대 한 방 사 선 의 학 회 지 1993 ; 29 ( 1): 39~ 45 Journal of Korean Radiological Society, January, 1993

Neurilemmoma of Extremities: MR Findings

Ki Bum Kim , M.D. , Kyung Jin Suh , M.D. , Duck Sik Kang, M.D.

Dφartmeηt 01 Radiology, Kyμngbμk Natioηal U.ηiversity College 01 Medicine

- Abstract-

Six patients with twenty histologically proven neurilemmomas of the extremities were studied using πlagnetic

resonance (MR) imaging.

The size , number , signal intensity on spin-echo T1Wl (TR 500-650ms/TE 14-25ms) and gradien t -echo

(TR 200-600ms/TE 14-20ms; J1 ip angle 25-30 0) image , enhancement pattern , detectability of nerve of origin ,

nerve-lesion relationship , and presence of a capsule were analyzed

The masses ranged from 1 to 12cm in longitudinal diameter and originated from the median nerve , ulnar

nerve, sciatic nerve , radial nerve , and tibial nerve. All the nerve tracts except for those of 5 lesions , which

could not be detected due to their small diameter , were visualized as low intensity tubular st ructures. All

visible nerve tracts were situated along the periphery of the lesion and this finding was considered to be

specific for neurilemmona. All neurilemmomas were isointense with the surrounding muscle on spin-echo

T1Wl and hyperintense on gradient-echo image . After a Gd-DTPA injection , all masses showed moderate

or m arked enhancement and more prominent inhomogeneity than that on nonenhanced scan . ln 19 out of

20 lesions (95 %), a low signal intensity capsule surrounding the m asses could be seen. Four of the six pa

tients showed multiple masses , which was unusual as neuri]emmoma usually arises as a solitary mass

ln conclusion , the MR findings , especially the eccentric location of the mass lesion from the nerve of

origin and the presence of a capsule , were useful in making a diagnosis of neurilemmoma of the extremity

and that multiple neurilemmomas were not uncommon

Index Words: Soft tissue , neoplasms , 40.37

Soft tissue mass , MR studies , 40.1214

Neoplasm , MR studies

INTRODUCTION

N eurilemmoma is a common benign tumor

arising from the neural sheaths of the peripheral

motor, sensory and cranial nerves. Although

there have been many reports dealing with MR

findings of spinal or cranial neurilemmoma (1-7) , only few literature has reported MR features of

the neurilemmoma of extremities (8)

We reviewed 6 patients with histologically

verified peripheral n eurilemmoma and attemp­

ted to find some specific features of this soft tissue

tumor. We evaluated the following MR

parameters:signal intensity on spin-echo T1WI

and gradient-echo image , detectability of the

nerve of ongm , nerve-lesion relationship , presence of a capsule , and number of lesions.

MATERIALS AND METHODS

A total of 20 lesions in 6 patients were examin-

이 논문은 1992년 6월 16일 접수하여 1992년 11월 2일에 채택되었음.

Received June 16, Accepted November 2, 1992

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Journa l of Korean Radiological Society 1993; 29 ( 1) 39~ 45

ed over a 10 month period. N 0 evidence of von

R ecklinghausen s di sease such as skin manifesta

tion of famil y history was identified in a ny of the

patients . The p a tients ranged from 24 to 64 years

of age ;four were m en and two were women. All

the examin tions were performed with a 0.5T

superconducting MR system (Max , GE m edical

system s, M ilwaukee , W1 , U .S.A) . A 10mm

thickness axial , coronal , and sagittal scan were

routinely used , and other parame ters such as

matrix size , field of view , and type of surface coil

varied according to size , site , and depth of the

lesion ‘ 1n all cases a sp in-ech o T 1 weighted se

quence (TR 500-650ms/TE 14-25ms) and

gradien t-echo (TR 200-600ms/TE 14-20ms ;f1 ip

angle 25 -30 ) sequ ence were performed. Gd

DTP A(O. l mmol/kg) enhanced T 1 W1 were ob

tain ed in each patie nts. Signal inten sity on the

spin-echo T 1 W1 and gradien t -echo image were

evaluated and expres sed as hypointense , isointen se , or hyperinte nse with muscle in tensi­

ty . T h e v isibili ty of the nerve of origin was also

dete rmined , as well a s it s relationship with th e

mass . The presen e of a capsule was determined

on th e MR imagings b y th e recognition of a low

signal inten sity rim a long the borders of the

lesion.

RESULT

T he masses originated from the median n erve , femoral nerve , uln a r n erve , scia tic nerve , radial

nerve , or tibial n erve , and most commonl y

Table 1. Ne rve of Origin and Num ber of the Lesion

Originated Nerves Number of Mass

Median nerve .Femoral nerve Ulnar nerve Sciatic nerve R ad ial nerve Tibial nerve

m 3

3

2

Total 20

a b c

Fig. 1. Case 1, A 44-yea r-old woman with multiple neurilemmomas of the medi an nerve. Tl-weighted (600/2 0) (a) and gradient-echo (300/20;flip angle 30 )coronal images . Six of eigh t 1ε s i on s are visualized (the 。 rher rwo lie distal to the carpal tunnel) as beaded appearance along rhe course of the medain nerve (arrows in b) , which is di splaced by the masses. The nodules show a homogenous intermediate signal intensity on TIWI and hi gh signal intensity on grad ient-e r:ho im age . A photom icrograph (c) of the tumor shows it to be composed of mainly Anton i A tissue

40 -

originated from the m edian nerve (Table 1). A

summary of our findings is presented in Table

2. Four of the six pat ients showed multiple

masses , up to eight les ion s (Fig. 1) , whi ch

or igin a ted from single or multiple nerves of on­

ly one extremity. All the neurilemmomas were

isointense with surrounding muscles on spin-echo

T1 WI and rela tively hyperintense on gradient­

echo image (Fig. 2)

Signal intensity was homogenous in 90 %

(18/20) and 80 % (16/20) on spin-echo T1WI and

gradient-echo image , respectively. Following in-

a

b

Ki Bum Kim , et al : Neurilemmoma of Extremities

travenous administration of Gd-DTPA , all the

tumors revealed modera te to marked enhance

m ent a nd signal inten sity was homogenous in

60% (12/20). The size ofthe tumors ranged from

1 to 12cm in longitudinal di a meter with a mean

of 3cm. When the les ion was m ore tha n 3cm in

longitudinal diameter , inhomogen eity was pro­

minent in those cases with cystic degenera tion

(Fig. 3). A low density capsule (Fig. 3a a nd 4c)

surrounding the m ass could b e seen in 19 out

of 20 lesions (95 % ). The nerve of origin , visuali z­

ed as a low intensity tubular structure (Fig. 3b) ,

Fig. 2. Case 2, A 55-year-old man with two neurilemmomas of th e sciatic nerve and one neurilem­moma of the femoral nerve . Pre contrast (left of a) and postcontrast (right of a) coronal Tl .weighted image (650/25) of the right thigh reveal two well-defìned solid lesions wi th a capsule (larger arrows in right of a) along the course of th e sciatic nerve (arrows in ri ght ofb), which displaced toward the peip­hery. 1n a precontrast image the le­sion is relatively homogenous, but a postcontrast image shows several nonenhanced cystic foci (thin a r­rows in right of a). Contiguous two coronal gradient-echo images (600/ 20; f1 ip angle 300

) (b) show homo­genous hyperintense femoral (left of b) and sciatic les ions. The lesion of the femoral nerve is the only one with no apparent capsule in this study.

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Journal of Korean Radi이 ogical Society 1993; 29 ( 1) : 39'" 45

a b c

Fig.3. Case 4, A 57-year-old man with cystic neurilemmoma ofulnar nerve. Precontrast coronal T1-weighted image (350/ 14) (a) shows a la rge inhomogenous insointense m ass with a thick capsule (a rrows in a). Gadolinium enhanced sagittal T1 WI (b) shows mostly cystic degeneration with only a sm all peripheral irregularly enhanced solid portion . T he di splaced ulnar nerve is well visualized (arrows in b ) . A photogra ph (c) ofthe m a ss shows it to be composed of m ainly Antoni B ti ssue .

a b c

Fig. 4. C ase6 , A 64-year-old woman with a neu ri lemmom a of the fem oral nerve. Sagittal T1 WI (500125) (a) and gradien t-echo image (600/20;flip an gle 30 0

) (b) ofright thigh reveal a 12 x 6 x 5cm , well-encapsula ted inhomogenou s and intermediate signal intensity (a) and a homogneous high signal intensity m ass . The nerve o f ori gin is located a long the posterior m argin of the m ass (arrow in a) . Axial postcontras t T1 WI (c) shows a thi ck low d en sity ca psule (arrows) surround ing the inhomogenou s m ass with multiple cystic components

” t

Ki Bum Kim , et al : Neurilemmoma of Extremities

Table 2. MR Findings of 20 Neurilemmomas

Presence of Capsule

MR Imaging Position T2WI Gd-enhancement of Nerve

No . of Size in Lesion long dia

Case/Age Nerve of (yrs)/Sex Origin TIWI

3/60/F

4/57/M 5/24/M

Yes Yes No Yes Yes Yes Yes Yes Yes Yes

Eccentric Eccentric Undetectable U ndetectable Eccentric U ndetectable Eccentric U ndetectable Eccentric Eccentric

Mod. (Hs) Mark. (1 ,1) Mark. (1)

Mark. (1 ,1) ) Mark. (1,’ H)

M‘o여d.‘ (H) Marg멘II때 (1) Mark. (H) Mod. (H) Mark ‘ (1)

Hyper (Hs) Hyper (H ,H) Hyper (H) Hyper (1 ,1)

Hyper (I ,H) Hyper (H) Hyper (1) Hyper (H) Hyper (H) Hyper (H)

Iso (Hs) Iso (H ,H) Iso (H) Iso (H ,H) Iso (H ,H) Iso (H) Iso (1) Iso (H) Iso (H) Iso (1)

1 (cm) 5, 3

3

4,2 2,1 1.5 6

1.2 1.5

12

no

n/---n/{

n/--i

il

--‘

l

’i

Median N Sciatic N Femoral N Median N Ulnar N Radial N Ulnar N Femoral N Tibial N Femoral N

1/44/F 2/51 /M

6/64/F

Note . -Iso = isointense; Hyper = hyperin tense; Mod. = moderate enhancement; H = homogenous; 1 = inhomogenous; Hs = all of 8 lesions are homogenous.

enhancement; Mark. = marked

paresthesia or local tenderness. In this study , however , 4 out of 6 patients showed multiple le­

sions and were associated with Tinel s sign or

tenderness . Occasionally a patient might have

multiple neurilemmomas which frequently are

associated with von Recklinghausen’ s disease , however in this study no case with skin

m a nifestation or family history was identified .

The tumors occured anywhere in the soft tissue or in the viscera , but the more common loca­

tion included the head and neck , especially the

lateral aspect of the neck , the extremities, trunk , mediastinum , and retroperitoneum (13)

Grossly , neurilemmomas commonly are

fusiform , round , or oval masses that are sharp­

ly circumscribed and encapsulated (9 ,10)

Neurilemmomas are usually less than 5cm in

diameter , however can be as large as 20cm. In

this study the size of the tumors ranged from 1

to 12cm in longitudinal diameter and the mean

diameter was 3cm. Larger lesions had cystic and

hemorrhagic foci (Fig. 3). It was possible to

dissect the tumor from the n erve of origin , since

the nerve of origin coursed along the periphery

of the tumor, f1attened along the capsule bu t not

encased within the substance of the tumor

The histologic appearance of neurilemmoma

alternates between compact cellular areas , which

” %

was detected in 15 1esions , but was unidentifiable

in 5. In all 15 lesions with detectable nerve

ongm , the nerves were located peripherally

around the mass

On microscopic examination , all the tumors

showed typical features of neurilemmoma com­

posed of compact cellular areas called Antoni A

regions and loosely arranged hypocellular areas

known as Antoni B region . However, no rela­

tionship could be established between the signal

intensity on spin-echo T1 WI and gradient-echo

image an d the histologic t y pe of the

neurilemmomas.

Neurilemmomas arise from the n eural sheaths

of the peripheral motor, sensory , and cranial

nerves , with the exception of the optic and olfac­

tory nerves, which lack Schwann cell sheaths and

are part of the central nerve system (9). They

occur in young and middle age adults , but no

age group is exepted (10). Women are affected

twice as often as men (11). The patients in this

study ranged from 24 to 64 years of age; 4 were

men and 2 were women. Neurilemmomas are

usually solitay and painless (12) , but when large

they can produce pressure symptoms of

DISCUSSION

Journal of Korean Rad io logica l SOciety 1993; 29 (1) 39~ 45

have historically been called Antoni A regions , and loosely ar ranged hypocellular areas known

as An ton i B regions ( 11 ,14) . Although all cases

of this stud y, like those described in the literature

(10 ,14) , revealed bo th Antoni A and B areas

within each of the tumors, small tumors less than

1cm in diam eter were composed of almost en­

tirely type A a reas (Fig. 1c) a nd large r tumors

tended to have the Antoni B component (Fig

3c)

Although a neuril emmoma is typi cally hy­

pointen se or isointense on spin-echo T 1 W1 and

hyperinten se on gradien t-echo image (2 ,4) , few

reports in the literature have described the MR

features of neurilemmoma of the extremities (8)

All of the 20 tumors studied were isointense with

the muscle on spin-echo T l W1 and hyperintense

on gradient-echo image. Eighteen (90 % ) out of

20 neurilemmomas showed a homogenou s signal

inten sity on spin-echo T1W1 , and on gradient­

echo image 16 (80 % ) were h om ogenous . On Gd­

DTPA enhan ced image , only 13 les ions (65 % )

were homogenous . T he causes of inhomogenei­

ty were cystic degenerat ion , hemorrhagic

necrosis , and fibrosis (4,13). Neurilemmomas are

frequ ently en capsulated whereas neurofibroma , which is on e of the most common peripheral

nerve tumors , is usually not (8). The MR detec­

tion of a capsule , visualized as a low in tensity

rim a long the rna rgin of the tumors , could

therefore be used as a crite rion to differentiate

neurilemmoma from neurofibroma (8). This

feature was found in 19 out of 20 lesion s (95 % ).

Neurilemmomas were located a lon g the nerve

trunks w hich could be visu a lized in 15 of 20 le­

sions (75%) on 1cm thickness contiguous sec­

tions. N ormal nerves appeared as low intensity

tubula r structures in all pulse sequences. Blood

vessels may h ave a similar appearence but they

could be distinguished from nerves by the ap­

precia tion of f10w phenomena within the lumen , such a s even-echo rephasing

1n conclu sion , combination of MR findin gs

such as peripherallocation of the nerve of origin , the presen ce of a capsule , and inhomogenous

signal in tensity primarily due to cystic degenera­

tion are helpfu l in making a diagnosis of

neurilemmoma. Even when the lesions a re multi­

ple , the possibility of neurilemmoma still exists

REFERENCES

1. Scotti G , Scialfa G , Colombo N , et al. MR im­aging of intradural extramedullary tumors of the cervical spine. J Comput Assist Tomorgr 1985; 9: 1037-1041

2. Hiroshi D , T sutoma T , Masumi K. et al. MR imaging of spinal neurinomas with pathological correlation. J Comput Assist Tomogr 1990; 14: 250-254

3. Lawrence M , Cohen AM , Schwartz S, David Rockoff. Benign schwannomas : Pathologic basis for CT inhomogeneities. AJR 1986; 147: 141 -1 43

4 박길선， 장기현， 한문희 등. 척추 신경 종과 수막종의

자 기 공 명 영 상 소 견. 대 한 방 사 선 의 학 회 지 1991 ; 27(3) : 337- 342

5. Takemoto K , Matsamura Y , H ashimoto H , et al. MR imaging of intraspinal tumors-capability in histological differentation and compartmen­talizat ion of extramedull a ry tumors. Neuroradiology 1988;30:303-309

6. Yasushi K , Tadayuki M , M asanobu N. et al.

Neurinoma of the oculomotor nerve: CT and MR features. ] Comput Ass ist T omogr 1990; 14: 658-66 1

7. Michael MA , Circic 1S . Wolff AP. MR diagnosis 01' acoustic neuromas . ] Comput Assist Tomogr 1 987 시 1 :232-235

8 ‘ Emilio C , Antonio L , Giorgio D , et al. MR of benign peripheral nerve sheath tumors. ] Com­put Assist Tomogr 1991 ;15:593-597

9. Michael LK. Tumors and tumorlike condition ofsoft tissue. 1n: KissaneJM , Anderson WAD , eds. Anderson's Pathology. 8th ed. St. Louis: Mosby, 1985;1 682-1684

10. Abell MR , Hart WR , OlsonJR. Tumors ofthe peripheral nerves system . Hum. pathol. 1970 ; 1 :503-504

11. Bonneau R , Bronchu P. Neuromu scular choristoma: a c1 inicopathologic study of two cases. AmJ Surg Pathol 1983;7:521-524

12. Alvira M , Mandybur T , Menefee G. Light

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microscopic and ult rastructural observat ions of

a m etastasizing m alignant epi theloid schwan­

nom a , Can cer 1976;38: 1977 -1 98 1

13 ‘ D asGupta T K , Brasfield RD , Stron g EW , et al.

〈국문 요약〉

Ki Bum Kim , et al Neuril em moma 01 Extremities

Benign solitary schwannom a (neurilem momas) .

C ancer 1969;24 :355-366

14 . Juan Rosai. Ackerman ’ s Surgical Pathology , 7 th

ed . St. Louis: M osby , 1989; 1564-1573

사지의 신경초종 : 자기공명영상 소견

경북대학교 의과대학 방사선과학교실

깅기 범 ·서경진·강 덕 식

병리조직학적으로 확진된 사지 신경초종 207H의 자기공명 영상소견을 종양의 크기， 갯수，Tl과 T 2 강조영상에서

의 신호강도， 조영증강소견， 종양발생신경의 발견 유무， 종양과 신경과의 위치 관계， 그리고 피막의 존재 유무를 중

심으로 분석하였다.

신경초종의 크기는 1- 12cm 이였고 종양이 발생한 신경은 157H (75%)에서 발견할수 있었다. 이들 신경은 모든 예

에서 종양의 주변부를 따라 주행하였고， 이 소견은 신경초종의 매우 특정적 소견으로 생각되었다. 모든 종양들은 Tl

강조영상에서는 근육과 동일한 신호 강도를 나타냈으며 gradient echo 영상에서는 고신호 강도를 나타냈다. 조영제

주입후 모든 종양들은 중등도 내지 현저한 조영증강을 보였으며 조영전보다 불균일하게 나타나는 경우가 많았다. 종

양을 둘러싸는 피막은 19예 (95%) 에서 발견되어 피막의 존재유무가 신경초종을 진단하는데 중요한 소견이라 생각되

었다. 총 6명의 환자중 4명에서 다발성 종양을 나타냈으며 이는 신경초종이 흔히 단발성이라는 대부분의 보고들과

차이를 보였다.

결론적으로 이러한 자기공명영상 소견들중 종양발생신경이 종괴 주변부에 위치하는 것과 피막의 존재등은 사지의

신경초종을 진단하는데 유용한 소견으로 생각되며 비록 다발성인 경우라도 이러한 소견이 관찰되면 신경초종을 의심

해야한다고생각된다.

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