Bilateral Femoral Nerve Compression by Iliacus

Surgery Today
Jpn J Surg (1993) 23:535-540
SURGERyTOOAY
© Springer-Verlag
1993
Bilateral Femoral Nerve Compression by Iliacus Hematomas
Complicating Anticoagulant Therapy
ZAIN ALABEDEENB. JAMJOOM,lABDULKARIMAL-BAKRy,2 ABDULKARIMAL-MoMEN,3 T AJUDDINMALABARy,4
ABDUL-RAHMANT AHAN,sand BASIMY ACDBS
Divisions of 1 Neurosurgery,
2 General Surgery,
PO Box 2925, Riyadh 11461, Saudi Arabia
-.
I
I
3 Hematology,
4 Radiology,
Abstract: An unusual case of bilateral femoral nerve compression caused by iliacus hematomas in a patient on anticoagulant therapy is herein reported with special reference
to the comparative diagnostic value of ultrasonography,
computerized tomorgraphy, and magnetic resonance imaging.
The importance of early surgical decompression is also
emphasized.
Key Words: femoral nerve compression, iliacus hematoma,
anticoagulants, imaging techniques
Introduction
,.
Femoral nerve compression caused by retroperitoneal
hematoma is a rare but well documented complication
of anticoagulant
treatment. 1-7 Heparin has been the
drug involved in most of the reported cases;2,S,8-12
however,
many patients with compressive
femoral
neuropathy
due to warfarin1,3,4,13 and phenindione7
treatment have also been reported.
Bilateral
retroperitoneal
hematoma
with femoral
neuropathy in patients on anticoagulants
is an exceptionally rare occurrence. We are aware of only four
such cases in the pertinent literature. 14-16In this report,
a fifth patient is described. The diagnostic value of
ultrasonography
(US),
computerized
tomography
(CT), and magnetic resonance imaging (MRI) in such
lesions is compared.
The most appropriate
surgical
approach
for the management
of bilateral
iliacus
hem atom a is also described.
Reprint requests to: Z.B. Jamjoom
(Received for publication on Jun. 8, 1991; accepted on
Sept. 11, 1992)
and 5 Neurology,
College of Medicine,
King Saud University,
Case Report
A 19-year-old single woman who had been receiving
estrogen and progesterone
for menstrual disturbances
developed a deep venous thrombosis of the left lower
limb. Anticoagulant therapy was begun with 1,000 units
of heparin infusion per h, and the dose was adjusted to
maintain
the activated
partial thromboplastin
time
(APTT) within 50-60 s. Ten days later, warfarin sodium
was added at a starting dose of 10 mg daily. The dose
was later gradually elevated up to 40 mg daily without
any change in the prothrombin time (PT). Three weeks
of warfarin treatment had elapsed when the patient
complained of a sudden onset of severe pain in the right
inguinal region.
The physical examination of the abdomen and right
leg was unremarkable
apart from some local tenderness
of the right inguinal area. The patient was afebrile. Her
PT was 16 s (control 15 s) and APTT 53 s (control
23-32s). An immediate US of the abdomen and pelvis
was reported to be normal. The patient was started on
analgesics while maintaining the anticoagulant therapy
as before. Her pain, however, became increasingly
worse; the next day a similar pain also appeared on the
left side. She felt numbness of the anterior aspect of
both thighs and held both legs flexed in the hip joints.
The neurological
examination
revealed bilateral incomplete femoral nerve palsy, right more than left. The
platelet count was 325 X 109/L, PT 12.8 s (control
12.5s) and APTT 66s (control 23-32s). Both heparin
and warfarin were discontinued. A repeat US of the abdomen (Fig. 1) revealed well defined, ovoid, and mixed
echoic lesions within both iliopsoas muscles, and the
possibility of bilateral iliacus hematomas or abscesses
was raised. A needle aspiration under US guidance was
attempted,
but only some 15 and 12 ml of dark blood
could be aspirated from the right and left lesions,
respectively.
A CT scan of the lower abdomen and
pelvis (Fig. 2) confirmed 2 days later the presence
536
Z.A.B.
Jamjoom
et al.: Bilateral Iliacus Hematomas
Skin
Subcutaneous
tissue
Hematoma in the
left iliacus muscle
Iliac bone
Gluteal
muscle
a
b
Fig. 1. a Ultrasonogram
of the left iliac fossa (longitudinal
section) showing a well-defined,
ovoid, and mixed echoic
lesion (±) in the iliac muscle, measuring 19 x 62mm. b
Fig. 2. Computerized
tomography
(CT) scan of the pelvis.
There are well-defined,
low-attenuation
areas (arrowheads)
in both iliacus muscles (measuring 28-41 Hounsfield units)
of two large low-density masses within both iliacus
muscles. The two masses proved to be of high signal
intensity on both Tl- and T2-weighted MRI, suggesting
subacute hematomas (Fig. 3). The clearest anatomical
details concerning location and extent of the hem atom as
were obtained from the coronal views of the retroperitoneal muscles of the lower abdomen and pelvis
(Fig. 4).
In the following days, the patient's condition gradually
deteriorated until the 7th day after onset of symptoms
the femoral nerve palsy was found to be complete
on the right side and moderately severe on the left.
Therefore, the surgical decompression of both femoral
nerves was considered to be the treatment of choice.
Drawing of a illustrating
the lesion and the neighboring
anatomical structures. A similar lesion measuring 27 x 65 mm
was found on the right side
A Pfannenstiel incision was made. At 2 cm lateral to
the outer edge of the rectus muscle and safegarding the
inferior epigastric vessels, the right external oblique
abdominal muscle and its aponeurosis were dissected
parallel to the direction of the muscle fibers. Similarily, the internal oblique and transverse abdominal
muscles were dissected laterally and posteriorly until
the iliopsoas muscle was exposed by an extraperitoneal
approach. The iliacus muscle appeared greenish under
the fascia and felt quite tense. The groove between
the iliacus and psoas muscles was rather shallow, and
the femoral nerve seemed to be compressed under the
lateral margin of the strong psoas muscle. The lower
part of the nerve was yellow-greenish. The iliacus
muscle was then incised along its fibers, and approximately 200 ml of the partially liquefied, partially clotted
hem atom a was evacuated from the muscle. The muscle
fibers surrounding the hematoma were necrotic, and
the hematoma cavity extended upward well beneath
the belly of the psoas muscle and downward almost to
the level of the inguinal ligament. The femoral nerve
appeared intact, and neurolysis was not performed.
The same procedure was then carried out on the left
side.
Postoperatively, there was a rapid reduction of both
the inguinal pain and paresthesia of the anterior surface
of the thighs. On the 3rd day after operation, the
patient was again able to stretch both her legs actively
in the knee joints, while a week later she was able to
walk independently for a short distance. On discharge 3
weeks after surgery, the femoral nerve functions had
returned to normal apart from a mild residual weakness
in the left quadriceps muscle.
Z.A.B. Jamjoom et al.: Bilateral Iliacus Hematomas
537
;
b
a
Fig. 3a,b. Magnetic resonance imaging (MRI) of the pelvis showing high-intensity lesions (arrows) in both iliacus muscles.
a Tl-weighted image (TR SE 640, TE 20). b T2-weighted image (TR SE 2100, TE 100)
anticoagulation for venous thromboembolism,
5 patients
(7%) developed
this complication.17
Based on the
anatomical location of the hematoma and the associated peripheral
neuropathy,
Reinstein
et al. 12 distinguished three distinct syndromes: (1) A hematoma
within the iliacus muscle resulted in isolated femoral
nerve dysfunction.
(2) A large hemorrhage
involving
the iliacus muscle and extending into the psoas muscle
caused both femoral and obturator nerve palsy. (3) A
retroperitoneal
clot extrinsic to both the iliacus and
psoas muscle was not associated with peripheral nerve
impairment.
Apter et al. 18 found that 3 of 27 cases
of femoral neuropathy
(11 %) were caused by retroperitoneal
hematoma
complicating
anticoagulant
treatment.
Fig. 4. MRI coronal section through retroperitoneum and
pelvis (TR SE 640, TE 20). It is obvious that both hematomas
(arrowheads) are limited to the iliacus muscles
Discussion
The exact incidence
of retroperitoneal
hematoma
during anticoagulant therapy is still not well known. In
a prospective study of 76 patients receiving heparin
Femoral neuropathy constitutes 74 % of all peripheral
compressive
neuropathies
complicating anticoagulant
therapy.l1
This disproportion ally high involvement
of the femoral nerve compared with other peripheral
nerves could be theoretically
accounted for by: (1)
topographical peculiarities of the course of the femoral
nerve, making it more vulnerable than other nerves to
compression by hematomas in the surrounding tissues;
(2) a predisposition
of the iliopsoas muscle to spontaneous intramuscular
hemorrhage in patients receiving
anticoagulant therapy; or (3) both.
The femoral nerve is a branch of the lumbar plexus,
originating from the nerve roots L2 to L4. Following
its initial course within the psoas muscle, the nerve
emerges from the lateral side of the muscle, where it
comes to lie between the iliacus and psoas muscle in a
shallow groove. Covered by the transversalis
fascia,
which is especially strong over the groove,19 the nerve
538
finally enters the femoral triangle, where it divides into
its terminaf branches.
Femoral neuropathy caused by retroperitoneal
hemorrhage presumably results from compression of
the nerve within its fascial compartment at two distinct
sites: (1) above the inguinal ligament by an iliacus
hematoma; and (2) within the femoral triangle by a
psoas hematoma.20,21 Injection studies in cadavers
have shown that the iliacus muscle is much less distensible than the psoas muscle. Therefore, small
volumes of fluid injected into the iliacus muscle would
produce a high-pressure swelling that would compress
the femoral nerve against the taut psoas tendon. The
inguinal ligament would act as a barrier, preventing
the diffusion of fluid into the femoral triangle, thus
augmenting the pressure on the iliac region.22 On the
other hand, large quantities of fluid must be injected
into the psoas muscle in order to produce pressure
upon the lumbar plexus divisions which make up the
femoral nerve within the muscle. Under these circumstances, however, a concurrent obturator nerve
palsy would also be expected.12,23 Therefore, it has
been assumed that in the case of psoas hematoma,
hemorrhagic dissection along the psoas muscle down to
the inguinal ligament would be necessary to cause
isolated femoral neuropathy. 23
It is possible that ischemia from compression of the
vasa nervosum also plays a role in the pathogenesis of
femoral neuropathy caused by iliopsoas hematoma.6,24
Brantigan et al. 25found ischemic necrosis of the nerve
and muscle in a patient who underwent delayed surgery.
It seems that the femoral nerve in the iliopsoas muscle
is not as richly vascularized as in the adjacent areas,
making the intramuscular segment of the nerve more
susceptible to ischemia.14 Nevertheless, there is no
explanation for the predisposition of the iliopsoas
muscle to intramuscular hemorrhage in patients on
anticoagulant drugs,
The clinical picture is fairly characteristic and consists of either an acute or subacute onset of severe pain
in the inguinal area associated with external rotation of
the leg and flexion at both the hip and knee. In addition
to tenderness of the groin, a swelling may be palpable
in the area. Signs of femoral nerve palsy ensue soon
after the onset of pain. These include numbness and
paresthesias on the anteromedial aspect of the thigh
and lower limb to the medial malleolus, corresponding
to the sensory distribution of the femoral nerve. The
knee jerk is either lost or becomes sluggish on the
affected side. Some weakness of the knee extensors is
always present, but it may be difficult to demonstrate in
the acute phase due to the pain.5,6,14 Some of the
patients develop a drop of the hemoglobin level or
even hypovolemic shock.5 As in the present case,
approximately 40% of the patients with compressive
Z.A.B. Jamjoom et al.: Bilateral IliacusHematomas
neuropathy by hem atom a complicating anticoagulation demonstrate laboratory clotting tests within
the accepted therapeutic range at the onset of
symptoms. 11
The lack of response to a relatively high dose of
warfarin in our patient is remarkable and raises the
possibility of potential warfarin resistance. This rare
condition may be hereditary,26,27 acquired as a result of
a special diet consisting of vitamin K-rich vegetables28,29
or nafcillin therapy, 30 or the result of extensive intestinal resection.31 In the present case, none of these
factors was present, and noncompliance was excluded
as warfarin was taken under the direct supervision of a
nurse. A study of the relatives was not conducted. To
our knowledge, this is the first case of presumable
warfarin resistance associated with retroperitoneal
hematomas. The hematomas are a complication of
the heparin therapy, and it is unlikely that warfarin
resistance played a role in their pathogenesis.
The differential diagnosis of compressive femoral
neuropathy includes incarcerated femoral hernia,
lumbar disc prolapse, or intraabdominal disease such as
appendicitis, diverticulitis, and peritonitis. 1,18,25Acute
suppurative arthritis or hemarthrosis of the hip may
present with similar symptoms, but is unlikely to cause
femoral nerve dysfunction?O
For an accurate diagnosis of a retropritoneal
hematoma it is essential to directly visualize the
clot and determine its exact local extension. Three
diagnostic modalities have emerged in recent years
which are capable of detecting retroperitoneal hemorrhages: high-resolution US, CT, and MRI. While US
imaging is the most simple, noninvasive, and inexpensive of all three methods, it provides only limited
information about the exact extent of the disease and
involvement of adjacent structures, especially when the
iliacus muscle is concerned.32 In contrast, a CT scan
permits clearer visualization of the retroperitoneal
structures.33,34 Pathological processes are usually
recognized by virtue of the asymmetry in size and/or
density they produce between the two sides of the
body.35 However, there are no pathognomonic signs
which allow for the distinction of various lesions, e.g.,
hematoma, abscess, or tumor.32,35 An exception is the
acute retroperitoneal
hemorrhage, which presents
usually as an area of elevated density values.36 In
comparison, an MRI study delivers better contrast
resolution, and when different pulse sequences are
utilized, both normal and abnormal tissues around the
muscles are more readily differentiable.32,37 Nevertheless, excluding subacute hematoma, which can be
diagnosed because of its high signal intensity on both
T1- and T2-weighted images, MRI does not seem to
offer, at present, any significant advantage over CT in
terms of specificity, 32,37
Z.A.B. Jamjoom et al.: Bilateral Iliacus Hematomas
The choice of management is controversial. While
some authors recommend a conservative approach,
others advocate immediate surgical decompression.
Nonoperative management consists in immediate discontinuation and, if necessary, the antagonization of
the anticoagulant therapy as well as the application of
strong analgesics followed by gradual mobilization.
Wells and Templeton5 estimated that 17 of 25 (68%)
patients reported in the literature had a good outcome
without surgery. They also expressed serious doubt
whether operative intervention would have improved
the outcome significantly. Other authors, on the other
hand, observed a high incidence of serious residual
neurological deficit in patients treated conservatively.7.1O.12.25
Surgical decompression often resulted in
a more rapid and complete recovery of the femoral
nerve function.6,14,15,20,21The best results were obtained when decompression of the nerve was carried
out within 48 h after the onset of symptoms. 11With the
availability of modern, high-resolution US, we believe
that aspiration of the hematoma under US guidance
should be always attempted prior to any operative
intervention. An adequate decompression by this relatively noninvasive procedure may well be expected in
cases of unclotted hematoma. However, once a clot
has formed, as in our patient, open surgery becomes
necessary. The extraperitoneal approach to the iliopsoas
muscle and the femoral nerve is the method of choice,
and a variety of incisions have been described, including
the subcostal,14 vertical midinguinal,15,19 oblique
anterolateral flank,6 and inguinal hernia incision.25
Bilateral iliacus hematoma has been usually approached
through two separate incisions. 15In our case, however,
adequate exposure of the pelvic retroperitoneum on
both sides was achieved through a single horizontal
suprapubic (Pfannenstiel) incision, which gives a better
cosmetic result, especially in the case of a young female
patient. Dissection of the oblique and transverse
abdominal muscles and their aponeuroses parallel to
the muscle fibers minimizes damage to the muscles and,
hence, the risk of postoperative abdominal wall
weakness.
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