Function preservation during brain surgery

In this article we will give a few examples of function preservation during resection of brain tumors.

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lemaanchem

The department of Neurosurgery in Rambam is the largest department providing neurosurgical service to the north of Israel. The department treats all neurosurgical illnesses, including head trauma, problems with blood vessels of the central nervous system, resection of brain tumors, surgical treatment of movement disorders, treatment for lesions in the base of the skull, complex surgeries of the spine, pediatric neurosurgery and others.
Neurosurgery for resection of brain tumors has developed over the years. A few decades ago, the main focus was on survival of patients after resection. Nowadays, the goals of surgery are maximal resection along with full preservation of function. In fact, the commonly used term is "functional-oncological balance". There is ample data in the scientific literature to show the risks in cases when the patient suffers a fixed neurological deficit. In fact, the prognosis of patients who have a postoperative neurological deficit is worse than those who have completed the resection unharmed. The accepted concept today is that in any given brain tumor – benign or malignant – it is preferable to have a subtotal resection of the tumor in order to prevent a neurological deficit.
Therefore, the department of Neurosurgery in Rambam has specialized in the past few years in resection of brain tumors with maximal preservation of function. In this article we will give a few examples of function preservation during resection of brain tumors.

Function preservation in operations of the posterior skull base
The field of skull base neurosurgery is led by Prof. Gill Sviri, chairman of the neurosurgery department. Tumors in the skull base are often benign, but they exert pressure on the cranial nerves, and may cause a deterioration of hearing or vision, disturbance of eye movement, problems with motor and sensory functions of the face.
During operations for tumor resection in the posterior skull base, there is often involvement of the facial nerve. This nerve controls the motor function of the face, and injury to the nerve may cause weakness or paralysis of half the face, and even consequent visual disturbance. Dysfunction of the facial nerve carries a significant physical and mental morbidity, and should be avoided at all costs. Prof. Sviri is extremely trained and experienced in these operations. Prior to the operation, while the patient is already under general anesthesia, special receptors are placed in the face muscles. The receptors are connected to a special monitor which measures the response in the facial muscles. During the resection, we use a special probe, which emits a low-voltage electrical current. The response is measured by the facial muscle monitors. This way we can accurately localize the facial nerve and avoid injury to it. The tumor may be gently dissected away from the localized facial nerve, and thus avoid injury to the nerve and the accompanying morbidity.

Hormonal functional preservation – pituitary tumors
Another part of skull base surgery is the treatment of tumors of the pituitary gland. The pituitary gland is the most important hormonal gland in the human bod; it controls the secretion of virtually all hormones in the body. The pituitary gland also controls secretion of hormones from other hormonal glands in the body, including the adrenal gland, the reproductive organs, the thyroid gland and others. Patients who suffer from injury to the pituitary gland may be dependent on hormonal replacement for the rest of their life. Therefore, preservation of hormonal function is of utmost importance during resection of tumors in the pituitary region. In many of these cases, the tumor is located under the normal pituitary gland. Therefore, an operative approach from below is oftentimes preferred to an approach through the skull. Prof. Sviri is also the director of the pituitary surgery service in Rambam. In these operations we cooperate with the department of otorhinolaryngology, and perform the operation using a rigid tube, inserted through the nose towards the base of the skull, in the area of the pituitary gland. Through this tube we insert a camera, which allows visualization of the surgical field, as well as surgical tools. Using this method, we reach the tumor directly, under the pituitary gland, and can avoid injury to the gland itself. We have prevented hormonal damage to hundreds of patients in the past few years, and enabled them a healthy life, free of hormonal replacement medication.

Motor function preservation in intrinsic brain tumors
Intrinsic brain tumors are tumors located within the substance of the brain. These may be tumors originated in the brain tissue itself, or may be metastases originating from cancer elsewhere in the body, which spread through the blood stream to the brain.
The field of resection of intrinsic brain tumors is led by Dr. Iddo Paldor, vice chairman of the department of neurosurgery in Rambam. During a three-year fellowship period, Dr. Paldor specialized in the two world leading centers in resection of intrinsic tumors.
Some of the intrinsic brain tumors are located in the motor area – the part of the brain that controls movement of the muscles in the opposite side of the body. Resection of intrinsic brain tumors in motor-related brain areas requires continuous monitoring of the motor function. In the beginning of the operation, after the patient is under general anesthesia, we place receptors in the muscles of the opposite side of the body. Once the brain is exposed, we use advanced technology to accurately locate the motor areas and the sensory areas in the brain, and guide the operation accordingly. In cases where the tumor infiltrates these critical areas, this technology enables us to reach optimal resection of the tumor, while preserving function, thus avoiding patient disability – motor or sensory.

Awake surgery for resection of brain tumors
The field of awake craniotomies (i.e. brain operations) for resection of tumors is also led by Dr. Paldor. As described earlier, motor and sensory function may be preserved even while the patient is under general anesthesia. However, there are specific brain functions, which cannot be monitored and preserved while the patient is anesthetized. Examples of these functions include speech, comprehension, memory and specialized motor activities. For instance, if the patient works as a watchmaker, and requires precise, fine motor abilities, then preservation of gross motor functions may not be sufficient. In these cases, an operation for resection of intrinsic brain tumors must be performed while the patient is awake. During the resection, the patient performs the specific task we are attempting to preserve (e.g. speech, comprehension or specialized motor function), and one of the team members ensures that the patient continuously succeeds in the task performance. This way we are able to reach optimal resection, and avoid affecting their ability to perform the specialized task.
Rambam Medical Center maintains a multidisciplinary team for performing awake craniotomies. The team includes a neuro-physiologist, an anesthesiologist who specialized in neurosurgical operations, a neuropsychologist and Dr. Paldor – a neurosurgeon who specializes in these operations. To date, many awake operations have already been performed in Rambam, with notable success achieving maximal safe resection, and preservation of unique, specialized abilities.
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