Nerve Root Block
The anatomy of the spinal cord
Some 31 pairs of spinal nerves arise from the spinal cord. They exit the spinal cord and spread through the peripheral body via intervertebral foramina. Every spinal nerve has a ventral and dorsal root which come together to form a unified segment – this intraforaminal segment is known as the spinal nerve proper or spinal nerve root.
Causes of nerve root pain
Spinal disc problems – including disc herniation or disc degeneration are a common cause of nerve root pain, as they can cause the impingement of the nerves. Swelling or inflammation in the nerve root region, which involves the accumulation of fluid, can pressurise the nerve roots. Nerve root pain and irritation can be caused by injury or trauma. Certain types of growths such as the enlargement of organs or tumours are rare causes of nerve root pain.
Nerve root block procedure
A nerve root block procedure, also known as a selective nerve root block, involves an injection which approaches the nerve at its exit level – the hole between vertebral bodies which is known as the foramen. Fluoroscopy (X-ray) is used to ensure that the right location for the injection is identified, and a contrast dye can be used to confirm this correct location. The injection – which is of typically a mixture of the lidocaine anaesthetic and a steroid which acts as anti-inflammatory medication – is administered, offering both a diagnostic and therapeutic treatment which is capable of reducing inflammation around the nerve root.
A nerve root block is a day case procedure performed using fluoroscopy (live X-ray) to help guide the needle accurately and avoid any nerve injury. The procedure will take place in theatre under full aseptic conditions with the patient on his or her stomach. A small needle in the back of your hand can be used to administer sedation or in case of an emergency. The skin is well cleaned before a small amount of local anaesthetic is applied in order to numb the injection area. The physician then directs a small needle close to the nerve root, injects contrast dye to confirm the correct location. The injection – which is of typically a mixture of local anaesthetic and a steroid which acts as anti-inflammatory medication – is administered, offering both a diagnostic and therapeutic treatment which is capable of reducing inflammation around the nerve root.
To prolong the benefit, Pulsed Radiofrequency treatment may be indicated if there is a significant reduction in the pain levels after the block. On a separate admission, the treatment involves a generator which after precision and safety tests sends out measured electrical pulses using thin insulated wires to the dorsal root ganglia. This procedure can be described as a ‘retuning’ of the nerves so they modulate pain transmission.
Patients are then monitored in a recovery area before transfer to the ward and discharge home. Patients may experience a numb feeling for a few hours. Pain at the injection site may increase for four or more days. It is advisable to rest for 24 hours and resume stretches and exercises when the pain eases. This window of pain relief should be utilised for performance of strengthening exercises and rehabilitation physiotherapy.
There is a variable response to injection treatment. It is important to discuss both the benefits and risks of the procedure with your doctor before any agreement to undergo the procedure is reached. Although the chance of any complications is generally low, as with all surgical procedures, there is an element of risk involved including failure to get benefit or pain aggravation. There may be an allergic reaction to the steroid or any of the medications, or that the injection causes an infection or bleeding. Paralysis, spinal cord or nerve damage is extremely rare.