Terminal and Nonterminal Myelocystoceles

Object: The purpose of this study was to report the author's experience with 14 cases of terminal and nine cases of nonterminal myelocystoceles and to highlight the differences between these two groups in regard to the embryological origins, clinical presentation, operative findings, results on neuroimaging studies, and prognosis for these lesions.

Methods: This is a retrospective analysis of 14 cases of terminal and nine of nonterminal myelocystoceles treated between January 1998 and January 2006. All patients underwent neurological examination, plain x-ray films of the spine, computed tomography scans of the brain, and magnetic resonance (MR) imaging of the spine. In seven of these cases, MR imaging included three-dimensional constructive interference in steady-state sequences, and in four cases MR myelography was also done. Follow-up duration ranged from 3 months to 4 years.

Results: All of the patients with terminal myelocystocele presented with swelling in the low back and varying degrees of neurological deficits, except four who had normal results on neurological tests. The MR images revealed classic features of terminal myelocystoceles in all patients. In each case, patients underwent excision of the meningocele sac and drainage of the syringocele with untethering of the spinal cord. During the last follow-up visit, there was no change in the neurological status of these children. In the nonterminal myelocystocele group, one lesion was cervical, six were thoracic, and two were lumbar lesions. All except one patient presented without neurological deficits; that patient had paraplegia with incontinence. Admission MR images revealed Rossi Type I nonterminal myelocystocele in six and Rossi Type II nonterminal myelocystocele in three patients. Children with Type I lesions underwent excision of the fibroneurovascular stalk and excision of the meningocele sac, whereas those with Type II lesions underwent drainage of the syringocele, untethering of the cord, and excision of the meningocele sac. There was no change in the neurological status postoperatively. During the follow-up period no patient in either group presented with retethering.

Conclusions: Myelocystoceles, both terminal and nonterminal, are different from other skin-covered masses in the back. A proper imaging evaluation is required to differentiate myelocystoceles from other skin-covered masses in this area, because the surgical treatment and prognosis are different for this subset of patients with occult spinal dysraphism. Terminal myelocystoceles are different from nonterminal ones embryologically, clinically, radiologically, surgically, and prognostically. These differences are discussed.