World leader in brain surgery and anatomy
cites strong scientific readiness to find a cure for TN
Neurosurgeon Albert Rhoton Jr., whose four decades as a brain anatomist, surgeon, teacher and surgical instrument designer won him world recognition as “the father of modern microscopic neurosurgery,” says surgical treatment for trigeminal neuralgia has remained fairly static during his career.
“Two-thirds of trigeminal neuralgia patients achieve permanent pain relief through the major operation called microvascular decompression, but the other third suffer pain recurrence. A less invasive operation, using radiofrequency heat to destroy the nerve, often stops the pain, but leaves parts of the face numb.” he said. “Diagnosis for nerve-related facial pain disorders remains very challenging because it is based largely on the patient’s description of the pain without the benefit of a specific diagnostic test. Many patients still end up shopping around for several years before their disease is identified.”
On the bright side, Rhoton, who is a founding trustee for The Facial Pain Research Foundation, said medical scientists have learned a great deal about the structure and function of the trigeminal nerve, and the kinds of nerve damage that activate facial pain. Researchers have access to better-than-ever brain imaging systems, microscopic surgical instruments and technologies such as stem cells and gene therapy to help rebuild injured nerve tissue.
“It is time to find a cure,” he said. “For the Foundation to achieve its goal of curing trigeminal neuralgia and other nerve-generated facial pains in 10 years would be a miracle, but it is a good goal. If we don’t take this road, we will probably never achieve a cure.”
Rhoton has led the way in vastly expanding knowledge of brain anatomy and microscopic surgical technique, and in providing surgical practitioners with new brain images that enhance the accuracy of surgery. He initiated a highly ambitious plan to remap the brain shortly after beginning his surgical career at the Mayo Clinic (Rochester) in 1965, coinciding with the time neurosurgeons adopted use of the surgical microscope. At the University of Florida College of Medicine where he has worked since 1972, he and two medical illustrators, Robin Barry and David Peace, have built the world’s largest collection of three-dimensional full-color images of the brain and the intricate blood vessel network running through it. The trigeminal nerve is one important region of Rhoton’s high-magnification study.
Based on his experience in treating more than 3,000 facial pain patents during his 40 years of surgical practice, he knows finding a cure is a steep challenge, given the complicated and variable nature of neuropathic facial pain. His tracking of clinical outcomes of trigeminal neuralgia treatment worldwide confirm that view.
In the realm of medications for neuropathic facial pain, he said the newer prescription drugs offer few pain-relieving advantages over Carbamazepine (brand names Tegretol, Tegretol XR and Carbatrol), the main drug-of-choice for TN since 1974. Yet even this drug sometimes produces adverse effects, including liver toxicity, impaired thinking, double vision, weight change and low sodium.
“Initially, I think every TN patient should try a prescribed medication and stay on that medication if their pain is relieved without bothersome or intolerable side effects,” Rhoton said. “But if any medication causes deficiencies in life function, the patient needs to consider an operative procedure.” He emphasizes, “The physician’s best ally is a well informed patient, which means every patient should know all the treatment options available.”
Rhoton emphasizes that achieving a cure calls for well-targeted research carried out by collaborating scientists with new resources at their command. He recommends for example:
· The majority of research should be focused at the junction where the trigeminal nerve exits the brainstem and branches into the three major areas of the face—the primary site where the nerve and its myelin coating are damaged, often by a blood vessel looped over or sagging down upon the nerve. This small area is where pain is most often activated, and is where microvascular decompression (MVD) is performed to separate the offending blood vessel from the nerve. In this space, exquisite surgical skill is required to avoid damage to the nerves that affect hearing and balance.
“All the evidence we have now shows that damage to the trigeminal nerve occurs in this junction leading into the brainstem and brain, actually between the brainstem and the nerve cells in the ganglion,” Rhoton said. “When damage occurs in this junctional area, there is no regeneration of nerve fibers and nerve function, but further toward the face, between the trigeminal nerve and the facial skin, ears and eyes, we DO often see nerve regeneration.”
· Brain tissue banks should be established to collect and store trigeminal nerves from deceased individuals with trigeminal neuralgia or other neuropathic facial pain disorders, as well as intact, undamaged trigeminal nerves from others, who had signed consent to donate their brains to medical science upon their death. Such banks would enable researchers to check out trigeminal nerve specimens for research.
“If we could compare the donor brain tissue of former TN patients with healthy control tissue, perhaps we could see some distinctive differences through imaging techniques such as electron microscopy,” Rhoton said. “Not just structural differences, but possibly differences in the molecular pathway through which the protective nerve coating known as myelin sheath is produced.”
· Scientists working to achieve a cure need to apply some of the latest technology out there, such as newly developed lines of stem cells that have the ability to rebuild nerve fibers or rebuild the myelin coating around the nerves. Funds will be needed to help eminent nerve researchers add another scientist or hire graduate students to work in specific areas of stem cell research applied to trigeminal nerve disorders.
· Researchers now focusing on the trigeminal nerve should team up with investigators of nerve damage associated with other diseases such as spinal cord injury, stroke, traumatic brain injury and multiple sclerosis. Rhoton notes, “Probably billions of dollars are now being spent on investigating myelin damage and repair in these other diseases, and many of these projects involve model approaches to research that might be applied to the trigeminal nerve.”
With the seniority of a hands-on tutor to more than 1,000 neurosurgeons around the world and as author of the best-selling encyclopedic guide to neurosurgery, Rhoton knows the “good news/bad news” aspects of contemporary treatments for trigeminal neuralgia and other nerve-generated facial pains. He said treatment decisions often come down to difficult choices among therapies associated with different risks. Many procedures intentionally destroy parts of the trigeminal nerve to stop pain in the damaged area, causing facial numbness that can be difficult to live with. Many patients find they must make a trade-off between repetitive agonizing pain and constant numbness.
“Microvascular decompression surgery (MVD), also called the Jannetta procedure in honor of Dr. Peter Jannetta who performed his first operation for TN in June 1966, remains the best option for pain relief without facial numbness,” Rhoton said. “This surgery helps many patients, but other patients, even after a second or third MVD procedure, may suffer resurgent pain months or years later. Risks for side effects are low percentage-wide, but may include such serious problems as loss of hearing, double vision (usually temporary), facial weakness or numbness, impaired balance, infection and paralysis.”
“MVD is a major operation, entering the skull through a small opening created behind the ear, which requires the patient to be under general anesthesia for several hours and in the hospital for two to three days or longer,” he said. Compression of the nerve is known to damage the myelin sheath, which explains why decompression of the nerve works in many cases to stop or reduce facial pain.
“Trigeminal neuralgia patients who want to undergo treatment with less risk than is associated with major surgery and who can accept facial numbness as a consequence of treatment, there are various ways to stop or minimize pain by destroying part of the trigeminal nerve,” he said. “Several procedures can be performed in an outpatient clinic under light anesthesia, and the patient can usually go home the same day.”
He notes, for example, the common use of radiofrequency heating current, delivered through a needle that is passed into the cheek on the side of the face affected by pain. The needle is directed under X-ray guidance through a small natural opening in the base of the skull into the trigeminal nerve. Target areas of the trigeminal nerve are destroyed by the heat, while the region of pain is rendered numb, in most cases permanently numb.
Rhoton, who performed this percutaneous (through-the-skin) radiofrequency lesion procedure in some 1,000 patients before he retired from surgical practice, said many patients tolerate facial numbness better than the sharp attacks of pain they previously suffered. “But others find that the area of numbness may feel irritated, aching, tingling, burning, or as if the skin is crawling. If a person finds the numbness disagreeable or intolerable, very little can be offered except mild tranquilizer medication.”
“Another option involves injecting glycerol into the region of the trigeminal nerve to damage the nerve and thereby relieve trigeminal pain, but in our clinical experience, we found this therapy had shortcomings when compared to the radiofrequency procedure,” Rhoton said. “Glycerol injection is less likely than the radiofrequency procedure to relieve the pain at the time of treatment. If the glycerol injection DOES relieve pain at the time of treatment, the chance of recurrent pain is greater than with the radiofrequency heating current.”
Other relatively non-invasive operative procedures include balloon compression, in which a soft balloon-tipped catheter is threaded into the target area, and the tiny balloon is inflated so that it squeezes part of the trigeminal nerve against the hard edge of the brain covering (the dura) and the skull. Still other patients undergo stereotactic radiosurgery, in which various computerized systems such as Gamma Knife®, the LINAC Scalpel® and Cyberknife® to direct tightly focused beams of radiation to the site where the trigeminal nerve exits the brainstem. This causes the slow formation of a lesion on the nerve that disrupts the passage of pain signals to the brain.
For trigeminal neuralgia patients, who are hesitant to undergo major surgery and uncertain whether they could tolerate the facial numbness associated with nerve-destructive treatments, Rhoton said a low-risk neurosurgical procedure can be done to help them make a decision. The surgeon can create a small lesion in the trigeminal nerve distant from the brainstem, which results in facial numbness that lasts only two to 12 months until the nerve fibers regenerate. When pain sensation returns, the patient can then decide whether facial numbness is an acceptable trade-off for striking facial pain, and whether to undergo MVD.
At age 78, Rhoton is a highly productive writer of scholarly papers, and is aiding the teaching of neurosurgeons throughout the world. His updated journal articles on brain anatomy, illustrated with the 3-D images, are now used as roadmaps and teaching aids for neurosurgeons at all levels of expertise. As he finishes an article, he donates the illustrations to the journals, so that the latest information quickly reaches neurosurgeons. He is the author of more than 400 journal articles and textbook chapters, plus four textbooks.
Within months, dozens of the latest 3-D brain images from his laboratory will be posted on the Website of The American Association of Neurological Surgeons, and made available for distribution to neurosurgical training courses and to neurosurgeons, who may project them in the hospital operating room to provide visual reference to the surgical team.
The impact of Rhoton’s up-to-date anatomical illustrations on neurosurgical training and practice was recently brought to light in a thank-you note from Neurosurgeon Thomas Santarius, M.D., at the esteemed Cambridge University in the UK. His handwritten note to Rhoton reads: “ Your work has been a great inspiration to me personally for years, and your words—‘to make the delicate, awesome and fateful work of the neurosurgeon more accurate, gentle and safe’—have been the motto of the Cambridge Lectures since their conception in 2005. The 3-D images are a major boost to the lectures and the quest to make our surgery more accurate, gentle and safe.”
Neurosurgeons in virtually every part of the world now turn to the best-selling reference book, RHOTON: Cranial Anatomy and Surgical Approaches, for updated descriptions and 3-D images of brain tissue. Chapter 4 features extensive information on the trigeminal nerve. The massive text, now in its fourth printing as a special publication by the Journal of the Congress of Neurological Surgeons, is being translated into other languages, including Chinese, Italian and Japanese, as well as Portuguese for Brazilian neurosurgeons.
Rhoton approaches every day’s work with the same sense of awe he expressed as a young surgeon contemplating the task of repairing an artery as tiny as the letter “o” in the word God on the penny. As a guest teacher or lecturer at neurosurgeons’ meetings around the world, he often describes the human brain as “the crown jewel of Creation with an amazing ability to see, feel and experience emotion, to conceptualize phenomena as vast as the universe more than a billion light-years across, and to conceptualize a microscopic world out of reach of our senses.”
He says his greatest career gratification stems from helping patients recover from life-threatening tumors and other brain lesions, and from the pain of trigeminal neuralgia.
At the University of Florida, Rhoton fills an endowed position as the R.D. Keene Professor and Chairman Emeritus in Neurosurgery. He is a 1959 graduate of Washington University School of Medicine where he also completed neurosurgical training. He served on the staff of the Mayo Clinic in Rochester, Minn. before joining the UF faculty in 1972 as a professor and chairman of the department of neurological surgery. He is a former president of six of the world’s leading organizations of neurosurgeons, as well as the Florida Neurosurgical Society. He has received many prestigious awards, including the 2001 Medal of Honor from the World Federation of Neurosurgical Societies, the 1998 Cushing Medal from the American Association of Neurological Surgeons, and the 2009 Golden Neuron from The World Academy of Neurosurgery. At UF, he has received a Distinguished Faculty Award and a Lifetime Achievement Award.