Main Causes of Conus Medullaris Syndrome
The main causes of conus medullaris syndrome include traumatic injuries (particularly thoracolumbar junction fractures), disc herniations, congenital malformations (especially tethered cord syndrome), and less commonly tumors, vascular lesions, and inflammatory conditions. 1, 2
Traumatic Causes
- Burst fractures of the thoracolumbar junction (T12-L1) are a common traumatic cause of conus medullaris syndrome, often resulting from falls or other high-energy trauma 3, 4
- Traumatic spinal cord injuries have an annual incidence ranging from 10 to 85 cases per million persons worldwide, with an increasing proportion occurring in older adults from low-energy falls 1
- Incomplete fractures at the thoracolumbar junction can cause direct compression of the conus medullaris 4
Disc-Related Causes
- Herniated discs at the thoracolumbar junction (T12-L1, L1-L2) can compress the conus medullaris 5
- Intradural disc herniations, though rare, can cause direct compression of the conus medullaris 5
- Cranially migrated disc prolapses can present with symptoms of conus medullaris syndrome in severe cases 6
Congenital Causes
- Tethered cord syndrome is a significant congenital cause of conus medullaris syndrome 1
- A conus medullaris that ends below the middle third of the L2 vertebra is considered tethered 1
- Spinal lipomas and fatty infiltrations of the filum terminale can cause tethering of the conus medullaris 1, 7
- Meningoceles and atretic meningoceles are rare congenital causes 1
- Myelomeningocele, the most common dysraphic malformation, is associated with conus medullaris syndrome 7
Vascular Causes
- Ischemic and hemorrhagic infarcts can affect the conus medullaris region 7
- Arteriovenous malformations affecting the blood supply to the conus medullaris 2
Inflammatory/Demyelinating Causes
- Transverse myelitis affecting the conus medullaris region 8
- Demyelinating diseases such as multiple sclerosis can affect the conus medullaris 7
Neoplastic Causes
- Primary spinal cord tumors (ependymomas, astrocytomas) affecting the conus medullaris 2
- Metastatic tumors to the conus medullaris region 7
Clinical Presentation
- Symptoms include bladder dysfunction (often presenting as urinary retention, urgency, or incontinence) 1
- Bowel dysfunction with early onset of fecal incontinence 1
- Back and/or leg pain that may be dull, aching, sharp, or dysesthetic in character 1
- Sensory disturbances in the lower limbs and perineal region 1
- With long-standing untreated conditions, progressive musculoskeletal deformities, scoliosis, and skin changes (thin, shiny, hairless skin of the legs and feet due to autonomic changes) may develop 1
Diagnostic Approach
- MRI is the preferred imaging method for diagnosing conus medullaris syndrome, providing better visualization of soft tissue, bone marrow, and spinal canal 1, 3
- Neurological examination should focus on assessment of perineal sensation, evaluation of anal tone, and testing of lower limb reflexes, which may be hyperreflexic below the level of lesion 1