Conus medullaris syndrome is caused by and injury or insult to the conus medullaris and lumbar nerve roots. It is a clinical subset of spinal cord injury syndromes. Injuries at the level of T12 to L2 vertebrae are most likely to result in conus medullaris syndrome.
Pathology

The conus medullaris lies in close proximity to nerve roots and injury to this region results in combined upper motor neurone and lower motor neurone features

Conus medullaris injury can result most commonly from:

lumbar canal stenosis due to herniation of intervertebral disc(s)
    
trauma  
        
direct
        
traumatic spondylolysis and spondylolisthesis

Clinical presentation

Patients present with a combination of upper and lower motor neurone palsies  and similar features as cauda equina syndrome which include:

saddle anaesthesia
    
loss of bladder reflex: urinary retention
    
loss of bowel reflex: incontinence 
    
lower limb motor weakness, paraesthesia and numbness
    
chronic lower backache

Treatment and prognosis

The prognosis depends upon patient presentation. Early diagnosis and treatment may facilitate improvement in symptoms. Approximately 10% of patients may regain functional improvement.