Case Report

Spinal arachnoid cyst as an atypical insidious cause of acute back pain^?,??

Abstract

Back pain is a common complaint in the emergency department with etiologies causing temporary discomfort to immediate life threats. Spinal arachnoid cysts are thought to be rare and usually asymptomatic entities that have been known to cause progressive back pain. We report a case of an atypical cause of acute back pain in an otherwise healthy man with no findings initially concerning for a serious cause of his symptoms. His pain resolved in the emergency department, but he returned the next day with lower extremity monoparesis due to a previously undiagnosed arachnoid cyst requiring decompressive surgery.

Back pain is one of the most common chief complaints reported in the emergency department (ED). It accounts for 1% of all ED visits and is the second most common cause of lost workplace time [1]. Affecting up to 90% of the general population at some point in their life, the Total costs of low back pain in the United States exceed $100 billion per year [2,3]. Although this complaint is not usually associated with significant underlying pathology, the differential diagnosis of back pain does include several potentially life-threatening etiologies. As a result, a systematic approach ensuring the absence of certain “Red flags” on history and physical examination is often used to identify those patients who may most benefit from conservative diagnostic and treatment management. Accepted historical red flags include pain longer than 6 weeks, age less than 18 years or over 50 years, unexplained weight loss (greater than 10 kg within 6 months), major trauma in a young patient, minor trauma in an older patient, neurologic complaints or incontinence, night pain, unrelenting pain, a history of cancer or intravenous drug use, and fever, chills, or night sweats [2,4]. Conventional physical examination red flags include: fever, point vertebral body

^? No funding or outside support information or financial interest to disclose.

^?? Disclaimer: The views expressed herein are solely those of the

author and do not represent the official views of the Department of Defense or Army Medical Department.

tenderness, neurologic deficits, and positive straight-leg raise test [2,4].

We present a case of an otherwise healthy man who presented to the ED complaining of the acute onset of back pain with an initial examination unrevealing for any of the red flags thought to herald the presence of serious causes of back pain. However, during a subsequent ED visit, he was noted to have several subjective and objective neurologic complaints that ultimately resulted in the diagnosis of a spinal arachnoid cyst. Spinal arachnoid cysts are rare but potentially devastat- ing entities that have not been previously reported in the emergency medicine literature as a cause of acute back pain. A 42-year-old man presented to the ED with the acute onset of cramping upper back pain exacerbated by inspiration and movement that began 45 minutes before arrival. He denied recent trauma or similar past episodes. Also absent were complaints of nausea, vomiting, fever, weight loss, incontinence, weakness, and other neurologic complaints. In addition, the patient had participated in his usual physical Training regimen the day before, which included a 10-mile run, without problems. He had no prior medical or surgical history, was not taking any medications,

and had no allergies or family history.

Upon examination, the patient was alert and appeared in mild discomfort. His pain was still present and rated as 4/10 in severity. Initial vital signs were as follows: blood pressure, 179/93 mm Hg’ pulse, 52 beats/min; respiratory rate, 16 breaths/min’ oxygen saturation, 98% on room air; and an oral temperature, 98.2 ?F. All components of his physical examination were unremarkable with the exception of tenderness to palpation over the left trapezoid that repro- duced the pain. There was no midline cervical or thoracic spine tenderness. Screening laboratory studies including a complete blood cell count and serum chemistry panel were obtained and were within normal limits. A chest radiograph was also normal. The patient’s pain resolved with morphine and diazepam. He was discharged in the care of his wife with ibuprofen and diazepam as needed for pain, instructed to follow-up with his Primary care clinic the next day, and advised to return to the ED if his symptoms worsened or he had any other concerns.

The following day, the patient returned to the ED complaining of an inability to move his left leg, accompanied by paresthesias along the anterior left thigh and foot. His blood pressure was 142/77 mm Hg; pulse, 53 beats/min;

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respiratory rate, 16 breaths/min; oxygen saturation, 99% on room air; and an oral temperature, 97.2?F. Physical examination revealed marked left lower Extremity weakness (strength graded 3/5 at left hip flexors and 1/5 at remaining distal flexors and extensors). Sensation and deep tendon reflexes were fully intact bilaterally. Tenderness to palpation of the midthoracic paraspinal muscles was also appreciated. A head computed tomography without contrast, as well as repeat blood cell count and serum chemistry panel, was obtained with unremarkable results. Because the etiology of his complaint and evolving symptoms was uncertain, a neurology consultation was requested, and the patient was admitted to the hospital for further evaluation including a magnetic resonance imaging (MRI) of the thoracolumbar spine.

The patient’s MRI revealed an intradural extramedullary cystic mass, further classified as an arachnoid cyst, at T4-7. The radiologist observed moderate anterior mass effect on the cord that was most likely the source of the patient’s symptoms (Fig. 1). The patient underwent an emergent T4-7 osteoplastic laminotomy with intradural exploration and wide fenestration of the cyst. A postoperative computed tomography myelogram showed no extension of the cyst and confirmed ongoing decompression. His strength continually improved, and the patient was discharged home 8 days later ambulating with the assistance of a front-wheeled walker.

Spinal arachnoid cysts occur at a rare but uncertain frequency and are usually asymptomatic. Typically, they are

Fig. 1 Sagittal (top) and cross-section (bottom) MRI with white arrows indicating areas of Spinal cord compression by the arachnoid cyst at the level of the fifth thoracic vertebra.

incidental findings on MRI imaging and do not require any specific treatment other than observation. The cause of arachnoid cysts is still unknown, but possible etiologies described in the literature include congenital, traumatic, infectious, and iatrogenic causes [5-10]. Symptomatic cysts tend to present in a variable manner such that incorrect Initial diagnosis is common [3]. Frequently reported findings include progressive back pain, which is worse at night or when recumbent, gait difficulty, spastic or flaccid paralysis, radiculopathies, and worsening of symptoms with a Valsalva maneuver [5,6,11]. Less commonly reported signs include noncardiac chest pain and isolated urinary urgency [5,7]. A search of available medical literature revealed an absence of cases reporting spinal arachnoid cysts as an acute cause of back pain associated with paresis such as seen in the patient presented here.

After plain radiographs to exclude bony abnormalities, MRI is the preferred imaging modality to determine the presence and extent of a spinal arachnoid cyst. Computed tomography myelography can be used for patients in whom MRI is contraindicated and may provide additional valuable informa- tion about cyst architecture and any fluid communication that may exist [10,12]. When imaging excludes other more likely causes of a patient’s symptoms and confirms the presence of a spinal arachnoid cyst, surgical intervention is the most effective treatment. Complete resection is the preferred method, but in cases where location or vigorous adherence to the cord prevents this, drainage by fenestration may be used [5]. Back pain is an exceedingly common complaint in the ED for which emergency physicians should evaluate to identify the absence of serious presenting signs and symptoms to facilitate the exclusion of rare and Serious conditions. The use of clinical red flags seems to be an excellent tool to assist in guiding the aggressiveness of the diagnostic pursuit of an underlying cause of acute back pain. However, because early symptoms may not herald a more Serious disease, it is crucial for patients to be given thorough and proper counseling and return precautions. As illustrated in the patient presented here, infrequent and serious causes of acute back pain such as that from spinal arachnoid cysts do exist and can rapidly progress even after a reassuring initial presentation. Physician awareness and patient educa- tion reflective of this as well as the initiation of more aggressive diagnostic tools in the appropriate setting may allow for the timely identification and intervention of such

potentially devastating disease processes.

David T. Um DO Jason D. Heiner MD Christopher S. Kang MD

Department of Emergency Medicine Madigan Army Medical Center Fort Lewis, WA 98431, USA

E-mail address: [email protected] doi:10.1016/j.ajem.2009.12.014

Case Report

References

1. Rogers KG, Jones JB. Back pain. In: Marx JA, Hockberger RS, Walls RM, editors. Rosen’s emergency medicine: concepts and clinical practice. 6th ed. Philadelphia PA: Mosby Elsevier; 2006.

p. 260-7.

1. Della-Giustina DA. Emergency department evaluation and treatment of back pain. Emerg Med Clin North Am 1999;17:877-93.
2. Katz JN. Lumbar disc disorders and low-back pain: Socioeco- nomic factors and consequences. J Bone Joint Surg Am 2006; 88(Suppl 2):21.
3. Bigos S, Bowyer O, Braen G, et al. Acute low back problems in adults. Clinical practice guideline, quick reference guide number 14. Rock- ville, MD: US Department of Health and Human Services, Public Health Service, Agency for Health Care Policy and Research, AHCPR Pub. No. 95-0643; 1994.
4. Hughes G, Ugokwe K, Benzel EC. A review of spinal arachnoid cysts. Cleve Clin J Med 2008;75:311-5.

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1. Khosla A, Wippold II FJ. CT myelography and MR imaging of extramedullary cysts of the Spinal canal in adult and pediatric patients. AJR Am J Roentgenol 2002;178:201-7.
2. Durmaz R, Ozturk Z, Delen E, et al. Symptomatic foraminal extradural meningeal cyst. Turkish Neurosurgery 2009;19:91-5.
3. Honda E, Fujisawa H, Tunemaro K, et al. Symptomatic spinal arachnoid cyst triggered by seat belt injury: case report. Neurol Med Chir (Tokyo) 1998;38:168-72.
4. Lolge S, Chawla A, Shah J, et al. MRI of spinal intradural arachnoid cyst formation following tuberculous meningitis: case report. Br J Radiol 2004;77:681-4.
5. Endo H, Takahashi T, Shimizu H, et al. Thoracic intradural arachnoid cyst associated with surgical removal of epidural hematoma: case report. Neurol Med Chir (Tokyo) 2004;44:607-10.
6. Liu SH, Ho JT, Lai PH, et al. Huge spinal extradural meningeal cyst in the thoracolumbar spine: a case report of a rare cause of low back pain. Kaohsiung J Med Sci 2005;21:427-32.
7. Kumar K, Malik S, Schulte PA. Symptomatic spinal arachnoid cysts: report of two cases with review of the literature. Spine 2003;28:E25-E29.