The aim of this exhibit is to demonstrate the common imaging manifestations of the dorsal spinal arachnoid web, a rare entity that can pose a diagnostic dilemma and should be differentiated from two other conditions with similar imaging findings: ventral herniation of the spinal cord and the spinal arachnoid cyst.

Case report: A 42 year old man was referred to our institutionby his general practitioner with 3 weeks of acute on chronic back pain. Concerningly, he had also developed new and worsening ataxiaandexperienced multiple falls over this time. Neurological examination revealed normal upper and lower limb powerwith preserved reflexes, howeverthere was reduced sensationthroughout the mid to lower body below the level ofT5-6. AnMRI of the spine performed externally had demonstrated an abnormalityat T6that was reported as a 'thoracic spinal lesion', prompting referral to the neurosurgical...

MRI MRI is the imaging modality of choice, withroutine axial and sagittal T1, T2 and T2 fat saturation sequences usually sufficient.Post contrast imaging can also be performed to exclude the presence of an enhancing mass. Several imaging features can help differentiate arachnoid webs from ventral cord herniation and spinal arachnoid cysts2,3. The classical imaging finding of a dorsal arachnoid web is that of a focal deformity of the dorsal spinal cord with associated prominence of the dorsal CSF and obliteration of the CSF spaceventral to...

This educational exhibit presents the spectrum of imaging findings that can be encountered in the evaluation of dorsal arachnoid webs and highlights the similarties and differences betweenthis entity andtwo other uncommon conditions, ventral cord herniation and spinal arachnoid cyst. MRI is theimaging modality of choice in the evaulation of such lesions, whileCT myelography can bean excellent toolinequivocal cases. Intra-operative ultrasound is currently the only modality which can directly visualise the thinconnective tissue which constitutes the arachnoid web. Accurate pre-operative diagnosis is essential to allow for...

George Harisis, Matthew Lukies, Alex Jarema and Madeleine Scicchitano are4th year radiology registrars at Alfred Hospital, Melbourne, Victoria.

1.Haitham, B.A et al, Spinal arachnoid web-A review article, J Spine Surg. 2018; 4(2): 446–450 2. Schultz R Jr. et al, Differentiation of idiopathic spinal cord herniation from dorsal arachnoid webs on MRI and CT myelography. J Neurosurg Spine, 2017; 26:754–759 3.M.A. Reardon et al. Dorsal Thoracic Arachnoid Web and the “Scalpel Sign”: A Distinct Clinical-Radiologic Entity. AJNR Am J Neuroradiol, 2013; 34:1104-1110 4.Srinivasan VM, Fridley JS, Thomas JG, et al.Nuances in Localization and Surgical Treatment of Syringomyelia Associated with Fenestrated and Webbed Intradural Spinal...