Research indicates that roughly half of the patients experience meaningful pain relief, which typically lasts between six weeks and six months. Image guidance helps confirm needle placement compared with landmark-only techniques. CT guidance provides detailed cross-sectional anatomical views and can be particularly useful in complex anatomy, prior surgery, severe stenosis, or difficult needle paths. 

A CT guided epidural injection delivers cortisone (a corticosteroid) and local anaesthetic directly into the epidural space surrounding the spinal nerves inside the spinal canal, using a CT scan (computed tomography) to guide the needle to the precise target. The procedure takes approximately 15 to 20 minutes and is performed under local anaesthetic, with no general anaesthetic required.

If your GP has referred you for a CT guided epidural injection, it is likely because weeks or months of lower back pain, leg pain, or sciatica have not improved enough with rehabilitation or oral medication alone. Having a referral in hand does not mean you need to walk into the appointment without understanding what you are agreeing to.

What Is A CT Guided Epidural Injection And What Does It Actually Do?

The epidural space runs along the inside of the spinal canal and surrounds the spinal nerve roots. When those nerve roots become inflamed, they produce the kind of sharp, radiating pain that travels from the lower back into the leg, or from the neck into the arm.

A CT guided epidural injection places a fine needle into that epidural space under real-time CT imaging. Once the needle is correctly positioned, a mixture of cortisone and local anaesthetic is delivered directly to the inflamed area. The local anaesthetic provides rapid, short-term pain relief. The cortisone injection works by reducing inflammation around the nerve root, which is the underlying mechanism of longer-term pain relief.

It is worth distinguishing this procedure from the epidurals used during childbirth. Those are also delivered into the epidural space, however they use much larger volumes of anaesthetic to block sensation across a wide area. A therapeutic epidural injection for back or leg pain uses a targeted, low-volume delivery to treat a specific source of nerve irritation.

This procedure is used to treat a range of spinal conditions, including disc herniation pressing on a nerve root, sciatica, lumbar radiculopathy (nerve root irritation in the lower back), spinal stenosis causing leg pain with walking, cervical radiculopathy producing arm pain and facet joint-related pain with secondary epidural irritation.

What Conditions Can a CT Guided Epidural Injection Treat?

An epidural injection for back pain is typically considered after a period of conservative management, such as rehabilitation and oral anti-inflammatory medication, has not provided sufficient relief. It is most appropriate for pain that is radicular in nature, meaning pain that originates from an irritated or compressed nerve root and radiates along the path of that nerve.

The most common indications include:

• Disc herniation with nerve root compression. When a disc bulges or ruptures, it can press against an adjacent nerve root. This is the most frequent reason patients are referred for an epidural steroid injection. Nerve root irritation in the lower lumbar spine produces radiating leg symptoms, whereas in the neck, the compression produces pain, tingling, or weakness radiating into the arm.
  
• Spinal stenosis. Narrowing of the spinal canal can cause lower back pain and where severe, can cause neurogenic claudication, which is leg pain or weakness that worsens with walking and eases with rest or bending forward.
  
• Facet joint-related pain with epidural involvement. Less common, but epidural injection can be appropriate when facet joint pathology results in irritation of the lining of the epidural space.
  
  

Who Is Not Suitable for This Procedure?

Not every patient with back or leg pain is an appropriate candidate for a CT guided epidural injection. If any of the following apply to you, discuss them with your referring doctor before your appointment, some can be managed with adjustments to the procedure or preparation, and some mean this treatment is not appropriate.

• Active spinal infection or spinal cancer.

These are absolute contraindications. Introducing cortisone into an infected or malignant environment carries serious risk, and these causes of back pain require entirely different management.

• Pregnancy.

Inform the clinic if you are or might be pregnant. CT-guided injections involve ionising radiation and are generally avoided during pregnancy unless the benefits clearly justify the risk (severe pain). However, alternative approaches may be considered by the treating doctor.

• Uncontrolled bleeding disorders or anticoagulant medication.

Patients taking blood-thinning medications may be able to have the procedure if they can safely pause their medication in advance. The specific stopping protocols depend on the medication involved.

What to Expect: Before, During, and After the Procedure

Before Your Appointment

A GP referral is required. Your referring doctor will also typically organise prior MRI or CT imaging of your spine to confirm the diagnosis, identify the affected level and plan the injection approach. Arriving without recent relevant imaging may delay the procedure.

If you take blood-thinning medications including aspirin, warfarin, or plavix, you will need to tell the clinic before your appointment. Some medicines may need to be paused, however this will be decided with the clinic and the doctor who prescribed the medication. The stopping period varies by medication, so confirm the specific requirements with the clinic when booking. Do not stop any medication without guidance from your doctor or the clinic.

You have the option of taking a light oral sedative to help you feel more relaxed during the procedure. If you choose sedation, you will need to arrive approximately one hour earlier than your scheduled appointment time, and you must have a driver with you. Even without sedation, you will not be permitted to drive after the procedure due to temporary numbness from the local anaesthetic, so arrange a driver regardless.

During the Procedure (Approximately 15 to 20 Minutes)

You will lie face down on the CT table. The skin over the injection site is cleaned with an antiseptic solution. A small amount of local anaesthetic is injected into the skin and underlying tissue. This produces a brief stinging sensation lasting roughly ten seconds, after which the area becomes numb.

The radiologist then advances a fine needle toward the epidural space under CT guidance, checking the needle’s position in real time before proceeding. A small amount of gas or contrast dye is injected to confirm the needle is correctly placed.

Once the position is confirmed, the cortisone and local anaesthetic mixture is injected. Some patients notice a brief sensation of pressure or warmth during the injection; this is normal.

After the Procedure

The local anaesthetic component provides immediate pain relief that typically lasts six to eight hours. As it wears off, you may notice your usual pain returning before the cortisone begins to take effect. This does not mean the injection has failed. Cortisone generally begins working within two to seven days, and patients are encouraged not to over-exert themselves during this window.

Some temporary numbness or heaviness in the legs or arms, depending on the injection level is expected for up to two hours after the procedure. This is why you cannot drive home.

Some patients experience a temporary worsening of symptoms for 24 to 48 hours after the procedure. Soreness at the injection site for one to two days is also common and can generally be managed with paracetamol.

Seek urgent medical attention if you develop fever, chills, progressive or severe increasing pain, or any new neurological symptoms such as weakness or loss of bladder or bowel control. These are warning signs that require immediate assessment. If you have concerns in the days following your procedure, contact the Melbourne Radiology Clinic team for guidance.

How Well Does It Work and How Long Does Relief Last?

This is the question most patients want answered before deciding whether to proceed, and it deserves a direct response.

Approximately 50% of patients experience meaningful temporary pain relief from an epidural steroid injection, based on published clinical data and figures consistent with those reported by the Cleveland Clinic. That means the other half of patients experience limited or no lasting benefit. This variability is real, and any resource that describes these injections as broadly effective without this qualification is overstating the evidence.

For patients with acute disc herniation producing clear nerve root irritation show high response rates. A 2021 study of 204 patients who received a CT-guided transforaminal epidural steroid injection for discogenic radiculopathy found that 46.6% achieved substantial pain reduction at four weeks. Patients with chronic degenerative changes and less clearly defined nerve involvement tend to respond less reliably.

When the injection works, relief can last from days to months. Many responders experience several weeks to a few months of benefit, however the duration depends on the underlying condition and individual response. Repeat injections are possible and are generally considered appropriate when a previous injection provided meaningful relief and symptoms have returned. Most clinical guidelines support a maximum of three to six injections per year, with intervals between each to assess the response.

The primary goal of this procedure is not to cure the underlying structural problem, but to reduce pain sufficiently to allow you to engage with physiotherapy and rehabilitation. The injection creates a window of reduced pain; what you do within that window matters for your longer-term recovery.

Finally, these injections can serve a diagnostic purpose. When an injection at a specific spinal level reliably reduces your pain, this helps confirm that level as the source, information that can guide further treatment planning, including surgery.

Before You Book

If you have been referred for a CT guided epidural injection and have further questions about what the procedure involves, it is worth reviewing the preparation requirements carefully before your appointment. If anything in the contraindications section applies to you, including current anticoagulant use, diabetes, or a suspected iodine allergy, raise this with your GP or referring specialist before confirming your booking.

Patients who want to request an appointment at Melbourne Radiology Clinic can do so directly. If you are weighing this option alongside other image-guided interventions your doctor has discussed, Melbourne Radiology Clinic also performs a broader range of cortisone injection procedures that your referring doctor may consider depending on your specific diagnosis.

Frequently Asked Questions

• How long does a CT guided epidural injection take?

The procedure itself takes approximately 15 to 20 minutes at Melbourne Radiology Clinic. Patients should allow additional time for preparation, consent, and post-procedure monitoring before driving restrictions are confirmed. If you have requested sedation, you will need to arrive approximately one hour earlier for an oral sedative dose.

• What can I expect after a CT guided epidural injection?

Immediately after the procedure, the local anaesthetic component typically provides pain relief for several hours. This relief will wear off as the anaesthetic clears, and some pain may return before the cortisone begins working, usually within two to seven days. Temporary numbness or heaviness in the arm or leg is common and resolves within a couple of hours. Light activities are generally manageable the following day, however strenuous exertion should be avoided for 48 hours. Contact the clinic immediately if you develop fever, chills, increasing pain, or any new weakness.

• How many CT guided epidural injections can I have?

Most clinical guidelines suggest a maximum of three to six epidural steroid injections per year, with adequate intervals between injections to assess the response to each. The number of injections is determined by your response to treatment and your referring doctor’s clinical judgement. If the first injection provides meaningful relief, repeat injections when symptoms return are generally appropriate. If two to three injections produce no response, the overall treatment approach is typically reviewed with your referring clinician.

• Are epidural injections safe for back pain?

CT guided epidural injections are generally safe when performed by a specialist radiologist under sterile conditions with image guidance. Serious complications are rare. The most common side effects are temporary and include soreness at the injection site, a brief worsening of symptoms for 24 to 48 hours, and temporary numbness in the treated region. Less common effects include a temporary rise in blood sugar in diabetic patients and short-term insomnia from the cortisone. Serious complications such as infection, nerve injury, or haematoma are very rare but are a known risk of any spinal injection procedure.

• What is the success rate of epidural injections for back pain?

Many patients do experience relief from the pain on a temporary basis from an epidural steroid injection. However, results are better for patients with acute disc herniation producing clear nerve root irritation than for those with chronic, non-specific low back pain. Relief typically lasts between six weeks and six months. The primary goal is to reduce pain sufficiently to allow physiotherapy and rehabilitation to progress. This is a pain management intervention, not a cure for the underlying condition and repeat injections may be needed as relief diminishes over time.