CYBERKNIFE IN TREATMENT OF TRIGEMINAL NEURALGIA
Dr.M.Balamurugan, Senior Consultant - Neuro Surgery
"The Suicide Disease" or tic douloureux(also known as prosopalgia) is a neuropathic disorder of the facial trigeminal nerve. The trigeminal nerve the fifth cranial nerve, is responsible for sensory data (pressure, tempereature & pain) and also responsible for the motor function of the muscles involved in chewing but not facial expression.
The disorder is characterised by episodes of intense facial pain that usually last from a few seconds to several minutes or hours. The attacks are said to feel like stabbing electric shocks, burning, pressing, crushing, exploding or shooting pain that becomes intractable.
Unfortunately, the symptoms of trigeminal neuralgia are often falsely attributed to a pathology of dental origin. Because of this difficulty, many patients go untreated unless a correct diagnosis is made.
There is evidence that points towards the need to quickly treat and diagnose TN. It is thought that the longer a patient suffers from TN, the harder it may be to reverse the neural pathways associated with the pain. Therefore it is essential that physicians are made aware of the seriousness of TN and the level of pain that their patient
Medical treatment may involve usage of Anticonvulsants such as carbamazepine, oxcarbazepine, topiramate, phenytoin, or gabapentin and sometimes low doses of some antidepressants such as amytriptiline is used.
Surgically there are five options available . Of the five surgical options, the microvascular decompression is the only one aimed at fixing the presumed cause of the pain. Three other procedures use needles or catheters that enter through the face into the opening where the nerve first splits into its three divisions. Excellent success rates using a cost effective percutaneous surgical procedure known as balloon compression are available. This technique has been helpful in treating the elderly for whom surgery may not be an option due to coexisting health conditions. Balloon compression is also the best choice for patients who have ophthalmic nerve pain or have experienced recurrent pain after microvascular decompression.
Other options involve using glycerol injections and radiofrequency rhizotomies. Glycerol injections involve injecting an alcohol-like substance into the cavern that bathes the nerve near its junction. This liquid is corrosive to the nerve fibers and can mildly injure the nerve enough to hinder the errant pain signals. In a radiofrequency rhizotomy, the surgeon uses an electrode to heat the selected division or divisions of the nerve. Done well, this procedure can target the exact regions of the errant pain triggers and disable them with minimal numbness.
Stereotactic Radio Surgery The nerve can also be damaged to prevent pain signal transmission using Gamma Knife or a linear accelerator-based radiation therapy (e.g. Trilogy, Novalis, CyberKnife).
Cyberknife Radiosurgery : Of these, the development of CyberKnife radiosurgery (Accuray, Inc., Sunnyvale, CA) in 1994 added a promising new treatment option for this disease. Using noninvasive head immobilization and advanced image-guidance technology, the CyberKnife dynamically tracks skull position and orientation during treatment, thereby ensuring targeting accuracy throughout the entire procedure, and patients are spared the discomfort of frame fixation onto their skulls. CyberKnife radiosurgery offers the ability to deliver nonisocentric, conformal and homogeneous radiation doses to nonspherical structures such as the trigeminal nerve. There are no risks of infection, cerebrospinal fluid leak or wound healing from Cyberknife Radiosurgery. However, some patients may develop additional numbness in the face or may experience abnormal facial sensations. This occurs in less than 10% of patients.
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