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J Electrodiagn Neuromuscul Dis > Volume 24(3); 2022 > Article
Kim and Uhm: Postoperative Lumbar Plexopathy Secondary to Retroperitoneal Liposarcoma: A Case Report

Abstract

Liposarcoma is a rare malignancy that usually originates in the extremities or the retroperitoneum. The lumbar plexus, a complex neural network formed by divisions of the first four lumbar roots, penetrates the psoas muscle before it exits the pelvis. Owing to their anatomical proximity, neoplasms in the vicinity of the psoas muscle may involve the lumbar plexus. We report a case of postoperative lumbar plexopathy following resection of a recurrent retroperitoneal liposarcoma located in the dorsal aspect of the psoas muscle. A 50-year-old man visited a rehabilitation clinic for evaluation of proximal weakness of the unilateral lower extremity after resection of a recurrent liposarcoma of the left psoas muscle. Physical examination showed weakness of left hip flexion and knee extension accompanied by sensory loss in the left anteromedial thigh and the medial lower leg. An electrophysiological study revealed left lumbar plexopathy with selective involvement of the posterior divisions of the lumbar plexus. The patient could walk independently without a walking aid on level surfaces while he underwent exercise therapy. A comprehensive evaluation, including physical examination, use of imaging modalities such as computed tomography for anatomical characterization, and electrophysiological studies, is important for accurate diagnosis.

Introduction

The lumbar plexus is formed within the psoas major muscle anterior to the transverse process of the lumbar vertebrae, which lie along the ventral aspect of the pelvis. The terminal branches of the lumbar plexus, including the femoral nerve, emerge from the lateral border of the psoas muscle before passing the groove between the iliacus and psoas muscles [1]. Iatrogenic lumbar plexus injury can be caused by surgical intervention, producing a variety of neurological symptoms. The symptoms range from mild sensory loss at the thigh level to profound weakness of the proximal lower extremity muscles [2].
Liposarcomas are the most common soft tissue sarcomas of mesenchymal origin, which may occur in any part of the body, including the extremities, retroperitoneum, pelvis, and inguinal region [3]. Retroperitoneal sarcoma accounts for 10% to 15% of all soft tissue sarcomas [4]. Retroperitoneal sarcoma originating from the psoas muscle is typically high-grade in nature, meaning that it is characterized by a high rate of distant and local recurrence. Therefore, retroperitoneal sarcoma should be managed with perioperative or postoperative radiation therapy or chemotherapy in many cases [5]. We report a case of postoperative lumbar plexopathy involving the posterior divisions of the lumbar plexus, following resection of a recurrent retroperitoneal liposarcoma located in the dorsal aspect of the psoas muscle.

Case Report

A 50-year-old man visited a rehabilitation clinic for an evaluation of proximal weakness of the unilateral lower extremity. He underwent surgical resection of a very large (18 cm) retroperitoneal liposarcoma of the left psoas muscle 1 year prior to presentation (Fig. 1). The tumor recurred in the left psoas muscle 10 months postoperatively. The size of the tumor was measured as 4.5 cm on a contrast-enhanced computed tomography (Fig. 2). One month after the imaging study, he underwent repeat tumor resection. His surgical record revealed severe adhesions secondary to previous surgery, and a well-circumscribed lobulated mass measuring 10 cm was found. The mass was firmly adherent and located inside the dorsal portion of the left psoas muscle at the ventral aspect of the pelvic bone, completely encasing the intramuscular nerves. A histopathological evaluation revealed recurrent myxoid liposarcoma with positive Ki-67 staining in 5% of tumor cells, reflecting rapid growth of the tumor. All resection margins were negative.
The patient experienced proximal left lower extremity weakness and left anterior thigh numbness after the second tumor resection surgery, and he was unable to climb the stairs using alternate feet. A physical examination revealed sensory and motor deficits in the left lower extremity. Left-sided hip flexion and knee extension were classified as grade 3 and 0, respectively, on manual muscle testing using the Medical Research Council scale. Otherwise, normal strength was noted in other muscles of the left lower extremity. We observed hypesthesia in the left anteromedial thigh and medial lower leg with absent left-sided knee jerk. Despite significant weakness of the unilateral proximal lower extremity muscles, the patient could walk independently (without a walking aid) on level surfaces.
An electrophysiological study was performed approximately 50 days after symptom onset; a compound motor action potential was not recordable in the left femoral nerve, and sensory nerve action potentials were undetectable in the left saphenous and lateral femoral cutaneous nerves on nerve conduction studies (Table 1). Other motor and sensory nerve action potentials, F-waves, and the H-reflex were normal. Needle electromyography revealed abnormal spontaneous activity in the left vastus medialis, rectus femoris, and iliopsoas muscles, which showed no motor unit action potentials (MUAPs) (Table 2). The patient was diagnosed with postoperative lumbar plexopathy with selective involvement of the posterior divisions of the lumbar plexus after resection of retroperitoneal liposarcoma in the left psoas muscle.
The patient received postoperative radiation therapy (50 Gy/25 fractions) to the left retroperitoneum after the second surgery. His neurological deficits did not show any change after radiation therapy. The patient showed a slight improvement in left lower extremity weakness at a 2-year follow-up after his initial visit. His left-sided hip flexion was still classified as grade 3, while knee extension improved to grade 2 on a manual muscle test. He additionally developed significant quadriceps atrophy and neuropathic pain in the left anteromedial thigh and medial calf over a period of 2 years. Fortunately, he showed no further deterioration in gait function while he received neuropathic pain medications. A follow-up electrophysiological study performed 2 years after the first study revealed findings similar to those observed on a previous nerve conduction study (Table 1). On needle electromyography, the iliopsoas and rectus femoris muscles showed polyphasic MUAPs, reflecting evidence of reinnervation (Table 2). Currently, he is receiving chemotherapy to manage a second relapse of liposarcoma with peritoneal seeding.

Discussion

In this report, we present a case of lumbar plexopathy that selectively affected the posterior division of the lumbar plexus in a patient with retroperitoneal liposarcoma. The lumbar plexus is a distinct network of peripheral nerves derived from the L1 through L4 nerve roots. These rami pass downward and laterally along the psoas major muscle, where they eventually form a plexus. During its intramuscular course through the psoas muscle, the lumbar plexus divides into anterior and posterior divisions. The posterior divisions unite to form the femoral nerve. The lateral femoral cutaneous nerve also emerges from the posterior divisions [1]. In this case, liposarcoma recurred at a somewhat different location within the psoas muscle compared with that at initial diagnosis. Initially, the sarcoma developed at the ventral aspect of the psoas muscle, leaving the intramuscular nerve intact, although the size of the tumor was larger. However, the recurrent sarcoma developed deep inside the psoas muscle, involving the dorsal portion of the psoas muscle just ventral to the iliacus, and encased the intramuscular nerves. Despite meticulous fine dissection, it is presumed that the surgical removal of the tumor inevitably caused nerve injury.
Liposarcomas are soft tissue neoplasms that arise from adipose tissue. These are classified into several subtypes, and myxoid liposarcoma is the second most common subtype [6]. Complete surgical resection at the time of initial presentation is the most important prognostic factor for survival in patients with retroperitoneal sarcoma [7]. The risk of recurrence in myxoid liposarcoma was reported to be low, even in large tumors. In contrast to extremity sarcomas, complete resection of a retroperitoneal tumor along with an adequate resection margin is usually challenging owing to the large adjacent neurovascular structures, which frequently cause incomplete tumor resection. Consequently, nearly 70% of patients with retroperitoneal sarcomas develop recurrence [8]. Despite frequent recurrence, palliative debulking surgery may serve as a useful therapeutic approach to improve symptoms and prolong survival in this patient population [7]. Unfortunately, the overall 10-year survival rate was reported to be approximately 60% in patients with metastatic and recurrent myxoid liposarcoma [6]. In the case reported herein, recurrence of the tumor was observed after the surgical removal of the very large initial sarcoma, although all resection margins were negative. A previous study has shown that tumor size and depth are more relevant for the recurrence or metastatic characteristics of a neoplasm than the resection margin status [9].
We observed significant weakness and atrophy of the iliopsoas and quadriceps muscles, and needle electromyography revealed no MUAPs in these muscles. The iliopsoas and quadriceps are the primary hip flexor and knee extensor muscles. The patient was able to produce partial movements of hip flexion and knee extension, and could walk without assistance, although the electrophysiological study findings were compatible with no motor function in the anterior thigh muscles. This can be explained through compensatory action by the completely spared hip adductor and abductor muscles, which are known to play a secondary role in hip flexion and knee extension.
Nerve structures can be directly injured by transection, stretching, suture ligation and diathermy. Several studies have reported lumbosacral plexopathy after renal transplantation, gynecological surgery, or spinal interbody fusion [10]. Additionally, an abscess or hematoma affecting the psoas muscle can cause lumbosacral plexopathy [1]. However, few reports have described neuropathy associated with the surgical removal of retroperitoneal sarcoma in the psoas muscle. Additionally, retroperitoneal liposarcoma showed frequent recurrence. Therefore, postoperative lumbar plexopathy following repeated surgery might occur inevitably as in this case.
In conclusion, we describe a case of lumbar plexopathy with selective involvement of the posterior divisions of the lumbar plexus after the repetitive surgical resections of a retroperitoneal liposarcoma. A comprehensive evaluation, including physical examination, use of imaging modalities such as computed tomography for anatomical characterization, and electrophysiological studies, is important for an accurate diagnosis, planning treatment, and prevention of complications. Additionally, this case report has significance of the following points. It objectively confirmed the extent and degree of postoperative lumbar plexopathy through an electrophysiological study, which is difficult to diagnose with images alone, reported the progress of recovery, and represents importance of detecting the occurrence of neurological complications.

Conflict of Interest

No potential conflict of interest relevant to this article was re¬ported.

Fig. 1.
Contrast-enhanced computed tomography scans of the abdomen and pelvis showing a well-defined, mildly enhancing soft tissue mass suggestive of a liposarcoma (arrows) in the left psoas muscle (maximal 14 cm) and the presumed location of the nerve structures within the psoas muscle (arrowheads). Coronal view (A), axial view at the level of L4 vertebral body (B), and sagittal view (C). The dotted line indicates the coronal plane corresponding to (A).
jend-2022-00101f1.jpg
Fig. 2.
Contrast-enhanced computed tomography scans of the abdomen and pelvis showing a bulging soft tissue lesion suggestive of a recurrent liposarcoma (arrows) at the posterolateral aspect of the left psoas muscle (maximal 4.5 cm) and the presumed location of the nerve structures within the psoas muscle (arrowheads). Coronal view (A), axial view at the level of L4 vertebral body (B), and sagittal view (C). The dotted line indicates the coronal plane corresponding to (A).
jend-2022-00101f2.jpg
Table 1.
Nerve Conduction Studies
Nerve and site Initial
Follow-up
Latency (ms) Amplitude Conduction velocity (m/s) Latency (ms) Amplitude Conduction velocity (m/s)
Motor nerve conduction
 Rt. peroneal nerve (EDB) 5.26 3.2 NA 5.36 4.5 NA
 Rt. tibial nerve (AH) 4.11 16.4 NA 3.85 15.8 NA
 Rt. femoral nerve (VM) 5.31 11.9 5.26 14.1
 Lt. peroneal nerve (EDB) 4.11 3.4 46.1 3.80 5.0 46.9
 Lt. tibial nerve (AH) 4.43 15.1 44.7 3.70 15.0 45.0
 Lt. femoral nerve (VM) No response No response
Sensory nerve conduction
 Rt. superficial peroneal nerve 2.50 9.5 2.45 14.7
 Rt. sural nerve 2.71 20.5 2.60 16.3
 Rt. saphenous nerve 1.72 9.7 1.67 7.3
 Rt. LFCN 1.72 8.5 1.77 5.6
 Lt. superficial peroneal nerve 2.76 14.1 2.29 16.1
 Lt. sural nerve 3.02 18.2 2.76 16.2
 Lt. saphenous nerve No response No response
 Lt. LFCN No response No response

Amplitudes are measured in millivolt (mV, motor) and microvolt (μV, sensory).

Rt., right; EDB, extensor digitorum brevis; NA, not assessed (proximal stimulation was not performed); AH, abductor hallucis; VM, vastus medialis; Lt., left; LFCN, lateral femoral cutaneous nerve.

Table 2.
Needle Electromyography
Muscle Initial
Follow-up
IA Fibrillations & PSW MUAP Recruitment IA Fibrillations & PSW MUAP Recruitment
Lt. Iliopsoas - 3+ No MUAP - 2+ Polyphasic Reduced
Lt. adductor longus - - Normal Normal - - Normal Normal
Lt. rectus femoris - 3+ No MUAP - 3+ Polyphasic Reduced
Lt. vastus medialis - 3+ No MUAP - 3+ No MUAP
Lt. tibialis anterior - - Normal Normal
Lt. tensor fasciae latae - - Normal Normal
Lt. gluteus medius - - Normal Normal
Lt. gluteus maximus - - Normal Normal
Lt. medial gastrocnemius - - Normal Normal
Lt. mid lumbar paraspinalis - - - -
Lt. lower lumbar paraspinalis - - - -

IA, insertional activity; PSW, positive sharp wave; MUAP, motor unit action potential; Lt., left.

References

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