Differentiation of idiopathic spinal cord herniation from dorsal arachnoid webs on MRI and CT myelography

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Dorsal arachnoid webs (DAWs) and spinal cord herniation (SCH) are uncommon abnormalities affecting the thoracic spinal cord that can result in syringomyelia and significant neurological morbidity if left untreated. Differentiating these 2 entities on the basis of clinical presentation and radiological findings remains challenging but is of vital importance in planning a surgical approach. The authors examined the differences between DAWs and idiopathic SCH on MRI and CT myelography to improve diagnostic confidence prior to surgery.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Review of the picture archiving and communication system (PACS) database between 2005 and 2015 identified 6 patients with DAW and 5 with SCH. Clinical data including demographic information, presenting symptoms and neurological signs, and surgical reports were collected from the electronic medical records. Ten of the 11 patients underwent MRI. CT myelography was performed in 3 patients with DAW and in 1 patient with SCH. Imaging studies were analyzed by 2 board-certified neuroradiologists for the following features: 1) location of the deformity; 2) presence or absence of cord signal abnormality or syringomyelia; 3) visible arachnoid web; 4) presence of a dural defect; 5) nature of dorsal cord indentation (abrupt “scalpel sign” vs “C”-shaped); 6) focal ventral cord kink; 7) presence of the nuclear trail sign (endplate irregularity, sclerosis, and/or disc-space calcification that could suggest a migratory path of a herniated disc); and 8) visualization of a complete plane of CSF ventral to the deformity.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>The scalpel sign was positive in all patients with DAW. The dorsal indentation was C-shaped in 5 of 6 patients with SCH. The ventral subarachnoid space was preserved in all patients with DAW and interrupted in cases of SCH. In no patient was a web or a dural defect identified.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>DAW and SCH can be reliably distinguished on imaging by scrutinizing the nature of the dorsal indentation and the integrity of the ventral subarachnoid space at the level of the cord deformity.</jats:p></jats:sec>

Clinical Outcomes of Surgical Treatment for Arachnoid Web: A Case Series

“…The pathologic states of SH are focal ventral or, less commonly, lateral protrusion of part of the cord through the dural defect. Randall et al 9) reviewed the findings on MRI and CT myelography for both AW and SH and found that the scalpel sign was positive in all the patients with AW and that a C-shaped deformity was present in 5 of 6 patients with SH. They also mentioned that the ventral subarachnoid space was preserved in all the patients with AW.…”

Letter to the Editor. Golf as a contact sport: possible solutions

“…Both are uncommon conditions and can result in significant neurological morbidity if left untreated. 7 The main aspect is related to the evaluation of the nature of the dorsal cord indentation, as well as the integrity of the ventral subarachnoid space at the level of spinal cord deformity. The "scalpel sign" is usually referred to as pathognomonic for SAW, consisting of dorsal spinal cord indentation and anterior cord displacement.…”

“…More recently, the "C-shape dorsal indentation" has been further reported for spinal cord herniation. 7 In practice, differentiating these two separate entities is crucial from a surgical perspective and not always straightforward preoperatively. 7 Their management is different.…”

“…7 In practice, differentiating these two separate entities is crucial from a surgical perspective and not always straightforward preoperatively. 7 Their management is different. The SAW is treated via laminectomy with intradural lysis of adhesions and resection of arachnoid bands, while the ISCH repair involves reduction of the herniation and restoration of the spinal cord to its normal position.…”

Letter to the Editor. Arachnoid webs: preoperative differential diagnosis and surgical exploration

“…Secondly, the clinical and radiological diagnosis should exclude other pathologies, which might mimic an SAW, in particular thoracic intradural spinal cord herniation (ISCH). Both are uncommon conditions and can result in significant neurological morbidity if left untreated 7 . The main aspect is related to the evaluation of the nature of the dorsal cord indentation, as well as the integrity of ventral subarachnoid space at the level of spinal cord deformity.…”