Dorsal thoracic arachnoid webs are due to a deformity in the formation of arachnoid membrane in the spinal arachnoid space. These webs usually occur in the upper thoracic spine and are viewed on imaging as a pathogonomic ‘scalpel’ sign because of the resemblance on sagittal MRI to a surgical scalpel. We describe a case of a patient with a neuropathic pain presentation. After MR imaging, a focal dorsal indentation of the upper thoracic spinal cord at the T3–T4 level with the scalpel sign was found. This sign indicates that the patient’s neuropathic pain was caused by the dorsal thoracic arachnoid web.
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ChangHSNagaiAOyaS. Dorsal spinal arachnoid web diagnosed with the quantitative measurement of cerebrospinal fluid flow on magnetic resonance imaging: Report of 2 cases. J Neurosurg Spine2014; 20: 227–233.
