The Resolution of Syringohydromyelia Without Hindbrain Herniation After Posterior Fossa Decompression

Bermans J. Iskandar, M.D., Gary L. Hedlund, D.O., Paul A. Grabb, M.D., W. Jerry Oakes, M.D., Division of Pediatric Neurosurgery and Department of Pediatric Imaging, Children's Hospital, Birmingham, Alabama

Neurosurg Focus. 2000;8(3) 

In This Article


Clinical and Radiographically Confirmed Improvement

Five consecutive patients (two boys and three girls) with syringohydromyelia and no hindbrain herniation (Fig. 1) were followed with clinical and radiographic studies for a mean of 13.6 months and a range of 2 weeks to 36 months (Table 1). The age at operation ranged from 4 to 15 years, with a mean of 10.6 years. All five patients showed significant improvement in symptoms, signs, and syrinx size postoperatively, as detailed in Table 2 and Fig. 2. Two (Cases 1 and 2) of the three patients (Cases 1, 2, and 4) who underwent both pre- and postoperative cine MR imaging demonstrated qualitative improvement of flow at the foramen magnum postsurgery. However, in a prospective reading of the preoperative studies obtained in Case 1 we found that the flow was normal. On retrospective comparisons of these studies to those obtained post-operatively, we suspected that flow at the craniocervical junction was compromised before surgery.

Figure 1. Sagittal MR images of the craniocervical junction and cervical spine in Cases 1 to 5 (A-E), respectively. Note the lack of hindbrain herniation.

Figure 2. Axial T1-weighted MR images of the spinal cord revealing the syrinx at the level of greatest preoperative expansion. The left column shows the preoperative images, and the right column shows the postoperative images at the corresponding spinal levels. These images represent Cases 1 to 5, from top to bottom.

Surgical Findings

Intraoperative findings (Table 1) included the following: one patient (Case 1) had midline bone defects of the posterior arches of C-1 and C-2; another (Case 5) had assimilation of the posterior arch of C-1 on the right; two (Cases 3 and 5) had significant intradural adhesions that were lysed; one (Case 2) had an obvious fourth ventricular "veil" of tissue that covered the opening of the central canal at the obex from the subarachnoid space. On disruption of the veil, good CSF flow was seen to emanate from the foramen of Magendie. In this same patient, the cerebellar tonsils were crowding the rostral aspect of the foramen magnum enough that we thought it would be helpful to shrink one tonsil with electrocautery. Finally, during operative exploration of the craniocervical junction in another patient (Case 3), the tonsils were noted to protrude mildly below the foramen magnum, although both prospective and retrospective evaluations of the preoperative MR images did not confirm that observation.

Previous Surgery

Prior to the craniocervical decompressions, two patients had undergone a syrinx-to-subarachnoid shunt placement. One of these (Case 2) had temporary improvement in syrinx size and scoliosis, both of which recurred within a few months. The second patient (Case 5) underwent two such shunt operations before the craniocervical decompression procedure. The first surgery produced only temporary improvement in hand weakness and syrinx size, whereas the second resulted no improvement in either. One patient was referred for evaluation after his brother, who had a typical Chiari I malformation, improved significantly after decompression.

Postoperative Complications

One patient experienced worsening of a cervicothoracic kyphosis several months postoperatively, and ultimately required a spinal fusion procedure. There were no complications or surgical interventions in any of the other patients.