eMedicine Specialties > Physical Medicine and Rehabilitation > Plexopathy

Neoplastic Lumbosacral Plexopathy: Differential Diagnoses & Workup

Author: Rajesh R Yadav, MD, Assistant Professor, Section of Physical Medicine and Rehabilitation, MD Anderson Cancer Center, University of Texas at Houston
Contributor Information and Disclosures

Updated: Dec 4, 2008

Differential Diagnoses

Leptomeningeal Carcinomatosis
Radiation-Induced Lumbosacral Plexopathy

Other Problems to Be Considered

Other causes of lumbosacral radiculopathy
Primary plexus tumors
Epidural cord compression
Chemotherapy toxicity associated with intra-arterial treatment
Aortic aneurysms
Diabetes mellitus
Diabetic amyotrophy
Obstetric procedures
Trauma
Intragluteal injections

Meningeal carcinomatosis or leptomeningeal disease also may cause low back or leg pain with subacute motor or sensory involvement; however, patients with these conditions often demonstrate mental status changes, headaches, cranial nerve palsies, and/or nuchal rigidity.

In cancer patients with thrombocytopenia, retroperitoneal bleeding can cause plexopathy accompanied by a rapid onset of pain and neurologic signs that usually are fully developed in 24 hours. Other associated findings include flank, thigh, or low back ecchymoses. A retroperitoneal bleed usually involves the femoral nerve and occasionally will spread to other parts of the plexus.

Other causes of lumbosacral plexopathy to consider are idiopathic in nature, aortic aneurysms, diabetes mellitus, obstetric procedures, trauma, anticoagulation therapy, retroperitoneal hematomas, surgical intervention for mesenteric thrombosis, kidney transplantation, tuberculosis, and intragluteal injections.6,7,8,9,10,11,12

Acute pain is common with aortic aneurysm, and the resultant weakness typically worsens over 1-2 weeks and then stabilizes. A pulsatile rectal or abdominal mass frequently is observed.

Acute thigh pain with acute or insidious onset weakness can result from diabetic amyotrophy and can be difficult to differentiate from the pain associated with an aortic aneurysm. In diabetic amyotrophy, weakness is more often noted proximally, with relative sparing of distal lower extremity muscles.

Workup

Laboratory Studies

  • Results of lab studies depend on the type of cancer and the extent of involvement. Erythrocyte sedimentation rate (ESR), complete blood cell (CBC) count, alkaline phosphatase, protein electrophoresis, prostate specific antigen (PSA), and other cancer-specific labs may be abnormal, depending on the clinical situation. Uremia and hydronephrosis may be an issue with ureter obstruction, especially in patients with gynecologic malignancy.
  • Cerebrospinal fluid (CSF) studies may reveal elevated protein with negative cytologic findings.

Imaging Studies

  • The clinical diagnosis of neoplastic lumbosacral plexopathy (NLP) is confirmed by magnetic resonance imaging (MRI) or computed tomography (CT) scanning of the affected areas. MRI is preferred, because it is more sensitive and provides better detail than CT scanning.13
  • MRI is more accurate in soft tissues. Hydroureter or hydronephrosis are common findings at the time of diagnosis. Diagnosis can be difficult if the scan does not show a mass lesion, but repeating the study in another 4-6 weeks often reveals pathology that was not initially apparent. Increased T2 intensity within nerve trunks, with or without enhancement, has been shown with NLP.14
  • CT scanning of the abdomen and pelvis is probably the most valuable in diagnosis and gives more information on bony structures. Tumor, bony erosion, and lymphadenopathy are seen in 78% of cases. Clinical findings and CT scan levels do not always demonstrate positive correlation.
  • Positron emission tomography (PET) scanning can aid in the detection of active malignancy in the plexus region.15 However, the sensitivity or specificity of PET scanning in the diagnosis of tumor plexopathy is not yet clear.
  • Bone scanning reveals pelvic, sacral, or vertebral uptake in 60% of patients with NLP.
  • Myelography can be abnormal with malignant plexopathy (in 28-45% of cases).
  • Routine spinal and pelvic roentgenograms reveal bone destruction in 50% of patients with NLP.

Other Tests

  • Electrodiagnostic testing (electromyography [EMG], nerve conduction studies [NCSs]) reveals abnormalities in almost all patients with neoplastic lumbosacral plexopathy.16
    • Typical changes include acute and chronic denervation of the lumbosacral plexus. The findings are observed more extensively than would be suspected clinically. Side-to-side comparisons are helpful.
    • Myokymic discharges are not observed.
    • In the segments involved, decreased amplitudes of the evoked motor responses with normal or borderline nerve conduction velocities are noted.

More on Neoplastic Lumbosacral Plexopathy

Overview: Neoplastic Lumbosacral Plexopathy
Differential Diagnoses & Workup: Neoplastic Lumbosacral Plexopathy
Treatment & Medication: Neoplastic Lumbosacral Plexopathy
Follow-up: Neoplastic Lumbosacral Plexopathy
References
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References

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Further Reading

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Keywords

neoplastic lumbosacral plexopathy, plexus, lumbosacral, breast cancer, sciatic nerve, colorectal cancer, psoas, neoplastic, psoas muscle, femoral nerve, iliopsoas, iliopsoas muscle, ilioinguinal nerve, obturator nerve, abdominal cancer, cervical cancer, pelvic tumor, retroperitoneal tumor, NLP, lumbosacral plexus, lumbosacral plexopathy, proximal lumbosacral plexopathy, malignant psoas syndrome, MPS, malignant lumbosacral plexopathy, lumbosacral carcinomatous, neuropathy tumor-induced lumbosacral plexopathy, tumor, lumbar plexus, sacral plexus

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Contributor Information and Disclosures

Author

Rajesh R Yadav, MD, Assistant Professor, Section of Physical Medicine and Rehabilitation, MD Anderson Cancer Center, University of Texas at Houston
Rajesh R Yadav, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation
Disclosure: Nothing to disclose.

Medical Editor

Robert J Kaplan, MD, Associate Professor, Department of Physical Medicine and Rehabilitation, University of Kansas School of Medicine and Medical Center
Robert J Kaplan, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, Association of Academic Physiatrists, International Spine Intervention Society, and Physiatric Association of Spine, Sports and Occupational Rehabilitation
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Michael T Andary, MD, MS, Residency Program Director, Professor, Department of Physical Medicine and Rehabilitation, Michigan State University College of Osteopathic Medicine
Michael T Andary, MD, MS is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, and Association of Academic Physiatrists
Disclosure: allergan Honoraria Speaking and teaching

CME Editor

Kelly L Allen, MD, Regional Medical Director, IMX-Medical Management Services
Disclosure: Nothing to disclose.

Chief Editor

Robert H Meier III, MD, Director, Amputee Services of America; Active Medical Staff, Presbyterian/St Luke's Hospital, Spalding Rehabilitation Hospital, Select Specialty Hospital; Consulting Staff, Kindred Hospital
Robert H Meier III, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation and Association of Academic Physiatrists
Disclosure: Nothing to disclose.

 
 
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