Journal of Surgical Oncology 39:8-16 (1988)
Nerve Sheath Tumors of the Sciatic Nerve and Sacral Plexus
EDWARD C. BENZEL, MD, DON M. MORRIS, MD, AND MARJORIE R. FOWLER, MD
From the Department of Neurosurgery (E.C. B.) and Pathology (M. R. F.) and the Department of Surgery and Oral and Maxillo-Facial Surgery (D.M. M), Louisiana State
University Medical Center, Surgical Service, Veterans Administration Medical Center (0. M. M), Shreveport
Eight patients with sciatic nerve and sacral plexus nerve sheath tumors, seen at Louisiana State University Medical Center in Shreveport, are presented. These cases illustrate the broad spectrum of pathology and modes of presentation of patients with nerve sheath tumors in this region. Patients can be divided into 4 groups. Group I includes subgluteal and/or thigh lesions with a well-defined mass on CT. Group I1 patients have neuroforaminal enlargement (defined by CT) and usually have radicular leg pain. Patients in group 111 have intrapelvic tumors with extension into the thigh.They usually have a poorly defined mass on CT. Group IV includes patients that have an intrapelvic mass (usually well defined) with radicular leg pain and/or mass effect.
CT scanning proved to be the diagnostic procedure of choice. It delin- eated the location and extent of the tumor and thus was important in determining resectability. The variable course of these tumors is empha- sized. A conservative nonoperative approach should be considered in asymptomatic and/or neurologically stable patients.
KEY WORDS: neurofibroma, schwannoma, Von Recklinghausen's disease
INTRODUCTION Nerve sheath tumors of the sciatic nerve and sacral
plexus are relatively uncommon. Their management re- quires knowledge of the characteristics of the tumor as well as the regional anatomy of the thigh and the sacro- pelvic region. In order to illustrate the variable clinical presentations and management schemes utilized, we are presenting a series of tumors treated at Louisiana State University Medical Center in Shreveport.
MATERIALS AND METHODS Eight patients with sciatic nerve and/or sacral plexus
nerve sheath tumors seen at Louisiana State University Medical Center in Shreveport, Louisiana, during the 2- year period ending July 1, 1984, are presented. Several patients were referred to Louisiana State University fol- lowing a surgical procedure elsewhere. Surgical excision of the tumor was performed if the patient had radicular pain or the tumor caused symptoms by virtue of its mass. Follow-up evaluation (3-5 years) included serial clinical observations and CT scans. 0 1988 Alan H. Liss, Inc.
RESULTS Clinical information concerning the eight patients pre-
sented is summarized in Table I. The patients were di- vided into four groups on the basis of their surgical presentation, tumor location, and CT findings (Table 11). Group I patients presented with radicular leg pain and/or a thigh mass. They did not have neuroforaminal enlarge- ment on CT scan and their tumors were well defined (cases 1-4). Group I1 patients presented with radicular symptoms and had neuroforaminal enlargement on CT (cases 6 and 7). Each patient in group 111 presented with a thigh mass with or without pain. These tumors were usually poorly defined on the CT scan (cases 5 and 8). Both patients in this group had Von Recklinghausen's disease. We did not treat any patients with group IV type tumors. This group is included because others have pre-
Accepted for publication October 14, 1987 Address reprint requests to Edward C. Benzel, M.D. , Chief, Division of Neurosurgery, Louisiana State University Medical Center, P.O. Box 33932-1501 Kings Highway. Shreveport, LA 71130-3932.
TA
BL
E 1.
Clin
ical
Sum
mar
y of
Cas
es
Cas
e N
o.
1
~ 2 3 4 5 6 I 8
Mod
e of
D
iagn
ostic
Lo
catio
n Si
ze
Oth
er
Sequ
elae
Tr
eatm
ent
ther
apy
... fo
llow
-up
Sex
Age
pr
esen
tatio
n V
.R.D
.d
proc
edur
e of
lesi
on _
_
(cm
) .
F F F F F F M
M
19
40
29
31
20
47
27 7
CT
Non
e
CT
mye
lo-
gram
C
T
CT
mye
lo-
gram
CT
rnye
lo-
gram
CT
mye
lo-
gram
CT
Thig
h 1
3X
6X
6
Tota
l sur
gica
l ex
tirpa
tion
Non
e
Non
e
Non
e
Non
e
Stab
le
Rad
icul
ar l
eg
+ pa
in d
urin
g pr
egna
ncy
thig
h m
ass
pain
pain
Larg
e bu
lky
-
Rad
icul
ar l
eg
+ R
adic
ular
leg
-
Thig
h pa
in
+
Thig
h 50
X 3
3 X
10
Su
rgic
al
debu
lkin
g To
tal s
urgi
cal
extir
patio
n To
tal s
urgi
cal
extir
patio
n B
iops
y
Scia
tic n
otch
6
X4
X3
Thig
h 10
X
10 X
8
Thig
h an
d re
trope
ri-
tone
um
Entir
e lo
wcr
ex
trem
ity
and
retro
peri-
to
neum
Prev
ious
hi-
opsy
and
at
tem
pted
su
rgic
al e
x-
cisi
on
else
whe
re
Man
agem
ent
inva
sion
of
iliac
vei
n
Dea
th fr
om
mal
igna
nt
nerv
e sh
eath
tu
mor
Pl
anta
r fle
x-
ion
wea
k-
ness
with
m
oder
ate
SI s
enso
ry
loss
St
able
Rad
icul
ar l
eg
-
pain
N
euro
fora
- m
ina
and
retro
perit
o-
neum
II
X2
X3
La
min
ecto
my
and
subs
e-
quen
t la
paro
tom
y
Rad
icul
ar l
eg
k
pain
and
pr
ogre
ssiv
e m
otor
and
se
nsor
y de
ficit
Thig
h m
ass
+
Ncu
rofo
r-
amin
a 6
X3
X2
In
itial
obs
erva
- tio
n fo
llow
ing
biop
sy
else
whe
re
Subs
eque
nt
rese
ctio
n of
tu
mor
and
L5
and
SI
nerv
e ro
ots
Thig
h an
d re
tropc
ri-
tone
um
Entir
e lo
wer
ex
trem
ity
and
retro
peri-
to
neum
Bio
psy
Prio
r atte
mpt
at
cxt
irpa-
tio
n an
d B
/K a
mpu
- ta
tion
plw
wh
prr
-.I- .
.
“Von
Rec
klin
ghau
sen’
s di
seas
e.
10 Benzel et al.
TABLE 11. Categorization of Sciatic Nerve and Sacral Plexus Nerve Sheath Tumors by Location and Clinical Presentation
Presenting CT appearance __ Location complaint Group -~
1 Subgluteal and/or thigh Radicular Icg and Well-defined mass
11
111 lntrapelvic with extcnsion Non-radicular pain Poorly defined usu-
thigh mass Neuroforarninal Radicular leg pain Neuroforaminal
enlargement
into thigh ally extensive
IV Intrapelvic without extcn- Radicular leg pain Usually wcll-de- mass
sion into thigh tined mass
Two patients presented with sciatica and had neurofor- aminal enlargement on CT scan with minimal if any myelographic pathology (cases 6 and 7; group 11). Patient 6 underwent a laminectomy for a suspected lumbar disc herniation. The preoperative myelogram (which had been performed several months before surgery) demonstrated minimal pathology. However, at the time of surgery, a histologically benign nerve sheath tumor (Fig. 4a) which extended into the retroperitoneum was found. The intra- spinal aspect of the tumor was resected wcll past the neuroforamina. A laparotomy was subsequently per- formed in an attempt to completely excise the tumor. The intraabdominal portion of the tumor was malignant and invaded the iliac vein (Fig. 4b). She was treated with radiation therapy postoperatively and died 1-1 / 2 years later.
Patient 7 had been biopsied elsewhere via a laminec- tomy and foraminotomy. This biopsy revealed a benign nerve sheath tumor. He subsequently underwent a radical
Fig. I . CT scan of a midthigh nerve sheath tumor. Note the clear resection Of the tumor Via a wide laminectomy and for& dcfinition of the tumor (arrows) from surrounding tissue. minotomy following a workup which included a CT scan
and rnetrizamide myelogram (Fig. 5). Prior to his second operation, this patient had progression of his neurologic deficit and an escalation of his radicular pain. The L5 and S1 nerve roots were sacrificed during the resection, due to the gross malignant character of the tumor and its
sented such cases [ 11. These tumors are located in the intimate relationship with these roots. In addition, frozen pelvis, do not extend into the thigh or the neuroforamina, section morphology demonstrated excess cellularity with and present with radicular leg pain or mass effect. some pleomorphism (Fig. 6 ) . It was felt that this radical
Four patients had tumors restricted to the sciatic nerve approach was indicated due to his previous surgery, the distal to the neuroforamina (cases 1-4; group I). Three gross and histomorphologic character of the tumor, and were removed in toto without sequelae following defini- its extent. Postoperatively the patient had a moderate tion of the tumor margins by CT scan (Fig. 1). All 3 of footdrop and a delayed mild hyperpathic pain syndrome. these patients presented with radicular leg pain. The Two patients with Von Recklinghausen’s disease pre- gross appearance of all these lesions was that of a sented with symptoms due to mass effect from tumors schwannoma (Fig. 2), but each proved to be a neurofi- involving the thigh and retroperitoneum (cases 5 and 8; broma histologically (Fig. 3). The fourth patient in group group 111) (Fig. 7). These patients were followed con- I (case 2), who had symptoms due to the tumor’s mass servatively after having undergone attempted surgical effect (50 x 33 x 10 cm), underwent debulking of the extirpation elsewhere. Neither has deteriorated clinically tumor without sequelae. over the last 2 years.
Sciatic Nerve Tumors 11
Fig. 2. Intraoperative photographs taken during tumor removal. a: Tumor of proximal sciatic nerve after exposure but before resection. Note fascicles in wall of tumor (arrowheads). margin of tumor (short arrows). and sciatic nerve (long arrows). b: The fascicles of the
sciatic nervc have been partially dissected from the tumor in a "bucket- handle" fashion. c: The tumor afkr dissection from the sciatic nerve. Fig. 2c appears overleaf:
U Benzel et al.
Fig. 2c .
ferred method of management for patients with these tumors is not well described. Robertson et al. presented a patient who had endured sciaticalike pain for 10 years before a CT scan demonstrated an intrapelvic sacral nerve sheath tumor which was surgically resected via a lapara- tomy [ l ] . This illustrates the unpredictable nature of these tumors. It is at times difficult to decide on appro- priate therapy for patients with these lesions because of this unpredictability .
Robertson et al.’s case also demonstrates the role of the CT scan in the diagnosis and management of patients with sciatic nerve and sacral plexus nerve sheath tumor 111. Powers et al. have illustrated the CT scan’s useful- ness in a series of 9 patients with peripheral nerve lesions [4]. We, likewise, found the CT scan to be a very useful
Fig. 3. myxomatous matrix which is characteristic of a neurofibroma. H.& tumor as well as its association with the sciatic nerve E. X400. and/or sacral plexus. This anatomic information aids in
the decision to attempt resection and in following the There were no group IV patients in this series. Robert- patient postoperatively.
son et al., however, have reported such a case [ 11. It is Patients in this series were placed into three of the four suspected that others have cared for patients with such categories of sciatic nerve and sacral plexus nerve sheath tumors but have not defined them as such in the literature. tumors presented here (Table 11). Group I tumors are
gencrally resectable and should be approached with the DISCUSSION intent of complete extirpation. Benign tumors with gross
Sciatic nerve and sacral plexus nerve sheath tumors are characteristics of schwannoma (Fig. 2) should be re- relatively uncommon [2,3]. The natural history and pre- sected without neurologic sequelae. It is possible to re-
A photomicrograph of the tumor from case 3. Note a loose tool. It allows the physician to view the extent Of
Sciatic Nerve Tumors l3
Fig. 4. (a): A photomicrograph of the tissue from patient 6’s first resection reveals a benign appearing Schwann cell neoplasm corn- posed of fairly uniform scattered Schwann cells with abundant inter- cellular myxoid matrix. H . & E. X400. (b): A photomicrograph of
tissue rcscctcd from thc rctroperitoneum at a subsequent operation reveals a highly cellular malignant area of the tumor which is invading retroperitoneal soft tissues. H. & E. X25.
Fig. 5 . (a) A metrizamide myelogram and (b) a CT scan through the SI neuroforamina in patient 7. Note the lack of gross myelo- graphic pathology even in the presence of prior surgcry (blunting but
not truncation of nerve roots). Also note the cnlargcment of the neuroforamina (arrows) and the enclosed tumor (arrowhead) on the CT scan.
move a schwannoma (while preserving all but one of the nerve fascicles) by peeling the nerve from the tumor itself in a bucket handle fashion (Fig. 2 ) . This was pos- sible in 3 of the 4 Group I patients in this series. Tumors in Group I patients can be removed via a posterior thigh sciatic nerve approach with the elevation of the gluteal muscles if necessary (Fig. 8). Stookey originally de- scribed this approach 151, which was elegantly illustrated by Henry [6 ] .
Group I1 patients offer a difficult therapeutic challenge due to the location of their tumors. The neuroforaminal region in the lumbosacral spine and the tissues just lateral to it are a “no man’s land.” The surgical exposure of the proximal neuroforamina is straightforward (via a lami-
impossible to reach without an extensive retroperitoneal
Fig. 6.
loose intercellular matrix H. & E. ~ 2 5 0 .
A photomicrograph of tissue removed from patient 7 reveals a somewhat cellular neurofibroma with mild pleomorphism and a nectomy)‘ The neuroforamina, however, is
14 Benzel et al.
Fig. 7. CT scan of a patient with Von Recklinghausen’s disease (case 5 ) and involvcmcnt of the retropelvic region demonstrated tumor
involvement (a) at the level of the acetabulam and the (b) midsacrum. The arrows outline the tumor.
dissection. A less-than-optimal chance for cure exists due to the limitations placed on the surgeon by the bony and soft tissue confines of the lumbosacral/pelvic region. In addition, the proximal tumors in this series (group 11) proved to be more aggressive than group I and group 111 tumors. Rubenstein has noted the aggressive nature of these lesions, especially those that originate in a nerve root 171. They may undergo malignant transformation to neurofibrosarcomas. A radical approach, as utilized in case 7, is warranted under these circumstances. Biopsy alone of these tumors may unnecessarily spread tumor cells and induce scarring. This makes a later curative resection difficult or impossible. Surgery, when appro- priate, should be undertaken with the intent of radical resection.
Group 111 patients usually harbor extensive disease, and unless the tumor mass causes great discomfort, the patient should be observed. The unpredictable nature of these lesions and their unresectability warrants a conser- vative approach.
Group IV tumors require resection via an infra- or intraperitoneal approach. A Pfannenstiel incision and a retroperitoneal exposure may be appropriate for most of these tumors 181.
The management of the patient with an undiagnosed tissue mass involving the leg and/or buttock depends primarily on the histology of the lesion. Because of recent advances in the treatment of patients with soft tissue sarcomas, an accurate diagnosis is mandatory be- fore undertaking a curative operation. Tissue must be obtained for histologic study. Although needle and aspi- ration biopsies may be attempted, they frequently do not provide adequate tissue for a definitive diagnosis. Inci- sional biopsy, which provides adequate tissue for study, is the method of choice. The tissue should be large enough so that the cell of origin can be determined and so that the neoplasm can be evaluated for cellularity pattern, pleomorphism, necrosis, and the frequency of mitotic figures. Consideration should be given to fixing tissue for electron microscopy. Judicious use of immu- noperoxidase stains can also be helpful with the diagno- sis. Although a definitive diagnosis may be obtained by frozen section, it can be frequently difficult and usually does not yield the amount of information that can be obtained from more extensive microscopic examinations. Ultimately, with malignant tumors, patients will often require two operations: one for diagnosis (biopsy) and one for treatment (tumor resection and/or amputation, etc.)
When performing an incisional biopsy on a soft tissue mass, the operator should enter the tumor at the easiest accessible point. Dissection should be minimal. An ade- quate nontraumatized piece of tissue should be obtained ( 1 cm x 1 cm x 1 cm). Hemostasis should be meticulous (some soft tissue sarcomas are very vascular and hemo-
A i i
Sciatic Nerve Tumors 15
l B
Fig. 8. An illustration of the sciatic nervc approach to proximal sciatic ncrve tumors. a: The superior aspect of a proximal midline incision may bc extended laterally. b: ’The “gluteal lid” is opened, thus exposing the tumor hidden under the gluteal muscles.
stasis may be difficult). Every attempt should be made to avoid wound infections or hematomas. The presence of either will make a subsequent curative operation much more difficult.
In areas where the lesions are reasonably accessible, this policy is not difficult to follow. However, in patients who have lesions that are “malignant by location” (mar- gins of resection are limited by anatomical considera- tions, and further growth will generally compromise the patient’s activity or functioning-such as some of our group 11 patients), the approach described above may not be practical. In these situations, judgments must be made on clinical findings.
CONCLUSIONS Patients with nerve sheath tumors of the sacral plexus
and sciatic nerve may be grouped according to their clinical and CT scan findings. Grouping allows the for- mulation of a management plan. This is especially impor- tant when considering the variable clinical course of these lesions. It allows a conservative nonoperative approach for the asymptomatic or neurologically stable patient and an operative approach when total extirpation without sequelac is thought to be possible. The CT scan deline- ates pertinent anatomy and allows the surgeon to make a reasonable assessment of resectability .
REFERENCES Robertson JH, Cropper GR. Dalrymple S, Ackcr JD, McClellan GA: Sacral plexus nervc sheath tumor: Case report. NeurosurRcry - . 13:78-81. 1983. Das G u m TK. Braslicld RD, Strong EW, Haidu S: Benign soli- tary schwannomas (ncurileniomas). cancer 24h.5-366, 1569. White NB: Neurilcmomas of the extremities. J Bone Joint Surg [Am] 49: 1605-1610, 1967.
16 Benzel et al.
4. Powers SK, Norman D, Edwards SB: Computerized tomography
5 . Stcokey B: The techniquc of nerve suture. JAMA 74:1380-3385,
6. Henry AK: “Extensile Exposure. 2nd ed.” Edinburgh:Churchill
7 . Rubenstcin LJ: “Tumors of the Central Nervous System, 2nd ed.” Washington, Arrncd Forces Institute of Pathology, Washington D.C., 1972, 213.
8. Ingram AV: Miscellancous affections of the nervous system. In “Campbell’s Operative Orthopacdics. 6th ed.” Edrnondson AS, Crenshaw AH (eds): St Louis: The C.V. Mosby Company, 1980.
of peripheral nerve lesions. J Neurosurg 59: 131-136, 1983.
1920.
Livingstone, 1973.
