Abstract
Background
For some patients with serious illness, usual analgesic therapies do not achieve adequate pain relief or are associated with intolerable side effects. 1 For example, ∼10% of patients with advanced cancer develop intractable pain despite standard analgesic therapies. 2 Interventional/neuromodulating therapies such as intrathecal pain pumps (see Fast Fact #98), indwelling epidural catheters (see Fast Fact #85), and sympathetic nerve blocks (see Fast Fact #97) all have a role for select patients with refractory pain. Yet, some may have too short a life expectancy (<12 months), are too cachectic to tolerate an implant, find that managing a device would be too burdensome, or have pain that is too widespread and/or at a high-level distribution to make neuromodulating therapies feasible. Neuroablative analgesic procedures utilize surgical or nonsurgical strategies to disrupt targeted anatomic locations along the pain signaling pathways. 3 They may be considered if an experienced clinician is available. 3 In this Fast Fact we highlight common neuroablative procedures for refractory pain. Of note, few high-quality clinical trials have evaluated these procedures; supporting evidence is based primarily on small studies, case reports, and expert opinion for cancer-related pain. 4
Cingulotomy
For decades, palliative cingulotomy has been performed for refractory pain and is a relatively low-risk procedure that ablates an anatomic region within the medial aspect of the cerebral hemisphere called the anterior cingulate cortex. This region is felt to modulate attention or emotional reaction to pain.3,5 The standard surgical procedure is performed by neurosurgeons under local anesthesia, usually requiring a brief inpatient stay of one to four days.2,6,7 Nonsurgical cingulotomies have been described utilizing radiation oncologists to target the cingulate cortex through stereotactic radiosurgery (SRS). 8 Availability and cost vary widely and is institution dependent. 9
Evidence: Two systematic reviews noted immediate and significant reductions in pain and opioid dosage in 32% to 83% of patients.4,5 Most exhibited adequate pain relief three months postoperation.2,4,5,7 A noncontrolled study of 13 patients with refractory pain from cancer and an average preoperative Visual Analog Scale (VAS) score of 9 reported a median VAS score reduction of 5 points as well as significant improvements in Karnofsky Performance Status (KPS) scores. 2
Patient selection: widespread pain, a life expectancy <12 months, and unlikely to benefit from other neuromodulator-based interventions.
Adverse effects: headache, nausea, vomiting, confusion, urinary incontinence, and gait disorders have been reported. Serious adverse events are rare and include postoperative spasticity, hemiparesis, bleeding, seizures, decreased memory, and personality changes such as apathy and decreased spontaneity.3,7,10 Most patients do not show significant cognitive changes. 7
Cordotomy
This procedure targets nociceptive pathways in the anterolateral column of the spinal cord, specifically the spinothalamic pathway. By targeting this anatomic site, fine touch and proprioception should be preserved while the transmission of pain and temperature perception is blocked on the contralateral side of the surgical lesion. 11 Neurosurgeons can utilize a variety of techniques depending on the site of pain (open, endoscopic, transdiscal, and percutaneous/image-guided) using radiofrequency lesioning. It can be an inpatient or outpatient procedure. 12 Availability and cost ($10,000–20,000) of each procedure are institution dependent. 13
Evidence: like cingulotomy, pain relief is often rapid and may occur in up to 80% of patients. 11 Improvements in KPS scores have been noted. 14
Patient selection: cordotomy is best for patients with nociceptive pain that is localized, unilateral, and below the C4 to C5 dermatome. 2 Since analgesia rarely lasts more than two years, this procedure is usually reserved for patients with a shorter prognosis. 15
Adverse effects: ataxia, paresis, sympathetic dysfunction, bladder dysfunction, acquired sleep apnea, or Horner syndrome has been described, primarily due to unintentional ablation of the nearby spinal cord. 11 Some patients may develop “mirror” postprocedure pain on the contralateral side of the initial site of pain, which is an unmasking of pre-existing pain that becomes more perceptible after the previously dominant pain subsides. 11
Myelotomy
Myelotomy is less commonly performed compared with cingulotomy and cordotomy. With this procedure, neurosurgeons target one of two locations. For a commissural myelotomy, the spinothalamic tract fibers are sectioned as they cross at the anterior commissure of the spinal cord to target bilateral visceral midline pain. 16 A punctate midline myelotomy targets the dorsal column and treats visceral type pain. 16 Studies suggest ∼90% of patients who undergo myelotomy achieve early pain relief, but pain tends to recur. Bladder, bowel, and sexual dysfunction are common, so it usually is reserved for patients with pre-existing bowel, bladder, or sexual dysfunction. 16 It can be done as an inpatient or outpatient procedure; availability is varied and cost ranges from $50,000 to $100,000. 17
Mesencephalotomy
This procedure, also performed by neurosurgeons usually through a stereotactic approach, targets pain pathways within the midbrain and is considered for patients with refractory cancer pain located in an anatomic region too high for other interventions (e.g., head or neck). 15 Although the use of mesencephalotomies has significantly diminished over the past few decades, it still may have a limited role for inpatients with unilateral pain syndromes above the C4 level. The procedure's cost is $10,000 to $30,000 and is institution dependent. 9
Limitations
Even though guidelines for neuroablative procedures in cancer pain have been developed by the American Association of Neurological Surgeons and the Congress of Neurological Surgeons, 4 several relevant factors contribute to their relative underutilization for refractory cancer pain including the ignominious history of psychosurgery, aversion to neurosurgical lesioning procedures, concern for adverse effects, hospice enrollment barriers, prognostic uncertainty, and the relative paucity of trained surgeons able and willing to perform these procedures.3,18