Peridural infiltration (PDI) and periradicular therapy (PRT)
In peridural infiltration (PDI) or periradicular therapy (PRT) of the herniated disc, painkilling, anti-inflammatory and tissue-clogging drugs are administered to the painful nerve root with millimeter precision under computer tomographic control. This leads to a containment of the “mechanical inflammation” taking place around the nerve root and to a decongestation of the nerve. In the case of a herniated disc, sometimes a shrinking of the displaced disc tissue can be observed.
While we use the PDI for herniated discs preferably in the lumbar spine, PRT is more recommended for the cervical spine. The procedure is not a substitute for surgical therapy, but can be used as an alternative to surgery in the case of pain resistant to other conservative treatment in the absence of or only minor neurological symptoms caused by the herniated disc. Even in the case of pain after disc surgery, in many cases a PRT can achieve freedom from complaints or symptoms.
The use of computer tomography is not absolutely necessary for this type of surgery in the lumbar spine area. Recently, such treatments are possible in an open MRT. PDI belongs to the conservative treatment of a herniated disc and stands for “peridural injection”.
The indication for a PDI is given when either other conservative methods do not work or when patients still suffer from pain after surgery. The PDI is generally used not only in the treatment of a herniated disc but also in the treatment of nerve root irritations, which are independent of a herniated disc. Before the lumbar region is anaesthetized with a local anaesthetic, the skin must be thoroughly disinfected and covered with a sterile drape.
The PDI is usually performed in a sitting, so-called “cat’s hump” position, or in a lateral position. The needle is inserted between the spinous processes of the vertebral bodies. The spinous processes must be palpated beforehand.
It is also important to know that the spinous processes of successive vertebral bodies are positioned differently to each other depending on the height of the spine. In the lumbar region, they are almost horizontal; in the thoracic region, on the other hand, they are more inclined like roof tiles. In any case, the hollow needle must be carefully advanced into the peridural space, the space between the dura mater and the periosteum.
This involves puncturing the ligamentum flavum (“yellow band”), which stretches between the spinous processes of the vertebral bodies. The whole procedure is carried out under CT control to ensure that the needle is really in the right place. Now that the needle is in the epidural space, the medication can be injected and distributed in the same space.
The drug is usually a narcotic mixture of cortisone and salt. This includes cortisone has an anti-inflammatory effect, i.e. it reduces swelling and reduces inflammation. The salt, on the other hand, dries out the prolapse, i.e. the protruding intervertebral disc, so that it shrinks and the nerve compression is released.
This reversible nerve compression was the cause of the pain symptoms and sensations, which are reduced by the PDI. Up to 6 injections must be made before pain relief is achieved, although the effect is sometimes felt after the first injection of the local anaesthetic. The whole thing can be administered as a “single” dose or a catheter can be inserted.
Complications are rather rare with a PDI; possible risks nevertheless exist. The sympathetic blockage can cause a drop in blood pressure, the injection area can become inflamed and the spinal cord can be injured when puncturing above L2. Since the epidural/peridural space contains a venous plexus in addition to fat and connective tissue, there is a risk of puncturing it.
Thus, in the case of an intravenous position, intoxication (poisoning) by the local anaesthetic may occur. Duraperfusion with the needle can lead to increased loss of cerebrospinal fluid, which manifests itself clinically as headache. An allergic reaction is also possible.
In general, it can be said that the peridural injection is not a substitute for surgery, but it can possibly lead to freedom from symptoms to such an extent that surgery is no longer necessarily necessary. PRT is a “periradicular therapy”, which is similar to the procedure of peridural injection. It is also used when patients suffer from a herniated disc, but also when they complain of other back pain, which mainly radiates to the extremities.
PRT is the most frequently used procedure for the treatment of a herniated disc. It has a high value, among other things because studies show that the conservative PRT procedure is in no way inferior to surgery, especially in terms of sustainability. Under computer tomographic control a drug is injected at the nerve root (lat.
radix = root). The medication is a mixture of a local anaesthetic and an anti-inflammatory agent. Bupivavain or scandicain can be used as a local anaesthetic and triamcinolone or Lipotalon® as a corticosteroid.
As an alternative to CT control, PRT can also be monitored by magnetic resonance imaging. Here, the needle can be placed even more precisely, in the millimeter range. Since the needle must be very fine for this, the drug can only be injected in small doses.
Recently, MRI has also been used for monitoring purposes due to the lack of radiation exposure. The advantage is that the organs are exposed to less radiation and thus less stress. However, the time required is greater and other materials have to be used, so metal-containing objects must never be in the vicinity of an MRI machine.
In PRT, the drug is now injected directly at the nerve root, where it develops its effect, which is very similar to the PDI: decongestant, anti-inflammatory and analgesic. As the swelling subsides, the irritated and compressed nerve has space again and the symptoms are reduced. In addition, the nerve irritated by a herniated disc no longer responds so strongly to the mechanical irritation thanks to the local anaesthetic, so that pain relief also results.
Optimally, a total of 2 to 4 treatments should be carried out at intervals of one week. An improvement should also have occurred by then. If this is not the case, a few more injections can be given if necessary, but generally an operation should be considered under this aspect, as the herniated disc is too severe for PRT therapy or the position is too unfavorable.
