Acta Neurochir (Wien) (1997) 139:954-960 Acta N e u r o c h i r u r g i c a �9 Springer-Verlag 1997 Printed in Austria

Giant Intrasacral Schwannomas: Report of Six Cases

J. Dominguez ~, R. D. Lobato 1, A. Ramos 2, J. J. Rivas ~, P. A. G6mez l, and S. Castro 1

1Department of Neurosurgery and 2Service of Neuroradiology, Hospital "12 de Octubre", Madrid, Spain

Summary Only 4 of the 30 previously reported cases of giant sacral

schwannomas have been studied with Magnetic Resonance Imag- ing (MRI). We are reporting 6 more cases, 5 of which had MRI studies. There were 5 women and 1 man (average age 45 years) with long lasting symptoms consisting of lumbosacral and radicu- lar pain accompanied by urinary disturbances and dysaesthetic sen- sations in the lower limbs. CT clearly defined sacral bone involve- ment but poorly demonstrated intraspinal tumour extension which was more evident in MRI studies. MRI also clearly showed the intrapelvic extension of the tumour, its relationship with the neigh- bouring structures and the dumbell growth pattern due to turnout extension through sacral foramina which are important data for making a properative diagnosis and surgical planning. Surgical treatment consisted of piecemeal turnout resection through a posterior approach in four cases. Two patients underwent operation through an abdominal transperitoneal approach followed by a sacral laminectomy. Total intracapsular resection was apparently achieved in 5 cases. Through an average follow-up period of 9.2 years and despite a rather conservative approach, the recurrence rate has been very low in our series and only one patient had to be re-operated on for tumour recurrence.

Keywords: Cauda equina; magnetic resonance; sacrum; schwannoma; spinal tumour.

Introduction

S c h w a n n o m a s are b e n i g n t u m o u r s tha t ar ise f r o m

the n e o p l a s t i c t r a n s f o r m a t i o n o f n e r v e shea th ce l l s

and t h e y are t y p i c a l l y f o u n d a l o n g p e r i p h e r a l n e r v e

roo t s o r c r an i a l ne rve s .

S p i n a l s c h w a n n o m a s are r e l a t i v e l y u n c o m m o n and

less than 1 - 5 % o f al l sp ina l s c h w a n n o m a s o c c u r in

the s a c r u m [2]. S c h w a n n o m a s a lso r e p r e s e n t a m i n o r

f r a c t i o n o f the d i f f e r e n t t ypes o f t u m o u r s a r i s ing f r o m

the s a c r u m [2, 22].

T h e r e are 30 p r e v i o u s l y r e p o r t e d cases o f sacra l

s c h w a n n o m a s [1 -4 , 7 - 1 2 , 14, 1 6 - 2 1 ] . W e are r epo r t -

i ng o u r e x p e r i e n c e w i t h s ix cases o f g i an t sacra l

s c h w a n n o m a w h i c h o r i g i n a t e d w i t h i n the sacra l c ana l

and e x t e n d e d into the r e t ro r ec t a l space by e r o d i n g the

an te r io r w a l l o f the s ac rum.

Patients and Methods Five women and one man with giant sacral schwannomas have

been surgically treated in our Hospital between July '76 and Octo- ber '95. The ages of the patients ranged from 17 to 68 years (mean 45 years) (see Table 1). Five patients were symptomatic at the time of presentation and the duration of symptoms ranged from six months to 15 years (average 6.7 years). Four patients complained of pain which was initially localized in the lumbosacral region and extended to the territories of one or more lumbar or sacral roots later in their progress. Three of them also developed urinary hesi- tancy. One patient who was diagnosed after being admitted for a moderate head injury, had had occasional urinary incontinence without lumbar pain during the past five years. Two patients com- plained of dysaesthesiae involving the lower extremities. Finally, in one patient the sacral schwannoma was incidentally found during a routine gynaecological examination.

Neurological signs present in the 5 patients symptomatic at pre- sentation included lower extremity weakness in 2 cases, decreased deep tendon reflexes in 4, and diminished peri-anal or lower extremity sensation in 4.

Radiologic Diagnosis

Plain roentgenograms of the spine revealed extensive lytic sacral lesions with sclerotic borders in five patients. The lesion was limited to the right sacral wing in one case whereas in the remain- ing patients there was diffuse sacral destruction. Small punctiform calcifications scattered through the lesion were seen in one case.

CT, which was performed in four patients, showed both bone involvement and the presacral mass but poorly defined the intra- spinal extension of the turnout. Partial sacral destruction with well defined borders was present in all cases. In addition, CT showed involvement of the right sacro-iliac joint in two patients and wide erosion of the $1-$2 foramen in two other cases.

MRI was available in five patients. In one case it was performed 17 years after initial surgery when the patient developed massive tumour recurrence. The turnouts appeared iso-intense to hyperin- tense on T1 weighted sequences and hyperintense on T2 weighted

J. Domfnguez et al.: Giant Intrasacral Schwannomas

images except in one case in whom a striking hypo-intense appear- ance was seen.

In the three cases in whom Gadolinium-DTPA was adminis- tered there was an intense tumour enhancement that was very help- ful in delineating the tumour margins, especially the cephalad intradural extension above the sacrum observed in three of our cases. The average size of the presacral extension was 4.5 cm (range 1-10 cm). Although the intrapelvic structures were dis- placed anteriorly in two patients, no signs of tumoural invasion were detected in any case.

Two patients showed round or oval intratumoural areas which appeared hypo-intense on T1 weighted images and hyperintense on T2 weighted images, probably reflecting cystic degeneration. In one of these cases, punctiform calcifications could also be seen as small foci of hyperintense signals on T1 and hypo-intense on T2. Another important MRI finding was tumour extension through the sacral foramina in all but one of the patients forming a dumb-bell giant shaped mass in three cases.

Surgical Resection

In four of our patients surgical treatment consisted of microsur- gical piecemeal tumour resection through sacral or lumbosacral laminectomy. In the other two cases, surgery was initially per- formed by an abdominal transperitoneal approach followed by a sacral laminectomy with intracapsular resection until total removal was achieved according to the surgeon's judgement. No attempt was made to resect the tumour capsule. Three schwannomas extended intradurally requiring open dural procedures and the

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remainder were entirely extradural. Intra-operative nerve stimula- tors were not used. Since none of our patients showed signs of lum- bosacral or sacro-iliac instability we did not perform fusion proce- dures in any case. One of the two patients (Case 2) who had been operated on by a combined posterior and anterior approach devel- oped a massive tumour recurrence seventeen years after initial surgery; this 76 year old women was re-operated on through a posterior approach but the turnout could only be partially debulked because of profuse bleeding and secondary haemodynamic insta- bility.

Pathological Diagnosis

The histological studies showed the typical findings of schwan- noma in 4 cases i.e., a tumour with densely cellular Antoni A areas with well developed nuclear palisading alternating with Antoni B areas containing thick-walled blood vessels, abundant microcyst formation, clusters of haemosiderin laden macrophages and vari- able amounts of collagen tissue. One tumour (Case 6) showed the characteristic features of a degenerated neurilemmoma or ancient schwannoma and another tumour (Case 5), showing significant hypercellutarity, was included in the group of cellular schwanno- mas.

Results

N o n e o f o u r p a t i e n t s s h o w e d n e u r o l o g i c a l w o r s e n -

i n g a f t e r s u r g e r y a n d t h o s e c o m p l a i n i n g o f u r i n a r y

h e s i t a n c y - i n c o n t i n e n c e i m p r o v e d f o l l o w i n g o p e r a -

Fig. 1. T1 weighted sagittal image (a) demonstrates a giant sacral schwannoma with extensive intrapelvic component. The uterus (U) and bladder (B) are displaced anteriorly but not invaded. Hypo-intense areas within the tumour (arrows) represent areas of cystic degeneration. Postcontrast sagittal image (b) shows intense tumour enhancement excepting for the degenerative cystic areas

956 J. Domfnguez et al.: Giant Intrasacral Schwannomas

Fig. 2. Coronal T 1 (a) and T2 (b) weighted images show a schwannoma iso-intense on T 1 and hyperintense on T2 that produces a clear ero- sion of the left S1 and $2 neural foramina

Fig. 3. T1 weighted sagittal images before (a, left) and after (a, right) intravenous contrast injection show a well delineated schwannoma. The tumour erodes the L5 endplate and destroyes the two first sacral vertebral bodies. The intradural sacral extension of the tumour is bet- ter appreciated on the postcontrast image. Axial CT scan (b) demonstrates diffuse sacral destruction with extension into the right sacro-iliac joint. There are small foci of calcification or residual bone within the mass

tion. At subsequent cl inical eva lua t ion the patients

r emained asymptomat ic except for the w o m a n with

late tumour recurrence who suffered lumbosacra l pa in

and ur inary hesitancy. All patients have had postoper-

ative MRI controls. In one pat ient with assumed total

tumour resection, the early postoperat ive MRI

showed a small residual tumour. This pat ient has

remained asymptomat ic for the next four years with-

J. Domfnguez et al.: Giant Intrasacral Schwannomas 957

Fig. 4. Lumbosacral radiograph (a) shows a sacral lyric lesion limited to the right sacral wing. On the axial CT scan (b) there is a a polylo- bulated lytic lesion at S 1 level with clear involvement of the right sacro-iliac joint and presacral extension (arrows). The axial T 1 weighted MRI at an inferior level (c), shows the tumour dumbbell appearance with a huge presacral component that extends through the right sacral foramina. The bladder (B) and the rectum (R) are displaced anteriorly but not infiltrated by the tumour

out showing any change in tumour size on subsequent MRI controls.

The follow-up period is shown in Table 1.

Discussion

Of the malignant tumours originating in the sacrum, chordoma, chondrosarcoma and metastasic

lesions are the most common. Benign sacral lesions include giant cell tumour, osteoblastoma and aneurys-

real bone cyst whereas schwannomas are very rare at

this site [6, 22]. Though the female/male ratio was 5/1 in our series, there was no sex predilection in the 30 cases published up to now [1-4, 7-12, 14, 16-21].

Lumbosacral pain with or without accompanying dysaesthesia was the most prevalent symptom both in our patients and in the cases previously reported.

Decreased deep tendon reflexes and diminished lower

extremity sensation are among the most frequent neu-

rological signs found in these patients. Because of the large capacity for regional expan-

sion of the intrasacral space and the slow growth rate

of the tumour, symptoms develop late in the course of the disease when the tumour has reached a large vol-

ume in contrast to schwannomas localized in the more

proximal segments of the spine which cause compres-

sion of the spinal cord leading to an earlier diagnosis

[14, 21]. MRI has supplanted previous radiological studies.

Though it is inferior to the CT scan for evaluating the degree of bone destruction, it provides a better topo-

graphic display of the presacral mass because of its direct multiplanar imaging capacity. In five of our

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Table 1. Clinical Summary of the Six Cases Reported

J. Domfnguez et al.: Giant Intrasacral Schwannomas

Age/Sex Symptoms Surgical approach Pathology Follow up

Case 1 38 F Lumbar Posterior 1976 Benign Asymptomatic, pain,dysaesthesiae Schwannoma no recurrence urinary hesitancy on MRI

Case 2 59 F Lumbar pain, Posterior, Benign Recurrence urinary hesitancy anterior 1 9 7 6 , Schwannoma 1993

Posterior 1993

Case 3 68 F Lumbar pain, Posterior 1991 Benign Asymptomatic, urinary hesitancy Schwannoma no recurrence

on MRI

Case 4 23 M Urinary Posterior 1993 Benign Asymptomatic, incontinence Schwannoma small residual

tumour on MRI

Case 5 17 F Asymptomatic Anterior, Cellular Asymptomatic, Posterior 1 9 9 5 Schwannoma no recurrence

on MRI

Case 6 39 F Lumbar pain, Posterior 1995 Ancient Asymptomatic, dysaesthesiae Schwannoma no recurrence

on MRI

cases it clearly demonstrated the intraspinal and intra- pelvic extension of the tumour as well as the relation- ship with neighbouring structures. It also recognized the dumb-bell growth pattern due to the extension of the tumour through the sacral foramina which is very useful for an appropriate pre-operative diagnosis and surgical planning in these patients.

The choice of the surgical approach in patients with a suspected sacral schwannoma is dependent upon the degree of both sacral destruction and intra- pelvic extension which are in direct relationship with tumour size. Most authors have recommended an aggressive approach with the aim of achieving a com- plete resection even if it results in the loss of bowel or bladder control [2, 18]. Though we used a conserva- tive approach, the recurrence rate in our series was 16% with a follow-up period ranging from 18 months to almost 21 years (average 9.2 years). Abernathy et al. [2] reported a recurrence rate of 54% after a conservative approach (intracapsular enucleation) in their patients who were followed for periods ranging from 5 months to 33 years (mean 9 years).

A combined abdominosacral approach allows an easier resection of the intrapelvic tumour components and carries low risk of injury to the pelvic vascula- ture, whereas the posterior approach allows a better exposure of the nerve roots and the canda equina [13, 21]. Though we do not have experience with the corn-

bined abdominosacral approach we believe that by using current neuro-imaging techniques the patient can be followed accurately thus avoiding aggressive surgical manoeuvres at initial operation which can seriously affect the quality of life for the patient.

For the rare patient with high anaesthetic or surgi- cal risk, as in one of ours who developed profuse intra-operative bleeding, radiation therapy may be considered. Of the two patients previously reported who were treated by radiotherapy one showed tumour growth arrest for five years [ 11 ] and the other did not respond at all [9].

Histopathologically, neither our patients nor other previously treated cases showed signs of malignancy [1-4, 7-12, 14, 16-21].

One of the tumours in our series was an ancient schwannoma which is an unusual pathological variant with a high propensity to haemorrhage, calcification and formation of degenerative cysts; this tumour also contains cells with large atypical nuclei that may sug- gest a malignant diagnosis, in spite of the fact that mitosis are usually absent [5, 15].

Another tumour showed a significant increased cellularity and was classified with the group of cellu- lar schwannomas of Woodruff et al. [23]. Another four cases of giant sacral cellular schwannomas have been reported and while the three cases in the series of Abernathey et al. [2], did not show a more aggres-

J. Domfnguez et al.: Giant Intrasacral Schwannomas 959

sive behaviour than conven t iona l schwannoma, the

cel lular s chwannoma reported by Fe ldenzer et al . [9]

showed a rapid growth causing the pat ient ' s death one

year after diagnosis despite addi t ional radiotherapy

and chemotherapy. Though the fol low up in our cases

is still very short the cl inical behaviour has been also

benign.

Conclusions

Though both the n u m b e r of patients and the length

of the fol low-up are relat ively short in our series we

can draw the fo l lowing conclusions: 1) The durat ion

of symptoms in patients with giant sacral schwanno-

mas is extremely long (average 6.7 years) probably

due to the large capacity for regional expans ion of the

intrasacral space and the slow growth rate of the

tumour. 2) MRI is a most useful diagnost ic tool. In the

five cases in whom it was performed it clearly showed

the intrapelvic and intraspinal extens ion of the

tumour as well as its re la t ionship to the ne ighbour ing

structures; it also recognized a dumb-be l l growth pat-

tern due to ex tens ion of the tumour through the sacral

fo ramina that is useful for an appropriate pre-opera-

tive diagnosis and surgical p lanning . 3) Though we

used a rather conservat ive approach, none of our

patients showed neurologica l worsen ing after surgery

and the recurrence rate has been very low.

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11. Kotoura Y, Shikata J, Yamamuro T, Kasahara K, Iwasaki R, Nakashima Y, Yamabe H (1991) Radiation therapy for giant intrasacral schwannoma. Spine 16:239-242

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Comments

This is a very straightforward report of a rare cIinical entity. The various aspects, including clinical and radiological diagnosis and treatment are clearly described. The advice for a rather conser- vative surgical approach, consisting of intracapsular removal, seems wise in view of the benign course of the disease. Personally I have experienced a patient with a sacral schwannoma who showed malignant degeneration in the course of the disease. After treatment with radiotherapy and chemotherapy the condition stabi- lized for many years. This article reminds me of the lesson I learned from one of my old teachers that on plain X-ray films of the lum- bar, sacral vertebral column, abnormalities of the sacrum are often overlooked.

C. Avezaat

The neurosurgical group from Madrid presents here six patients, operated on for giant size intrasacral schwannomas. The

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first two patients were operated on 1976, one re-operated 1993, all the others have been treated in the 90's. Median follow-up is 3 years, mean follow-up 9.2 years and presented in the summary, what is not suitable for such extremely varying follow-ups.

The syndrome is not very common, and may he underdiag- nosed. I think that the authors are giving an important message, the tumour behaves in a benign way and it can be treated by conserva- tive intracapsular surgery either posteriorly or by a combined ante- rior and posterior approach.

All the patients were adults by the time of the operation, mostly symptomatic with duration between 6 month and 15 years. Lower extremity pain and dysaesthesia were the major symptoms, together with urinary difficulties. Diagnosis and operative planning were based on MRI, but CT also gave important information. All the cases are presented in one informative table, with the outcome

J. Domfnguez et al.: Giant Intrasacral Schwannomas

of the patient. There are 9 pictures of 4 patients, all very informa- tive.

The most important differential diagnostic lesions of sacrum are presented in the discussion part of the paper with good coverage of this subject. Conclusions are careful. Is there any connection of this syndrome to NF 1 ?

M. Vapalahti

Answer from the authors:

None of our cases showed NF1 criteria.

Correspondence: Jaime Domfnguez, M. D., Servicio de Neuro- cirugfa, Hospital "12 de Octubre", Ctra de Andalucfa Km 5.4, Madrid 28041, Spain.