Author Affiliation Maiya Smith, MD Morgan Ketterling, DO Alexander Gallaer, MD Rowan Kelner, MD Christine Raps, MD Allison M. Beaulieu, MD, MAEd

Case presentation
Discussion

ABSTRACT

Case Presentation

We describe a case of a 57-year-old male with multiple medical comorbidities who presented to the emergency department with a two-week history of upper back pain with associated numbness. Physical exam demonstrated sensory loss in a bilateral third and fourth thoracic dermatome distribution. The diagnosis of spinal arachnoid web was made based on neurological exam and imaging findings.

Discussion

Spinal arachnoid web is a rare diagnosis, but consideration is important, as early recognition and surgical intervention can resolve symptoms and prevent worsening neurological sequelae.

CASE PRESENTATION

A 57-year-old male with history of type II diabetes mellitus, renal transplant, coronary artery disease, and hypertension presented to the emergency department (ED) for numbness in his chest for two weeks, with associated upper back pain radiating to his chest bilaterally, and shortness of breath. He presented to an outpatient clinic for similar complaints one day prior and was started on a four-day course of prednisone for presumed pleurisy.

On examination in the ED, the patient was found to have decreased sensation in his third and fourth thoracic dermatome in a band-like distribution without additional neurologic deficits or skin findings. Magnetic resonance imaging (MRI) of the cervical and thoracic spine were obtained, showing a dorsal spinal arachnoid web (SAW) with slight compression of the spinal cord located at the third and fourth thoracic levels (Image, Video).

 

Image.

Magnetic resonance imaging with and without contrast showing focal anterior displacement of the thoracic spinal cord at the third and fourth thoracic levels (arrow). In the setting of a prominent dorsal subarachnoid space with altered cerebrospinal fluid flow dynamics, the findings demonstrate a dorsal arachnoid web.

Neurosurgery was consulted, evaluated the patient and reviewed imaging. No surgical intervention was offered at that time due to the patient’s significant comorbidities and moderate symptoms. He was discharged home from the ED with recommended close outpatient follow-up.

DISCUSSION

Spinal arachnoid web is a rare diagnosis. Within the meninges, there are three layers: the dura, arachnoid, and pia. The arachnoid is a thin membrane between the dura and pia that adheres to the brain and spinal cord.
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A SAW specifically refers to a focal thickening of the arachnoid, typically in the thoracic spine, which causes compression of the spinal cord and interferes with the free flow of spinal fluid within the dorsal subarachnoid space. It is thought that SAW represents a variant of arachnoid cyst formation. While this patient did not have radiographic evidence of syringomyelia, SAW is typically associated with syringomyelia and does not seem to be associated with trauma, hemorrhage, or inflammation.
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Presenting symptoms include back pain, upper/lower extremity weakness, and numbness.
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Imaging includes MRI or computed tomography myelography and often demonstrates a “scalpel sign” deformity at the site of the SAW, representing the focal dorsal indentation caused by the web, reminiscent of the pointed edge of a scalpel.
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However, the only definitive diagnosis for SAW is through surgical confirmation.

Spinal arachnoid web is likely under-recognized and under-diagnosed given its rarity. Diagnosis usually takes years, and treatment involves surgical lysis of the arachnoid band.
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Surgical intervention can completely resolve symptoms.
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Failure to diagnose SAW may result in worsening spinal cord function and neurologic function. Patients who have progressively worsening pain, paresthesia, or weakness in a dermatomal distribution without trauma or prior neurosurgical intervention should prompt consideration of this diagnosis. Emergency physicians need to be aware of this rare diagnosis given its possibly irreversible neurological sequelae including pain, numbness, weakness, and paralysis.
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Footnotes

Section Editor: Rachel Lindor, MD, JD

Full text available through open access at http://escholarship.org/uc/uciem_cpcem

Conflicts of Interest: By the CPC-EM article submission agreement, all authors are required to disclose all affiliations, funding sources and financial or management relationships that could be perceived as potential sources of bias. The authors disclosed none.

Address for Correspondence: Maiya Smith, MD, Department of Emergency Medicine, Helix Building, 5050, 30 N Mario Capecchi Drive, Level 2 South, Salt Lake City, UT 84112. Email: maiya.smith@hsc.utah.edu
8:300 – 301

Submission history: Revision received January 10, 2024; Submitted March 7, 2024; Accepted March 8, 2024

The Institutional Review Board approval has been documented and filed for publication of this case report.
Patient consent has been obtained and filed for the publication of this case report.

REFERENCES

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SUPPLEMENTARY MATERIAL

 

Video.

Magnetic resonance imaging with and without contrast demonstrating the “scalpel sign” seen at the third and fourth thoracic levels (arrow) due to the spinal arachnoid web.

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