Hedvig

Hricak,

Cervical Evaluation

MD

#{149} Yoshi

C. F. Chang,

MD2

#{149} Christopher

E. Cann,

PhD

#{149} Julian

T. Parer,

MD,

PhD

Incompetence: Preliminary with MR Imaging’

The ability of magnetic resonance (MR) imaging to demonstrate cervical incompetence in nonpregnant women was investigated in a prospective study of 41 volunteers referred in random order. These included 20 patients with normal cervices, 11 with cervical incompetence of traumatic or congenital origin, and 10 with clinically small cervices due to in utero diethylstilbestrol (DES) exposure. On MR images of the normal patients, cervical length was 33.0 mm ± 1.0 (mean ± standard error of the mean) and the width of the internal cervical os was 3.3 mm ± 0.1. In patients with cervical incompetence, the cervical length did not significantly differ from those in the normal group. However, the internal cervical os was significantly wider (4.5 mm ± 0.3, P < .001), and localized irregularity of the endocervical canal was demonstrated in two patients. The MR appearance of the cervical stroma varied from normal, uniformly low signal intensity (n = 4) to uniformly (n = 3) or partially (n 4) medium-to-high signal intensity on T2-weighted images. In the patients with in utero DES exposure, the mean length of the cervical canal (22.9 mm ± 1.7) was significantly shorter than that of the normal group. The width of the internal cervical os and the MR signal intensity of the cervical stroma were normal. In summary, MR findings of a cervical length shorter than 3.1 mm (95% confidence limit), an internal cervical os wider than 4.2 mm (95% confidence limit), or abnormal signal intensity in the cervical stroma are highly suggestive of incompetent cervix and should assist in planning further therapeutic decisions.

C

incompetence occurs in 0.05%-1% of all pregnancies but may be responsible for up to 16% of middle second or early third trimester abortions (1). Three main groups of factors are considered responsible for cervical incompetence: (a) acquired, including obstetric or gynecologic trauma; (b) congenital, including congenital uterine malformation, in utero exposure to ERVICAL

diethylstilbestrol

(DES),

and

de-

creased collagen content; and (c) other, including hormonal disorders, increased prostaglandin production, and multiple gestations (1,2). Despite the use of various diagnostic imaging procedures, an obstetric history of repeated, painless, second-trimester fetal loss and the visual and digital confirmation of an open cervical os during pregnancy remain the most important basis for the diagnosis (2). However, the clinical criteria for accurate diagnosis of incompetent cervix are often difficult to define (2), and, in the primipara with congenital cervical incompetence who lacks a suggestive history or premonitory symptoms,

physical

examination

may

fail to uncover the potential risk of fetal loss. Furthermore, an objective method for recognizing a patient at risk for adverse pregnancy outcome

Index terms: Uterus, S Uterus, MR studies,

abnormalities, 854.1214

(ie, perinatal loss) in whom cervical cerclage would be beneficial is not available (3). Ultrasonography (US) has been advocated as an objective way of securing the diagnosis of incompetent cervix during pregnancy (4,5). However, artifacts can interfere with US imaging of the cervix (6). To our knowledge, there has been no reported study of the ability of US to permit discrimination between the competent and incompetent cervix in nonpregnant patients. From the very beginning of its use in clinical practice, magnetic resonance (MR) imaging has shown to be an accurate, noninvasive method for demonstrating the uterus and cervix (7). This prospective study was designed to explore the potential of MR imaging in facilitating diagnosis of cervical incompetence in nonpregnant patients. MR imaging findings were compared to findings from the patient’s obstetric history and from physical examination during pregnancy.

854.14785

PATIENTS Twenty

nonpregnant

1990;

ings

174:821-826

I From the Departments of Radiology, Box 0628, C309 (H.H., Y.C.F.C., C.E.C.) and Obstettics, Gynecology, and Reproductive Sciences (J.T.P.), University of California School of Medicine, San Francisco, CA 94143. Received October 17, 1988; revision requested December 20; final revision received November 3, 1989; accepted November 6. Address reprint requests to H.H. 2

Current

address:

Veterans Administration no, Calif. © RSNA, 1990

Department

Medical

of Radiology,

Center,

Fres-

METHODS women

with

an

obstetric history of normal cervices and 21 nonpregnant women with incompetent cervices were randomly selected from the gynecology clinic population. All 41 women had been pregnant at least once. The cervix was defined as normal or incompetent

Radiology

AND

from

based

the

patient’s

on

unequivocal

obstetric

find-

history

and/or from physical examination during pregnancy. All women were 12 months or more postpartum. The women seen consecutively in the clinic who met these criteria for inclusion and agreed to undergo MR imaging composed the study group.

Abbreviations: DES diethylstilbestrol, HSG = hysterosalpingography, LE/LC ratio of length of endometrial cavity to that of cervical canal, SD = standard deviation, SE spin echo, SEM = standard error of the mean, TE echo time, TR = repetition time.

821

#{149}

..

Table 1 Clinical Findings in 21 Women Incompetent Cervices

with *

No. of Women with Incompetent Cervices 1,;L

No. of Live Births

Obstetric History G1,P1 G2,P1 G2,P2 G2,P2 G2,P2 G3,P3 G3,P3 G3,P3

Acquired or Congenital (n = 11)*

0 1 0 1 2 2 1 0

DES Exposure (n 10)t

1

1 1

3 3

3 2 1

1 3

Figure

2

Note.-G = number of pregnancies, P number of births after 20 weeks gestation. * All 1 1 women had previous spontaneous second trimester losses and documented dilated cervices.

Seven pregnancies,

women had previous including five cases cervical dilation and two cases of ture of membranes, three patients term pregnancies, but bed rest was

complicated

t

The

20 women

with

had uncomplicated no

abnormal

women

vida, petent

n

=

prenatal niphad previous required.

normal

term

obstetric

n

at clinical

and 21

of in

utero

details

the women given

in

ranged

DES

evaluation

section

(n

exposure

of the obstetric

with incompetent Table 1. Women

in age

from

=

gynecology

history

of are

(mean,

clinic.

All

was then scheduled for the sephase of the patient’s menstrual cycle. The two participating radiologists analyzed and recorded the MR findings

cretory

patient

trician

in conference of the judgment

or of the

physical collected

from

one-way

MR image

multiple

sample

MR

tamed tune,

with an elliptical 55 X 40 cm) or with

body

coil (aperture section

0.35-T San

groups

level

imaging (MT/S

Francisco,

magnet

in

with

a

.05

was

among

magnet

Diasonics, superconducting and with (Signa;

was

(aper-

10 mm

sections. February

T2-weighted

A section

with

(In studies 1985,

images

section

T2-weighted

T2-weighted

T). Four Ti-weighted

used

for

TR

of 5 mm

gaps between

was

sagittal

images

images

were

ob-

The standard resoThe image matrix T) or 256 X 128 (at

excitations per sequences,

T2-weighted

line and

were two

used were

Image

Specifically

a

age

from

the level

South

of the GE

Medi-

su-

recorded the

level

were

endometnial

(a)

of the

internal

os,

cavity from

the

cervi-

sagittal

im-

(b)

as measured the

junction,

fundus

Used

“transi-

endocervi-

(spindle

scnibed nition

for

and

MR

of the have

Because

required

in

brief

summary supplemented MR imaging tion follows.

of

this

field

precise

defi-

of the cermeasure-

investigation,

a

MR findings

published

by additional unpublished results and anatomic correla-

images,

strength,

the

is demonstrated

as

mucosa

of the

of higher

regardless

normal

extending from Os; it surrounds

ty cervical

de-

been

the

of anatomic landmarks vix is essential for the accurate ments

the

Image

cervix

(7,9-li).

stripe external

(f) on the intensity

on Ti- and T2All measurements hard-copy image. Bein millimeter increa separate 1-mm

characteristics

uterus

area on

(myo-

the

as

manufacturer.

Criteria Analysis

niphery

os to the length

canal funnel

to be incorporated routinely available

On T2-weighted

on the

of the external

the sagittal image metrial-endometrial

the

stroma

as measured

stnoma, lower uterine

or widened and irregular, of the cervical stroma image, and (g) the signal

was designed the 5-mm scale

from

sequences.

Analysis

of

tubular

os, os as

as the disof the

or

contour

as either

of the cervical stroma weighted sequences. were taken from the cause measurements ments were required,

the

cal length

a 1.5-T

shaped) thickness sagittal

scale into

image margins

(isthmus)-endocervical tubular (cylindrical)

(e) the

leio-

cervical cervical

cervical of the

configuration

corpus

or a 95%

with

the

MR imaging

was

sections.

transverse

tamed in all patients. lution mode was used: was 256 X 256 (at 0.35 1.5

the

internal internal

low-signal-intensity (d)

and the TE was 60

thickness

i-mm

and

MR

performed

before

For

Ti-

for

unequal

Technique

Calif) 22 patients

Radiology

#{149}

by

(8).

system;

perconducting

822

with

and

analyzed

differences

T2

55 cm).

thickness

no gap between

and

were

body coil a quadrature

diameter,

2,000 or 2,200 msec

analysis of vanby a Newmantest

and

thickness was 7 mm with a 3-mm gap between sections.) With the 1.5-T unit, a quadrate-system body coil (aperture, 55 cm) was used, and images were considered Ti weighted with a TR of 600 msec and a TE of 20 or 25

data

histories

Data were

to isolate

Imaging

MR

analysis

obstetric

range

sizes

the three confidence

the

used

a

internal

Submucosal

the sagittal the inner

on

segment either

when a TR of 2,000 msec and a TE of 60 msec were used. Images were ob-

msec.

the

were

the

visible.

to the of the

between

cal canal

msec.

and

investigation,

single-factor followed

(ANOVA)

Keuls

history

zone”) width

shaped,

used

of the

correlated with physical findings. the

and without of the obste-

findings.

At the end

ance

obstetric

images were conwhen a repetition

15 or 30 msec

Standard

imaging

of each knowledge

tional the

shaped.

is also

(L)

(TR) of 500 msec and an echo time

performed

the

19 patients. system, multi-

weighted 10).

is spindle

myoma

of

The women were referred for MR imaging in the same random order that they in

canal

time

with

seen

(SE)

in

therefore

15 demarcated by the entrance of the uterme vessels (v). External os of the cervix (white arrow) is demonstrated. Endocervical

(TE)

33 years).

were

Milwaukee) 0.35-T imaging

spin-echo Ti weighted

sidered

cervices in all groups

21 to 43 years

Systems, the

With

and

cerin-

Os

tance cal

com-

waist,

measured

2; multigrato have incom-

prised two subgroups-those with acquired (history of obstetric or gynecologic trauma) or congenitally incompetent cervices (n 11) and those with a

history Further

discernible

(c)

cervices

pregnancies histories. The

(primigravida, 19) determined

cervices

of premature

Figure 1. Sagittal MR image (0.35 T, SE 2,000/60 [TR msec/TE msec]) of a normal cervix in a multigravida, multipara (G2P2) patient. co = corpus uteri and lus lower uterine segment. The level of the internal cervical os (io) is marked by the entrance of the uterine vessels and/or narrowing at the uterine waist (arrow). Note the uniform low signal intensity of the cervical stroma extending across the internal os into the lower uterine segment. Lower uterine segment and endocervical canal are tubular.

2. Sagittal MR image (1.5 T, SE 2,000/60) of an incompetent cervix. The vical stroma is thin and of higher signal tensity toward the internal os (black arrows). External shape of the uterus lacks

the

and

a low-intensity

internal to the the high-intensi-

mucus.

stroma

is often

signal

intensity,

proaches

that

transition patients.

between At histologic

of

the

The seen

that

myometrium

the

of

cervical

two varies examination,

March

peas

an

ap(7). The among the

1990

proximately

at the

level

of the

internal

os

(17). Another

landmark for the location of the internal os is a uterine contour change referred to as the “uterine waist” (Fig i).

RESULTS In the 20 multiparous women with normal mean

length



nonpregnant cervices, the

standard

deviation

[SD]) of the endometrial 52.5 mm ± 5.3, the mean the the

cervical mean

canal was ratio of these

(LE/LC)

was

width

3.3 mm

Figures

Sagittal MR images (0.35 T, SE 2,000/60) of two incompetent cervices. (3) CO internal os, and EO external os. The endocervical canal is irregular and widened (long white arrow), and the stroma in the same location is indistinct. (4) The cervical stroma is of uniformly abnormal medium-to-high signal intensity, and the internal cervical os (arrows) is wide. The isthmus-endocervical canal is funnel shaped. 3, 4.

uteri,

10

Table 2 MR Image Group

of the Normal,

Normal

20

Incompetent

10

DES-exposed

10

Note-Values *

t

Length Endometrial

No. of Patients

reported

Significantly Significantly

(mm)

of Cavity

± 1 SEM,

from width from width

with

in normal in normal

and DES-exposed

Length Cervical

52.5 ± 1.2 (50.0-55.0) 52.8 ± 1.6 (49.3-56.4) 47.2 ± 1.9t (42.8-51.4)

as means

different different

Incompetent,

95%

confidence

interval

and DES-exposed group, P < .001.

also referred ment, is an

ma, and

are

better

(around

the

uterine

periphery

of the

developed

stro-

laterally

(mm) of Cervical os

for the

mean

canal

patients.

The

the

cervical

1.5.

It

thian within

P < .001.

were cervix

In the cervices

1 1 women of acquired

igin,

mean

length

myometnium

connective

and tissue

the

stroma

ent

predomiof the

cervix is usually gradual, occurring over the course of 5-10 mm (i2). The isthmus, to as the lower area of transition

uterine between

segthe

from

those

ma! cervices width of the

intensity

shaped

most stroma

extends to various degrees across the ternal cervical os (Fig 1). The isthmus sphinctenic and is functionally rather

of low

signal

internal

intensity. cervical os,

fibromuscular cervix from

junction, the corpus.

the

of the of the

location

menclature in the literature. anatomy is

The

internal uterine

After

literature

Volume

most between

174

Number

#{149}

called

os and segments

a review

(i2-i7),

the description transition

also

the

demarcates the The description

the

of the following

commonly the

3

smooth

of

the novary

used. mus-

stripe

of the

cervical

stroma inis

than anatomically determined (i6). The widths of the isthmus (14) and internal os (i4,18) change during the menstrual cycle. Because the MR appearances and the width

of the

isthmus

and

internal

os can

be similar, the level of the internal os can be recognized by the location of entrance of the uterine vessels, which traverse the broad ligament and reach the uterus ap-

with

nor-

± 0.9) was significantly greater that in the normal or DES-exposed groups (P < .001) (Table 2).

connective

The

or-

mm than

the isthmus-endocervical tubular in six patients

tion

found patients.

2). The mean cervical os (4.5

while the periphery, which is composed predominantly of smooth muscle bundles, is of medium signal intensity. For discussion of the incompetent cervix, the

tissue of the cervical stroma is important (i3), and the term cervical will refer only to the inner por-

±

(± SD) of the

of women (Table internal

internal os) (15). Below the histologic internal os, the cervical stroma is predominantly fibrous (16). On T2-weighted images, a transition can be seen as the low-

either

of

mm

with incompetent or congenital

cervix and corpus and is bounded supenionly by the upper os, termed the anatomic internal Os, and infenionly by the lower Os, termed the histologic internal os (the latter is conventionally referred to as the

anteriorly or posteriorly on T2-weighted images which is predominantly nective tissue, is of low

than

43.3

incidentally in three

(12). Therefore, the inner stroma, collagenous consignal intensity,

vessel)

in

signal intensity and from the interos (Fig 1). Nabo-

of

cysts the

tubular thickness

was

low uniformly external

was

the

were mean

stroma

extended nal to the

in parentheses.

mean

os was

cervical canal (32.5 mm ± 4.2), the length of the endometrial cavity (52.8 mm ± 4.9), and the LE/LC (1.64 ± 0.3) were not significantly differ-

located

nantly

all

3.3 ± 0.1 (3.2-3.5) 4.5 ± 0.3* (4.2-6.6) 3.0 ± 0.1 (2.7-3.3)

groups,

cle of the

the

Width Internal

33.0 ± 1.0 (31.0-35.0) 32.5 ± 13 (29.4-35.6) 22.9 ± 1.7t (19.0-26.8)

cervix is found to be composed predominantly of fibrous connective tissue (i2). The strands of smooth muscle constitute approximately 10%-i5% of the stroma, are towards

(mm)of Canal

Cervix

the

cervical

errors of the mean (SEMs). The uterme waist or narrowing of the uterine contour at the level of internal os was demonstrated in 18 patients. In the same patient group when the uterine waist was used as a point of reference for the location of the internal os, the mean (± SD) endocervical length was 3.5 mm ± 0.3. The isthmus and the

endocervical Measurements

33.0 mm ± 4.3, two lengths

± 0.2, and

internal

was of

± 0.3. Table 2 shows these as means ± standard

measurements

corpus

1.61

of the

cavity length

The

uterine

in seven

waist

of the

The endocervical in seven patients,

was

demonstrated

1 1 patients

(Fig

2).

canal was tubular spindle shaped

in

two (Fig 2), and bulky and irregular in two (Fig 3). The configuration of

in three

(Fig

canal

was

and funnel 4). In two pa-

tients in whom the endocervical canal was wide and irregular, the isthmus was tubular. The entire length of the cervical stroma was of abnormal medium-to-high signal intensity

in three patients tients, the stroma

(Fig 4). In four pawas of medium-to-

high signal intensity proximally toward the level of the internal os (Fig 5). Cervical stroma was of uniformly normal low signal intensity in four

Radiology

823

#{149}

Figures

5-7.

(5) Sagittal MR image (0.35 T, SE 2,000/60) of an incompetent cervix. The proximal cervical stroma is of medium signal inteninternal cervical os. (6) Sagittal MR image (0.35 T, SE 2,000/60) of a small cervix in a patient exposed to DES in utero. The cer(cervical length less than 2 cm), but the cervical stroma is of normal low signal intensity. Arrows internal cervical os. (7) Sagit-

sity. Arrows vix is short

=

tal MR image of high

signal

cervical

os.

patients.

those

(0.35

T, SE 2,000/60)

intensity

The

four

(black

width

patients

of the

varied

3.5 mm. The sample small for statistical

of a normal-appearing

arrows)

seen

stroma

in

from

size was analysis.

2 to too

the

than that in the normal (P < and incompetent cervix (P < groups. The length of the endo-

.001) .001) metrial cavity (47.2 ± 6.0) was also significantly shorter when compared with that in the normal group (P < .001) or the group with incompetent cervices (P < .001). The mean LE/LC (2.16 ± 0.6) was not significantly different when compared that in the normal or incompetent

cervix

group

multiple

(with

were,

cavity range

val of 31.0-35.0 50.0-55.0 mm (Fig eight

7). The of the

width rowed

(95%

(Fig

in

in two pacervix and

for cervix

that

endocervical

narrow

canal

and mean

cervical

normal

tubular thickness

stroma

was

Radiology

#{149}

and

identified

signal inwas idenwoman

vaginal

in two

adenosis

others

(Fig

7).

Hysterosalpingography (HSG) (14,18) and US (4-6) have been advocated as adjuncts to clinical evaluation of the incompetent cervix. In the

shaped these

ther

patient, HSG can show internal os and funnel-

endocervical findings were

reliable

nor

ings

diagnostic

(18). cervix

or greater

cervical

during

the

US is

US findos of 15 mm

first

trimester

(4). Hour-glass

fetal

The

isthmus

of the

membrane, thinning of the lower uterine segment, and shortening of the cervix have been reported (19) as adjunct findings. Although initial US

studies

were

recent

clinical

most

encouraging,

experience

shown

in all patients.

numerous reliable



of the

demonstration

of cervical

compliance

± 0.4 and

(6). Therefore,

physical examination remains the most for diagnosis of the

SD)

during accurate

incompetent

pregnancy means

cervix.

MR

The

White

imaging

focal

arrows

length

of the

lesions

internal

offers

evaluation

a new

of the

approach

cervix.

endocervical

and

The

canal

the

external

consistently demonstrated. nal os is more difficult

can

os is

The to define,

interand

a landmark of either the entrance of the uterine vessels or the narrowing at the uterine waist can be used. The characteristics on

of the

T2-weighted

normal

images

low-signal-intensity

to the

cervical

cervix tensity

the have

cervix

include stripe

the

corre-

connective

stroma

high-signal-intensity sponding to the mucus (7,10,11).

tissue

and

the

of

inner

area correcervical mucosa and Shortening of the

and a change in the signal inof the cervical stroma during third trimester of pregnancy been

described

(9).

This

clinical

observation was further supported by laboratory studies of rhesus monkeys, in which the MR signal intensity of the cervical stroma changed in response to the injection of relaxin

(Genentech, Calif) (20).

South

corresponded

ings

of stromal

In the determined

San

These

ings

more

has

that patient physique and technical artifacts preclude

3.0 mm

were

herniation

exposure.

to the

the

pa-

women,

open

DES

adenosis.

sponding

however, to be nei-

incompetent on nonpregnant

In pregnant of an

canal; found

utero

be measured,

DISCUSSION

nonpregnant a widened

in

vaginal

inter-

demonstrated normal low signal intensity in nine patients. In the remaining patient, anterior cervical

824

was

group,

with

to represent

and

group.

and

patient

at surgery

sec-

the

for endometrial cavity) uterine waist was seen in 10 patients. The mean

of the

a multigravida

and 20 mm or greater during the ond trimester have been considered diagnostic of cervical incompetence

within

confidence

mm

in

found

lips were of heterogeneous tensity. Cervical carcinoma tified on MR images of one

tients.

6).

of the internal os was narbut not significantly different

from

The

was

were

evaluation for not performed

variations

measurements; length of the

endometrial normal

test)

however,

the length tients, the

with

Newman-Keuls

composition

There

cervix

vagina

in this

In the 10 DES-exposed women, mean length (± SD) of the cervical canal (22.9 ± 5.4) was significantly shorter

in the

imaging

to

histologic

edema

present

Francisco,

MR

all patients

referring

cian to have normal cervices mal-appearing cervices on ages. The low-signal-intensity

cal stroma patient

nal cause

was

demonstrated

and extended to the external the

width

of

find-

(20).

study,

by the

find-

from cervical the

obstetrihad

norimcervi-

MR

in each the interos. Be-

internal

os

March

1990

changes during the menstrual cycle, all the patients were imaged during the secretory phase, when the internal Os iS normally the narrowest (14,18,21). The mean measurement of the width of the internal os made at HSG study (4.43 mm ± 0.23) (22) is

incompetent cervix and in our study was seen in two of 11 patients. Another HSG finding reported with incompetent cervix is the funnelshaped isthmus-endocervical canal. This was detected in three patients in our series. In summary, MR imaging

larger

findings

than

the

one

reported

here.

The discrepancy may be due to a number of factors: (a) The HSG studies

are

performed

during

the

proliferative phase when the internal os is wider compared with its width in the secretory phase, (b) there is distention of the internal os from the injection of contrast mediurn during the HSG study, and (c) MR imaging measurements were done in the sagittal plane only. The endometrial cavity (including the endocervical canal) is not a true cayity but merely a potential slitlike space flattened in the anteroposterior diameter. Therefore, the HSG measurements, which are obtained in the transverse diameter, would differ from the measurements of MR images obtained in the anteropostenor diameter. Nevertheless, our data also do not represent the true width of the internal os because the endocervical cavity is not seen-the measurements therefore include the thickness of the mucosa. In patients with the clinical diagnosis of incompetent cervix, a number of MR features were observed, many of which were previously described clinically, were demonstrated on HSG studies, or were shown at histologic examination. Shortening of the cervical canal has been reported in the pregnant patient with an incompetent cervix (23), but, to our knowledge, the length of the cervical canal has not been investigated in the nonpregnant patient. In our patients with a history of incompetent cervices, the mean length of the cervical canal was not different from that of women in the normal group. This may explain why findings at pelvic examination are often normal in nonpregnant patients with a clinical history of incompetent cervices. The dilated internal cervical os is a known feature in patients with incompetent cervices (16) and has been previously documented clinically and at HSG. The wide internal cervical os was seen on MR images as well. The importance of the shape of the endocervical canal, whether tubular or spindle or funnel shaped, is the subject of controversy. Irregular asymmetric

widening

of the

vical canal as described however, is considered Volume

174

Number

#{149}

endocer-

by Lash suggestive 3

(24), of

combine

the

findings

de-

scribed clinically or demonstrated by HSG with a better tornographic anatomic display. Furthermore, MR imaging offers the additional information of tissue characterization. The MR signal intensity of the cervical stroma was partially or uniformly increased in seven of 1 1 patients with incompetent cervices. In our studies, histologic spedmens were not available for comparison, and therefore, the MR imaging findings

were

compared

with

known

histologic findings described in the literature (12,13). It has been postulated (12) that the connective tissue of the cervical stroma allows the cervix to act as a barrier to maintain the conceptus within the uterus. Histologic study performed on patients with incompetent cervices demonstrate fewer elastic fibers and more smooth muscle in the incompetent cervix as compared with that found in patients with normal cervices (a reflection of decreased elastin and desmosine content) (13). These histologic findings are probably responsible for the increased MR signal intensity of the cervical stroma and appear to correlate with obstetric outcome in our study. The worst pregnancy outcome occurred in the three patients in whom the cervical stroma was of uniformly high signal intensity

on

T2-weighted

images.

In

these patients, repeated middle trimester pregnancy losses occurred even with the use of cerclage. When the signal intensity of the cervical stroma was only partially high, use of cerclage produced a successful outcome in three of the four patients. In our study, the length of the cervix in DES-exposed women was significantly shorter than that in the normal group. Shortening of the exocervix (portio cervix) is a known (22) clinical finding in patients exposed to DES in utero. The width of the internal os and thickness of the cervical stroma were less than those in the normal group, but the difference was not significant. The signal intensity of the cervical stroma was normal in nine of 10 patients. Morphologic studies (22) demonstrate normal connective fibrous tissue of the cervical stroma in DES-exposed women. MR findings support the hypothesis (25)

that the cervices of patients with in utero DES exposure are different than the incompetent cervices of congenital or traumatic origin. While pregnancy outcome with cerclage has been successful (26), some investigators (25,27,28) have cautioned against the liberal use of cerciage in DES-exposed patients because of the underlying differences. In summary, MR imaging can noninvasively demonstrate the distinctive features of the cervix in the nonpregnant

patient

with

a history

of in-

competent cervix or of small due to in utero DES exposure.

cervix Be-

cause

mea-

of variation

in uterine

surements depending on the patients’ habitus and obstetric history, these data are preliminary as they are based on a relatively small number of patients in each group. The patient selection was such that only patients with clinically unequivocal diagnoses of normal cervix, incompetent cervix, or in utero DES exposure were included. A larger prospective study to demonstrate a range of findings and determine the impact of MR imaging in the management of patients with suspected cervical incompetence is needed. At present, due to the wide variation of the severity of etiologic factors of this condition, we feel that a normal MR appearance of the cervix, including its measurements and tissue characteristics, cannot preclude the diagnosis of incompetent cervix. However, when MR findings of a short cervix (cervical length less than 3.1 mm, 95% confidence limit), widened internal os (internal

os wider

than

4.2

mm,

95%

confidence limit), or stroma of abnormal signal intensity are present, they can be used as an adjunct to the clinical evaluation when diagnostic or patient management decisions in cases of possible cervical incompetence need reinforcement. U References 1.

2.

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Cervical incompetence: preliminary evaluation with MR imaging.

The ability of magnetic resonance (MR) imaging to demonstrate cervical incompetence in nonpregnant women was investigated in a prospective study of 41...
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