Neuro-oncological surgery, a rich and exciting discipline

It is very important not to damage the delicate nervous tissues which can cause especially motor paralysis, during brain and spinal cord surgery which involves risks for both the surgeon and the patient. This is where the most popular method of recent years comes in: Multimodal Intraoperative Neuromonitoring…

Surgeons try to perform the surgery in such a way as to avoid complications with their knowledge, skill and experience by paying attention to all the anatomical and pathological features during the surgery. Despite all these precautions, it is very difficult in particular to distinguish normal nervous tissue from tumors of the spinal cord and spine. Therefore, the risk of hemiplegia increases.

Over the past 10 years, Multimodal Intraoperative Neuromonitoring has made it possible to reduce this risk; this method gained popularity and began to be used in Turkey and the rest of the world at the same time. For example, by securing the nerve pathways innervating the upper and lower limbs, this technique ensures early prevention of paralysis.

In fact, briefly, to avoid complications of loss of mobility, the surgeon is informed in time with the continuous records of the patient’s mobility capabilities. We can say that it is the most reliable method today to identify tissue as nerve tissue with the naked eye or under a microscope during surgery. However, it should not be forgotten that this method is not yet used on certain patients such as those who have undergone major brain surgery and patients who have pacemakers. The Director of the Neurosurgery Department of the ANADOLU Medical Center, Prof. Dr. Serdar Kahraman explains the details on this topic…

How to use it ?

We can briefly describe neuromonitoring as a process that records and measures incoming and outgoing nerve impulses during surgery, starting with the brain, then the spinal cord and finally those of the nerves of the upper and lower limbs. In fact, it is a process comparable to an ECG recording that monitors heartbeats and that everyone knows. But the electrical waves recorded by neuromonitoring are evidence of motor and sensory functions. Currently, it is one of the preferred methods frequently used in many healthcare facilities to help perform safer surgery. We can say that it can be installed in any operating room as a simple portable alert and recording system software. At the end of the intervention, the recordings are recorded and saved in the patient’s file.

Regarding the application: before the intervention, when the patient is under general anesthesia, the muscle stimulation and recording electrodes are placed on the appropriate parts of the scalp, upper and lower limbs.

At the beginning of the operation, the sensory, reflex and motor electrical responses are recorded using specific devices. The doctor or the neurophysiologist carrying out the Intraoperative Neuromonitoring informs the surgeon by observing the responses during the surgery, if there is or not a change or if the responses remain stable, therefore if the nerve fibers are protected or damaged. Because of the monitoring and recording of all these electrical responses, it is called multimodal monitoring, that is to say the monitoring and recording of sensory and motor functions.

If the surgery causes nerve tissue and spinal cord damage, the stimulated electrical responses obtained are indicative of deterioration. The Intraoperative Neuromonitoring specialist immediately alerts the surgeon and the anesthesiologist, thus helping to reduce the risk of irreversible damage.

Changes and deteriorations in electrical responses alert the surgeon with approximately 90% certainty during surgery. Nevertheless, sometimes, even if it seems correct, there can be deteriorations in electrical responses that the monitor could not register and neurological deficits can occur in the patient post-operatively. The reverse can also occur, ie even if it appears that the electrical responses are disturbed, the patient may have no problem after waking up.

These probabilities are very minimal, neuromonitoring makes it possible to secure the surgical intervention as much as possible and offers great comfort to the surgeon during the surgical intervention.

In what other surgeries is this technique used?

We can see that the use of neuromonitoring increases the success of surgical interventions for certain congenital diseases of the spine and spinal cord. For example, during surgery for Tethered Cord Syndrome in children, the damaged anatomical structures causing the cord to come together at the bottom of the spine and stretch, are electrically stimulated with using electrodes and it can be seen whether the nerve roots are performing their motor functions or not. With this method, the surgeon can distinguish which damaged tissues are stretching the spinal cord; he thus safely severs the part that does not work and frees the spinal cord. During Tethered Cord Syndrome surgery, specific nerves such as the pudendal nerve play an important role in urinary, sexual, and digestive functions; they are electrically monitored to ensure that these functions are well protected.

We can also say that the important precise positive results obtained by the Multimodal Intraoperative Neuromonitoring method in spine and spinal cord surgeries will steadily increase in the years to come. Of course, these results seem to progress in parallel with the development of other surgical technologies such as the microscope and intraoperative imaging techniques.

Which nerves are tracked?

There are two main pathways of neural structures followed during monitored surveillance during surgical procedures. The first is the monitoring of PEM (Motor Evoked Potentials), the second is the PES (Sensitive Evoked Potentials). Apart from these checks, it is possible to measure the electrical potentials of the nerve roots, using the EMG technique.

It is thus possible to obtain information concerning the nerve roots of the operated part. Motor Evoked Potentials are obtained by visualizing motor pathways from the brain to the muscles of the upper and lower limbs. The deterioration of these pathways on the operated part can cause paralysis in the patient upon awakening.

Therefore, it is very important to notify the surgeon in case of deterioration of electrical responses and to follow the patient closely throughout the surgery. Sensitive Evoked Potentials allow us to follow the paths of deep sensitivity. During drops in blood pressure, hypotension or blood loss, the ESPs – being very sensitive to them – begin to be disturbed; the anesthesiologist and the surgeon are then alerted.

In addition, during spinal surgery, the roots of the spinal motor nerves innervating the muscles are monitored by EMG. It is possible to visualize on the EMG the disturbance of the nerve roots that may occur during the surgical intervention.

Thus, the surgeon is immediately alerted by the neuromonitoring specialist that a problem occurs in the motor nerve roots and the surgery is stopped without causing irreversible motor deficit or the operating strategy is modified.

“We can also say that the important precise positive results obtained by the Multimodal Intraoperative Neuromonitoring method in spine and spinal cord surgeries will increase steadily in the coming years,” said Prof. Dr. Serdar KAHRAMAN.

For more information on oncological surgery, please visit the ANADOLU Medical Center website: Oncological Surgery

Leave a Comment