Radedasia

WHATS THE NORMAL POSITION OF THE CONUS ?

THE NORMAL CONUS

To determine if the cord is low lying or potentially tethered its important to know what is the lowest level you can see a conus and still call it normal.

The radiology literature varies with a conus at the L2/3 disc or L3 level considered within the normal range.

NORMAL DEVELOPMENT
  1. At birth the normal conus will most commonly be at the L1/2 level but can also be at the L2/3 level. The thecal sac is at the S2 level.
  2. This because the cord grows at a slower rate than the vertebral column.
  3. By 2/12 the conus usually lies around the L1/2 level.

 

NORMAL LOCATION OF CONUS
This is the statement from the International Society of Paediatric Neurosurgeons.

” Any conus medullaris lying caudal to the mid-body of L2 is considered abnormally low (95% confidence limits) and therefore potentially tethered.” ( Link to reference below).

spine mri normal position conus tethered radiology education asia

  1. NORMAL: Conus at or above mid L2 is normal at any age ( orange).
  2. ABNORMAL: Conus below mid-L2 abnormal ( green)

 

 REFERENCE LINK:
The ISPN Guide to Pediatric Neurosurgery: Ascent of the Conus Medullaris

 


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March 1, 2019