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S1 radiculopathy due to adenocarcinoma: a case study.

Abstract: What may initially appear to be a classic presentation of a common condition--in this case sciatic radiculopathy from presumed disc herniation--can sometimes reflect a more ominous process. This article discusses the presentation, diagnosis, and management of a patient initially referred for neurosurgical consultation for S1 radiculopathy suspected to be due to a work-related injury. Final diagnosis was metastatic adenocarcinoma of the rectum.

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A 52-year-old white female was referred to our neurosurgery practice for management of severe low back pain with pain and paraesthesias radiating down the posterior aspect of the left lower extremity with worsening plantar flexor weakness. Approximately 1 month earlier, she had noted some left-sided low back pain while stocking some shelves at her place of employment. Along with back pain, over the next few days she began to note posterior left leg pain radiating to the lateral foot and began to walk with a slight limp. She saw her primary care physician, who, noting a positive straight leg raise test and depressed Achilles reflex on the left, prescribed a Medrol dosepak for presumed radiculopathy. Over the next few weeks her left leg pain and weakness worsened. Her primary care physician ordered a magnetic resonance imaging (MRI) scan of the lumbar spine and referred her for neurosurgical consultation for this suspected work-related injury.

The MRI scan demonstrated evidence of mild degenerative disc disease at the L4-L5 and L5-S1 interspace without significant compression of neural structures, with normal appearing vertebral bodies and curvature. The exiting nerve roots were clearly visualized on axial images. This was essentially a normal MRI scan for a patient of her age, although the study was somewhat limited by a degree of motion artifact reducing the image quality, and a contrast study had not been ordered by the primary care physician.

Past History and Family History

The patient's father had expired secondary to gastrointestinal cancer, the specifics of which were unavailable. Review of systems was negative. In particular, she reported no gastrointestinal symptoms whatsoever and denied any weight loss or gain. She had quit smoking several years ago, but had accumulated a 20-year pack-per-day history.

Physical Examination

The neurological examination revealed a pleasant, moderately obese female with an antalgic gait, favoring the left leg. Range of motion (ROM) of the lumbar spine was severely limited in all directions, accompanied by left-sided lumbosacral junction and left gluteal discomfort at the extremes of flexion and extension. The straight leg raise test was positive on the left at approximately 45 degrees and was negative on the right. Motor examination revealed a mild degree of gastrocnemius atrophy with severe weakness of plantarflexion on the left with the patient unable to raise the heel up off the floor. Ankle dorsiflexor strength was within normal limits as was testing of the proximal lower extremity muscle groups. The sensory examination revealed a deficit to pin prick in the S1 dermatomal distribution on the left and intact vibratory and position sense.

The Achilles reflex was only faintly obtainable, utilizing the Jendrassik maneuver. The right Achilles reflex was 2+ as were the remainder of the reflexes of the upper and lower extremities. The abdomen was soft and nontender.

In summary, the patient presented all of the signs of a classic unilateral S1 radiculopathy--sciatic distribution weakness, pain, paraesthesias, and reflex deficit with positive provocative test--without evidence of compression of the S1 nerve root on the MRI scan. She had failed to improve with steroids and relative rest and was requiring increasing amounts of narcotic medication for adequate pain relief. Even the patient voiced doubts that the relatively benign workplace back strain she had reported could be related to her current difficulties.

Differential Diagnoses

Diagnostic considerations included peripheral neuropathy, occult herniated nucleus pulposus not visualized on the MRI scan, or lumbosacral plexopathy of unknown etiology. Although diabetic peripheral neuropathy is far more commonly associated with femoral rather than sciatic neuropathy, it was deemed prudent to obtain a fasting and 2-hour prandial blood glucose level to rule out diabetes. An EMG-NCV study of the lower extremity is often helpful in differentiating radiculopathy from plexopathy or neuropathy, but not always conclusive. In this particular patient's case, the EMG-NCV could not be scheduled in an appropriately timely fashion. Consideration for a weight-bearing lumbar myelogram was also entertained because, at times, disc herniation can be appreciated on upright images but remain occult on recumbent MRI study.

It was decided, however, that the most efficient and useful initial approach would be to obtain a computed tomography (CT) scan of the abdomen and pelvis without and with contrast in consideration of a possible mass lesion causing a partial lumbosacral plexopathy. The CT scan revealed an infiltrating lesion within the S1 vertebral body with an adjacent left-sided mass and enlarged iliac lymph nodes. The lesion was much more clearly identifiable on the contrast CT study than on the earlier MRI.

Discussion

The lumbosacral plexus is formed by the ventral branches of the second to fifth lumbar nerves. The lower division of the fourth lumbar nerve joins the fifth, and the lumbosacral trunk thus formed becomes part of the sacral plexus, which includes the first four sacral nerves. The branches then supply pelvic and gluteal structures and lower limbs. Compression of the plexus can mimic radicular-type pain and cause motor, sensory, and reflex deficits, most commonly associated with herniated nucleus pulposus. Large lesions may present as neurogenic claudication or sphincter dysfunction, such as seen in cauda equina syndrome. Lesions affecting the upper plexus may be confused with femoral neuropathy when anterior thigh pain and paraesthesias or quadriceps weakness are the presenting symptoms. Apart from tumors, other causes of sciatica-type pain in the absence of radiculopathy due to herniated nucleus pulposus include the following: arachnoiditis, discitis, hip disease, compartment syndrome of the posterior thigh, sciatic nerve injury from intramuscular injection or projectile, Lyme disease, herpes zoster, and piriformis syndrome (Greenberg, 2001).

A percutaneous CT-guided needle biopsy of the lesion demonstrated moderately differentiated adenocarcinoma consistent with a gastrointestinal origin. A subsequent colonoscopy revealed the presence of a small lesion within the rectum, adenocarcinoma by pathology. Treatment options were discussed in consultation with radiation oncology, gastroenterology, and oncology specialists. The primary site was asymptomatic in terms of bowel obstruction or bleeding. The sacral metastasis was close in proximity to the primary lesion, yet surgery to attempt resection would likely result in significant functional deficit and unacceptable decline in quality of life without being curative. A combination of chemotherapy and palliative radiotherapy was felt to offer the best hope of alleviating pain and treating the sacral metastasis. The rectal lesion was also included in the radiation port. Concurrent radio-sensitizing doses of 5FU were begun along with the radiation therapy.

Following delivery of 3,500 rads tumor dose in 15 treatment fractions, the patient was pain free with improved leg strength and pelvic sensation. She is to continue on a chemotherapy regimen of Camptosar, Leucovorin, and 5FU.

Summary

Radiculopathy due to herniated nucleus pulposus is a common condition, frequently associated with traumatic injury. If a patient presents with symptoms coinciding temporally with a work related injury, this may obscure determination of the true etiology as the natural and legal inclination is to presume a causal relationship. However, when a patient has failed to respond to conservative management and standard imaging studies demonstrate no significant evidence for compression of central or foraminal neural structures, the differential diagnosis should include a plexus lesion. An electromyogram/nerve conduction velocity study and/or CT/MRI scan of the abdomen and pelvis should be considered because an abdominal or pelvic lesion should be a consideration when a patient presents with otherwise classic radiculopathy without evidence for disc herniation.

Reference

Greenberg, M.S. (2001). Handbook of neurosurgery. 5th ed. (p. 527) New York: Thieme.

Questions or comments about this article may be directed to: Mark C. Coles, MSN BA RN CCRN NP-C, by phone at 757/460-0455 or by e-mail at markco9917@aol.com. He is a nurse practitioner at Atlantic Neurosurgery, Virginia Beach, VA.
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Article Details
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Author:Coles, Mark C.
Publication:Journal of Neuroscience Nursing
Date:Feb 1, 2004
Words:1331
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