Yasuyuki Kazuhiro

Yamashita, Yoshizumi,

MD MD

#{149} Mutsumasa

Spinal Cord of Ligaments:

Index

terms:

Ligaments,

cord,

MR

Spine, 33.7811

studies,

341.1214,

intervertebral #{149} Spine, MR

disks, studies,

MR studies, #{149} Ligaments, #{149} Spinal

361.77 351.1214,

31.7811, 3i.i2i4,

spicord,

O

of the

of OPLL

A total

AND

(mean,

were

55.6

years)

(14 men

years

basis

had

and

(mean,

or

MR im-

cases.

OPLL and was selected

was

and

were

performed

presence

of radiographic

tent with obtained

ossification. at various

of OYL.

findings

The

type

findings.

MD

ematively

were

of the

consis-

and

cation of the ossification were classified on the basis of the plain-radiographic

lo-

in 16 cases;

evaluated

diologic

and

performed most

early

preop-

of these

cases

in the series.

All ma-

evaluations were made by conreading by three experienced radi-

sensus oiogists.

The

clinical

symptoms

included ic spine

cervical pain in

in five.

Myelopathy

degrees,

ous

esthesia

in these

spine 15, and

in

patients

pain in 65, thoraclumbar spine pain

was

including

of the

tremities

present

in van-

dysesthesia

upper

or hyp-

and/or

lower

and

spasticity

88 patients

cxor

motor weakness in 55 patients. Severe weakness, muscle atrophy, and/or anesthesia was observed in six patients. Some patients had only myelopathy without back pain. Twenty-one patients underwent surgical decompression (posterior laminectomy and/or facetectomy); the memaining patients were treated consemvatively.

OPLL

was in the cervical

spine

in 95

patients, the thomacic spine in four, lumbar spine in four, and both the cal and thoracic spine in three. The of cervical OPLL were divided into types on the basis of the plain-radiographic findings according to Seki’s system

(Fig

1) (7).

The

the cervicases two clas-

segmen-

tal type was defined as ossification of the ligament confined to the posterior edge of the vertebral column. This type was observed in 45 patients. The continuous type was defined as ossification that cxtends continuously at the vertebral body and disk levels. This type was observed in 50 patients.

were

of the

level. spine in

Three

cases

of thomacic

of the segmental continuous

OPLL

were

OPLL

type,

and one case

type.

All cases

observed

at the

of disk

OYL was observed in the cervical in five patients, the thomacic spine

11, and

patient

the

had

lumbar

both

OYL. OPLL

spine

cervical

in

and

was associated

eight cases and nuchal ligament

one.

One

thomacic

with

OYL in

with ossification in four cases.

of the

was performed

on a 0.5-T

superconductive Philips Medical tients and with

MR unit (Gyroscan S5; Systems, Tokyo) in 51 paa 0.22-T resistive MR unit

Abbreviations:

OPLL

posterior

and

Myelography

were

MR imaging

as

basis

MR images were levels, corresponding

symptoms.

Sakamoto,

CT myelography

lumbar

in

performed

on the

tomographic

was

OYL. on at

in 10 cases

appropriate

clinical

38-

had OYL.

tomography, and com(CT). of the cervical, thospine were obtained in

Tomography

of OPLL

pa-

aged

findings

considered

to the

Sixteen

women),

of characteristic

CT and MR imaging

1990

with

58.1 years),

#{149} Yuji

sification

OPLL

OPLL.

two

plain radiography, puted tomography Plain radiographs macic, and lumbar 41 cases

RSNA,

with

examined

Eight patients had both The patient population

all

©

METHODS

of 108 patients

OYL or both

77

From the Department of Radiology, Kumamoto University School of Medicine, 1-i-i Honjo, Kumamoto 860, Japan. From the 1989 RSNA annual meeting. Received October 6, 1989; revision requested November 6; revision received January ii, 1990; accepted February 20. Address reprint requests to Y.Y.

lon-

aging at Kumamoto University and its affiliated hospitals between June 1986 and March 1989. One hundred patients (78 men and 22 women), aged 19-76 years

the

1

posterior

in non-Onientals

PATIENTS

MD

to Ossification

(1-4). Magnetic resonance (MR) imaging has proved to be a useful diagnostic method for evaluation of the spine and spinal cord, and the morphologic and signal-intensity characteristics of the spinal cord ligaments in both the normal and pathologic states have also been assessed with MR imaging (5,6). However, the MR appearance of ossification of the ligaments has not, to our knowledge, been described in detail. In the present study, we evaluated the detectability of and nadiologic findings in OPLL and OYL, with emphasis on the MR appearance.

361.1214

1990; 175:843-848

Matsuno, MD

Kojima,

due

SSIFICATION

reports

tients

32.7811, 32.1214,

#{149} Yasuharu

gitudinal ligament (OPLL) and ossification of the yellow ligament (OYL) are both important clinical entities responsible for compression of the spinal cord in Onientals. Although these have been regarded as “Oriental diseases,” theme are several

Spinal

#{149}

33.1214

Radiology

MD #{149} Ryutaro

Compression MR Imaging’

A total of 108 patients with ossification of the posterior longitudinal ligament (OPLL) (n 92), ossification of the yellow ligament (OYL) (n = 8), or both (n 8) were exammed with magnetic resonance (MR) imaging performed with 0.5-T superconductive and 0.22-T resistive units. OPLL was demonstrated as a low-signal-intensity band between the bone marrow of the vertebral body and the dural sac on Ti- and T2-weighted images. Continuous cervical OPLL was easier to diagnose than segmental cervical OPLL. T2-weighted images were more useful for detection of ossification of the ligaments. OYL was recognized as an impression on the posterior dural sac. Formation of bone marrow within an area of ossification, shown as increased or intermediate signal intensity, was observed in 56% of the cases of continuous OPLL, ii% of the cases of segmental OPLL, and none of the cases of OYL. The degree of cord compression was more severe in continuous OPLL. Degeneration of the disk was frequently associated with both types of OPLL

319.1214, 329.1214, 339.1214 nal, 319.811, 329.811, 339.811 compression, 341.77, 351.77,

Takahashi, Oguni, MD

#{149} Tatsuro

cation

longitudinal of the

yellow

ossification ligament,

ligament,

OYL SE

=

of the =

spin

ossifiecho.

843

(J

(J

(j

c:3 c

c:::

c

#{182}: #{182}3 c

b

a

Figure 1. Classification of OPLL. ous type is defined as ossification

tends column ously type

along

posterior

Continuthat

cx-

edge of the vertebral

and at the disk level either continu(a) or discontinuously (b). Segmental (c) is defined as ossification confined

the posterior

edge

of the vertebral

to

column. a.

Toshiba

(MRT-22A;

Medical

Systems,

b.

To-

kyo) in 60 patients. Three patients with OPLL were examined with both units. A spin-echo (SE) 400-450/30 (repetition time msec/echo time msec) sequence was used for Ti-weighted images, an SE 1,600-1,800/50 sequence was used for proton-density images, and an SE 1,600-

1,800/100 sequence was used for T2weighted images on the 0.5-T superconductive unit. An SE 400-500/34-40 sequence was used for Ti-weighted images, an SE i,600-2,000/40 sequence was used for proton-density

images,

and

an SE

i,600-2,000/60-80 sequence was used for T2-weighted images on the 0.22-T resistive unit. pensation

Cemebrospinal was performed

fluid flow comwith use of an

electrocardiographically on T2-weighted images. thickness

was

10 mm

gated technique The section for the

0.22-T

and 6 mm for the 0.5-T unit. ings and

were

used

unit

Four

for Ti-weighted

images

of the dural sac and space and the degree

cord compression were four degrees of severity findings

There

30 lesions

compression,

degree

with

46 lesions

shows

of a 57-year-old

continuous

OPLL

woman

at C-4

to C-6

with

continuous

(arrowheads).

CT scan at C-5 demonstrates of area of ossification, defined

cervical Lower

OPLL.

(a) Tomogram

of

margin

OPLL as well as the distance

of ossification is unas dural sac compression.

from

the posterior

edge

of the vertebral column to the posterior edge of the main area of OPLL as measured with axial or myelogmaphic CT. (c) Sagittal MR image (SE 400/30) obtained with 0.5-T unit shows imregular compression of the spinal cord anteriorly at C-4 to T-i . Arrowhead indicates C-4. (d) Axial MR image (SE 1,800/100) obtained with 0.5-T unit at same level as l shows dural sac compression by OPLL (arrowheads), correlating well with myelographic CT appearance.

into

cord

30 lesions

mild

sions cord

with severe cord compression atrophy. Five lesions had been

ed previously

compression,

with

RESULTS

compression

compression,

cord

sac

a minimal

with

and eight

surgery.

le-

or treat-

(Patients

who

OPLL was recognized by the pnesence of an increased distance between the posterior edge of the yentebral

had multiple lesions were counted separately [ie, theme were 1 19 lesions in i08 patients].) The thickness of ossification (the dis-

cord OYL

tance

from

tebmal

body

mediate

the posterior to the

area of OPLL

edge

of the ver-

posterior

edge

at the main

portion

fication) was measured myelographic images tances were compared

of the

of ossi-

on axial CT or CT (Fig 2). These diswith the MR find-

bone

#{149} Radiology

marrow

or amachnoid was recognized

sion on the spinal cord seen

and

the

intensity areas

spinal

space (Figs 2-6). as an impres-

posterior dural (Fig 7). Increased

signal within

tectability location weighted depicting

ings.

844

Images

clear. (b) Myelographic Bar indicates thickness

the of

no dural

with

of subamachnoid

without

2.

on the basis of on T2-weighted images (8).

seen

were

classified

Figure spine

two for proton-density and T2weighted images. Images were acquired with use of a spine coil with a 256 X 256 matrix. Compromise subamachnoid

d.

C.

avemag-

sac

was

of OPLL.

cation positively detected with MR imaging was 5.41 mm ± 1.76, while

often

the mean thickness 1.01 in cases that with MR imaging.

de-

of OPLL and OYL at each is shown in Table 1 T2images were superior in ossification.

Continuous

± 1 .68 [mean ± standard deviation]) than in segmental OPLL (2.95 mm ± 0.98). The average thickness of ossifi-

and or inter-

The .

cervical OPLL was more easily recognized at MR imaging than segmental cervical OPLL. The thickness of the area of ossification was significantly greaten in continuous OPLL (5.89 mm

was 2.80 mm ± were not detected Ossification of

more than 3.2 mm was detected on T2-weighted images in 53 of 58 cases (91%). Detection of lumbar OPLL was June

i990

b.

a. Figure 3. ous OPLL

Images extending

of a 71-year-old man from C-4 through

c.

with continuous C-S (arrowheads).

cervical OPLL. (a) Lateral plain radiograph The spinal canal is narrowed at this level.

of the cervical spine Narrowing extended

shows to C-6

continu(not visi-

ble on this image). (b) Sagittal MR image (SE 400/30) obtained with 0.S-T unit shows a band of low signal intensity between the vertebral body and the cord extending from C-4 through C-6. The cord is slightly compressed. (c) Sagittal MR image (SE 1,800/100) obtained with 0.S-T unit also shows a band of low signal intensity and compressed dural sac. Slightly high signal intensity in the spinal cord is observed at C-4 to C-6 (arrowheads).

sion was more on MR images

graphs

and

the lower spine (Fig significantly ous OPLL 50 patients

OPLL (16%)

cervical and upper thoracic 3). Cord compression was more severe in continu(P < .01). Seventeen of the (34%) with continuous

and with

increased nal cord

clearly demonstrated than on plain radioCT scans, especially in

seven of the 45 patients segmental OPLL showed on

signal intensity T2-weighted

4, 5). Increased spinal

cord

signal was

also

in the images

intensity

spi(Figs

in the

observed

in one

case of thoracic OPLL and two cases of thomacic OYL. Degeneration of the disk was frequently

associated

OPLL (Figs generation very difficult. Image quality with the 0.5-T unit was superior to that with the 0.22-T unit (Fig 6). Although detectability of an extradunal defect was better with the 0.5-T unit than with the 0.22-T unit, there were no significant differences between the two units. The MR findings in OPLL and OYL are summarized in Table 2. Intermediate on high signal intensity within areas of ossification, considered to represent bone marrow associated with ossification, was observed Volume

i75

Number

#{149}

3

in 28 cases

cal OPLL sity

(56%)

(intermediate

in 25 and

three)

and

mental signal

cervical intensity

Soft

tissue

tion

was

of continuous

within observed

signal

high

five

cervi-

signal

cases

(11%)

OPLL in all

inten-

intensity

(intermediate cases) (Fig

an area at CT

ossification,

longitudinal

of dein seg-

mental and continuous types. Lumbar OPLL was also associated with lumbar disk disease. Ossification of other ligaments was significantly more frequent in cases

of continuous 4).

cervical

degree equal

segmental

OPLL OPLL

than

in cases

of

(P < .05).

of ossificain only

three

cases (all continuous type). This observed in one case of thoracic OPLL and in no cases of lumbar OPLL and OYL. Although MR imaging cannot pict

in

of seg-

with

4, 5). The was almost

DISCUSSION

was Compression

OPLL de-

exten-

1838 nized 1960,

was

of the

reported

spinal

cord

by

by Key as early

as

(9). However, it has been recogas a clinical entity only since when Tsukimoto described the

Radiology

845

#{149}

Figure

4.

segmental

Images

of a 45-year-old

cervical

OPLL.

heads).

The spinal levels.

(b)

with

Lateral plain spine shows segand C-6 (arrow-

radiograph of the cervical mental OPLL at C-3, C-4, at these

man

(a)

canal

is slightly

Axial

CT scan

narrowed obtained

after intrathecal administration of contrast material at C-4 clearly demonstrates OPLL and slightly compressed dural sac. (c) Sagittal MR image (SE 400/30) obtained with 0.5T unit shows slight compression of the spinal cord onstrated

at C4-5 and C5-6. OPLL is not demon this image. (d) Sagittal MR

image

(SE i,800/iOO) obtained dumal sac compression

unit shows generation

of the

disk

6. Differentiation spondylosis intensity

C4-5

with

at C3-4,

of OPLL

is difficult. in the spinal

0.5-T

with deC4-S, and CS-

from

cervical

Slightly high cord is observed

signal at

(arrowheads).

autopsy has been

findings considered

in OPLL (10). OPLL endemic to Japan

b.

a.

until recently. A large comprehensive epidemiologic study was performed in Japan, and the frequency was reported to be 2.4% (ii,i2). Recently, there have been a number of reports on OPLL in non-Onientals (1-4). The clinical, radiologic, and pathologic manifestations of OPLL in non-Onientals have been meported

to be very

Orientals fuse

similar

(4). In the

idiopathic

to those

United

skeletal

in

States,

dif-

hyperostosis

is

a common disease in middle-aged and elderly patients. According to Resnick et al (13), the frequency may reach 12%, and OPLL is associated with the disorder in 50% of patients. OYL was reported by Polgar as early as 1920 (14). mon diseases

or thoracic lopathy

dence but

It is one of the that compress

spinal

cord.

as well

has not it has

It causes

radicu-

as myelopathy.

been

been

most comthe posteni-

fully

reported

of Onientals

older

(15). Histologic

study

Its mci-

investigated, to occur

than

65 years

c.

d.

in 20%

of age Table

of OPLL

and

2

MR Findings

OYL

Cervical

in autopsy cases has demonstrated the active stages of ossification, showing initial proliferation the ligament and mation (16). Areas

bone

formation

of small vessels subsequent bone of membmanous

contain

marrow

in for-

dc-

ments (17). Histologic correlation was not possible in our study, because all patients who underwent surgical decompression underwent only posterior laminectomy and/or facetectomy. It is

to be expected,

however,

and fat elements sification would signal intensity

ages,

similar

that

marrow

within the areas of oshave displayed high on Ti-weighted im-

to that

observed

Radiology

#{149}

MRFinding

Signals in areas ossificationt

Cord

Thoracic OPLL (n4)

Lumbar OPLL (n4)

OYL (n16)

of 28

5

1

0

0

compressiont 4

None Minimal

Mild Severe

Postoperative High-intensity in cord

weighted Disk

Segmental (n45)

16

3

1

19

20

0

3

16 7 4

8 0 1

1 0 0

0 0 0

6 4 5 1 0

17

7

1

NA

2

24 11 15

22 9 14

3 0 1

0 1 3

NA NA NA

signals on

T2-

imagesl

degenemationf

None Mild Severe

in other

osseous tissues (18). Cervical OPLL can be divided into segmental and continuous types at plain radiography (7). The MR findings in these types were different. The continuous type displayed a thick area of hypointensity, which was easily detect-

846

Continuous (n50)

OPLL

Note.-Values are numbers of cases. Patients with two lesions were evaluated separately. NA not available. * Sixteen cases consisted of four with cervical lesions, 10 with thomacic lesions, one with both cervical and thoracic lesions, and one with lumbar lesions. t Difference between continuous and segmental types of cervical OPLL was significant (P < .01, x2 test). I No significant difference between continuous and segmental types of cervical OPLL in prevalence or degree of severity of finding.

June

i990

b.

Figure

C.

5. Images of a 64-year-old man with continuous cervical OPLL. (a) Lateral plain radiograph of the cervical spine shows continuous extending from C-2 through C-6. Ossification at C-3 to C-4 shows a tram-track appearance (arrowheads). (b) Axial CT scan at C-3 soft-tissue attenuation in area of OPLL. (c) Sagittal MR image (SE 400/30) obtained with 0.5-T unit shows intermediate to high signal within area of dumal sac compression.

OPLL shows intensity

on the other hand, is reported to be closely associated with disk degeneration (19). frequently

However, observed

which

suggests

is also

a contributory

that

in this study, it was in both types,

disk

degeneration

factor

in

the

pathogenesis of continuous OPLL. More study is needed to clarify whethem the two types of OPLL represent different degrees of the disease or whethen they have different pathogenetic characteristics. MR imaging may give us some

help

in answering

this

ques-

tion. Although ossification of the ligaments is not depicted with MR imaging, we can recognize it as an impression on the dural sac on T2-weighted images. On Ti-weighted images, slight ossification cannot be differentiated from cerebrospinal fluid. We can recognize most ossifications measuring more than

a.

b.

Figure

6.

Images

of a 62-year-old man with continuous cervical OPLL. (a) Sagittal MR image (SE 400/30) obtained with 0.22-T unit shows extradumal compression at C4-5 (arrowheads). (b) Sagittal MR image (SE 1,600/100) obtained with 0.22-T unit also shows dumal compression at C-4 to C-S (arrowheads). Dural sac compression is also observed at C3-4 and C5-6 (arrows). Although the image quality is inferior to that obtained with the 0.5-T unit, dunal sac compression is clearly demonstrated.

ed with mediate sidemed

MR imaging. A band of interor high signal intensity, conto represent bone marrow, was

frequently observed within areas of ossification. The degree of cord compression was more severe than in segmental OPLL. The segmental type displayed a thin area of hypointensity,

and

signal

Volume

was 175

less frequently Number

#{149}

3

observed

within types

to have

3.2 mm

in thickness

in cervical

OPLL. Areas of continuous more easily detected than

areas

of ossification.

of cervical different

The

two

OPLL are considered clinical manifestasymptoms are severe

tions. Clinical in the continuous type. Some cases of the continuous type are associated with diffuse idiopathic skeletal hyperostosis and with genetic, metabolic, and hormonal disorders. The segmental type,

OPLL were areas of seg-

mental OPLL, because the former were significantly thicker than the latter. Lumbar OPLL was very difficult to

demonstrate ossification

with MR imaging. Sites of were at the disk level in all

cases of lumbar cult to differentiate

OPLL. from

They were diffidisk disease.

MR imaging can directly and noninvasively demonstrate the location and degree of cord compression. In our previous report, there was good conrelation between the degree of extradural cord compression, including OPLL, seen at MR imaging and the degree of myelopathy (20,21). MR imaging is superior to CT in the evaluation of the lower cervical-upper thoracic area be-

Radiology

847

#{149}

a.

b.

d.

C.

a 60-year-old

woman with thoracic OYL. (a) Plain radiograph (arrowhead). (b) Axial CT scan obtained after intrathecal administration of contrast yellow ligament on the left (arrowheads) and a compressed dural sac. (c) Sagittal tiple impressions on posterior spinal cord by OYL. Arrow shows level of axial CT with 0.S-T unit clearly shows severe dural sac compression. Arrow shows level of at T-10 were considered to represent nonossifying yellow ligament hypertrophy. ment hypertrophy with MR imaging. Figure

7.

Images

of

cause of shoulder girdle artifact images. CT is superior to plain raphy

ing

and

MR

minute

ments

imaging

spinal

of the

canal

liga-

stenosis

(15).

The differential diagnosis of a lesion of low signal intensity on both Ti- and T2-weighted images around the spinal cord or dural sac includes an area of low proton density due to calcification or ossification (eg, calcified meningioma), flowing blood or cerebrospinal fluid (as in an arteriovenous malformation), and the presence of a paramagnetic substance (eg, hemosiderin) (22).

If high

signal

intensity

is observed

within a low-signal-intensity Ti- and T2-weighted images

area

be considered. diagnosis

1.

3.

cannot

hypertrophy

ligament (8). The recognition sified ligament is important,

the cord

is easily

be

of the of an osbecause

damaged by slight inwith OPLL. Plain radi-

jury in patients ography, tomography,

or CT can

used to easily differentiate other conditions. The pathologic changes cord in OPLL have been

OPLL

ation, crosis

including

from

in the spinal well de-

myelomalacia (23). The high

the spinal

cord

is considered

848

edema,

Radiology

#{149}

to

cavitation, and signal intensity

represent

these

12.

13.

14. 15. 16.

nein

images patho-

Bakey L, Cores HL, Smith RJ. Ossification in the region of the posterior longitudinal ligament as cause of cervical myelopathy. Neurol Neurosung Psychiatry 1970; 33:263268.

Hyman

RA, Merten

CW,

Liebeskind

AL, et al.

Computed tomography in ossification of the posterior longitudinal ligament. Neuroradiology 1977; 13:227-228. C}rin WS, Oon CL. Ossification of the postenor longitudinal ligament of the spine. Br Radiol 1979; 52:865-869.

5.

Ho

6.

7. 8.

9.

Yu S, Sether

LA,

et al.

Ligamentum

flavum: appearance on sagittal and coronal MR images. Radiology 1988; 168:469-472. Grenier N, Greselle JF, Vital JM, et al. Normal and disrupted lumbar longitudinal ligaments: correlative MR and anatomic study. Radiology 1989; 171:197-205. Seki

H.

Clinical

study

of 185 cases

to ossification

within

Tsuyama longitudinal

the

cervical

spinal

cation of the posterior longitudinal ligament. AJR 1978; 131:1049-1053. Polgar F. Uber interarkuelle wirbelverkalkung. Fortschr Geb Rontgenstr Nuklearmed Erganzungsband 1920; 40:292-298. Tsuchiya T. Tanaka N. Seikeigeka mook. 50. Tokyo: Kinbara, 1987; 44-58. [Japanese] Tsuzuki N. Ossification of the posterior gitudinal ligament (OPLL) of the cervical

its incidence

and

Vol lon-

histopathology.

Niti-

dokuihou 1987; 32:11-22. [Japanese] Batnitzki S. Powers JM, Schechter MM. Falx “calcification”: does this exist? Neuroradiology 1974; 7:255-260. Tobias JA, Solla KP, Sheldon JJ, Shapiro R.

Terayama

of falx ossification:

differential

K.

longitudinal

21 .

those

liga-

Ossification of the posterior ligament of the spine. Clin Orthop 1984; 184:71-84. Resnick D, Guemra J, Robinson CA, Vint VC. Association of diffuse idiopathic skeletal hyperostosis (DISH) and calcification and ossifi-

nition and 8:577-578.

20.

than

from

N.

MR demonstration 19.

other

diagnosis.

Ossification ligament.

recog-

AJNR

1987;

of the posterior

J Jpn

Orthop

Assoc

1976; 50:415-442. Takahashi M, Sakamoto Y, Miyawaki M, Bussaka H. Increased MR signal intensity secondary to chronic cervical cord compression. Neuroradiology 1987; 29:550-556. Yamashita Y, Takahashi M, Sakamoto Y, Kojima R. Atlantoaxial subluxation: radiography and magnetic resonance imaging corre-

lated

with

myelopathy.

Acta

Radiol

1989;

30:135-139. 22.

Luetkehans longitudinal

AJNR 23.

1987;

Hashizume

T.

Ossification

ligament

Pathology

by

S. Kishimoto

of spinal of the

Acta

of the posterior

diagnosed

MR.

8:924-925. Y, Iijima

ossification

ment.

TJ.

posterior

Neuropathol

cord

H, Yanagi

lesions

caused

longitudinal

by liga-

1984; 63:123-130.

of ossifi-

cation of posterior longitudinal ligament. Seikeigeka 1974; 25:704-710. [Japanese] Takahashi M, Yamashita Y, Sakamoto Y, Kojima R. Chronic cervical cord compression: clinical significance of increased signal intensity on MR images. Radiology 1989; 173:219224. Key CA. On paraplegia depending on dis-

ease 10.

PSP,

18.

defects

be differentiated

canal. Arch Jpn Chin 1960; 29:1003-1007. [Japanese] Tsuyama N, Terayama K, Ohtani K, et al. The ossification of the posterior longitudinal ligament of the spine (OPLL). J Jpn Orthop Assoc 1981; 55:425-440.

spine:

McAfee PC, Regan JJ, Bohlman HH. Cervical cord compression from ossification of the posterior longitudinal ligament in nononientals. J Bone Joint Sung [Am] 1987; 69:569-575.

demyelin-

on T2-weighted

1 1.

4.

be

scribed. Chronic compression or minor trauma produces cord compression with various degrees of pathologic

changes,

severe

References

However, of cervical

ligament

more

dural

cannot

ing

obbe-

17.

ossification

from

changes (8,20). It is frequently in cases of continuous OPLL

in b. Posterior

ossification

Acknowledgment: We thank Gene W. McCartney, MD, for revising the manuscript.

2.

of the

CT scan

In summary, although ossification of the ligaments is not demonstrated, MR imaging nonmnvasively provides useful information about the degree and cxtent of spinal cord compression, as well as the character of the ossification. Conrelation of MR and pathologic findings in autopsy cases will be required in the future. U

disk hemniation, spondylosis, and segmental OPLL is often difficult with the use of only MR imaging. In addition, differentiated

axial

Ligament

on

between the vertebral body and the spinal cord, OPLL, especially of the continuous type, should the differential

logic served

cause this type can cause cord compression.

in demonstrat-

ossifications

and

on CT radiog-

shows irregular ossification of yellow ligament at TiO-1 1 material at T-10 clearly demonstrates ossification of the MR image (SE 400/30) obtained with 0.5-T unit shows mulscan in b. (d) Sagittal MR image (SE 1,800/100) obtained

of the ligaments

Rep 1838; 3:17-34. Tsukimoto H. A case drome of compression

of the spine. report: of the

autopsy spinal

Guys

Hosp

of syncord ow-

June

1990