Chapter 78: Chemical Neurolysis

INDICATIONS

Neurolytic techniques have long been used in the treatment of pain. The underlying principle for neurolytic blocks is prolonged relief of intractable pain, most often in patients with malignancies. Pain associated with cancer may be visceral, somatic, and/or neuropathic in origin. Many cancer patients have a combination of these pain types at the time of their diagnosis. Pain is often reported when visceral structures are compressed, invaded, or distended. Visceral pain is often described as vague, dull, deep, constricting, crampy, or colicky in nature. Empirical data suggests that visceral sympathetically-mediated pain responds more favorably to neurolytic therapy than neuropathic pain.¹

Neurolysis, or destruction of neural tissue, was once performed surgically under direct visualization. As advancements in imaging and ablative techniques continued to progress, these procedures can now be done percutaneously² chemically, thermally with radiofrequency, or by freezing via cryoneurolysis.

The indications for chemical neurolysis include³:

• Severe, intractable pain that persists after less invasive treatments

• Intolerable side effects of analgesic therapy

• Intrathecal catheter, with or without a pump, is not a viable option

• Advanced or terminal malignancy

• Pain well localized:

  • Unilateral pain, localized to the trunk

  • Involves only a few dermatomes or one peripheral nerve

• Primary somatic pain mechanism

• Absence of intraspinal tumor spread

• Pain relieved with prognostic local anesthetic block

• No undesirable effects after local anesthetic block

• Realistic expectations by patient and family

• Informed consent clearly explains potential complications

BASIC CONCERNS AND CONTRAINDICATIONS

Risks and benefits should always be weighed prior to undergoing any intervention. Extensive communication with the patient is necessary before proceeding.

Some concerns include:

• Potential risk for infection in immunocompromised patients

• Metastatic cancer spread to the region

• Thrombocytopenia secondary to chemotherapy

• Difficulty in positioning due to tumor and pain location

Absolute contraindications for injection include:

• Infection, systemic or localized to injection site

• Coagulopathy

• Patient refusal

Relative contraindications include:

• Autonomic nervous system no longer the main transmission of the pain source for visceral pain (eg, carcinoma of the pancreas that has begun to invade the body wall)

• Distorted or complicated anatomy (eg, large aortic aneurysm)

RELEVANT ANATOMY

Visceral neurolytic blocks are particularly effective for cancer-related pain. The paravertebral sympathetic chain consists of sympathetic neural tissue from several sympathetic plexuses that run along the paravertebral region of the body (Figure 78-1). There are several sites for neurolytic blockade of the sympathetic nervous system for the treatment of cancer pain (Table 78-1).¹ These axial sympathetic chains include the cervical, thoracic, and lumbar sympathetic ganglia.