Neurolytic Procedures

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 (eg, postherpetic neuralgia), kidney diseases, or nerve compressions such as entrapment, peripheral nerve injury due to trauma, cancer, or a combination of the above. Although treatment strategies for neuralgia usually start with pharmacotherapy with medications such as membrane-stabilizing agents (eg, gabapentin or pregabalin), anticonvulsants (eg, carbamazepine, topiramate, and lamotrigine), antidepressants (eg, amitriptyline), and muscle relaxants (eg, 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 adverse events with poor improvement in the quality of life. Therefore, it is often necessary to resort to nonpharmacological 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, require the early application of minimally invasive analgesic techniques to manage symptoms effectively.

A neurolytic block involves the deliberate injury of a nerve by freezing, heating, or applying 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 chemical agents or producing damage with a physical method such as cold (ie, cryotherapy) or heat (ie, radiofrequency ablation).

Neurolytic blocks can be seen as a natural advancement from neurotomy. Neurotomy involves the transection or partial resection of a nerve, typically performed on small peripheral nerves that are exclusively sensory. This technique has historically been applied for treating conditions such as trigeminal neuralgia and pelvic pain syndrome (presacral neurotomy), as well as nonpainful conditions like spastic dysfunction of the elbow. However, as the surgical cutting of a nerve may lead to complications such as painful neuromas or differentiation over time, neurolytic approaches are generally preferred over surgical ones.

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

Currently, the specialty of pain medicine defines neurolysis as the selective, iatrogenic destruction of neural tissue aimed at alleviating pain. As understanding of nervous system pathophysiology has deepened and techniques and tools have been refined, the applications for these techniques have expanded. For instance, advances in medical imaging have enhanced the precision and efficacy of interventional pain management. As a result, using peripheral neural blockade and neuro-destructive techniques has increased for the treatment of chronic intractable pain. Additionally, peripheral nerve blockade is now recognized as a valuable treatment for muscle spasticity.