Nerve Blocks

What are Nerve Blocks?

How do they work?

What kinds are there?

• Local anesthetics (‘freezing’) are used to perform nerve blocks which are intended to be temporary in their effect. This may be done to diagnose a pain site, or to ‘interrupt pain signals’ with the intent of allowing recovery of more normal function. Treatments can range from a single administration, multiple injections or a continuous infusion. The injection may be done into a major nerve plexus or group, into single specific nerves, into damaged nerve areas (i.e. ‘scar neuroma’),  into joints or tendor points called ‘trigger points’. Local anesthetics typically last for a few hours after administration. Examples; 
  • Sympathetic nerve blocks: A sympathetic nerve block refers to the application of a local anesthetic to any part of the sympathetic nervous system such as the stellate ganglion in the neck for arm pain, or the lumbar sympathetic ganglion for leg pain. There is low quality, inconclusive evidence suggesting sympathetic nerve blocks may be useful for complex regional pain syndrome. 
  • Paravertebral nerve blocks: Local anesthetics are injected beside the nerve roots coming from along the spine (thoracic region) to achieve paravertebral nerve blocks.  There is weak, moderate quality evidence suggesting that paravertebral nerve blocks could be used to treat postherpetic neuralgia.  
• A neurolytic block is a procedure where the nerve is intentionally damaged to prevent the feeling of pain. This can be done a variety of ways, including the application of chemicals, heating or freezing of the nerve cells. Neurolytic blocks aren’t permanent in nature; nerve connections can regrow, but may not regrow with normal function depending upon which agent is used to damage the nerve- for example alcohol is often associated with increased nerve pain when nerve function recovers. For this reason, neurolytic blocks have become restricted to use in palliative care when patients are not expected to survive as long as it takes for the nerve to recover its function.
• A neurectomy is when a neurosurgeon actually cuts the nerve cells or removes it altogether. This procedure, due to its invasive and irreversible nature, is typically reserved for a time when other treatment options have been explored and deemed unsuccessful. Neurectomy is typically considered in cases where sensory nerves are damaged. After the nerve(s) is removed, the individual may experience numbness which gradually reduces as surrounding nerves fill in. 

Related evidence