Cutting filum terminale is very important in split cord malformation cases to achieve total release.

AIM: Split cord malformations (SCMs) are rare congenital anomalies of the vertebrae and the spinal cord. Tethered cord syndrome (TCS) is a clinical condition of various origins that arises from tension on the spinal cord. Radiographic findings may include and/or associate split cord malformations and the other neural tube defects. However, the spinal cord can even be tethered by a filum terminale with normal appearance and normal level conus medullaris in magnetic resonance imaging (MRI). The aim of our study is to show whether SMC patients with normal or abnormal MRI findings had all histological abnormal filum terminale and also to show that the standard SCM repairing operation without cutting filum will not achieve total release.

MATERIAL AND METHODS: We have reviewed 33 SCM patients between July 2005 and December 2013. They were operated by adding untethering procedure of filum terminale following standard surgical intervention, and a part of the filum was taken for histopathological examination even though MRI did not show the presence of abnormality of filum terminale.

RESULTS: We found that abnormal filum terminale with a normal appearance may had dense collagen fibers, wide and numerous capillaries, and hyaline formation, while normal filum terminale is a mixture of collagen fibers and blood vessels. We did not obtain positive Verhoeff elastic fiber staining. The elastic fibers had disappeared in all fila terminalia, except control cadaver group.

CONCLUSION: Our results showed that all fila of SCM patients had loss of elastic fibers and increased of hyalinization, which means loss of elasticity of filum terminale. Less severe traction may remain asymptomatic in childhood and present with neurological dysfunction later in life. For this reason, surgical procedure of SCM patients including releasing of filum terminale seems more beneficial for the patients and be better for long term.