Neurosurgical Procedures
Minimally Invasive Spine Surgery
Recent advances in surgical technology have meant that the focus of treatment for spinal conditions has progressed towards preservation of normal spinal motion and sparing of structures adjacent to problem areas. This has meant reductions in time spent in the operating room and hospital. The length of the surgical incisions are much less and the pain associated with surgery is minimal in most cases. In most minimally invasive spine cases the patient can walk on the day of surgery and is home within one to two days. Long term mechanical consequences of surgery are decreased compared to long segment operations and spinal fusions. The most common procedures are microdiscectomy, microforaminotomy, and rhizolysis. Endoscopic discectomy utilizes a circular retractor and endoscopic instruments. In general minimally invasive spinal surgery is appropriate for pain, weakness, and numbness due to nerve compression and has little role to play in mechanical or arthritic back pain.
Microvascular Decompression
Microvascular decompression (MVD) is a surgical procedure for the treatment of cranial nerve compression syndromes. The commonest of these syndromes is Trigeminal Neuralgia (severe pain affecting one side of the face). Other syndromes include Hemifacial Spasm (severe involuntary twitching of one side of the face), and Glossopharyngeal Neuralgia (severe pain in one side of the throat associated with swallowing).
The surgery involves making a hole in the skull behind the ear, opening the lining of the brain (dura) and inspecting the origin of the affected cranial nerve using the microscope for magnification and illumination. In most cases a blood vessel, usually an artery, sometimes a vein, is found to be compressing the origin of the nerve. The vessel is carefully moved away from the nerve. It is held away with one or more small pieces of woven fabric (Teflon), which remains in place and cushions the nerve from the vessel.
The surgery is successful in more than 85% of cases and allows the patient with severe Trigeminal Neuralgia to wean off the anticonvulsant medication which has been the mainstay of their medical treatment.
Peripheral Nerve Surgery
The brain and spinal cord make up the Central Nervous System (CNS). Surgery involving nerves outside the CNS is referred to as Peripheral nerve surgery. Nerves originating in the spinal cord in the neck leave the spinal cord and form a network of nerves called the Brachial plexus before dividing into specific nerves of the arm. Similarly, nerves originating in the lumbar spine form the Lumbosacral plexus before dividing into specific nerves of the leg.
The commonest indications for peripheral nerve surgery include trauma to nerves, tumours in nerves and entrapment syndromes involving nerves. Carpal tunnel syndrome (CTS) is the commonest entrapment syndrome and Carpal tunnel release (CTR) is the most common procedure performed worldwide. Symptoms of CTS include pain and numbness in the hands and sometimes up the arm, typically occurring at night or when driving the car. Other common entrapment syndromes involve the ulnar nerve at the elbow, common peroneal nerve at the knee, and posterior tibial nerve at the ankle, to name just a few.
Many types of Tumours occur within nerves, but the most common are benign tumours called Schwannomas or Neurofibromas. Mostly these are one off sporadic cases, but rarely are part of an inherited syndrome such as Familial Schwannomatosis or Hereditary Neurofibromatosis.
Trauma to nerves may take the form of sharp or blunt (stretch) injuries. Generally sharp injuries are surgically repaired early, while blunt injuries are observed for a short time to see if spontaneous recovery occurs.
Base of Skull Surgery
Tumours and vascular abnormalities such as aneurysms frequently occur at the base or floor of the skull. These abnormalities provide a significant surgical challenge in view of the fact that most of the major blood vessels to and from the brain, as well as most of the cranial nerves traverse this space.
In recent times neurosurgeons have developed specific skills and equipment to allow surgery to be done safely in this domain which was previously thought to be inoperable. Advances in magnification and illumination with state of the art operating microscopes, computer generated neuronavigation equipment, laser technology, flexible and rigid endoscopes allowing minimally invasive keyhole surgery, rigid fixation retractor systems and intraoperative stimulation and monitoring machines, have all made this type of surgery more feasible.
Combined approaches with Ear, Nose and Throat Surgeons and Head and Neck Surgeons have allowed North Shore Neurosurgeons to remove difficult tumours at the Base of Skull via trans-nasal and cranio-facial approaches. Advances in endoscopes and specific drills allow this delicate surgery of the brain to be done through the nose.
Pituitary Surgery
Surgery in and around the Pituitary gland is a relatively common neurosurgical procedure which is often done through the nose (endonasal transsphenoidal). Pituitary tumours represent about 15% of all brain tumours, however behave very differently to intrinsic brain tumours. The indications for surgical treatment are hormonal imbalance, due to over production of hormone, or pressure on surrounding structures (most commonly the eye nerves). Untreated they may lead to progressive health decline or loss of vision and blindness. Some abnormalities within the area of the pituitary gland may be treated non-surgically or simply followed with scans. Malignant pituitary tumours are rare. With more recent minimally invasive operative techniques, including the use of endoscopes, the operation has become safer and more effective at treating these conditions. Very large tumours may sometimes need to be treated with craniotomy (window of bone in the skull) and approach under the brain similar to other brain tumours.
Cervical Spine Surgery
There is a wide range of conditions that require cervical spine (neck) surgery, from nerve and spinal cord pinching to instability and pain. The most common surgical problem is brachialgia(arm pain from a pinched nerve). This condition in the majority of cases will improve without surgery, however, it may be required in those with weakness or severe unrelenting pain. Surgery is often done through a minimally invasive approach using microdiscectomy and microforaminotomy. Occasionally brachialgia may need to be treated by a complete discectomy and then either fusion or arthroplasty (artificial disc). Spinal cord pinching is rarely resolved with a minimally invasive approach due to the nature of the condition, however, may require surgery from the back or front of the neck. Surgery for conditions such as whiplash and arthritic neck pain is rarely indicated.
Functional Neurosurgery
Functional Neurosurgery has been in existence for about 60 years, really commencing at the end of the second World War. Although originally focused mainly on the surgical treatment of Parkinson’s Disease, since the development of Levodopa in 1968 and the re-emergence of this surgery as being a subspecialty in Neurosurgery, the surgical emphasis has become more widespread treating other conditions such as essential tremor and dystonia etc. The current technique is almost exclusively deep brain stimulation of the Subthalamic nucleus, Thalamus and Globus pallidus.
Dr Cook is currently the busiest functional Neurosurgeon in Sydney being a founder of Sydney Deep Brain Stimulation, reference www.sydneydbs.com. Further information about functional neurosurgery can be obtained from this website.
Brain Tumour Excision
The group has widespread experience in surgery for brain tumours. The charity that was formed by the group, Sydney Neuro-Oncology Group, is in the process of collecting all the relevant data on neuro-oncology patients and entering this into its comprehensive database linked to the Australasian Brain tumour bank, which it established 8 years ago. The group has a huge input into the Kolling Institute through Royal North Shore and it’s attachment with the University of Sydney involved in the supervision of PhD students doing research into causation and treatment of brain tumours. The group has a very broad and wide experience of all the surgical techniques in removing the most complex brain tumours from the adult brain. It has at its access the latest equipment including stereotactic navigation, ultrasound aspiration, and Zeiss microscope along with dedicated theatre personnel who on average would operate on 6 brain tumours every week. The group has as an active awake functional resection of brain tumours in eloquent areas, a technique not widely adopted in Sydney but quite popular in many cities around the world who deal with complex brain tumours. The group has at its disposal the latest in MR imaging with 3 MR’s on the North Shore campus including 3Tesla capacity.
It is actively developing functional MRI scans for localization of eloquent brain areas prior to awake surgery. Having had such a high through put of brain tumours allows the group to perform quite complex neurosurgical procedures as a routine within the group members. The group has forged a very close association with neuro-oncology to form an extremely busy neuro-oncological service, a service that is often referred to from outside the confines of the North Shore Area Health Service.
Minimally invasive, Endovascular treatment of cerebrovascular pathology
In the past 2 decades we have seen a phenomenal new technology develop which has permanently changed the landscape of treatment in cerebrovascular disorders, such as aneurysms and AVMs. This technique has developed from conventional angiography, and allows treatment to occur without the need for open brain surgery.
Coiling of Aneurysms
An aneurysm is an abnormal outpouching of an arterial blood vessel which usually only becomes evident when it has ruptured. The consequences can be devastating. Traditional treatment involves open brain surgery and the application of a pre sprung Titanium clip to occlude the inflow region of the aneurysm. With coiling however, the entire treatment is performed through a remote site. High tech, specially designed platinum coils are placed inside the aneurysm “dome” to seal it off from the inside. Occasionally a special scaffold is needed to support the coil mass. This is called a stent. This new treatment paradigm has become so successful that in many countries, the majority of aneurysms are treated in this manner. At Royal North Shore Hospital and North Shore Private, we have a team of highly experienced interventionalists and neurosurgeons who decide the optimal treatment for each case.
Embolization of Cerebral and Dural based AVMs
Cerebral arteriovenous malformations are congenital abnormalities characterized by a local or regional group of arteries that connect directly into the venous system to create a complex, high-flow tangle of blood vessels. These local high flow areas are associated with a significant life-long risk of haemorrhage and disability. Dura based AVMs are acquired lesions fed by enlarged extracranial arteries. They can also be dangerous if the flow becomes intracranial. Interventional techniques have made the operative treatment of AVMs much safer and technically easier. By placing a special glue-like substance in the feeding vessels, the flow through the AVM can be dramatically reduced, thereby reducing surgical time and risk.
Embolization of Tumours
Many tumours are supplied by abnormally recruited blood vessels, or may even consist of densely packed blood vessels. These can be difficult to access through a direct surgical approach, but can often be safely embolized with endovascular treatment. Small particles are placed in the tumour blood vessels to block them. This in turn reduces the bleeding risk at surgery.
The use of intracranial and extracranial Stents
Blockages or narrowings of important arteries supplying the brain, can cause stroke or disabling TIAs. It is now possible to open up these blockages by placing a stent across the narrowing, and allowing it to progressively expand and dilate the area of narrowing. Stents represent the latest advances in interventional radiology and are becoming more widely used for stroke prevention.
MICROSURGICAL CLIPPING OF ANEURYSMS
Background
An aneurysm is an abnormal ballooning of part of the arterial wall. It is estimated that between 2 and 5% of the population will harbour an intracranial aneurysm. They typically occur at branching points of an artery. The risk associated with harbouring an aneurysm is that spontaneous haemorrhage can occur, which can cause devastating consequences. Whenever possible it is preferable to treat an aneurysm, if known to be present, prior to rupture. In certain cases, a microsurgical approach may have considerable advantages over an endovascular approach. This is often the case if the aneurysm has a very broad neck and is easily accessible surgically. The goal of microsurgical treatment is to place a permanent, occlusive clip, externally across the neck of the aneurysm to prevent its filling.
Surgery
Aneurysm surgery remains the gold standard technique in terms of durability of effect, and is still the treatment of choice in some patients. Recent advances in cranial surgery have taken place to minimize the trauma associated with traditional surgery, as well as greatly improve cosmetic results. The use of a precision operating microscope, specialized micro-instruments, advanced technology Titanium aneurysm clips, and a better understanding of the pathophysiology of aneurysm development and rupture risks, have combined to steadily improve outcomes from aneurysm surgery. Progressive refinements in all of these tools continues to this day.
The surgery involves opening up the normal pathways and spaces that exist around cerebral vessels and defining clearly the anatomy and relationship of the aneurysm and adjacent normal arteries. One or more permanent clips is then placed across the “neck” of the aneurysm. Exciting, new technology being employed to further assist the surgeon includes fluoroscene angiography, and intraoperative angiography, both of which confirms preservation of adjacent normal vessels and exclusion of the aneurysm.
Microsurgery for arteriovenous malformations
There are a number of types of cerebral vascular malformations. Arteriovenous malformations (AVM) are the most concerning and complex. They are congenital and are cuased by an aberration in the normal vascular development process. The malformation consists of a network of arteries that connect directly with the venous system. Most of the abnormal vessels are located in what is known as the nidus, or central connection point of the AVM. The nidus may be discrete or diffuse. The haemodynamic consequences of this arrangement is that abnormally high flows are conducted through these connections. Arteriovenous malformations most commonly present with haemorrhage secondary to rupture but they may also present with seizures and neurological problems. Diagnosis is achieved through complimentary tests including CT, MRI and cerebral angiography. The treatment is quite variable and depends on size and location, haemodynamic properties and morphology, clinical presentation and age. The options range from observation and serial imaging to surgical excision. In some cases focussed radiation treatment may be appropriate. In many cases, the surgery has now been made much safer with the ability to perform preoperative embolisation using endovascular techniques.
The surgical strategy is to progressively identify and occlude dedicated arterial feeders to the AVM, while preserving normal vessels. Once it is fully disconnected from its inflow, the venous outflow is ligated. At the North Shore campus, treatment decisions are made by a team of experts, including endovascular neurosurgeons, interventional radiologists and radiation oncologists.
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