Symptomatic Thoracic Intramedullary Arachnoid Cyst: “A Rare Entity” Report of Two Cases with Short Review of Literature

Abstract

Spinal arachnoid cysts are uncommon benign lesions of spine axis and most commonly present as compressive myelopathy. Intramedullary arachnoid cyst is uncommonly seen, hence, not much discussed in literature. Due to rarity of this entity, many questions are yet to be answered and should be addressed properly, particularly related to etiopathogenesis, accustomed course, behavior, differential diagnosis, and the best treatment modality. We report the clinicopathological profile of thoracic intramedullary arachnoid cysts in two adult patients, and present a detailed review of available literature on the spinal intramedullary arachnoid cyst. Most of the literature concerning with intramedullary arachnoid cysts are in the form of case reports from pediatrics population. As far to the best of our knowledge, only a few cases excluding our two were found in both pediatrics and adult population.

Intramedullary arachnoid cyst: A rare cause of medullary compression

“…It also allows the exact topography of the lesion, its size, extent, and relationship with the spinal cord to be determined non-invasively. The imaging appearance is that of an extra-or intradural lesion, intramedullary form is exceptional; it appears hyposignal in T1, hypersignal in T2, and does not enhance on gadolinium injection [2,8,9]. The recommended surgical technique is to evacuate the cystic contents and to remove as much of the cystic wall as possible, leaving the portion adherent to the spinal cord in place to avoid damaging the healthy spinal cord tissue, thus allowing decompression of the spinal cord [1].…”

Conus medullaris intramedullary arachnoid cyst- case report and review of the literature

“…Like in the previous reports, the dorsal cord is the most common site reported for IMAC in both the pediatric and adult age groups in our literature review as well. [ 3 , 18 , 19 ] Three cases of conus IMAC have been reported previously. [ 14 , 19 ] Similar to our patient, other reported arachnoid cysts which were located in conus presented with weakness, saddle anesthesia, and decreased anal tone.…”

“…[ 3 , 18 , 19 ] Three cases of conus IMAC have been reported previously. [ 14 , 19 ] Similar to our patient, other reported arachnoid cysts which were located in conus presented with weakness, saddle anesthesia, and decreased anal tone. They usually produce a radiological dilemma, with the diagnosis being made intraoperatively or on histopathology.…”

“…The reasons speculated for recurrence were incomplete excision of the cyst, an unnoticed ventral subarachnoid channel, postoperative adhesion, and fibrosis. [ 13 , 19 ] Zekaj et al . reported a case of development of an IMAC on follow-up after near-total removal of an intradural extramedullary cyst, with a small part of cyst wall left behind.…”

“…Although reported at different spinal levels, they are commonly found in the dorsal region in both pediatric and adult age groups. [ 19 ] Cysts in the conus medullaris represent a distinct entity with respect to the peculiar clinical presentation due to the particular anatomy of the conus. [ 15 ] We report a 30-month-old symptomatic male child with an IMAC in the region of conus medullaris who underwent marsupialization of the cyst.…”