Neuronavigator and Neurophysiological Monitoring in Neurosurgical Interventions

Can you explain the concept of neuronavigation?

Surgeons are guided during surgical interventions by our anatomical knowledge, preoperative anatomical and pathological images of each patient as well as our experience in similar cases.

Despite this background, there were certain possibilities of “getting lost” in the surgical field, not reaching the right place where the lesion was or invading important anatomical-functional areas, with the consequent risk of leaving neurological sequelae.

In the last decade the technical maturity of navigation systems has been reached, both in cranio-encephalic and vertebro-medullary surgery. These essentially consist of a system that positions the preoperative image in the real surgical field, in 3D and with an error limit of less than 1mm. This neuronavigation system, similar to GPS systems, has meant an enormous surgical advance and a drastic reduction in postoperative sequelae, apart from serving to store our experience on a case-by-case basis.

Not all neuronavigation equipment, as is the case with GPS systems, has the same possibilities. The most advanced ones provide the surgeon not only with anatomical information (3D reconstruction, lesion contours, vascularization…) but also with information on the functional areas and communication pathways between nerve centers.

What does neurophysiological monitoring mean and what is it used for?

Another great advance of this century has been the possibility of controlling in real time, during surgery, neurological functions such as vision, hearing, mobility and sensitivity, as well as the function of other pairs or cranial nerves (ocular mobility, sensitivity and mobility of the face or the complex mechanism of swallowing).

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In the past, this was done while the patient was awake. This was impossible to do in certain interventions. Today it is possible to monitor all these functions under general anesthesia. Except for language, where the patient must be awake and cooperative during surgery.

This neurophysiological monitoring requires a great technological effort and a great professional capacity on the part of the neurophysiologist who is present during the entire surgical procedure. Sometimes there are more than 50 cables between the patient and the monitor collecting and sending signals.

In this way, tumor lesions or other types of lesions that need to be treated or removed are approached today in a complementary way: anatomically (with the help of the neuronavigator) and functionally (neurophysiological monitoring). In this way, the safest routes are designed to access the lesion and we have control of the possible damage we could cause if we go beyond the limits of the lesion and enter functionally important risk areas.

What are the advantages of these advances in neurosurgical interventions?

Today, therefore, we have a new conception of the surgical procedure. In addition to the surgeon’s knowledge and experience, real anatomical and functional data are added, in real time, during the entire surgical time.

This serves as a guide for the neurosurgeon. It makes you more aware of the anatomy (often distorted by the injury) and warns you of the risks of producing sequelae, before a pathway or an important nerve center is definitely injured.

In fact, this means that neurosurgery is becoming the safest surgery in existence, in terms of the lowest percentage of producing sequelae or irreversible lesions.

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And, posing the problem in reverse, it is increasingly inconceivable that lesions in functionally important brain structures can be treated if these means are not available. And it is becoming clear that, apart from the professional quality of the neurosurgeon, the availability of increasingly sophisticated neuronavigation and neurophysiological monitoring systems is directly related to good results.