Nerve root block

A nerve root block is an injection into a nerve to reduce or prevent pain in an arm or leg. The nervous system follows the spine down the back and then branches into the various limbs and body parts along the way. Persistent pain in one specific place can be blocked by disabling the ability of a particular nerve to transmit it. A nerve root block is the process of stopping the transmission of pain along the nerve. The root of the nerve is where it meets the spine and the block is that prevention.

The detail is that a nerve root block is the injection of a local anaesthetic into the nerve along with some steroids. X-ray guidance is usually used to approach the specific nerve to be blocked. The value of the procedure is that sometimes pain follows the path of a single nerve. In the absence of some obvious cause the solution is to block the ability of the nerve to carry the pain. A nerve root block is therefore exactly that. Identify where the pain is in the limb, trace that back to where the responsible nerve joins to the spine and then block it at that point.

A nerve root block is a temporary solution which can last up to some months. A permanent cut or cauterisation of a nerve is more properly known as a sympathectomy, something not usually done for pain management reasons. If the root block is successful in managing the pain then the process can be repeated if it wears off over time.

It is possible for a nerve root block to be used as a diagnostic tool, to check that the pain is indeed nerve related. If the block stops the pain then that's proof of the location and likely cause. This diagnostic use would be by a consultant neurologist. A nerve root block is also used as a therapy for pain. This is when the cause and location have been identified, and it is treatment, not diagnosis, that is required.

A nerve root block is effective at reducing and usually removing pain. It does not solve the underlying cause of it unless, that is, it is the nervous system itself creating it.

The problem a nerve root block solves is continued neuropathic pain. That is when there is ongoing pain with no obvious other physical cause to it. If there is some direct cause for the pain then the treatment is of that specific cause. Some pain is simply there.

The treatment becomes to be able to block the transmission of the pain through the nervous system. This is exactly what a nerve root block does. Removes the ability of the nerve at that location to carry the pain signal to the brain.

The nervous system itself radiates out from the spine to the varied limbs and parts of the body. If we identify where the pain is then we can block the specific nerve that is carrying it. When we do see pain that is travelling along the one nerve, rather than being more general over an area, then that's the candidate for the blocking of that pain pathway. This is also known as a “facet block”.

The necessary precondition for a nerve root block to work is that ongoing pain along the route of the one nerve.

One possible use of a nerve root block is if there is a specific problem in an area and physiotherapy is the correct solution.

However, the ongoing pain makes the performance of that exercise and manipulation too painful to continue. At which point the nerve root block can be used to allow the actual treatment to proceed, to remove the pain while it continues.

A nerve root block is an injection of steroids and local anaesthetic. You should have no food or liquids from the night before the procedure.

If you are taking any blood thinners – Warfarin, Plavix and so on – then you must stop well before the nerve block. Your doctor will advise you how far beforehand you need to do this.

The nerve root block will be preceded by the cleaning of the necessary area of your back and the application of a local anaesthetic.

X-ray guidance may be used to locate the correct nerve and guide the needle. Then the injection itself and a wait to make sure that it has taken hold.

After a nerve root block your blood pressure will be monitored for perhaps 20 to 30 minutes. At which point it is possible to leave.

It is not possible to drive immediately after the procedure, you will need to either have a driver or take another transport option. The dressing will be a simple plaster and this can be removed the next day.

You should not have a hot bath or shower for the rest of the day after the nerve root block – no heat or soaking in water.

It is possible that there will be local tenderness for two or three days, an ice pack can be used to alleviate this. The steroid will take about the same time to fully take effect.

As with any procedure there are remote risks of infection, nerve injury, bleeding – which is why no blood thinners – and possibly allergic reactions. These will all be monitored alongside your blood pressure immediately afterwards.

The major risk is that the procedure does not fully work. That is, that even having had a nerve root block, the pain remains. It is possible, unlikely but possible, that the nerve was not fully anaesthetised. If this is so then the procedure can be repeated at a later date.

A nerve root block will also wear off over time. This is a temporary treatment, not a permanent cure. The pain itself may well recede over time. The underlying condition might correct itself. It is possible to repeat the nerve block if pain returns after 6 to 9 months. The indication that a second block would be useful is that the first one did work. If the nerve root block provides a substantial and sustained alleviation of pain than when that wears off it can be repeated.

A nerve root block should not be undertaken if you have influenza, an active infection of any other kind, a cold, fever or very high blood pressure. These all add to the risks and so if you have them the procedure will not go ahead. Any delay will be until you are free of these factors.

It is also possible to feel muscle weakness afterwards. If it happens this is because the medication itself has numbed the motor fibres of the muscles themselves. This passes in a few hours and is not normally of any more concern than that.