Morphological Organization of Cauda Equina

ABSTRACT

OBJECTIVE: Topographic arrangement and morphometric pattern of cauda equina are studied. METHODS: In 10 adult formalin fixed cadavers, the entire dural sac of lumbosacral spine including extradural nerve roots was extracted. After paraffin fixation, serial cross section from sacral nerve roots to conus medullaris was performed. We investigated following structures at each disc level using a slide scanner after haematoxylin and eosin and Masson's trichrome stains 1) location of filum terminale(FT), 2) arrangement of motor and sensory bundles, 3) morphometric characteristics of sensory bundles to motor bundle of each spinal nerve root. RESULTS: The FT was located in the dorsal half of midline at L2-3 disc level and in the most dorsal portion of midline from the L4-5 disc level and downward. All bundles of each nerve root showed an oblique arrangement. Motor bundle of each spinal nerve root was always located in the anterior or anteromedial portion of the corresponding sensory bundles. At L4-5 and L5-S1 disc levels, S1 to S4 nerve roots were arranged inverted V-shape centered FT. The sensory root was composed of several bundles whereas the motor root was always composed of a single bundle. The areas occupied by sensory bundles were larger than 2 to 4 times in S1-3 sacral nerve roots and 1.9 to 2.4 times in L3-5 lumbar nerve roots compared with those occupied by the corresponding motor roots. CONCLUSION: This study will be helpful to prevent the nerve root injury during the operation of cauda equina and predict postoperative complications.