Jared R Green MD, Presenter: Nothing to Disclose

Barth A Green MD, Abstract Co-Author: Nothing to Disclose

Robert M. Quencer MD, Abstract Co-Author: Nothing to Disclose

Describe a cohort of patients who were thought to have an idiopathic syringomyelia but who on close inspection were found by imaging to show very subtle findings suggesting a coexistent adjacent developmental arachnoid cyst.

The imaging, clinical and surgical reports of patients presenting with known syringohydromyelia and spinal arachnoid cysts were retrospectively reviewed. Patients with a known underlying cause, including infection, tumor, trauma, previous surgery or Chiari malformation, were excluded. Four patients who satisfied the inclusion criteria were preoperatively evaluated with MR imaging (1.5T) of the cervical and thoracic spine with pre and post contrast sagittal T1 FSE, T2 FSE, GRE axial T2, and phase contrast CSF flow studies. All patients subsequently underwent surgery for cyst removal and syrinx  decompression. Monitoring of the surgery was performed with intraoperative spinal sonography (7.5/13Mhz).

Focal syrinx cavities were identified in the upper thoracic cord of four patients whose only changes on MR, in addition to the syrinx cavity, were minor contour changes along the cord surface. Subtle alterations in the appearance of the cord in two patients included abnormal cord flattening and ventral displacement within the canal. A third patient demonstrated abnormal dorsal CSF flow interruption on cine MR images, corresponding to the level of the arachnoid cyst. A fourth patient demonstrated abnormal flattening of the cord along its dorsal surface, due to the arachnoid cyst, and was associated with posterior transdural herniation of the cyst. Intraoperative findings of each patient confirmed the presence of a cyst that was felt to arise within the layers of the arachnoid.

Focal syrinx cavities in the upper thoracic cord are easily visualized on preoperative MR, yet the findings of an underlying congenital arachnoid cyst are subtle on routine examination. Careful examination of MR images, with particular attention to cord contour, is recommended in cases of idiopathic syringomyelia as these findings may suggest an associated underlying arachnoid cyst. Cine MR is a useful adjunct in the evaluation of an occult arachnoid cyst in the setting of idiopathic syringomyelia.

Evaluation of cord contour and Cine MR flow in "idiopathic" syringomyelia may reveal an arachnoid cyst causing syrinx formation. These findings may alter clinical and surgical management.

Green, J, Green, B, Quencer, R, Occult Arachnoid Cysts: An Unrecognized Cause of “Idiopathic” Syringomyelia?.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008319.html