioccipital bone in 11 of the 13 patients. Marked cupping at the basioccipital-exoccipital synchondrosis was observed in three. Neurologic deficits included blindness (n = 11), conductive hearing loss (n = 11), and facial nerve palsies (n = 4). Delayed myelination was seen with MR imaging in two of five retarded infants, including one with a docu-

mented

coexisting

neuronal

storage

defect. Prominent extracerebral cerebrospinal fluid spaces were present

over the frontal eight

lobes

in five of the

developmentally

normal patients, representing either subclinical parenchymal disease or a phenome-

non related rates

to discordant

between

skull

Key, MD2

#{149}

in Autosomal

Base

II#{149} Skull

L. Lyndon

MD

O

STEOPETROSIS

a family

represents

of bone abnormalities characterized by a generalized increase in the density of the skeleton. In part I of this series (1), we described in some detail the radiologic abnormalities in portions of the skull derived pnncipally from membranous bone, including the mandible, middle of the face, and calvarium. In this part, we describe the computed tomographic (CT) and magnetic resonance (MR) imaging findings in those portions of the skull derived principally from cartilage, including the central skull base, temporal bone, and occipital bone. We also discuss imaging findings related to involvement of the central nervous system that may accompany the bone abnormalities.

SUBJECTS

AND

METHODS

The patients consisted of 13 infants and children with biopsy-proved osteopetrosis referred

for cranial imaging over a 6-year All of the patients had at least one set of conventional skull radiographs, a period.

routine cranial CT scan, and high-resolution (1.5-mm) CT scans of the orbits, skull base, and temporal bones. Six patients underwent cranial MR imaging, and follow-up CT scans and/or MR images were available in nine patients. Details of patient history and technical factors pertain-

vous

system

MR studies

was

were

evaluated

ophthalmologist,

can be

at

least

All

once

a pediatric

and nerpatients

by a pediatric

neurologist,

Departments of Radiology (A.D.E., and Pediatrics (L.L.K.), Bowman Gray School of Medicine, Wake Forest University, Medical Center Blvd, Winston-Salem, NC 27157-1022. Received August 30, 1991; revision requested October 14; revision received October 23; accepted November 13. Address reprint requests to A.D.E. 2 Current address: Department of Pediatrics, I

From

extensive.

the

E.G.T., M.Y.M.C.)

Index

Bones,

terms:

Bones,

abnormalities,

osteochondrodysplasias,

growth

and

development,

iO.i2i4 10.1211

#{149} Nerves,

cranial,

#{149} Skull,MR,10.12i4

12.1552

12.1552

#{149} Brain,

iO.i552

#{149} Brain,

iO.1552

#{149} Skull,

MR. CT,

Medical ton,

Radiology

1992;

183:137-144

MD

Recessive

found in part I of this series (1). Clinical evaluation of the head

growth

Y. M. Chen,

Brain’

ing to the CT and

and brain.

Michael

#{149}

©

SC. RSNA,

University 1992

of South

Carolina,

Charles-

and an otolaryngologist. and/or

brain

Audiograms

stem-evoked

potentials

obtained in every case. Specialized logic tests (such as visually evoked sponses

and

were

neurore-

electroencephalography)

were performed in selected cases to supplement the clinical and radiologic examinations. A summary of the clinical findings in

these

patients

is presented

Criteria for optic based on standards children established (2).

We

used

a 3-mm

limit for normal patients

younger

in Table

diameter

as the lower

size of the optic canal in than 2 years of age and 4

mm for those aged 2-12 years. the optic nerve was diagnosed

diameter

1.

canal stenosis were for healthy infants and by Harwood-Nash

on coronal

images

Atrophy of when its

was less than

3mm(3).

RESULTS A relatively large number of new and consistent findings concerning involvement of the skull base by osteopetrosis were observed. We now describe, illustrate, and tabulate these findings on a region-by-region basis. A summary of these findings is presented in Table 2.

Occipital The sents

Bone mature a fusion

occipital of several

bone

repre-

components

with different embryologic origins (squamous, exoccipital, and basioccipital). Its involvement with osteopetrosis will therefore depend on the particular subregion specified. The appearance of the occipital bone is also a function of patient age, and hence, duration of disease. The squamous part of the occipital bone, ossifying in membrane, has an appearance similar to that of the membrane-derived calvarium described in part I of this series (1). In the three youngest patients, we observed a three-layer pattern of the squamous occipital bone with a highattenuation inner table, low-attenuation diploic space, and slightly 137

higher-attenuation outer portion on CT scans (Fig la). In these patients, a low-attenuation band was also noted immediately adjacent to the basioccipital-exoccipital synchondrosis. With advancing age (Fig ib), the occipital bone had a more uniformly dense texture. Marked sclerosis was noted along the anterior occipitomastoid suture in all eight

patients

(Fig

ib).

Such

was

never

older

focal

6 months

however,

separately

posterior

portion

possible

than

sclerosis,

that

seen

along

of this

this

Table 1 Ophthalmologic,

It is

phenomenon

was

patients. marked

observed

In three “cupping”

drosis

was

also

in nine

of the

observed

(Fig

can

also

of the

be seen

in the

base. A prominent

in the basal

cipital

bone

cipital bones

synchondrosis. have long

common

portion

radiologic

4/M

3 mo

Blind

CHL, effusions

5/M

5 mo

Normal

CHL,

6/F 7/F

7 mo 9 mo

Blind Blind

CHL, tubes CHL, effusions

1y I y

reasonable

assume

that

might

Normal

Normal SNHL,

Seizures, neuronal

peripheral

hypotonia, storage

disorder Normal

tubes

Normal Normal

Hypotonia,

develop-

vision

CHL, tubes CHL, tubes

delayed

Normal Bilateral

CN VII develop-

mentally iO/F

1y

Extremely

il/F

2 y

vision Blind

12/M

4y

Blind

decreased

delayed,

weakness Right CN VII palsy

CHL, tubes SNHL, possible effusions

CHL,

Hypotonia, mentally

CHL

developdelayed

Left CN VII palsy, developmentally

i3/M

9y

Decreased sion,

conductive

=

color viacuity

hearing

delayed Right CN VII palsy,

CHL, tubes

normal

loss, CN

seizures cranial

=

nerve,

SNHL

=

sensorineural

hearing

loss.

Table

2 of Abnormalities

Summary

Seen

in the Skull

Base and Brain in Osteopetrosis Abnormalities

Region

Occipital

bone

Sclerosis

along

anterior

occipitomastoid

suture,

sclerosis

along basioccipital-exoccipital synchondrosis, cupping of basioccipital-exoccipital synchondrosis, endobone in basioccipital Sphenoid

bone

Sclerosis

bone

along

in midline,

oc-

sella turcica, Temporal

synchondrosis,

dorsum

thickened

sellae,

clinoid

endobones

reduced

processes,

volume

of

no pneumatiza-

tion of sphenoid sinus, optic canal narrowing No formation of mastoid air cells, enlarged subarcuate fossae, channels for subarcuate vessels, ossicular involvement, narrowing of middle ear cavity, stenosis of facial nerve canal, stenosis of internal auditory canal, middle ear effusion, deformity of stapes Delayed myelination, white matter disease (storage disor-

bones

Brain

as a

spheno-occipital spiculated

der), basal ganglia tubular frontal

skeleton

to

acidosis), extracerebral

and deep

cerebral

calcification

atrophy, hydrocephalus, cerebrospinal fluid

(renal

prominent space, optic

nerve

atrophy

be found

base. from trotic

Bone

Prominent

the low-signal-intensity bones of the skull

Small,

sclerosis

along

both

rectangular

bones

were

led appearance

noidal

and

was frequently cially on the

spheno-occipital

of the sclerotic encountered, sphenoidal

side.

synchondrosis

margin espeThe

was

easily visualized on Ti-weighted sagittal MR images. The higher-signalintensity fibrocartilage within the synchondrosis was easily differentiated

Radiology

base

osteope(Fig 2b).

endobones

were

encountered in the midline of the sphenoidal body in 11 of the 13 patients (Fig 2d). Generally, two endo-

sides of the spheno-occipital synchondrosis was noted in eight of the 13 patients (Fig 2c). An irregular, speck-

#{149}

Normal

Normal CHL, possible effusions

Decreased Blind

of osteo-

It is therefore

138

at-

palsy,

of this endoand usually spheno-oc-

(Fig if).

Sphenoid

3 mo

13 patients

feature

also

3/M

rophy Blind

Note.-CHL

of the

in the

they

Early optic nerve

skull

petrosis

in the skull

Normal

2 mo

a

Such endorecognized

been

3 wk

was

location midline, to the

Neurologic Findings

i/F

disease

central

in 12 of the

(Fig le, 2a). The bone was strictly in close proximity

Otologic Findings

ib),

“endobone”

noted

Ophthalmologic Findings

2/F

8/M 9/F

13

of these patients at the synchon-

manifestations

Findings

mentally

which was judged to be out of proportion to the curvilinear irregularity normally seen at this developing suture. Both metaphyseal lucencies and cupping are common features of osteopetrosis in the peripheral skeleton (Fig ic). Presumably, some of these same

and Neurologic

is a

manifestation of differing rates of growth of the skull base along different portions of this suture. The appearance of the basioccipitalexoccipital synchondrosis was also variable. In three younger patients, a band of low attenuation was present on both sides of the synchondrosis at CT (Fig la). A frank sclerosis along the basioccipital-exoccipital synchondrosis

Age at First Imaging Evaluation

Patient No/Sex

the

suture.

Otologic,

portions

lated dorsum

seen,

one

one

in the

of the

bone.

or “comblike” sellae

was

in the

presphe-

postsphenoidal A peculiar

appearance encountered

ance on lateral radiographs. Actual sellar volumes were not calculated, however, since none of our patients had pituitary dysfunction, and hypopituitarism is not a recognized feature of osteopetrosis. The optic canals were determined to be narrowed

at CT

spicu-

patients

of the

optic

nerves

in

with

MR imaging

four patients (Fig 2e). Prominent thickening of the posterior and antenor clinoid processes was commonly noted, giving the sella a small appear-

(Fig

atrophy

was

demonstrated

easily

scopic

These were

of clinical findings

13

of the

or CT in eight

tients (Fig 3b, 3c). findings, however,

predictors

in 12 of the

3a). Frank

(Table

pa-

radiologic only crude

and

ophthalmo-

1).

April

1992

Figure 1. Involvement of the occipital bone in osteopetrosis. (a) CT scan shows threelayer pattern in the bone similar to that de-

scribed the

for the calvarium.

three

bands sides

This was seen in

patients.

Characteristic

of low attenuation of the

drosis the

youngest

(arrowheads).

advancing

developed

a more

appearance.

sclerosis

along

both

synchon-

(b) With

bone

dense

marked

along

basioccipital-exoccipital

occipital

formly

are seen

the

age, uni-

CT scan

shows

anterior

(black

arrow) but not posterior (arrowhead) occipitomastoid suture, which was seen in eight of the 13 patients. Sclerosis and cupping at the

basioccipital-exoccipital

(white

arrow)

was

(c) Radiograph sclerosis, hires

ton-in

b.

a.

scan rosis in the shows row) in i2

V

*

and

shows

of osteopetrosis

the knees

_:

I

..

(AJ d.

C.

6

cupping,

errors-typical in the

fea-

peripheral

of the same

skele-

patient.

(d) CT

shows a featureless thickening and scleof the occipital bone; this was observed three oldest patients. (e) CT scan a prominent midline endobone (arin the basioccipital bone; this was seen of the i3 patients (see also Fig 2a).

shows

in-bone, which are ings in the peripheral

.

metaphyseal

remodeling

(0 Radiograph

fr

synchondrosis

also characteristic.

also

endobones

or bone-

characteristic skeleton.

find-

The subarcuate fossae were enlarged in all patients, although this feature was less noticeable with advancing age. A prominent vascular channel believed to represent persistence of subarcuate vessels was observed in five of the 13 patients (Fig 4a). This appearance was similar to the vascular channels made by the anterior and posterior ethmoidal arteries in the dense ethmoid bone, as demonstrated in part I of this series (1).

The middle in size or only osteopetrotic

ear cavity was normal slightly narrowed by encroachment.

The

ossi-

des were prominently involved in nine of the 13 patients (Fig 4b, 4c). Sclerosis of the optic capsule was noted in all cases, but the oval window was not preferentially involved. A consistent finding in all but the two youngest patients in our series was the presence of a middle ear effusion. Tympanotomy tubes were placed in 10 of the i3 patients at some time during the clinical course while undergoing follow-up at our institution. An important clinical correlate of middle ear disease is that some degree of hearing loss was experienced e.

f.

Temporal

Bones

Like the other base, the temporal formly and osteopetrotic

bones of the skull bones were uniseverely involved by the process.

mastoid

air cells

Volume

183

were

Number

#{149}

Pneumatized

not 1

encoun-

tered in any of the i3 patients. However, the aditus ad antrum and epitympanic space were well formed in every case. Substantial stenosis of the external auditory canal was not noted in any case.

by all of the

patients

older

than

3

months of age. Furthermore, this hearing loss was primarily conductive and improved in those patients subsequently receiving tympanotomy tubes (Table i). In only one patient was there definite evidence for primary sensorineural hearing loss. Peripheral facial nerve palsies were observed in four older patients and Radiology

139

#{149}

were unilateral in three and bilateral in one. Unfortunately, neurologic testing most of precise patient, associated and the

near

was

not

these

sufficiently

cases

detailed

to document

in

the

site of the compression. In one decreased lacrimation was with the facial nerve palsy, lesion was believed to be at or

the

geniculate

ganglion.

this patient revealed rowing of the facial

the

geniculate

less

involvement

limb

(Fig 5).

CT in

substantial nerve canal

ganglion

with

of the

narnear

rather

descending

impairment ranging from mild developmental delay to severe mental retardation. One patient (patient 3) had generalized seizures and marked hypotonia; results of fibroblast culture revealed a lysosomal storage disorder. MR imaging in this patient showed cerebral atrophy and delayed myelination (Fig 6). A second patient (patient 7) was also suspected of having a neuronal storage disorder, but died before full evaluation could be undertaken. Her MR image revealed moderate cerebral atrophy and delayed myelination but no focal abnormalities.

Brain The

neurologic

patients Excluding

are summarized peripheral

cranial

nerves

tients

findings

had

II, VII,

normal

in our

i3

in Table compressions

i.

or VIII,

of

six pa-

neurologic

exami-

nations. One additional patient (patient 13) had a history of complex partial seizures with a temporal lobe focus but was otherwise neurologically normal.

The

remaining

varying

degrees

six patients of general

had neurologic

Figure bone

2. Involvement in osteopetrosis.

prominent

sclerosis

moderate delay

mild was

use9, who

was

with

referred

to our

institution

upper extremity weakness, severe developmental delay, blindness, and bilateral facial nerve paralysis. CT performed at admission revealed hydrocephalus. MR imaging (Fig strated brain stem compression obstruction of cerebrospinal

7) demonand

fluid flow by impingement at the foramen magnum. A clear cause for gross neurologic dysfunction was apparent in most however, in two.

the cause was not Each of these children

cerebral also

sessed

or marked and

had

atrophy

noted

that

developmentally

of

at cranial five

CT. It

of the

normal

variable

devel-

evidence eight

patients

degrees

pos-

of cerebral

atrophy and prominent extracerebral cerebrospinal fluid spaces over their frontal convexities. A representative example is shown in Figure 8 (patient 6), which

shows

sion of ventricular 4-month interval. sessment

showed

advanced skills

MR imaging proved extremely ful in the evaluation of patient

cases; obvious

exhibited opmental

for

in both her

age

the

interval

progres-

enlargement Developmental this

patient

intellect of ii

over a asto be

and

motor

months.

DISCUSSION Involvement of the skull base has long been recognized as a prominent and invariable feature of osteopetrosis. On conventional radiographs, these cranial findings include basilar sclerosis, thickening of the posterior clinoid processes and, to a lesser degree, the anterior clinoid processes, decreased volume of the sella, obliteration of the sphenoid and mastoid sinuses,

and

narrowing

of the

basilar

foramina (4-6). To our knowledge, cranial CT findings in osteopetrosis

of the sphenoid (a) CT scan shows

along

both

sides

of the

spheno-occipital synchondrosis with an irregular, speckled appearance (curved arrow). Note also the basioccipital endobone (straight arrow). (b) Ti-weighted MR image (repetition time, 500 msec; echo time, 20 msec [500/20j) shows that the fibrocartilage within

the spheno-occipital has an intermediate easily differentiated tensity osteopetrotic

(c) Sagittal

oblique

synchondrosis

(arrow)

signal intensity and is from the low-signal-inbones at the skull base.

CT reformation

of the

spheno-occipital synchondrosis (arrow) provides an appearance similar to that of b. S = sella turcica. (d) CT scan shows midline rectangular endobones (arrows) in the sphenoidal body; this was seen in 11 of the 13 patients. Two endobones could usually be identified, one in the presphenoidal portion

and (1’

o’e ‘

r

in the postsphenoidal scan

shows

portion. comblike

d.

C.

140

a peculiar,

Radiology

#{149}

e.

April

1992

have once

been previously (7). Now, with

scanning techniques tient population,

firm,

correct,

these

observations

reported improved and

only CT

a larger

we were able extend many

and

from

the

pa-

to conof

earlier

radiology literature. An interesting and, to our knowledge, previously unreported feature of osteopetrotic involvement of the skull base was the frequent visualization of endobones within the sphenoid and occipital bones. Such endobones

are

skeleton

frequently

seen

of patients

in the

with

Caffey

(9) referred

bones

as “inserts,”

Beiler

(iO) apparently

phrase

“bone

Figure tients.

3. Optic (b, c) MR

live as a simple

while

in the

nerve images

and

which

involvement. (500/20) show

was

of the

Patholo-

first recognized retain representaof the development

Engfeldt

et al (i2)

with

small

amounts

in evaluating

these

seen

directly

the

anterior

to specuvestiges of

presphenoid Similarly,

in the

and the

middle

of the

of the occipital bone a remnant of the fetal ossification center. How-

development

of the

is exceedingly complex drawing a one-to-one

dence

of

between

these

skull

(i3,14), correspon-

endobones

and

a select few of the many intermediate ossification centers that appear during development may represent a gross oversimplification of the process. Narrowing of the optic canals with

of

which we have previ(1), the embryologic sphenoidal and occipi-

narrowing nerve

endobone

base and

tal endobones are more obscure. When seen, there were usually two midline endobones within the body

optic

separate bones.

ever,

that

spongy bone. the triangular endobone

one

the fetally postsphenoid basal portion may represent basioccipital

con-

in their elegant demonstrating

sphenoid,

to the other. It is tempting late that these represent

is built up of remnants bone, that is, mainly cal-

cartilage

unresorbed Unlike

(a) CT scan demonstrates direct atrophy of the

examination

removed.

concept studies,

the mandible, ously described origins of the

the

bone,”

ophthalmologic

cified

miniature

coined

(ii). this

the endobone of medullary

axial

Hinkel

are normally

gist Carla Zawisch that marble bones tions of all stages firmed histologic

textbook,

to these

that

latinized to “os-in-os.” thus represent fetal yescontain embryonic strata

of bones

osteopetroas early

sis, having been recognized as 1934 (8). In his original

subsequently Endobones tiges and

subsequent

nized

of the optic canals (arrows); chiasm, or tracts (arrowheads);

visual

loss

complication

this was however,

is a well-recog-

of osteopetrosis.

documented MR imaging

in 12 of the 13 pawas not as sensi-

patients.

1

#{149}1 b.

a. Figure 4. consistent

Temporal finding.

tamed

through

tremely

high

Volume

183

bone Persistent

involvement channels

the temporal attenuation.

Number

#{149}

bone. A middle

1

c.

in osteopetrosis. (arrowheads)

The internal ear

effusion

for

(a) Axial CT scan shows the subarcuate arteries

auditory

canal

is noted

with

(arrow retraction

enlargement were seen

in b) is short of the

and

of the subarcuate fossae (arrow), in five of the 13 patients. (b, c) Coronal

somewhat

trumpet-shaped,

and

which was CT scans

the ossicles

have

a ob-

ex-

drum.

Radiology

141

#{149}

Clinical present similar

nerve

evidence of visual loss was in ii of our i3 patients, and high percentages of optic

involvement

other series encroachment canal

by

are reported

in

(7,iO,15-22). Although of the optic nerve

osteopetrotic

bone

in its

is the

commonly accepted mechanism for visual loss in most of these patients, primary retinal degeneration may be implicated in others (17,2i). Surgical unroofing of the optic canals failed to arrest or reverse the visual decline in two of our patients. In conjunction with similar failed procedures reported by others (i7), we thus strongly caution against the use of CT mea-

a.

surements showing progressive optic canal narrowing to justify aggressive surgery in these patients.

Figure 5. Facial nerve canal stenosis. CT scans in a patient with left facial nerve palsy and decreased lacrimation in the left eye. Marked narrowing is seen in the region of the geniculate ganglion (arrow in a). Descending facial canal was not as severely affected (arrow in b).

b.

Our findings concerning osteopetrotic involvement of the temporal bone are in general agreement with those reported in the CT (7) and pathology literature (23-26). We found no evidence of mastoid sinus formation, although the middle ear cavities were well preserved. Frank thickening and enlargement of the ossicles were encountered in several cases. We did not find trumpet-shaped internal auditory canals except in our youngest

patients;

we

thus

can

only limited support to the “persistent fetal state” description of the teopetrotic temporal bone endorsed by Bartynski

.:

I

give

Os-

et al (7).

We do agree,

however, that prominent subarcuate fossae are frequently encountered in these patients, giving the bone a somewhat fetal appearance. The subarcuate fossa is a de-

a.

pression

Figure

on

the

posterior

the petrous temporal the internal auditory the projection of the posterior semicircular fossa

is uniformly

surface

of

bone just above canal and within superior and canals. This

seen

in the

healthy

newborn but is gradually obliterated over the first 2 years of life. In most of our patients with osteopetrosis, how-

ever, the subarcuate

fossae

remained

prominent for several years. Additionally, persisting large channels for penetrating subarcuate vessels were noted in five of the i3 patients. Because

the

mastoid

does

not

pneuma-

tize properly, but remains filled with osteopetrotic bone and nests of marrow, the subarcuate vascular supply remains robust. Failure of these yessels

to regress,

coupled

with

generally

slow remodeling of the entire temporal bone due to osteoclast deficiency, contributes to a prolonged fetal or neonatal appearance, which may persist

throughout

We agree 142

Radiology

#{149}

the

with

ist

other

year

of life.

investigators

b. 6.

Coexisting

osteopetrosis

tient 3). (a) Ti-weighted eralized cerebral atrophy

that

hearing

symptom sis. Unlike

loss

and

(500/20) and and delayed

neuronal

with

osteopetro-

several

early reports, howthat conductive loss (rather than sensorineural loss) dominates the clinical picture. Audiometry and brain stem-evoked responses documented that, in nine of the iO

ever,

we believe

patients

with

hearing

loss,

it was

disorder

in a 6-month-old

(3,000/100)

axial

boy

MR images

(pa-

reveal

gen-

caused by middle ear inflammatory disease; this, in turn, may be secondary to stenosis of the eustachian canal and poor mechanical drainage of the middle ear cavity. Other contributory factors to the conductive loss may include immobilis primarily

is a prominent

in children

storage

(b) T2-weighted myelination.

pri-

manly due to a conductive defect; sensorineural loss was dominant in only one case. Additionally, all iO of these patients had recurrent bouts of otitis media, which were believed by the otolaryngologist to be contributory to their hearing loss. Furthermore, iO of these patients underwent the placement of tympanotomy tubes with subsequent improvement in hearing. It thus seems likely that hearing loss in children with osteopetrosis

ity of the tympanic

of the fication ligaments, ossicles

malleus and encroachment,

oval

and

incus

round

from obliteration

epi-

windows,

ossi-

of the mallear and incudal and replacement of the by osteopetrotic bone (i6).

do not doubt that eventually develop symptoms.

We

may

personally

docu-

have

mented this in one adult nign form of the disease. children with osteopetrosis, it is our

experience

hearing

loss

We

older patients sensorineural

dominates

that

with the beIn young however, conductive

the

early

clini-

April

1992

Figure 7. Utility of MR imaging in a patient with weakness and spasticity (patient 9). CT

scan (not shown) revealed hydrocephalus, which is also seen on the T2-weighted axial MR image (2,600/80) (a). Sagittal Ti-weighted MR

image

(b) shows

(500/20)

compression

and

magnum.

Note

brain stem

narrowing tonsillar

at the foramen herniation

(arrow).

associated with a neuronal storage disorder. Fitch et al (29) first called attention to this association in a 40week-old stillborn with osteopetrosis, hydrocephalus, cerebral malformations,

and

axonal

dystrophy.

et al (i9) described of laminar cortical acid-Schiff-positive axonal spheroids

a.

trosis. ,.

:‘

Ambler

et al (30)

pathologic storage

evidence disorder

Lehman

autopsy findings necrosis, periodic neurons, and in a case of osteopeprovided

of a neuronal probably

caused

by

a lysosomal enzyme deficiency in a third patient with osteopetrosis. In addition to providing insights toward understanding the ultimate biochemical defect in osteopetrosis, identifying the presence of a coexisting neuronal storage disorder has several immediate practical consequences provides

in patient prognostic

treatment. information

First,

it to

the families of such patients, portending an ultimately dismal neurologic outcome. Second, the presence of an associated

a.

b.

Figure

8.

Prominence of subarachnoid spaces in this developmentally (a) Baseline CT scan obtained at 7 months. (b) Follow-up CT scan shows progressive atrophy despite normal intellect.

normal

obtained

cases logic

(16,24,27,28).

Two

mechanisms posed: (a) ischemia stenosis

at any

pathophysio-

have been profrom facial canal

point

from

the

genicu-

late ganglion to the stvlomastoid foramen and (b) dehiscence of the facial nerve canal above the oval window with compression by bony overgrowth from the epitympanum and into the immobile stapes (26,27). Although we could identify the facial nerve canal along its entire course in every

patient,

able

to predict

Volume

183

we

the

were

Number

#{149}

generally

site,

cause, I

un-

or even

degeneration

(3i).

patient.

at age 11 months

CT is insensitive for demonstrating the presence of a coexisting neuronal storage grees

cal picture. Tympanotomy tube ventilation of the middle ear is a simple and effective method to improve hearing in most of these patients. Facial nerve paralysis is a common affliction in malignant osteopetrosis, occurring in 10%-50% of reported

neuronal

represents a relative contraindication to bone marrow transplantation, the only known curative procedure for the bone component of the disease

presence with CT. Gross

of facial

nerve

neurologic

dysfunction

impairment

or

developmental delay was documented in five of our 13 patients. Similar findings have been reported in other clinical studies of osteopetrosis (i8,19). In some cases, such as our patient with extraventricular obstructive hydrocephalus and brain stem compression, an obvious and easily treatable cause can be established. In other cases,

the

cause

icit remains sessment

of the

obscure. of such

The children

more

difficult

when

sider

the

of severe

role

neurologic

one

def-

clinical

as-

is made

must sensory

condepri-

vation (visual and auditory) in the origin of their developmental delay. In certain cases, such as patient 3 in our series, osteopetrosis may be

disorder, of atrophy

since variable or ventricular

deen-

largement can be seen in many developmentally normal patients with osteopetrosis. The ability of MR imaging to depict delayed myelination in addition to atrophy provides a noninvasive

method

group

of patients

possess

to identify

who

a neuronal

that

sub-

potentially

storage

disease

or

other metabolic derangement. In another rare association (not encountered in this series), osteopetrosis may

coexist

with

II deficiency

and

renal

sis (32).

may

result

This

carbonic

anhydrase

tubular

acido-

in extensive

intracranial parenchymal calcifications, which may be seen with CT (33) or MR imaging (34). Such patients, however, are usually neurologically normal. In conclusion, we documented in this

and

the

preceding

part

(1) many

Radiology

143

#{149}

new clinical and radiologic findings in cranial osteopetrosis. We have attempted to illustrate those features of the disease we believe are both common and characteristic, as well as to demonstrate the rich diversity of imaging findings possible within the disease spectrum. We have been able to relate some of our radiologic observations in the skull to similar manifestations of osteopetrosis in the peripheral skeleton. Ideally, this comprehensive study of cranial osteopetrosis will lead to better understanding and management of the cosmetic, otolaryngologic, ophthalmologic, and neurologic complications of this rare disease. #{149}

5.

6.

7.

8.

9. 10. 11. 12.

The authors express sinto Beth Hales for her assistance of this manuscript.

in

References 1.

Elster

14. AD, Theros

EG, Key

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in autosomal

Cranial

2.

3.

MYM.

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Virapongse C, Sarwar M. Development of the skull. In: Newton TH, Hasso AN, Dillon WP, eds. Computed tomography of the head and neck. New York: Raven, 1988; 1.1-1.20. Bosma JF, ed. Symposium on development of the basicranium. Bethesda, Md: National Institutes of Health Publication no 76-989, 1976. Loria-Cortes R, Quesada-Calvo E, CorderoChaverri C. Osteopetrosis in children: a report of 26 cases. J Pediatr 1977; 91:43-47. Wong ML, Balkany TJ, ReevesJ, Jafek BW. Head and neck manifestations of malignant osteopetrosis. Ann Otol Rhinol Laryn-

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atrophy in osteopetroi968; 79:234-241. bones and optic atrophy. Am J Ophthalmol i941; 24:874-878. Myers EN, Stool S. The temporal bone in osteopetrosis. Arch Otolaryngol 1969; 89: 460-469. Miyamoto RT, House WF, Brackman DE. Neurotologic manifestations of the osteopetroses. Arch Otolaryngol 1980; 106:210214. Hawke M, Jahn AF, Bailey D. Osteopetrosis of the temporal bone. Arch Otolaryngol i981; 107:278-282. Suga F, Lindsay JR. Temporal bone histopathology of osteopetrosis. Ann Otol 1976; 85:15-24. Johnson C, Lavy N, Lord T, et aL Osteopetrosis. Medicine 1968; 47:149-167. Hamersma H. Osteopetrosis (marble bone disease) of temporal bone. Laryngoscope 1970; 80:15i8-1539. Fitch N, Carpenter S, Lechance RC. Prenatal a.xonal dystrophy and osteopetrosis. Arch Pathol 1973; 95:298-301. Ambler MW, Trice J, GraverholzJ, O’Shea PA. Infantile osteopetrosis and neuronal

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Coccia PF, Kriuit W, Cervenka J, et al. Successful bone marrow transplantation for infantile malignant osteopetrosis. N

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Keith CG. Retinal sis. Arch Ophthalmol Riser RO. Marble

MP,

Sundaram V, et al. II deficiency in 12 famautosomal recessive syn-

anhydrase

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acidosis and cerebral calcification. N EnglJ Med 1985; 313:139-145. Cumming WA, Ohlsson R. Intracranial calcification in children with osteopetrosis caused by carbonic anhydrase II deficiency.

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April

1992

Cranial imaging in autosomal recessive osteopetrosis. Part II. Skull base and brain.

The authors reviewed cranial imaging studies (radiographs, computed tomographic scans, and magnetic resonance [MR] images) in 13 infants and children ...
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