A percutaneous cervical cordotomy is a procedure where the spinothalamic tract is surgically interupted or ablated. The procedure can be undertaken to relieve severe unilateral pain in cancer patients. The procedure is not commonly used and is only available in limited centres around the world, being performed by a small subset of either neurosurgeons or pain physicians experienced in its use.
Background Information and Anatomy
Pain sensation is transmitted to the brain via the spinothalamic tract as shown in the two digrams below:
- Figure above: a diagram showing the pathway by which pain fibres enter the spinal cord and ascend the cerebrum.
- Figure above - A transverse section of the spinal cord showing the various tracts including the spinothalamic tract.
Sensory fibres initially enter the spinal cord through the dorsal root and synapse with second order neurons. Here the pain fibres cross the midline near the central canal and enter and ascend the spinothalamic tract. The principle behind a cordotomy is to destroy the spinothalamic tract prior to it entering the brainstem and thus stop the sensation of pain entirely on the contralateral side.
Percutaneous cervical cordotomies are indicated for unrelieved unilateral pain below the C5 level due to malignancy, including:
- Pancoast lung or breast cancer with brachial plexus
- Unilateral pelvic tumours invading the sacral or lumbar plexus
- Limb tumour
In experienced hands there is approximately a 10% technical failure rate where there proceduralist is unable to locate the spinothalamic tract. In another 10% of patients no analgesia is brought about. 80% of patients report significant improvement in pain, with approximately 40% reporting complete analgesia and 40% reporting some analgesia.
A percutaneous cervical cordotomy is performed in theatre with the patient lying flat and still whilst awake. A needle is inserted under fluoroscopic guidance between C1 and C2 and the meninges is pierced. An electrode is then inserted through the needle and pushed into the spinal cord. The electrode is then stimulated at a frequency that will stimulate motor fibres. It is slowly moved within the spinal cord until neck muscles begin to twitch. The twitching neck muscles represent stimulation of the motor fibres which are located adjacent to the spinothalamic tract. The electrode frequency is then modified to an appropriate frequency for stimulation of sensory fibres and the probe is slowly moved in the spinal cord until the patient complains of unusual temperature sensations in the contralateral limb which indicates that the probe is located within the spinothalamic tract. Microwaves are used to heat the probe to a temperature of approximately 80 degrees Celsius which causes cellular necrosis. During the procedure the patient is asked to raise his or her leg to ensure that the motor fibres are not being damaged.
Adverse Effects and Complications
Common complications of percutaneous cervical cordotomies include:
- Transient ataxia, motor weakness, urinary retention second to temporary surrounding oedema inhibiting the normal function of nearby spinal tracts
- Death with approximately 0.2% of patients dying peri-procedurally
An expected adverse effect in successful procedures is the contralateral loss of pain and temperature sensation. Some patients find this quite distressing.