XXXX and the arachnoid web.

@entity1 @entity1644 @entity602 @entity717 @entity2443
Three cases of @entity1644 associated with arachnoid webs are reported. Each @entity1 presented with progressive @entity602 and had thoracic syringes detected on magnetic resonance imaging (MRI). In one @entity1 the web was also visible. At operation a thoracic arachnoid web was found, obstructing the subarachnoid compartment in each @entity1 . One @entity1 had intraoperative ultrasound, which demonstrated @entity717 with each cardiac systole. The webs were divided and shunts inserted into the syringes. All @entity1 improved clinically, and on follow-up MRI. Arachnoid webs are likely to represent a focal band of @entity2443 and are difficult to visualise on standard preoperative MR imaging. A reduction in the subarachnoid space compliance with resultant increase in pulse pressure and potentiation of an arterial pulsation driven perivascular flow could explain the associated syringes. Treatment should be aimed at restoring compliance, and involve division of the web with or without shunt insertion.
