Conus medullaris syndrome

Last revised by Assoc Prof Frank Gaillard on 03 Sep 2018

Conus medullaris syndrome is caused by an 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.

Patients present with a combination of severe back pain and upper and lower motor neuron deficits, similar to cauda equina syndrome, which include 1-3:

  • saddle anesthesia
  • loss of bladder reflex: urinary retention
  • loss of bowel reflex: incontinence 
  • lower limb motor weakness, paresthesia and numbness (mixed upper and lower motor neuron pattern)

Unlike cauda equina syndrome which will only have lower motor neuron deficits, conus medullaris will have a combination of upper and lower motor neuron involvement 3

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

Conus medullaris injury can result most commonly from:

Depending on the suspected etiology in addition to MRI that is almost invariably indicated,  CT and catheter angiography may also be required. The features will vary according to the causative pathology and are therefore discussed separately. 

The prognosis depends on upon the timing of patient presentation, the severity of deficits and underlying pathology. Early diagnosis and treatment may facilitate improvement in symptoms. Approximately 10% of patients may regain functional recovery.

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Cases and figures

  • Case 1: spinal cavernoma
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  • Case 2: metastasis
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  • Case 3: myxopapillary ependymoma
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  • Case 4: spondylodiscitis
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