Peripheral Neurolytic Blocks

Excerpt

Peripheral nerve neuralgia or peripheral neuropathic pain may result from damage of a nerve due to various etiologies including medical conditions such as diabetes, infections (e.g., postherpetic neuralgia), kidney diseases, or nerve compressions such as entrapment, as well as peripheral nerve injury due to trauma, cancer, or a combination of the above. Although treatment strategies for neuralgia usually start with pharmacotherapy with antineuropathic drugs such as membrane-stabilizing agents (e.g., gabapentin or pregabalin), anticonvulsants (e.g., carbamazepine, topiramate, and lamotrigine), antidepressants (e.g., amitriptyline), and muscle relaxants (e.g., baclofen) to reduce the excitability of the peripheral nerve and central connections, drug treatment often fails to obtain effective results and can expose the patient to side effects with poor improvement in the quality of life (QoL). Therefore, it is often necessary to resort to non-pharmacological strategies such as neurolytic blocks. These approaches, however, are not only applicable when pharmacological strategies have failed but are to be integrated into the context of multimodal schemes. Moreover, some types of painful conditions, such as pain from pancreatic neoplasia, must necessarily be managed through the use of minimally invasive analgesic techniques, already at the onset of symptoms.

A neurolytic block is a form of block involving the deliberate injury of a nerve by freezing or heating or the application of chemicals to cause a temporary degeneration of targeted nerve fibers, causing an interruption in the signal nerve transmission. In particular, neurolysis implies the destruction of neurons by placing a needle close to the nerve and either injecting neurodestructive chemicals agent or producing damage with a physical method such as cold (i.e., cryotherapy) or heat (i.e., radiofrequency ablation, RFA).

In exemplary terms, neurolytic blocks would represent the natural evolution of neurotomy that is another approach for the treatment of neuropathies. It represents a transaction or partial resection of a nerve performed on small peripheral nerves that are exclusively sensory. It has long been used to treat trigeminal neuropathy, pelvic pain syndrome (presacral neurotomy), and other painful and no-painful conditions (e.g., spastic dysfunction of the elbow). Because the surgical cutting of a nerve can induce over time a painful neuroma or differentiation, neurolytic approaches are usually preferred over the surgical blocks.

Neurolytic blocks, however, are not a recent discovery. The first report of chemical neurolysis for the treatment of pain was made, in 1863, by Luton who administered neurolytic agents into painful areas. Neural blockade with neurolytic agents has been documented for the treatment of pain for over a century. In 1904, Schloesser was the first to report alcohol neurolysis for the treatment of trigeminal neuralgia. Later on, in 1928, Doppler used phenol neurolysis to destroy presacral sympathetic nerves for the treatment of pelvic pain.

Nowadays, the specialty of pain medicine defines neurolysis as the selective, iatrogenic destruction of neural tissue to secure the relief of pain. Over time, indeed, knowledge of nervous pathophysiology, refinement of the techniques and tools available, have increasingly flooded the indications of these techniques. Advances in medical imaging, for instance, have allowed precision and, therefore, better efficiency in the practice of interventional pain management. The previous pain treatment algorithms have been progressively modified to include peripheral neural blockade and neuro-destructive techniques. Again, peripheral nerve blockade represents one of the therapeutic possibilities to treat the spasticity of various muscles.