The MR appearance of XXXX : new observations.

@entity1 @entity1644 @entity5 @entity1645 @entity602 @entity5219 @entity5326 @entity130
Fifty-eight @entity1 with spinal cord cavities were studied with MR imaging. @entity1 were separated into four groups, and the appearance of the cavities were compared. There were 24 @entity1 (41.4%) with communicating @entity1644 (associated with the @entity1645 ). Sixteen @entity1 (27.6%) had posttraumatic @entity1644 , nine @entity1 (15.5%) had associated @entity5 , and nine @entity1 (15.5%) had idiopathic @entity1644 . The characteristics of each syrinx, the spinal cord, and the appearance of the cerebellar tonsils were analyzed on T2- and T1-weighted images. There is a striking similarity in the appearance of many syrinx cavities regardless of the cause. Characteristics that were found in some @entity1 in every group included areas of increased intensity on T2-weighted images, the presence of the CSF flow-void sign (CFVS) in the syrinx cavity, eccentric cavities, "beaded" cavities, and @entity602 . @entity5326 alone does not indicate that a syrinx is of the "communicating" type, since it was present in two of 16 @entity1 (13%) with @entity130 and in two of five @entity1 (40%) with @entity5 . T1-weighted images were most useful in evaluating the anatomic characteristics of the syrinx and the cerebellar tonsils. Most syrinx cavities involved the cervicothoracic junction. The average length was between five and nine vertebral segments (depending on category) but varied between one and 20 vertebral segments. T2-weighted images revealed areas of increased intensity in the spinal cord in 13 @entity1 without @entity5 . Two of these cases were shown to represent @entity5219 on histopathologic review. The CFVS was present in the syrinx cavities of 23 @entity1 (40%), probably reflecting pulsatile movements of the syrinx fluid. It has been proposed that such movements are a cause of syrinx propagation, and the observation of the CFVS may have prognostic significance. The development and progression of the CFVS was documented in serial MR examinations in one @entity1 over an 18-month period. The theories of syrinx development and propagation are reviewed.
