Spinal injection is a valid way for diagnostic and/or therapeutic purposes of certain spinal diseases and conditions. It mainly gives a temporary improvement of the acute symptoms, however, its value is maximum in buying time until the underlying acute condition resolve, like acute disc herniation or acute disc annular tear. It also gives a maximum diagnostic value in certain conditions like multiple degenerative foramenal stenosis and we want to diagnose the symptomatic nerve compression by targeting it with injection, any improvement of the symptoms may give a good evidence of future improvement after surgical decompression in the next stage. Some are mainly for diagnostic purposes. It is not always possible to say exactly where the pain comes from. A ‘test’ injection can be a diagnostic tool to see how much it improves the pain or not.
Most injections contain a mixture of long-lasting local anaesthetic drug (i.e.Bupivacain) and Steroid (i.e. Triamcinolone) and the idea of this mixture is to give an immediate effect after the injection(effect of the local anaesthesia), this will give confidence and reassurance that the injection is in the right place. While the steroid will acte as local anti-inflammatory and decrease the swelling of the neural tissue by decreasing the edema and inflammation, then it will give long lasting effect. However, the affects of injections are varied depending on many factors like, the significance of nerve compression, patient response to these medication,the experience of the surgeon, etc.
Spinal injection is a shared practice and experience between different specialties like Neurosurgeon, orthopedic, pain clinician, radiologist etc. It can be given with multiple modalities depending on the preference of the treating doctors. Most of the neurosurgery delivered injections are radiogically guided injection that when we use X-ray, ultrasound or CT scan guidance to insert the needle.
There are 4 types of spinal injections
- Lumbar or Cervical spinal epidural block
- Nerve root block.
- Facet joint block.
- Caudal epidural block
Epidural injection
Injection of the steroid and the local anaesthetic solution at the epidural space, out side the thecal sac but inside the spinal canal. The medicine will infiltrate the whole bundle of the nerves and also other structures in the spinal canal. It mostly given in the lumbar spinal canal but can be given in the cervical canal as well. It’s effective in many conditions like spinal stenosis, radiculopathy, annular tear etc.
Caudal injection
This is similar to epidural injection but the medicine will be delivered through a small opening in the base of the spine (sacrum) rather than directly from the back. Although some doctors give caudal epidurals without x-ray control, the later should always be x-ray guided. This is to avoid injection too deep into the cerebrospinal fluid. the caudal injection is usually targeting pathology in the bottom of the spine, sometimes it’s easier to do especially in obese people or in patients with severe spinal degeneration.
Facet joint injection
In severe cases of back pain related to facet arthropathy(osteoarthritis of the back joints), facet joint injection may give diagnostic and therapeutic value. If the pain resolved after injection, the patient may be a target of facet de-innervation of even spinal fusion. The other indication, is the facet joint cysts that may respond very well to spinal facet injection. This is an injection into the facet joint It can be given in the neck and lower back. The facet joins are on either side of the spine and in the majority of cases injections are give to both joints of a level. It is often difficult to say exactly which facet joint is causing the pain. Therefore most doctors will inject two or three levels at the same time.
recently, only diagnostic facet joint injections can be done under surgical team according to recent NHS England protocol.
Nerve root block
In this type of injection, the medicine will deliver to single or multiple nerves but outside the spinal canal. It has a great diagnostic value to identify the responsible nerve of pain and radiculopathy. It also can be therapeutic in improving acute symptoms in acute stage of the disease. CT guided injections are more popular at the cervical spine due to the risk of injury of vascular structures in the neck.
Complications of injections
The risk of complication is very small, but it’s not zero. There is a small risk of infection, bleeding with blood collection at the spinal canal that may needs urgent surgery. There is a risk of injury to the neural tissue with numbness or paralysis of arms, legs or sphincters depending on the level of injection (this is usually transient but can be permanent in extremely rare cases). failure to improve symptoms is a common complication of spinal injection. Cerebrospinal fluid (CSF) leak is also not uncommon complication of spinal injection, especially the epidural injections. CSF leak is usually asymptomatic. However, some patients can develop headache if the leak continues. This is due to the change in pressure in the head (so-called low pressure headache) which improves with lying down. In cases of persisting headache a ‘blood patch’ can be administered to seal the tiny whole in the dura.
Some of the patient may develop funny sensation and tingling around the genitalia and the lower limbs after the injection but this shouldn’t cause any loss of power or sensation in the lower limbs. If any of weakness or sphincters problem, this needs an urgent medical attention
Generally the outcome of spinal injections is good, most of the patient can go home after 2 hours, however, patient should arrange for somebody to pick them up for safety and it’s not advisable to drive at least for 6 hours after the injection.