The brain is insensitive to pain because it has no nerve endings. This is why neurosurgical interventions can sometimes be performed on awake and conscious patients.
It is he who manages everything we feel, including pain, from our nervous system and the areas that control our emotions. Yet the brain itself is insensitive to this pain. This explains why neurosurgical operations, such as the one which has just been carried out on a 53-year-old violinist operated on for a brain tumor at King’s College London, can be carried out without difficulty and are in fact quite frequent. During her operation, the patient, awake and conscious, was able to play her instrument to guide the surgeons so that they did not touch the motor zones of her left arm and this without causing her the slightest pain.
Why is this central organ of our nervous system insensitive to pain? Quite simply because it does not have nerve endings which are the vectors of pain sensation. This goes well through the brain but through fibers (known as nociceptive fibers) present throughout the human body and which transmit their nerve impulses to it, including the signals which generate pain.
Skip the arachnoid envelope
This does not mean that surgery on the brain is completely painless. First there is a need in these interventions to open the skin of the skull, a painful incision as on any other part of the body. Then you have to cross the bones of the cranial box and, above all, pass the barrier of the arachnoid envelope — this name comes from the fact that it looks like… a spider’s web — which surrounds and protects the brain and which does not have blood vessels. But there, no more question of escaping pain: this arachnoid membrane is full of nerve endings and its incision is extremely painful.
“Once one works on the brain after passing this membrane, the patient feels no pain. This is why we can perform neurosurgery under hypnosis, or even wake up the patient so that his reactions guide the work of the surgeon so that essential areas are not affected”explains Professor Alain Serrie, head of the pain medicine department at Lariboisière in Paris.
This is how the patient operated on for a brain tumor at King’s College London was able, without suffering, to play the violin to guide the doctors so that they did not accidentally “injure” the area of the brain that controls the movements of his left arm.
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