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Facet Nerve (Medial Branch Block) Injections

Facet nerve injections are diagnostic procedures that identify the source of irritation in the nerves that run along the outer edge of the facet joints within the spine. If multiple levels of pain exist within the facets, several injections may be required on different days to pinpoint the pain source in each location.

By anesthetizing these nerves, the physician can determine whether the nerve irritation should be treated with medication or by radiofrequency (RF) rhizotomy. Pain relief varies for each patient ranging from short-term to long-term relief.

Procedure preparation

A technologist or nurse will contact you 24-48 hours prior to your appointment to review medications you are currently taking, especially pain medications and blood thinners, discuss known allergies and your medical history, as well as answer your questions.

Contact your doctor before you stop taking any medication.

Please bring previous imaging study results (MRI, CT, x-rays) such as films, reports, or CD-ROMs, if available.

You will need a driver for your appointment. If you are unable to drive or arrange transportation, call us for assistance.

Please notify a member of our staff if you are nursing or if there is a chance you may be pregnant.

What to expect during the procedure

Using x-ray guidance (fluoroscopy), the radiologist will advance a thin needle adjacent to your spinal column, at the location of the facet nerve.

X-rays are taken, and a combination of an anti-inflammatory (steroid) and anesthetic (numbing) medications are then injected for pain relief.

You will remain awake during the 10-20 minute procedure, and may experience some slight pressure or discomfort during the injection.

Please inform the radiologist how it differs from your usual symptoms.

You will be asked to wait 30-40 minutes after your procedure before leaving.

What to expect after the procedure

You may experience numbness and/or relief from your symptoms for up to six hours after the injection.

Your usual symptoms may then return and may be worse than usual for a day or two.

The beneficial effects of the steroids usually require 2-3 days to take hold, but may take as long as 5-7 days. If there is no change in your symptoms after a week, your doctor may want to investigate other possible sources for your pain.

If an initial injection provided a certain amount of relief, a second injection might strengthen the pain relief effect. Also, if your pain subsides, but begins to return weeks or months later, additional injections – up to four a year – are possible.

Keep track of how long relief lasts and report it to your physician. If there is no change in the pain, then investigation can be focused on other possible sources of your pain. In either case, the information is useful to the doctor who referred you for this procedure.

Potential side effects

Steroid medications may cause facial flushing, occasional low-grade fevers, hiccups, insomnia, headaches, water retention, increased appetite, increased heart rate, and abdominal cramping or bloating.

These side effects are bothersome in only about 5% of patients and commonly disappear within 1-3 days after the injection.