This information is designed to help patients talk with their surgeon about this operation. The results and complications will vary between centres especially because this operation has become quite rare.
The stereotactic mesencephalotomy operation is designed to destroy the pain pathways coming from the head and neck before they reach their target in the brain. This can be ideal for patients with pain on one side of their head or neck due to cancer. We have recently published our results in the peer reviewed British Journal of Neurosurgery.
Download a copy of our paper: Mesencephalotomy BrJNSx 2016
Cancer pain is most often due to a tumour destroying the normal tissue around it. Pain from the body is carried up to the brain through a well known pathway in the spinal cord called the spinothalamic tract. If the spniothalamic tract is deliberately cut (or burned) by a neurosurgeon, then no pain from that part of the body can be transmitted to the brain. This operation is called a cordotomy and is described elsewhere. It is ideal for unilateral pain below the shoulder (i.e. from the body).
For cancer pain from the head and/or neck (i.e. above the shoulder), we use the stereotactic mesencephalotomy operation. This operation blocks the pain pathway higher up – while it is passing through the midbrain.
This can be a wonderful benefit to patients with severe cancer pain if:
1. their medications can not block the pain, or
2. the high dosage of the medications required to block their pain is causing intolerable side effects (e.g. sedation)
The operation at our centre is performed with local anesthesia and a brief bolus of sedation. The procedure begins with a stereotactic head frame attached to the head with local anesthesia. An MRI is then done to visualize the target area within the brain. The patient is then transferred to the operating room and the procedure takes about an hour. The top of the head is shaved and cleaned (3 cm) and then frozen with local anesthetic. A small (2 cm) incision is made in the scalp and a small hole (1 cm) drilled in the skull. An electrode is then lowered down to the brain target (patients can not feel this as there are no pain sensors in this part of the brain). When the electrode is at the correct anatomical location, we confirm with physiologic testing. Small pulses of electricity are released from the tip of the electrode and the patient is asked what they feel. If the electrode is in the correct physiologic target, the patient will feel warmth or pain in the desired region (i.e. where their cancer pain is located). A small sedative is given and the pain pathway is then destroyed by heating. After the lesion, the patient will no longer feel pain from the desired region of their body.
The benefits and risks of this procedure must be discussed directly with your neurosurgical team.
is elimination of cancer pain on one side of the head or neck. As a side effect, the patient will not be able to sense temperature (hot or cold) in the same area but this usually has no significance for the patient. Interestingly, the patient is still able to feel touch – they are not numb and do not describe ‘pins and needles’ – they just lose the ability to feel pain within the targeted area. The benefit has been reported to typically last a year and therefore patients are usually selected for this operation if their expected lifespan is less than a year.
include but are not limited to incomplete or temporary pain relief, numbness in the head or body, double vision, and a rare but devastating stroke causing weakness, paralysis or death.
After the operation, the palliative care team typically aggressively reduces the pain medications (e.g. morphine). Occasionally all these medication are stopped but usually some is still given by mouth.