Brain Tumors – Keyhole, Endoscopic and Minimally Invasive Surgery

Brain Tumors – Keyhole, Endoscopic and Minimally Invasive Surgery

What is a brain tumor?

A brain tumor is a growth of abnormal cells in the brain. Brain tumors can develop in any part of the brain or skull, its covering (dura), the base of the skull , the brainstem, supra and infratentorial compartments and the sellar region, along the CSF pathways, and many other areas.

Are all Brain tumors a cause of concern?

Yes,Braintumors are a cause of concern because the volume inside the skull has to be a constant all the time and this extra volume can suddenly decompensate with the patient worsening(herniationof brain structures),by causing compression over other vitals structures and infiltrating them causing loss of function and they can spread to adjacent parts of brain and along CSF pathways to other areas too.

What is a brain lesion and how is it different from a tumor?

Brain lesions also include Brain tumors.Lesion can be non-tumourousalso(example:tumefactivedemyelination,vascular lesions etc.).A brain tumor is a specific type of brain lesion that consists of growth of abnormal cells. Other brain lesions can be caused by stroke, injury, encephalitis and vascular malformation.

Classify brain tumour based on growth potential?

Slow growing tumours in the brain are called Benign tumours and they rarely spread and grow slowly.They can cause problems by compressing the nearby vital structures,say a nerveand cause clinical deficits. Benign brain tumors located in a vital area of the brain can be really problematic. Rarely, a benign tumor can become malignant.

Malignant brain tumorsare cancerous(eg.Glioblastome/gliosarcoma). They typically grow rapidly and infiltrate surrounding healthy brain.They can be primary(arising in the brain) or secondary tumors(spreading from other parts of body). In elderly patients,the most common type of brain tumours are metastatic tumours from primaries elsewhere in the body.

Symptoms of Brain tumors?

Due to the Munroe-kellie doctrine,tumor’s size and how fast it’s growing will only decide how early patient will have symptoms.Tumours situated near nerves and other vital structures like arteries may present early with symptoms due to the compression of the structure and the ensuing clinical deficits. Example, a brain tumor compressing or infiltrating the cerebellum may cause trouble with movement, walking, balance and coordination. If thetumor affects the optic nerves,disturbances in vision may occur.

What makes brain tumors difficult to detect early?

Brain tumorscan be asymptomatic for a long time till they grow to considerable size and this makes detecting them early very difficult.Patients have symptoms only after they become large enough to infiltrate or compress important structures and cause clinical deficits or to cause obstruction to the flow of CSF and cause increase in intracranial pressure.

Keyhole and Minimally invasive approaches

What is keyhole surgery for brain tumors?

Keyhole surgery is the concept of safely removing brain & skull base tumors through smaller, more precise craniotomies that minimize collateral damage to the surrounding brain, blood vessels, and nerves and improve patient outcomes.This needs improved understanding of intracranial anatomy and different technology and instrumentation with skilled neurosurgeons who are trained in these approaches.Eventhough the spectrum of conditions that can be handled with these approaches increase by the day,not all conditions can be dealt with these approaches.

The ideal surgical approach for each patient is determined by the specific tumor type and location. Regardless of the route chosen, our goals are to maximize tumor removal and minimize manipulation of critical structures. Thereby avoiding complications and patient disfigurement, while promoting a more rapid, complete and less painful recovery.

Keyhole and Minimally invasive approaches

Supraorbital Eyebrow Craniotomy

This versatile, minimally invasive approach minimizes normal tissue disruption and brain retraction, allowing for a more direct approach to lesions. This approach is typically performed with the assistance of an endoscope, allowing for further visualization. As such, patients recover well and have good cosmetic outcomes long term.

Endoscopic endonasal surgery

Endoscopic Endonasal Surgery (through the nostrils) is ideal for most pituitary adenomas, craniopharyngiomas, chordomas, sinus carcinomas, olfactory neuroblastomas and some midline meningiomas of the tuberculumsellae, clivus, cavernous sinus, Meckel’s cave, orbital apex and orbit.

Mini-Pterional Approach

The Mini-Pterional Approach is used for certain sphenoid wing and parasellarmeningiomas,aneurysms, other tumors of the cavernous sinus and Meckel’s cave, orbital lesions as well as temporal lobe gliomas.Patients recover relatively quickly in comparison with traditional pterional operations, with potentially less pain, chewing difficulties and facial muscle atrophy.

Gravity-Assisted Brain Tumor Surgery Approaches

Endoscopic Trans-Ventricular Route

For tumors and cysts within the ventricles: colloid cyts, gliomas, metastatic brain tumors and pineal tumors.

Tubular retractor/Brain Port Approach

MIOT neurosurgeons can navigate between the natural folds and neural structures in the brain, to minimize collateral damage to the surrounding brain along the path to reach the tumor or blood clot.

Awake Brain Surgery

Awake brain surgery, also called awake craniotomy, is a type of procedure performed on the brain while you are awake and alert. Awake brain surgery is used to treat some brain (neurological) conditions, including some brain tumors when the tumors are very near areas which control movement,vision or speech. This is mainly done to preserve these functions and to improve patient outcomes after surgery.It also helps neurosurgeons to maximise tumor resection without the fear causing deficits in their patients.

For whom it is ideal?
A cooperative and motivated patient is the most important part of a successful awake craniotomy.Before surgery, your neurosurgeon or a speech-language pathologist may ask you to identify pictures and words on cards or on a computer so that your answers can be compared during surgery.Tumor and lesional size and characteristics also feature in when the surgeons decide on whether awake procedure is the right choice.

Multidisciplinary team effort is the cornerstone of a successful awake procedure with Neurosurgeons,speech and language pathologist,anesthesiologist playing their parts as a team. Awake craniotomy in done in either sleep-awake-sleep method or sleep-awake-awake method.Patient will be woken after the craniotomy is done with anesthesia with the pain taken care by the anesthesiologist.Baseline assessment of motor and language functions done and the surgery is proceeded with excision of the lesion with constant monitoring of the functions.After maximal resection with preserved functions,patient is again put to sleep to complete the procedure.

This is the fool-proof gold standard when it comes to the preservation of functions when compared to any other method.What can prove the preserved functions in a patient undergoing surgery under anesthesia than awakening the patient and checking the functions ourselves?

At MIOT, with the help of the multidisciplinary team available,we have performed many successful awake craniotomies leading to better functional outcomes in patients alongside maximising the extent of tumor resection.

INTRA-OPERATIVE NEUROMONITORING

Intraoperative neurophysiological monitoring (IONM)is an enormously helpful armamentarium in the operating room for a neurosurgeon as it gives a continuous monitoring of integrity of neural structuresand helps the surgeon to have a rough idea of how the patient will be after the procedure with regards to the functional status.It has been proven to improve the post op functional status of patients and also helps to increase the margin of tumor resection as the surgeon will be confident of his patients outcome while removing the tumor. The Aim of IONM is to identify intraoperative insults that allow early intervention to eliminate or to significantly decrease irreversible damage to the neurological structure and prevent a postoperative neurologic deficit. The use of IONM needs special techniques in anesthesia as patient cannot be paralysed and selective gases can only be used.

INDICATIONS:

Intraoperative neurophysiologic monitoring (IONM) is recommended for individuals at increased risk of neurological injury during surgical procedures. The following are the indications for IONM.

Somatosensory Evoked Potential (SSEP) or Motor Evoked Potential (MEP)

Spine and spinal cord surgery including scoliosis and Kyphosis correction with instrumentation, spinal cord decompression/stabilization, anterior and posterior spinal fusions (cervical, thoracic, and thoracolumbar), the release of tethered cord, correction of spina bifida, resection of the tumor, cyst, aneurysm or arteriovenous malformation of the spinal cord

Brain and brain stem surgeries including craniotomy for tumor removal, craniotomy for aneurysm repair, arteriovenous malformation repair, localization of cortex during craniotomy, thalamotomy

Why IONM?

Intraoperative neurophysiological monitoring (IONM) is considered the standard of care during many procedures, including spinal, intracranial, and vascular surgeries, where there is a risk of neurological damage. IONM team collaborates with the surgical and anesthesiology team to optimize signal acquisition and provide real-time analysis, interpretation, and timely communication of signal changes, which allows the surgeon to operate safely and avoid neural tissue injury.

At MIOT,most of our brain and spine surgeries are done with intraoperative neuromonitoring guidance towards providing better functional outcomes for our patients.

Brain mapping with Functional MRI and Diffusion tensor imaging

Functional MRI is a noninvasive imaging method that measures small changes in blood flow to parts of brain as a person performs set tasks. It detects the part of brain which is activated while the task is performed (e.g., speaking or moving). It localises the function to a particular part of brain(functional localization) while all other imaging methods are structural based.

Diffusion tensor imaging (DTI) detects the white matter tracts that connect different parts of the brain and that is why its called tractography.Intraoperatively also it can be fused to theintraop navigation to prevent injury to these tracts.

How does functional MRI work?

When we start a activity, neurons in our brain responsible for the action use more oxygen. Functional magnetic resonance imaging (fMRI) can detect the difference in signal caused by the increase in blood flow and hence more oxygen delivery to specific areas of the brain by a method called BOLD-Blood oxygen level dependent.

Diffusion Tensor Imaging (DTI) is a technique that detects how water travels along the white matter tracts in the brain . White-matter tracts connect different parts of the brain and must be protected during surgery.This imaging is very useful in deep seated lesions and lesions in the brainstem.

What does a functional MRI show?

Functional MRI gives detailed of brain areas which are active. It is used to determine precisely which part of the brain is handling critical functions such as thought, speech, vision, movement and sensation so that those can be localized intraoperatively also. It can also show the effects of stroke, trauma or Alzheimer’s on brain function in these degenerative diseases.

These imaging studies are important in planning surgery – called brain mapping – that helps surgeons remove tumors to the greatest extent possible without causing deficits in functions that are critical to a patient’s quality of life.

Brain mapping is essential in not only tumour resection surgeries but also in all surgeries where preserving function is essential Examples being Epilepsy surgery/Functional disconnection surgeries.

MIOT Neurosurgeons use Pre-op Brain mapping merged into the state of art intra-op navigation that is integrated with intraoperative CT scan for better outcomeofpatients.