Prof GK Prusty, Neurosurgeon, The CMRI, Kolkata gives an outlook about minimally invasive neurosurgery
Traditional brain surgery requires opening up the skull to access the brain. Similarly for spinal surgery the part of the spine is cut. Consequent to the development of microneurosurgical instrumentation and procedures, the improvement and reliability of diagnostic neuroimaging methods (MRI and CT scanning), and the availability of sophisticated anaesthetic techniques major advances in neurological surgery have taken place over the past 30 years. The concept of minimally invasive neurosurgery introduces highly refined techniques and approaches, to the neurosurgical treatment of brain and spinal diseases.
Minimally invasive neurosurgery utilises small, flexible, lighted tubes called endoscopes. This incorporates a brilliant light source together with a sophisticated, miniaturised high-resolution video camera system and ‘working’ channels through which small, elongated instruments can be passed in order to perform, intricate surgery with little or no trauma deep within the body. Endoscopes serve as small microscopes, magnifying critical anatomical structures of brain, skull base and spinal cord etc. Throughout the surgery, the tiny video camera on the end of the endoscope projects large-scale images of the inside of the brain onto a computer screen, helping the surgeon see the various diseased areas which requires repair, removal, or replacement. Because the use of endoscopes is much less intrusive into these anatomical structures than conventional surgery, endoscopic neurosurgery is referred to as minimally invasive neurosurgery.
Benefits to consider
For example, endoscopic neurosurgery in general does not require large incisions on the scalp or skull, or extensive dissection through brain tissue. The skin incision can be width of the thumb and an entry into the brain smaller than a pushpin. The result is a faster and simpler procedure with greatly reduced post-operative complications, faster recovery, less pain and scarring, shorter stay in hospital and reduction in overall cost. The actual removal or repair of the problem is done as effectively, safely and completely as with conventional ‘open’ surgery. These minimally invasive operations can benefit people of all ages, from newborns to older adults.
Three types of endoscopic operations are available for neurosurgical procedures inside the skull (brain surgery), as well as inside the spinal column.
Endoscopic surgery
This is an operation conducted entirely through the endoscope. The endoscopes are introduced into the brain through very small skull openings. All the instruments that are used in the operation are introduced through the small, working channels that are incorporated within the endoscope. Examples of this type of surgery includes: Anterior third ventriculostomy (for hydrocephalus), intraventricular operations for removal of tumours such as intraventricular meningioma or a colloid cyst and fenestration/resection of intracranial arachnoid cysts, endoscopic tumour biopsy and removal of intra cerebral haematoma among other procedures.
Endoscopic assisted surgery is conducted using a sophisticated neurosurgical operating microscope for visualisation and advanced microneurosurgical techniques, to surgically manage a disease process. During the operation an endoscope is introduced into the operative area to permit visualisation of structures beyond the range of the operating microscope, such as around corners or ‘underneath’ other deep anatomical structures. The endoscopic image can be viewed on a television monitor, or through a ‘heads up’ display projected to the operating microscope. Examples of this type of neurosurgical operations include aneurysm and skull base and brain tumour surgery.
Endoscopic directed surgery is performed with the endoscope as the primary visualisation system rather than the operating microscope. In these operations, the endoscope’s image is viewed on a television screen with surgical tools being used ‘Outside’ (that is, beside and around) the endoscope (rather than introducing the instruments through the endoscope’s narrow internal channels). Examples of these minimally invasive microendoscopic intracranial operations include transsphenoidal resection of pituitary tumours, skull base tumour removal, microvascular decompression (MVD) of cranial nerves for trigeminal neuralgia, intraventricular tumours, and aneurysms.
The pituitary gland is the endocrine band master located within the cranium at the lower part of the brain in the pituitary. Tumours of pituitary cause a variety of hormone problems and can grow to large size, compressing important nerves and arteries at the base of the brain. When this occurs, surgery is needed to remove the tumour, especially when vision is at risk. Tumour removal often reverses endocrine problems and restores normal hormone balance.
With endoscopic directed surgery pituitary tumours are removed through the nose using minimally invasive technique. The patient is given general anesthesia. The nasal cavity is prepared with antibiotic and antiseptic solution. An image-guidance system may be placed on the patient’s head. This device is like a global positioning system (GPS) and helps the surgeon navigate through the nose using a 3D ‘map’ created from the CT or MRI scans.
The surgeon inserts the endoscope in one nostril and advances it to the back of the nasal cavity. The surgeon passes long instruments through the nostril while watching the monitor. The front wall of the sphenoid sinus (an air-filled, mucous-lined cavity in the skull located behind the nose between the eyes) is opened. At the back wall of the sphenoid sinus is the bone overlying the pituitary gland, called the sella. The thin bone of the sella is removed to expose the tough lining of the skull called the dura. The dura is opened to expose the tumour and pituitary gland. Through a small hole in the sella, the tumour is removed by the neurosurgeon in pieces. It may be difficult to completely remove the tumour without causing injury to the nerves and vessels. Any tumour left behind may be treated later with radiation.
At some hospitals, operation theatre is with intraoperative MRI scanner. The patient can undergo an MRI during surgery. This gives the surgeon real-time images of the patient’s brain to know exactly how much tumour has been removed before ending the procedure. This technology enables more complete tumour removal and may reduce the need for a second operation.
After the tumour is removed, the surgeon prepares to close the sella opening. If needed, a small (2 cm) skin incision is made in the abdomen to obtain a small piece of fat. The fat graft is used to fill the empty space left by the tumour removal. The abdominal incision is closed with sutures. The hole in the sella floor is replaced with bone graft or synthetic graft material. Biologic glue is applied over the graft in the sphenoid sinus. This glue allows healing and prevents leaking of cerebrospinal fluid (CSF) from the brain into the sinus and nasal cavity.
Soft, flexible splints are placed in the nose along the septum to control bleeding and prevent swelling. The splints also prevent adhesions from forming that may lead to chronic nasal congestion.
What happens after surgery?
The patient awakes in the postoperative recovery area soon after surgery. Occasionally he may spend a night in the neuroscience intensive care unit (NSICU) for closer monitoring. Discharge from hospital can be planned in a day or two.
Precautions
To prevent injury to the surgical site, the patient should avoid blowing his/her nose, coughing, sneezing, drinking with a straw, or bending over/straining on the toilet for four weeks. Since it is impossible to predict whether or when a tumour may recur, periodic monitoring with MRI scans is needed to watch for changes or regrowth.
What are the risks?
No surgery is without risks. General complications of any surgery include bleeding, infection, blood clots and reactions to anesthesia. Specific complications related to pituitary surgery include:vision loss, damage to normal pituitary gland, diabetes insipidus, cerebrospinal fluid (CSF) leak, meningitis, sinus congestion, nasal deformity and nasal bleeding
Compared to open surgery with endoscopic surgery the visual function improves more, there is less post operative seizure and less diabetes insipidus.
Spine surgery
Minimally invasive microendoscopic spine operations use the smallest aperture retraction systems possible. Posterior (from the back) approaches to the spine can be done in a way that preserves the function of the large muscles that course vertically along either side of the spinal column.
The technology for minimally invasive spine surgery allows for an incision just off the midline to the side of the pathological process (such as a herniated intervertebral disc and/or spinal stenosis [narrowing of the spinal canal]). Instead of stripping muscle from bone, the muscle fibres are separated and held retracted by narrow diameter tubes. In point of fact, the diameter of these tubes varies in size from 14 millimeters to over 26 millimeters (one inch). Minimally invasive microendoscopic spine operations are being conducted for spinal cord tumours, herniated intervertebral disc, spinal stenosis, lateral recess and/or foraminal stenosis, cauda equina claudication and spondylolisthesis. These minimally invasive techniques allow for operations such as laminotomy, laminectomy, transforaminal lumbar interbody fusion (TLIF) and placement of pedicle screw and rods for spinal instability requiring a fusion operation. Spinal cord tumours are difficult and dangerous problems. With the introduction of minimally invasive spine surgery techniques there are improvements in the management of these conditions compared to standard operations for the removal of spinal cord tumours. Cervical spine conditions that do lend themselves to minimally invasive technique include far lateral extruded cervical intervertebral discs, foramenal stenosis secondary to cervical facet hypertrophy, spinal stenosis secondary to hypertrophic ligamentum flavum as well as some spinal cord tumours.
The results of this means: less pain, less requirement for powerful pain-relief medications, early discharge from hospital, less complications and earlier return to work activities. This, too, reduces overall healthcare cost. Not every patient, however, is a candidate for a minimally invasive approach to spine surgery. A patient with spinal tumours, deformity, trauma, or degenerative disease must be fully evaluated by a surgeon knowledgeable and experienced in these minimally invasive techniques.
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