Learning objectives
To describe the characteristic magnetic resonance imaging findings of the arachnoid web
To show the usefulness of 2D-myelography in the diagnosis of this pathology
Background
Definition and location
The arachnoid web is an intradural extramedullary transverse band of arachnoid tissue that extends to the dorsal surface of the spinal cord within the subarachnoid space, causing mass effect and dorsal indentation. This membrane-like structure shows free moving to and fro in synchrony with the cardiac cycle in intraoperative ultrasound. Pathological examination shows fibroconnective tissue, cuboidal, simple epithelium with meningothelial appearance and nonspecific chronic inflammatory infiltrate.
In almost all cases the arachnoid web affects the upper level of the dorsal spine.
Epidemiology...
Findings and procedure details
Computed tomography
Computed tomography myelogram that relies on the principle of obstruction to CSF flow, can be used for the diagnosis, but it can miss webs as these do not usually cause complete obstruction. In our center, this study is not used.
MRI- conventional sequences
MRI is the gold standard investigation method of the arachnoid web and these are the main features found in the 16 patients included in our retrospective descriptive study between 2013 and 2019 using conventional spinal MRI sequences (T1W, T2W, STIR,...
Conclusion
The dorsal arachnoid web is a rare pathology, probably underdiagnosed and whose etiology is still unknown.
MR imaging is the gold standard investigation. However, the “scalpel sign” may be subtle, so other sequences like CISS and CINE MRI are used to localize the webs and analyze the CSF flow. We propose another MRI sequence, a 2D MR-myelography, that can improve the sensitivity in identifying the scalpel sign and diagnosing a dorsal arachnoid web, which was positive in 100% of the patients of our study.
Its...
Personal information and conflict of interest
M. M. Manrique Zegarra; Madrid/ES - nothing to disclose J. Romero Martínez; Madrid/ES - nothing to disclose M. F. Arenas García; Madrid/ES - nothing to disclose M. J. García Redondo; Madrid/ES - nothing to disclose P. Patilla Vázquez; Madrid/ES - nothing to disclose P. Elvira Ruiz; Madrid/ES - nothing to disclose M. Valera Melé; Madrid/ES - nothing to disclose
References
Reardon MA, Raghavan P, Carpenter-Bailey K, Mukherjee S, Smith JS, Matsumoto JA, et al. Dorsal thoracic arachnoid web and the “scalpel sign”: a distinct clinical-radiological entity. Am J Neuroradiol 2013; 34: 1104-10.
Grewal SS, Pirris SM, Vibhute PG, Gupta V. Identification of arachnoid web with a relatively novel magnetic resonance imaging technique. The Spine Journal 2015; 15: 554-555.
Chang HS, Nagai A, Oya S, Matsui T. Dorsal spinal arachnoid web diagnosed with the quantitative measurement of cerebrospinal fluid flow on magnetic resonance imaging. J Neurosurg...