Organ
Conus medullaris
Tapered end of the spinal cord containing its lowest segments
High-yield
Its sacral circuits contribute to bladder, bowel, sexual and perineal function. A lesion may combine cord and adjacent root findings, so a neat upper-versus-lower motor neuron rule can be misleading.
Overview
The conus is the narrowing tip of the spinal cord. In adults it usually ends around the L1–L2 vertebral region, although its position varies. Descending cauda equina roots lie beside it, and the filum terminale continues from its tip.
Reference facts
- Location
- Lower end of the spinal cord in the upper lumbar vertebral region in most adults; vertebral position is variable
- Parts
- Mainly the lowest sacral and coccygeal cord segments, commonly described as S2–S5 and Co1; the lumbar enlargement lies higher
- Blood supply
- Anterior and posterior spinal arterial branches connect around the conus in an arterial basket; segmental arterial reinforcement contributes to the lower cord supply
- Relations
- Adjacent to descending cauda equina roots within the meningeal sac; continuous inferiorly with the filum terminale
- Function
- Contains sacral sensory, somatic motor and autonomic circuits important for the perineum, pelvic viscera and sphincter control
Clinical correlation
Conus injury can produce saddle numbness and bladder or bowel dysfunction, with or without leg weakness. Findings may be fairly symmetrical, but overlap with cauda equina syndrome is substantial. New symptoms need emergency assessment and usually imaging to identify the affected structures.
Frequently asked questions
Where is the conus medullaris located?
Lower end of the spinal cord in the upper lumbar vertebral region in most adults; vertebral position is variable.
What does the conus medullaris do?
Contains sacral sensory, somatic motor and autonomic circuits important for the perineum, pelvic viscera and sphincter control.
What are the parts of the conus medullaris?
Mainly the lowest sacral and coccygeal cord segments, commonly described as S2–S5 and Co1; the lumbar enlargement lies higher.
What is the blood supply of the conus medullaris?
Anterior and posterior spinal arterial branches connect around the conus in an arterial basket; segmental arterial reinforcement contributes to the lower cord supply.