Normal Variations of the Spinal Cord Termination

ABSTRACT

OBJECTIVE: To determine the level of conus medullaris in normal subjects by the magnetic resonance imaging (MRI). METHODS: The corresponding vertebral level of tip of conus medullaris was evaluated in MRIs (sagittal T1 and T2-weighted imaging) of 226 subjects composed of Koreans (138 males, 88 females) with no spine fracture or significant spinal deformity. The termination of the spinal cord was determined by locating the corresponding vertebral point of the lowest end of the conus medullaris to the three-points (upper, middle, and lower) of the nearest vertebral body and intervertebral discs between the T11 and S3 vertebral bodies. RESULTS: If the male and female groups were combined, the most frequent level of cord termination was the mid-portion of L1 (24.5%) which was followed by the lower portion of L1 (22.1%) and the L1-L2 intervertebral disc level (20.8%). In a female group, the tip of conus was one third of vertebra lower than in a male group with a statistical significance (Mann- Whitney test, p=0.025). CONCLUSION: The spinal cord terminates at the mid-portion of L1 most frequently and the termination level distributes from the mid-portion of T12 to the intervertebral disc level of L1-L2. In a clinical setting, variable levels of the spinal cord termination should be considered in a diagnosis for the determination of the neurological level of the spinal cord associated with a vertebral injury and an unexpected neurological complication after a spinal anesthesia or injection.