Why is anterolateral cordotomy effective at treating unilateral pain, specifically by disrupting pain signals originating from the opposite side of the body as they travel up the Spinothalamic Tract (STT)?

From the Guidelines

Anterolateral cordotomy is effective at treating unilateral pain because it disrupts pain signals originating from the opposite side of the body as they travel up the Spinothalamic Tract (STT), with a high success rate of 80% in the early postoperative period, as confirmed by a systematic review published in 2014 1. The procedure involves creating a lesion in the anterolateral quadrant of the spinal cord, which contains the spinothalamic tract fibers.

• The key to understanding its effectiveness lies in the anatomy of the pain pathway, where pain signals enter the spinal cord and synapse with second-order neurons whose axons cross to the opposite side (decussate) before ascending in the spinothalamic tract.
• Cutting the anterolateral quadrant on one side of the spinal cord interrupts pain transmission from the contralateral (opposite) side of the body. This procedure is typically reserved for intractable cancer pain that is confined to one side of the body, particularly below the neck, such as incident pain (movement-related pain) related to pathological fractures in the long bone, pubic rami, or pelvis related to local metastatic disease, as recommended by the mesothelioma framework published in 2007 by the UK’s Department of Health, and supported by a prospective case series of 45 patients undergoing cordotomy, where 80% of patients reported > 75% pain relief at 4-week follow-up 1. The pain relief is immediate but may diminish over time in some patients, and side effects can include temporary weakness, bladder dysfunction, and in rare cases, development of new pain syndromes.
• Cordotomy should be offered in a multidisciplinary team (MDT) setting with palliative medicine, oncology, and pain medicine teams to support the care pathway, and surgical cordotomy remains an option for patients who are unable to tolerate percutaneous cervical cordotomy, as carried out by neurosurgeons 1.

From the Research

Mechanism of Anterolateral Cordotomy

• Anterolateral cordotomy is effective at treating unilateral pain by disrupting pain signals originating from the opposite side of the body as they travel up the Spinothalamic Tract (STT) 2, 3, 4.
• The procedure involves mechanical disruption of nociceptive pathways in the anterolateral column, specifically the spinothalamic and spinoreticular pathways, to relieve pain while preserving fine touch and proprioceptive tracts 3.
• The spinothalamic tract is responsible for transmitting pain and temperature sensations from the body to the brain, and disrupting this tract can result in the loss of pain perception on the contralateral side of the body 3, 5, 4.

Efficacy of Anterolateral Cordotomy

• Studies have shown that anterolateral cordotomy can be an effective treatment for intractable cancer pain, with a high success rate and significant reduction in pain intensity 2, 3, 4.
• The procedure can be performed using various techniques, including percutaneous and open approaches, and can be tailored to the individual patient's needs 2, 3, 4.
• While complications can occur, such as ataxia, paresis, and sympathetic dysfunction, the benefits of anterolateral cordotomy can outweigh the risks for patients with severe, unilateral pain that is unresponsive to other treatments 3, 6.

Patient Selection and Outcomes

• Patient selection is critical to the success of anterolateral cordotomy, and patients with unilateral, nociceptive pain that is refractory to best pharmacological treatment and has a limited life expectancy are typically considered good candidates for the procedure 2, 3, 4.
• Outcomes can vary depending on the individual patient and the specific technique used, but studies have reported significant pain relief and improved quality of life for many patients 2, 3, 5, 4, 6.
• However, some patients may experience increased pain or new pain after cordotomy, particularly if they have bilateral pain, and this should be carefully considered when evaluating the potential benefits and risks of the procedure 6.