Neuroendoscopy describes the use of endoscopes to gain access to the brain, spine or peripheral nervous system, allowing a minimally invasive approach to some lesions.
Neuroendoscopy may be useful in managing hydrocephalus, cystic lesions of the brain and spinal cord, tumours, vascular lesions, degenerative spine disease and nerve entrapments. Dr Steel was the first surgeon to report the successful use of an endoscope to remove a haematoma (blood clot) causing spinal cord compression in 1998. By performing this surgery via the endoscope, the size of the incision and size of the opening through the scalp are considerably reduced.
Examples of neuroendoscopic procedures include:
- Ventriculoperitoneal (VP shunt placement and revision)
- Third ventriculostomy
- Fenestration of multiloculated ventricular cysts
- Choroid plexus coagulation
- Tumour biopsy and excision
- Transsphenoidal procedures for pituitary tumours
- Colloid cyst excision
- Fenestration and excision of arachnoid cysts
- Spinal discectomy
In conjunction with members of the otarlaryngology/ENT department at St Vincent’s and Concord Hospitals, Dr Steel routinely performs endoscopic surgery for tumours of the pituitary region and anterior cranial fossa. Virtually all pituitary tumour surgery is now performed using an endoscope and an endonasal (through the nose) approach. The older procedure, using an incision above the lip and below and between the nose and palate causes considerable disruption to the intra-nasal anatomy and often leads to discomfort and difficulties with breathing. By performing surgery with an endoscope, the disruption to the nasal anatomy is considerably reduced. Increasingly, surgeons are able to remove large tumours in the anterior cranial fossa using an endoscopic approach. This removes the need for a large scalp flap with neurostimulation.
Neurostimulation is a method of therapy that uses electrical stimulation to cause changes in the nervous system. It is a form of treatment that is used mainly with people who have chronic pain that is unresponsive to other treatments. There are different pain pathways in the human body: those controlled by the brain and spinal cords and those controlled by other peripheral nerves (nerves that extend out from the spinal cord). It is possible to stimulate any one of these pain pathways to reduce pain in a patient, and replace it with a feeling that resembles tingling or ‘pins and needles.’ This alteration in sensation is called paraesthesiae. Neurostimulation is used for many other purposes. For example, it can be used in the brain to treat Parkinson’s disease. Neurostimulation is a neurosurgical form of therapy. This means that it is a surgical procedure that needs to be performed by a trained specialist. There are many forms of neurostimulation that are relatively safe, reversible and adjustable.
Development of neurostimulation
Neurostimulation has been used for the past 50 years. Its use has been increasing recently due to new technology that allows for a safer and less invasive form of treatment.
Types of Neurostimulation
Spinal Cord Stimulation (SCS)
Spinal cord stimulation is commonly used to treat back and leg pain that is not responsive to other treatments. The stimulator is placed in the spinal cord, generally in the mid to lower spinal region. The stimulator causes feelings of paraesthesiae in the lower back and down the legs. The precise positioning during surgery is conducted with the patient awake so the stimulation carries the area of the pain.
Patients who may benefit from SCS include those suffering:
- Complex regional pain syndrome (CRPS), a condition where the patient has pain in an area of the body due to nerve damage
- Failed back surgery syndrome (FBSS), where a patient has continued pain after unsuccessful spinal surgery
- Extremity pain due to peripheral neuropathy (for example, phantom limb pain or following spinal cord injury)
- Pain due to lack of blood supply in the limb, usually due to diseased blood vessels supplying the leg
- Other applications of SCS that have been developed in recent years include
- Chest pain, or angina in patients with cardiac problems
- Urinary incontinence
- Occipital neuralgia
Dr Steel was the first surgeon in Australia to implant spinal cord stimulators for angina. He presented his experience with spinal cord stimulation for patients with angina at the Royal Australian College of Surgeons Annual Surgery Congress in Canberra in 2001.
How Spinal Cord Stimulation Works
Patients are generally awake when SCS is performed. A minimally invasive exposure is made and a small battery is implanted under the skin. This is connected by wires to a small, plastic plate or wire that is tunnelled next to the spinal cord or the peripheral nerve.
The battery is similar to a cardiac pacemaker, and depending on the patient’s usage may need to be replaced every five to seven years. This can be a highly effective technique for patients with chronic pain that have not responded to other treatments.
World-first BMP study
Dr Steel has just completed a randomised control trial of the efficacy of bone morphogenic protein in lumbar spine fusion, the first of its kind in the world.
This study should allow surgeons to assess how much and how rapidly the bone morphogenic protein facilitates bone fusion in the lumbar spine. This study has formed part of Dr Michael Ow-Yang’s Masters of Surgery. It was his major research work as part of his research fellowship in 2008. The second phase of the trial will be performed by Dr Ellen Freydenberg as a part of her Spine Fellowship in 2010.
Bone Morphogenic Proteins (BMP)
Certain bone morphogenic proteins (BMPs) have been studied for decades because of their ability to heal bone and eliminate the need for bone graft harvesting from the hip. About 20 BMPs have been discovered, but only six appear capable of initiating bone growth. Of these, RHBMP2 has been studied more than any other BMP and is approved by the US Food & Drug Administration for use in spinal and tibial surgeries. Naturally occurring BMP is found within the bone itself. However, it is only available in small amounts. To provide clinically useful and reproducing amounts of isolated human BMP is impossible; it cannot be economically extracted from donor bone and must be manufactured (genetically engineered). The preferred method for manufacturing RHBMP-2 is by a process called recombination. Scientists isolated the gene for one protein (BMP2) from the bone tissue and used well-established molecular biological techniques to create genetically engineered cells. These cells then reproduce large quantities of BMP2. A similar process is used to manufacture other proteins, like insulin. The recombinant form of BMP2 is identical to the natural both in its chemistry and its ability to heal bone.
How BMP is used in surgery
During surgery, RHBMP-2 is soaked onto a sponge designed to disappear over time. As the sponge dissolves, the BMP2 stimulates the cells to produce new bone and ultimately to heal.
After a few weeks, the RHBMP-2 also goes away, but it has completed its task to initiate the normal bone healing process. In the spine, the BMP grows bone in the disc space to join or heal the vertebrae and stabilise the spine. The use of bone morphogenic protein means we do not need to harvest a bone from the iliac crest or hip in virtually any surgical procedure. Harvesting bone from the iliac crest is a major source of pain following spine surgery and can be a source of significant complication in up to 20 percent of patients. With the use of bone morphogenic protein, considerably less bone is required to achieve bone fusion.