[Spinal cord tethering in myelomeningocele and lipomeningocele patients: the second operation]

Spinal cord rethetering can occur after the primary surgical repair of myelomeningoceles (MMC) and lipomeningoceles (LMC) and produce devastating physical and psychological consequences. The inadvertent introduction of skin elements at the time of the initial surgery can lead to the growth of intraspinal epidermoid or dermoid cysts.

To review the incidence of spinal cord tethering following surgery for open and occult spinal dysraphism and to analyze factors that might influence the appearance of this complication. We also aimed to search technical measures at the time of the primary operation that might prevent the occurrence of symptomatic cord retethering.

We reviewed the medical records of patients submitted to surgical repair of MMC (n=162) or occult spinal dysraphism (n= 54) during the period 1975-2005 who developed symptomatic tethered cord syndrome.

Eleven of 162 (6.79%) patients with MMC and 2 of 54 (3.7%) with LMC developed clinical symptoms and signs of spinal cord tethering after intervals ranging from 2 to 37 years after the initial surgical repair of their back lesions. Indications for surgical re-exploration were based mainly on clinical grounds. Postoperative fibrosis was a constant finding in all instances. Other surgical findings included inclusion tumors of cutaneous origin (n=3), lumbar canal stenosis (n= 2), foreign body reactions (n= 2), residual lipoma (n= 1), and a tight hyalinized filum (n=1). Interestingly, 3 of 162 (or 1.85%) myelomeningoceles were found to harbor an intradural epidermoid tumor at the time of spinal cord dethetering, accounting for an incidence of cutaneous inclusion tumors of 27% in cases of post- MMC repair tethering. After a mean follow-up time of 5.5 years, eight patients were improved, two were unchanged and one was worsened.

Neurological deterioration is not a necessary consequence of the natural history of patients with MMC or LMC. Early or late clinical deterioration can be due to spinal cord re-tethering and deserves timely investigation and surgical exploration. Results of surgical intervention were rewarding as 92% of the patients showed improvement or stabilization in their otherwise deteriorating condition. We also report two infrequent causes of spinal cord deterioration: lumbar canal stenosis and intense foreign-body reactions to implanted materials.