What is a transforaminal epidural?
This is an image-guided interventional procedure where steroids or other medicines are injected inside the neural foramen of the spine. This procedure is called a transforaminal epidural, nerve root block, or transforaminal epidural steroid injection. This is a similar procedure to epidurals, but here the epidural space is accessed through the neural foramen.
Where are the neural foramina situated?
Our spine has several small pieces of bones and there is a canal inside. This is called the spinal canal. The spinal cord starts from the brainstem and passes through this spinal canal. The spinal canal has several openings on either side and these are called neural foramen.
The nerve roots which start from the spinal cord come out of the spinal canal through these neural foramina and are distributed throughout our body as peripheral nerves.
These neural foramina are connected with the epidural space around the spinal cord. So, if any medicines are injected in the neural foramen bath the nerve roots first and then go into the epidural space if large volumes are injected.
What are the other names of the transforaminal epidural procedure?
This procedure is also known as selective nerve root injection, nerve root sleeve injection, dorsal root ganglion injection.
What is the anatomy of the neural foramen and what is its content?
The neural foramen are apertures that are like windows of the spinal canal. This window is bounded above and below by pedicles, anteriorly by the vertebral body and intervertebral disc, and posteriorly by superior and inferior articular processes of facet joints.
Apart from nerve roots that come out through the upper part of the foramen, there are several other structures. There are blood vessels that accompany the nerve roots, ligaments that hold the nerve root in position, and loose fatty tissues.
How many types of transforaminal epidurals are there?
There are two types. In one type the injection is done through the upper part of the neural foramen and in another type, the injection is done through the inferior part of the foramen.
Injection through the upper part of the foramen is also called subpedicular or supraneural or safe-triangle approach. Safe-triangle approach is a misnomer and injection through this part is risky as there are nerve roots and blood vessels in this area.
Injection through the inferior part of the foramen is called Kambin’s triangle approach or infra-neural approach. Nowadays, this approach is preferred for fewer complications and side effects.
What are the indications of a transforaminal epidural?
Inflammation of nerve roots because of a slipped disc or prolapsed disc is the best indication for a transforaminal epidural. But it is also indicated in the following conditions:
- Acute herpes zoster or post herpetic neuralgia
- Lateral canal stenosis
- As diagnostic procedure as a selective nerve root block
- Failed back surgery syndrome
How is a transforaminal epidural procedure done?
The transforaminal epidural is a potentially dangerous procedure and is always done under real-time image guidance like C-arm or fluoroscopy guidance. Sometimes it is also done under ultrasound guidance. It must be done by expert physicians who are well trained in performing interventional pain management procedures.
What are the medicines injected in a transforaminal epidural?
The steroid is the most common medicine used in transforaminal epidural and that is why this procedure is also called a transforaminal epidural steroid injection. The most common medicine injected are triamcinolone, methylprednisolone, dexamethasone, or betamethasone. Other than these steroids, dyes like iohexol, normal saline, and hyaluronidase are also injected in specific indications.
What is transforaminal neuroplasty? Is it the same as transforaminal epidural steroid injection?
In conditions like failed back surgery syndrome, there are adhesions around the nerve root which causes symptoms. In transforaminal neuroplasty, these adhesions are broken down with the help of special catheters and after breaking adhesions, a steroid is injected.
What are the complications or side effects of transforaminal epidurals?
There several possible complications. Though these complications extremely rare in expert hands. The complications are:
- Nerve root injury is possible but not that common. This can be easily avoided by doing the procedure without general anesthesia or deep sedation. If the physician touches the nerve root, there will be complaints of unpleasant paraesthesia and won’t allow proceeding further.
- Injection of a particulate steroid into the blood vessels is a potentially dangerous complication but avoided by performing the procedure under C-arm with dye/contrast confirmation.
- Infection is a rare possibility as the procedure is done at the operation theatre under sterile conditions.
Other side effects like pain at the injection site, muscle spasms, transient numbness, or weakness are common and are temporary.
As a whole, the transforaminal epidural is a very useful procedure for radicular pain and sciatica and it is also a frequently done procedure by pain physicians. But this procedure must be done by experienced and best doctors for back pain treatment.