The MRI signs of spinal arachnoid diverticula.

Our goal was to find MRI signs of use for identifying a spinal arachnoid diverticulum. Three cases of spinal arachnoid diverticula, one extradural and two intradural, were examined on a 1.5 T imager. There was obvious mass effect on the adjacent structures in one case and increased signal intensity in the diverticulum on proton density- and T2-weighted images in two cases. Signal changes due to turbulent movement of the spinal fluid inside the diverticula were seen in all cases on sagittal fast spin-echo (FSE) proton density- and T2-weighted images; it was difficult to tell whether these signal changes imply a communication or are simply FSE artefacts. On contrast-enhanced studies, all cases showed partial enhancement inside the diverticula. There thus are four signs of diverticula: mass effect, the increased signal, signal void sign and partial enhancement; the last of these, the most reliable, has never been reported before.