Diagnosis and surgical treatment of arachnoid web

The term “arachnoid web” was first mentioned by Mallucci et al. [1] in 1997 as one of the possible causes of idiopathic syringomyelia. They reported that arachnoid webs or pouches create syringomyelia by partially blocking the flow of cerebrospinal fluid (CSF) and can originate from the septum posticum. Then, the disease entity of arachnoid web was verified by Paramore [2] in 2000. He reported two cases of arachnoid web characterized by focal indentation of the dorsal thoracic cord that was not true arachnoid cyst but blocking CSF flow in magnetic resonance imaging (MRI) and computed tomography (CT) myelogram. Both patients presented with weakness of lower extremities and were treated with surgical resection, which produced improvement clinically and radiologically. Since then, a few case reports and studies have been pubArachnoid web is a rare disease entity that can cause progressive myelopathy and most often develops at the upper thoracic level. Its pathophysiology is unclear, but may be associated with degeneration of the septum posticum in the dorsal subarachnoid space, which alters the flow of cerebrospinal fluid (CSF) and subsequently leads to cord compression and syringomyelia. It often presents with pain, paresthesia, and extremity weakness. Arachnoid web is diagnosed by a typical pattern of displacement of the spinal cord, known as the scalpel sign, with intact ventral dura mater and disturbed but conserved CSF flow. Arachnoid web should be differentiated from other disease entities sharing the feature of ventral displacement of the dorsal spinal cord, such as arachnoid cyst or spinal cord herniation. The treatment for arachnoid web is surgical resection. We report a 66-year-old female who was diagnosed with arachnoid web in the dorsum of the spinal cord at the T3 level. She had suffered from weakness of both legs for 3 months. She underwent laminectomy of T3 and T4 and the dura was opened. The web was resected and the displacement of the spinal cord then improved.