History of Tethered Cord Syndrome With a Normally Positioned Conus in Children
Understanding of Disease
1944 – description of normal level conus in adults: In 1944 Reimann and Anson (22) reviewed 801 adult spinal cords and found that the conus medullaris was above the L2-L3 disk level in 98% and that the mean conus location was at the lower third of the L1 vertebra. Saifuddin et al. (25) also found that the mean termination of the conus is at the lower third of the L1 vertebra. It has been shown that the conus may terminate differently according to race and ethnicity (22).
1953 – tethered filum syndrome: Garceau (6) described the tethered filum syndrome with and without caudal descent of the conus in 1953.
Late 1980s and 1990s – description of normal level of conus in infants: Using sonography, Robbin et al. (23) refuted the idea of ascension during childhood and posited that by approximately 19 weeks gestation, the conus should have achieved its adult position. Wilson and Prince (38) concluded that a conus positioned at L2-L3 should be considered normal at any age. DiPietro (4) added to these data, showing that children younger than 2 months of age had a mean conus termination at the lower third of the L1 vertebral body, whereas children between the ages of 1 and 4 years had a mean conus termination at the upper third of the L1 vertebral body, and furthermore that the conus of children between the ages of 4 and 13 years was located at the upper third of the L1 vertebral body. Their study (4) also concluded that criteria for the determination of conus level should be age-dependent. Another sonography study (23) found that the conus was located above the L2 vertebral level in 92.1% of term babies, whereas it was at the L2-L3 disk level in only 6.3%.
MRI: Improved imaging modalities (e.g., MRI) have provided the clinician with the ability to accurately define intraspinal anatomy and in particular, to more accurately estimate the location of the distal spinal cord (33, 41).