Background: Dorsal arachnoid webs constitute abnormal formations of arachnoid that tend to occur in the upper thoracic spine and can lead to spinal cord displacement. Patients typically present with back pain, sensory disturbances, and weakness. It may also obstruct the cerebrospinal fluid (CSF) flow, leading to syringomyelia. In magnetic resonance (MR) studies, the "scalpel sign" is a classical finding, and it may also be accompanied by syringomyelia attributed to CSF flow. Definitive surgical resection is the mainstay of treatment.
Case description: A 31-year-old male presented with mild weakness in the right leg and diffuse lower extremity sensory changes. The MR showed the typical "scalpel sign" at the T7 level consistent with diagnosing a spinal arachnoid web. He underwent a T6-T8 laminotomy for lysis of the web and decompression of the thoracic cord. Postoperatively, his symptoms improved markedly.
Conclusion: Surgical resection is the treatment of choice when an arachnoid web is documented on an MR and correlates with the patient's clinical symptoms/signs.
Keywords: Laminotomy; Scalpel sign; Spinal arachnoid web; Syringomyelia; Thoracic dorsal arachnoid web.
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