Benign Lower Thoracic Intradural Schwannoma Compressing the Conus Medullaris and Mimicking Thoracolumbar Myofascial Trigger Point Pain: A Case Report

Original Article

Benign Lower Thoracic Intradural Schwannoma Compressing the Conus Medullaris and Mimicking Thoracolumbar Myofascial Trigger Point Pain: A Case Report

Christopher B. Roecker, DC, MS, DACO1, Gerald A. Anzalone, DC2, Casey S. Okamoto, DC3, Matthew J. Roes, DC, MD (deceased)4

1Assistant Professor, Palmer College of Chiropractic Life Science & Foundations Department

2 Adjunct Instructor, Kirkwood Community College

3 Doctor of Chiropractic, VA Medical Center Minneapolis, MN

4 Medical Doctor and Doctor of Chiropractic, Hiawatha, IA

Published: June 2017

Journal of the Academy of Chiropractic Orthopedists

June 2017, Volume 14, Issue 2

This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The article copyright belongs to the author and the Academy of Chiropractic Orthopedists and is available at: http://www.dcorthoacademy.com. © 2017 Roecker/Anzalone/Okamoto/Roes and the Academy of Chiropractic Orthopedists.

Abstract

Background The purpose of this report was to describe the clinical course, management, and outcomes of a male with thoracolumbar spine pain associated with an intradural schwannoma.

Case presentation A 49-year-old male sought care at an interdisciplinary medical clinic with rapid onset of paraspinal pain to the left of the thoracolumbar junction. The initial examination indicated myofascial trigger point pain of the left quadratus lumborum. The patient’s management included manual myofascial trigger point pressure release, active and passive muscle stretching, trigger point injections, prescription anti-inflammatory medication, prescription muscle relaxant medication, and narcotic pain medications over an 8-week period with a moderate reduction in pain. Following six treatment sessions, the patient reported a progression of left thoracolumbar paraspinal pain intensity, nocturnal low back pain, left hip and thigh pain, and bilateral leg weakness. The patient was referred for thoracolumbar spine magnetic resonance imaging, which demonstrated a lower thoracic spine intradural tumor effacing the conus medullaris. The patient was immediately referred for neurosurgical excision. Following surgery, the patient experienced complete remission of thoracolumbar spine pain and recovered his lower extremity strength. Histological evaluation later revealed the mass to be a lower thoracic intradural extramedullary schwannoma causing compression of the conus medullaris.

Discussion Clinicians managing persistent paraspinal trigger points with progressive pain and neurological dysfunction should be aware of the possibility of undiagnosed co-morbidities as complicating factors in clinical presentation. Progressive pain and neurological findings warrant referral for advanced imaging to screen for undiagnosed complicating conditions, such as an intradural mass. In this case, conus medullaris compression mimicked the clinical presentation of myofascial trigger point syndrome within the quadratus lumborum musculature and was later discovered to be associated with a lower thoracic benign intradural schwannoma.

Conclusion This case report describes the clinical presentation of a lower thoracic benign intradural schwannoma initially presenting with characteristics of myofascial pain. Serious neurological conditions may present with symptoms mimicking common musculoskeletal disorders.

Keywords (MeSH TERMS)

Spinal Cord Tumor; Compression, Spinal Cord; Myelopathy, Compressive; Myofascial Pain Syndrome; Trigger Point; Chiropractic

Background

Myofascial pain is pain that arises from muscles or fascia, and identification of this condition is particularly relevant to musculoskeletal clinicians.1,2 Myofascial pain is estimated to affect 44 million Americans annually3-5 and is one of the most common disorders encountered by physicians in clinical practice.6 The defining characteristic of myofascial pain is the presence of a myofascial trigger point (MTrP3,4,6-9, which manifests clinically as a hyperirritable nodule.2,3,10,11 MTrP pain has been reported to affect approximately 30% of pain patients reporting to general practitioners,12 and is thought to be the leading diagnosis among pain management specialists.4,13

The presence of MTrP pain has become recognized as a legitimate entity that is clinically significant within a musculoskeletal practice,1,6,13 but remains one of the most under-diagnosed or misdiagnosed conditions.6The diagnosis of MTrP pain remains purely clinical,2 and there is no universally accepted MTrP diagnostic criteria.2,3,10,11 While no well-validated diagnostic criteria exist for MTrP, common clinical features have been identified as being the most consistent and clinically relevant for diagnosing MTrP pain.2,9 A systematic review of the literature identified the four most commonly reported criteria cited for diagnosing MTrP and are listed in Table 1.9

Table 1: The 4 most commonly reported criteria for diagnosing a myofascial trigger point (MTrP)*

Criteria

1.

Tender spot (or nodule) in a taut band

2.

Patient pain recognition on tender spot palpation

3.

Predicted pain referral pattern (according to Travell and Simons)

4.

Local twitch response on muscle palpation

Table 1. Footnotes

*Derived by kind permission of Lippincott Williams & Wilkins from Tough EA, White AR, Richards S, Campbell J. Variability of criteria used to diagnose myofascial trigger point pain syndrome–evidence from a review of the literature. Clin J Pain. 2007 Mar-Apr;23(3):278-86.

Travell JG, Simons DG. Myofascial Pain and Dysfunction. The Trigger point Manual. Baltimore: Williams & Wilkins; 1983.

Management of myofascial pain is usually directed toward treatment of the MTrP along with the removal of perpetuating factors and should be systematically investigated for each patient.2,14 Therapy intended to alleviate MTrP pain includes various forms of manual myofascial release and soft tissue massage techniques, muscle stretching, acupuncture, therapeutic ultrasound, drug treatments, and MTrP injection.2,3 Correction of perpetuating factors may include addressing: abnormal posture, abnormal muscle activation patterns, anatomical defects (e.g. limb length inequality), mood disorders, or nutritional inadequacies.2 Currently, MTrP injection and muscle stretching is considered by some to be the standard management option for myofascial pain and has been demonstrated to improve patient outcomes.2,15,16

The purpose of this paper is to describe the case of a man treated for myofascial pain with manual trigger point release techniques, active and passive muscle stretching, soft tissue massage, trigger point injections, and prescription anti-inflammatory, muscle relaxant, and narcotic pain medications over an eight-week period. The patient’s pain was initially diagnosed as left thoracolumbar junction paraspinal MTrP pain, which occasionally referred pain to the left lateral hip and sacroiliac region. The thoracolumbar MTrP pain persisted, despite temporary pain relief immediately following treatment. Eight weeks after the patient’s initial presentation, neurological signs and symptoms rapidly developed. These progressive neurological findings prompted a thoracolumbar spine magnetic resonance imaging (MRI), which revealed a lower thoracic intradural extramedullary schwannoma and immediate neurosurgical decompression was performed.

Case presentation

Consent for publication of clinical information was provided by the patient, provided anonymity was preserved.

A 49-year-old white male sought chiropractic care for “moderate to severe” thoracolumbar spine pain at an interdisciplinary medical clinic. The symptoms began one day before seeking care and onset gradually following moderately intense housework. This initial pain onset was severely intense and rated as a 9/10 on an 11-point Numeric Rating Scale (NRS). The patient reported “dull” and “achy” pain localized to the left thoracolumbar paraspinal musculature without any pain referral or radicular symptoms. Moderate physical activities also provoked the patient’s pain.

The initial physical examination indicated left thoracolumbar paraspinal tenderness to palpation. Localized thoracolumbar paraspinal pain was provoked while assuming prone, supine, and seated positions, while performing lumbar spine flexion, right lateral bending, and right rotation active ranges of motion. The examination demonstrated normal lower extremity motor, sensory, and myotatic (stretch) reflex evaluations. Additionally, the exam failed to reveal tenderness to palpation and percussion along the thoracolumbar spine, and palpation of the thoracolumbar and pelvic soft tissues revealed localized pain and hypertonicity of the left quadratus lumborum (QL) musculature. Further palpation of the left QL reproduced the patient’s familiar pain, revealed a twitch response localized to the left QL, and caused a subtle involuntary withdrawal (jump sign).6 The patient did not reveal indications of constitutional symptoms, progressive neurological symptoms, or other “red flag” conditions; therefore, additional special studies or advanced imaging were not deemed necessary for diagnosis determination or to guide treatment of this condition. Following the physical examination, the patient was diagnosed with MTrP syndrome of the left QL.

The patient agreed to begin pain management care, involving combined chiropractic and medical sessions, home-based low back stretching and strengthening activities, and prescription medications pro re nata (PRN). The combined chiropractic and medical care consisted of manual MTrP pressure release (ischemic compression) 2, active and passive muscle stretching, soft tissue massage, postural modification, intramuscular trigger point injections (2.0 mL 2.0% lidocaine, 2.0 mL 0.5% Marcaine, 2.0 mL of Traumeel®), and prescription medication (Table 2). Immediately following the initial treatment, the patient casually reported an “80% improvement” in his left thoracolumbar muscle pain. The patient was instructed to continue with home-based strengthening and stretching, prescriptions medications as indicated, and to return to the clinic PRN.

Table 2: Medication management prescribed by the medical doctor following the initial evaluation

Class

Medication

Dose

Frequency

Count

Refills

Narcotic analgesic

hydrocodone/APAP

5/500 mg

PRN*

30 tablets

none

NSAID

Naproxen

500 mg

BID

60 tablets

none

Muscle relaxant

Metaxalone

800 mg

QID

40 tablets

none

Table 2. Footnotes

APAP, N-acetyl-p-aminophenol (acetaminophen); PRN, pro re nata (as needed); NSAID, non-steroidal anti-inflammatory; BID, bis in die (twice per day); QID, quater in die (four times per day)

*Not to exceed 1 tablet every 6 hours

Following the first treatment, the patient returned six days later with the return of the original dull and achy thoracolumbar pain along with emergence left sacroiliac (S-I) and hip region pain. The progression of symptoms prompted a reexamination, which revealed normal lower extremity sensory, motor, and myotatic reflex evaluations. The patient’s gait was unremarkable with a normal base of support. The patient rated his pain as 8/10 on a NRS. Thoracolumbar and pelvic soft tissue palpation revealed the persistence of the left QL MTrP pain with accompanying QL MTrP pain referral pattern.17 Following reexamination, the patient agreed to left QL MTrP pain management consisting of trigger point injection, manual trigger point release, passive stretching, and soft tissue massage. The patient casually reported an immediate and marked reduction of the thoracolumbar pain and abolition of the S-I region and groin pain.

Treatment continued six times over the eight week management period, consisting of continued trigger point injections, manual trigger point release, passive stretching, and soft tissue massages. The patient consistently reported relief of his pain complaints following treatment with a consistent and gradual return to pretreatment status. The patient reported overuse activities (e.g. prolonged sitting and repetitive lumbar flexion or rotation) correlating with each reemergence and overuse was thought to precipitate the left QL MTrP pain. The clinical presentation remained consistent with MTrP pain of the left QL and there was consistently an absence of abnormal neurological findings. Following each of the six visits, the patient reported immediate relief of his pain pattern by approximately 80%, with marked pain reduction following left QL MTrP injection therapy. Following six treatment sessions, at eight weeks after initiation of care, the patient returned to the clinic with severe pain, rated as a 10/10 on the NRS, and described the pain as “a different kind of pain.” The patient described spontaneous onset of nocturnal pain the previous night. He characterized this pain complaint as left localized thoracolumbar paraspinal pain of an intense “deep achy” quality associated with radicular pain into the left S-I and left hip regions, which caused him to assume an antalgic posture of combined lumbar flexion and right lateral bending. Additionally, the rapid onset of pain was associated with onset of bilateral lower extremity weakness while weight-bearing that was more pronounced on the left side. The patient reported an inability to ascend or descend stairs resulting from the lower extremity muscle weakness and antalgia. He also reported this recent onset of pain prevented him from obtaining comfort in the seated, side-lying, or supine positions, which prevented him from falling asleep. Again, the progression of symptoms prompted a reexamination. The physical examination elicited the original left QL MTrP pain upon palpation with reproduction of the referred pain pattern into the left sacroiliac and left hip regions. Lower extremity motor examination revealed reduced strength in left hip flexion and left knee extension, both graded 4/5 and lower extremity deep tendon reflexes revealed left patellar and Achilles hyperreflexia, graded as 3+. Lower extremity sensory examination was within normal limits and there was an absence of constitutional symptoms. A standard two-view lumbar spine x-ray series (anteroposterior and lateral) was performed following the physical reexamination. Lumbar spine plain film radiographs revealed the presence of mild lumbar levoscoliosis, hypolordosis, mild degenerative disc disease, and lower lumbar facet arthrosis.

In this situation, the presence of increased pain intensity and progressive neurological symptoms necessitated referral for a lumbar spine MRI to evaluate for the presence of neural compromise or myelopathy. The patient underwent a non-enhanced MRI immediately following the reexamination. The presence of abnormal signal patterns prompted the radiologist to suggest performing an enhanced MRI, using intravenous gadolinium, to optimize visualization of a suspected lesion. Impressions from the gadolinium-enhanced MRI revealed a heterogeneous high T2-weighted signal structure measuring 1.8 x 1.7 cm in the anteroposterior and transverse dimensions within the left aspect of the thecal sac, extending from mid T11 through the T12 level (Figures 1 and 2). The lesion appeared to arise from the left aspect of the conus medullaris with effacement of the right aspect of the thecal sac (Figures 1, 2, and 3). Thin circumferential contrast enhancement surrounded the tip of the filum terminale and extended to the L1 level.

C:\Users\christopher.roecker\Dropbox\Research Projects\Thoracolumbar Schwannoma\MRI\Images\1.jpg

Figures 1: Sagittal thoracolumbar spine MRI demonstrating the presence of a benign intradural schwannoma at the T11-T12 level

C:\Users\christopher.roecker\Dropbox\Research Projects\Thoracolumbar Schwannoma\MRI\Images\2.png

Figure 2: Fat-suppressed sagittal lumbar spine MRI demonstrating the presence of a benign intradural schwannoma at the T11-T12 level

C:\Users\christopher.roecker\Dropbox\Research Projects\Thoracolumbar Schwannoma\MRI\Images\3.png

Figure 3: Axial lumbar spine MRI demonstrating the presence of a benign intradural schwannoma at the level of T11-T12

The patient was referred for immediate neurosurgical consultation and emergency spinal surgery was performed to remove the mass. The patient underwent a decompression laminectomy of T11-L1 with resection or the intradural tumor under microscopy. Subsequent histological findings identified the mass as a benign intradural schwannoma.

Discussion

This case report describes a patient with an intradural schwannoma, mimicking a MTrP referral pattern and initially responding to conservative management before rapid onset and progression of neurologic symptoms. Re-evaluation, subsequent imaging including MRI with and without gadolinium contrast, and post-surgical histological findings revealed that an intradural schwannoma had arisen from and compressed the conus medullaris, resulting in conus medullaris syndrome (CMS). Spinal pain is known to arise from intradural and epidural tumors.18 Pain referral patterns from a MTrP located within the quadratus lumborum have been identified to project into the sacroiliac joint, lower gluteal region, iliac crest, adjacent lower abdomen, greater trochanter, and groin regions.17

CMS injuries occur in the region between the spinal cord and nerve roots; therefore, resulting in a variable clinical presentation of upper and lower motor neuron manifestations.19 Although there are no definitive diagnostic criteria, CMS is commonly associated with rapid onset of symmetrical neurological deficits. These neurological deficits typically involve a combination of saddle anesthesia, bowel or bladder incontinence, lower extremity hyperreflexia, and mild lower extremity weakness.19

This case was atypical in that the patient did not experience saddle anesthesia or bowel and bladder dysfunction, possibly as the result of early symptom detection and subsequent intervention. Also notable, the patient only exhibited hyperreflexia and motor weakness on the left side. One explanation for this could be the uncommon location of the tumor. Schwann cells, and thus schwannomas, are characteristically associated with the peripheral nervous system. Surprisingly, this schwannoma arose not from the nerve roots but from the conus medullaris, disproportionately affecting the left side. Intramedullary schwannomas are exceedingly rare, accounting for only 50 cases between 1931 and 2002.20 Isolated CMS is commonly the result of a non-traumatic primary intradural pathologic conditions (e.g. tumors or vascular lesions) and treatment typically involves early surgical decompression to recover neurological integrity.19

Schwannomas are the most common intradural extramedullary spinal tumor, representing 43% to 67% of tumors in this category.21-24 Schwannomas typically demonstrate an onset between the ages 30 to 50 years and may have a slight male predominance.25 Spinal schwannomas occur at all spinal levels and are typically intradural.25,26 Safavi-Abbasi et al have noted that the most frequent clinical presentation of schwannomas is pain and that most spinal schwannomas in non-neurofibromatosis cases can be surgically removed with very few postoperative deficits; however, preoperative autonomic dysfunction does not improve significantly after surgical management.26

Regarding neuroimaging, conus medullaris tumors may have similar features on MRI including infiltration of spinal cord tissue with compression of adjacent cord tissue, avid contrast enhancement and cystic or hemorrhagic components. The two most common differential diagnoses with these features include ependymoma and astrocytoma. As they have similar features on MRI, it is important to remember that biopsy is necessary to confirm diagnosis of conus medullaris tumors.

Musculoskeletal practitioners involved in the management of spinal pain conditions and/or myofascial pain syndrome should be aware of the possibility of undiagnosed non-musculoskeletal conditions that may mimic the clinical presentation of musculoskeletal pain conditions. Emphasis should be placed upon reexamination and consideration of special studies to inform an accurate diagnosis in the presence of unexplained progression of clinical presentation. In this case, an undetected lower thoracic benign intradural schwannoma was mistakenly managed as QL MTrP pain and later diagnosed as signs of CMS began to develop. The accurate diagnosis allowed the patient to receive decompressive neurosurgery, resulting in the immediate recovery of neurological functioning and elimination of thoracolumbar spine pain and referred pain patterns.

Conclusion

Serious neurological conditions such as CMS may present with symptoms mimicking common musculoskeletal disorders, including MTrP pain. Persistence or progression of neurological signs or symptoms and increasing spinal pain suggest non-musculoskeletal etiology and are indications for immediate advanced diagnostic imaging to evaluate for complicating neurological involvement.27

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying image. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

List of abbreviations

AP: anteroposterior

CMS: conus medullaris syndrome

e.g.: exempli gratia (for the sake of example)

L1: lumbar vertebra #1

L3: lumbar vertebra #3

L4: lumbar vertebra #4

MRI: magnetic resonance imaging

MTrP: myofascial trigger point

NRS: 11-point (0-10) Numeric Rating Scale

PRN: pro re nata (as needed)

S-I: sacroiliac joint

T2-weighted: spin–spin relaxation magnetic resonance imaging

T11: thoracic vertebra #11

T12: thoracic vertebra #12

QL: quadratus lumborum musculature

3+: a very brisk stretch reflex response (hyperreflexia)

Competing interests

The authors declare that they have no competing interests. Disclaimer: The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of Veterans Affairs or the US Government.

Authors’ contributions

CBR participated in the conception of the report, the revision, and coordination of the final manuscript. GAA was involved in the care of this patient, conducted the initial review of the case, and helped to draft of the manuscript. CSO contributed to the drafting of this report and made substantive contributions or the organization of this report. MJR was involved in the care of this patient and assisted in the early drafting of this report, prior to his death. All authors made substantive intellectual contributions to the report and meet the criteria for authorship.

Acknowledgements

The authors would like to thank Brenton L. Harris, MD for assisting with the neuroradiological interpretation involved with this case. The authors would also would also like to thank Siri Leech, DC, DABCR for her additional guidance on the interpretation of neuroimaging involved with this case.

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