Image-Guided Surgery: Latest Advancement In Removal of Brain Tumour

Dr Arun Naik and Dr N C Prakash

Image-guided surgery, which helps surgeons navigate through the body of the patient, has made great strides in patient care. Hosmat Institute of Neurosciences recently added another feather to its cap after it successfully conducted image-guided surgery on 61-year-old lady to remove a difficult brain tumour by using BrainLab neuronavigator.

The patient, who had developed sudden onset of headache and weakness of left side of her body, was evaluated by a neurologist and subsequently referred to Hosmat for management. The MRI scan of her brain revealed a brain tumour, known as glioma in her right brain. The tumour was located on a highly sensitive area called ‘Motor strip’, which is responsible for the movements of the limbs. The brain tumour found in her is a type of ‘glioma’, which is very difficult to tackle. The main concern for neurosurgeons in this case was the proximity of the tumour to the ‘Motor strip’.

In comparison with image-guided surgery, conventional neurosurgical procedure relies on surgeon’s visualisation of the tumour. In some types of tumours, surgeons may not completely visualise the tumour and this leads to unduly handling of the brain and thus may cause significant problems like paralysis, loss of speech, blindness etc. Image-guided surgery has an edge over conventional procedure as it involves minimal morbidity and maximises patient comfort. Brain surgery is considered one of the oldest of all practiced medical arts. There is evidence of brain surgery as early as 3000 BC in Africa. Back in those times, surgeons didn’t know about the function of the brain as studying dead bodies was considered a sin. But, as the facts about brain and its functions was known, surgeons were more careful and precise in dealing with it.

When treating brain tumuors, tumour resection is the initial treatment. Today, computer-based neuronavigation or image-guided surgery assists the surgeon during all phases of the operation. This allows the surgeon to keep the operation minimally invasive and to avoid critical structures of the brain. Thus, the risks of paralysis or other impairments after surgery are minimised and recovery time is considerably reduced.

What Is Image-Guided Surgery?

Image-guided surgery has been employed in neurosurgery since the mid-1990s. This new technique relies on a powerful computer system, which assists the surgeon in precisely localising a lesion, in planning each step of the procedure via a 3D model on the computer screen, and in calculating the ideal access to the tumour before the operation. The tumour and its surroundings can be viewed from different angles and in relation to landmark structures, such as the optic nerve or the brain stem. During the operating procedure, the movement of the instruments in use inside the brain can be tracked on the monitor with a precision of 1-2 millimeters, through which damage to healthy tissue and to critical areas can be avoided as much as possible.

The tumour’s location and its position relative to the sensitive structures in the brain will be pinpointed so that sensitive structures can be avoided and the incision can be kept as small as possible. This is particularly useful in reaching a tumour located deep inside the brain, areas traditionally considered to be difficult to reach. During the procedure, the computer tracks instrument movement with an extremely high precision, providing the surgeon with total control inside the brain at all times using “real-time” imaging. The surgeon can also check if the tumor has been removed as planned. This improves the outlook for the patient.

Various Types Of Image-Guided Surgeries

Stereotactic Biopsy

A stereotactic biopsy is performed in order to obtain an exact diagnosis of the tumour and to differentiate it from healthy tissue or infective tissue. A small tissue sample is obtained from a defined region of the brain by using a long and very thin needle, which is passed through a skin puncture and tiny opening in the skull to the location of the tumour. The tissue sample is then examined by a pathologist and the nature of the lesion is determined. If the lesion proves to be a tumor, the type of tumor will be determined. The image-guided surgery system assures that the tissue sample is taken from the area of interest and not accidentally from the neighboring region. Most patients are discharged from the hospital the very next day.

Craniotomy

The most commonly performed surgery for the removal of a brain tumour is called a craniotomy. The objective of the surgery is to excise as much of the tumour as possible. Even if only a portion of the tumour can be removed, this can still lead to an improvement of symptoms. For the surgery, a portion of the scalp is usually shaved, and an incision is made through the skin. A piece of bone is removed to expose the area of brain over the tumor, then the tumor is removed. After the tumour has been removed, the bone is generally replaced and the incision closed.

In a conventional craniotomy, surgeons guide themselves by what they can visualise, their knowledge of anatomy and their interpretation of the pre-operative scans. This is purely a ‘hand to eye’ technique. With the use of this technology, the tumour as well as different brain structures can be well identified and viewed on the computer screen. The surgeon can navigate precisely to the tumour while avoiding sensitive structures. The depth of the tumour can be mapped, as well as critical structures that might lie on the other side of the resection plane. Such navigation increases the precision of the procedure, and can increase the speed at which surgery can be performed.

Shunt

Occasionally, patients with brain tumours develop increased intracranial pressure due to accumulation of excess fluid in the ventricles (brain chambers). To relieve the pressure, a shunt procedure to drain excess or blocked fluid might be necessary. A small hole is drilled in the skull through which a catheter is inserted into the brain chamber. The other end of the tubing is threaded to the abdomen from where the fluid is absorbed.

Implants

In many cases, patients with brain tumours are treated by the insertion of radioactive material (brachytherapy) or genetic material into the cavity left by the tumor’s removal. Neuro Navigation is able to ensure the accurate placement of an implant into the defined area.

Functional Neurosurgery

Mapping tools can improve the safety and effectiveness of surgery by locating the exact areas of the brain responsible for speech, comprehension, sensation or movement. Specific areas of the brain are stimulated by a tiny electrical current, through which their functionality can be determined. This allows these areas to be avoided during surgery.

Advantages Of Neuro Navigation

• Proper definition of the ‘target area’ by detailed 3D reconstruction.
• Precise placement of the craniotomy flap.
• Accurate delineation of tumor and vital brain structures
• Identification of eloquent areas of brain and their preservation.
• Minimal brain handling: minimally invasive neurosurgery.
• Reduces overall morbidity.

The writers are consultant neurosurgeons at Hosmat Institute of Neurosciences, Bangalore