Injections périradiculaires

Foraminal and extraforaminal disc herniations : Foraminal and extraforaminal hernias exert a compression on the nerve at the level of its exit from the column and are therefore a good indication for this kind of infiltration.
Periradicular fibrosis : After isthmotomy (classic operation for foraminal and extraforaminal hernias) or TLIF (spondylodesis by lateral approach), there is unfortunately often a significant fibrosis (scar) in the periradicular region, which can cause pain. Periradicular infiltration can help this scar to interfere with the nerve less.

If the needle is advanced too far, it will reach the ganglion of the nerve. It is imperative to recognize this malposition of the needle, because an injection into the spinal ganglion causes chronic pain with sensory disturbances in the form of paresthesias (tingling) and dysesthesia (sensations of burning most often to the touch). For this reason, these infiltrations must imperatively be carried out under fluoroscopic guidance .
In the event of a median or paramedian disc herniation, the indication for periradicular infiltration is questionable because the injection site is relatively far from the zone of compression on the nerve and from the herniated disc. An anatomical risk is also present, because the median and paramedian hernias compress the nerve which will come out on the underlying floor and it is therefore important not to err on the level!
A disadvantage of the periradicular route is the rapid elimination of the drug because this area is very well vascularized.

On a radiculogram (left image), foraminal and extraforaminal herniated discs are difficult to see
On the CT-scan (right image) and MRI, foraminal and extraforaminal hernias, on the other hand, are easy to see.
A foraminal or extraforaminal L4-L5 hernia compresses the L4 root (exiting at the same level)

A paramedian L5-S1 hernia compresses the S1 root (exiting to the underlying level)
This is probably not a good indication for periradicular infiltration