|Arnold Chiari Malformation and Decompression Surgery
Chiari Malformation, or ACM, is a rare congenital brain deformity that can cause severe and painful symptoms. Though difficult to diagnose because of four progressive types, its diagnosis is becoming more and more common because of new technology. Diagnosis often depends on the type of symptoms the patient is experiencing. The most common symptoms of Chiari Malformation Type I are headaches, neck pain, vertigo and disequilibrium, though often patients with ACM Type I are asymptomatic. Types II, III and IV are progressively more severe and painful and therefore easier to diagnose by X-ray, CT scan or MRI, the former being the most popular.
Surgical decompression is most often used to treat ACM types II, III and IV and increases in popularity with the progression of the malformation. Upon diagnosis of Chiari Malformation Type I, surgical decompression is becoming more widely used over other treatment options such as drug therapy. With the growing use of surgical intervention to treat ACM Type I there is controversy over the possibility of necessity for reoperation and the complications associated with major surgery. However, the development of new decompression techniques is opening the door to safer and more successful operations. Continuing research and development makes surgery a viable treatment option for patients hoping to relieve the symptoms associated with Chiari Malformation Type I.
Many people diagnosed with Chiari Malformation Type I experience little or no symptoms and are found to have the deformity during the investigation of another medical issue. Those who do experience symptoms are often misdiagnosed because of the wide range of symptoms reported in studies and because of differences in its presentation in children versus adults (Green). The most common symptoms are severe headaches, visual disturbances, scoliosis, vertigo and difficulty swallowing (Green). Such symptoms are caused by excessive pressure on the brain due to an undersized skull. Though other therapies are available, a surgical decompression to open more space around the brain is common practice.
A Chiari Malformation decompression surgery is a major operation, usually lasting more than five hours. ACM Type I requires the simplest of decompression procedures, but the variety of procedural options make for a difficult decision. A typical procedure involves the removal of the dura, “the outer covering of the brain”, and placement of a larger graft and a cervical laminectomy, “the removal of the bone forming the back of the vertebra or lamina” (“Chiari Type I Malformation”). Depending on the severity of the malformation, only one of these procedures may be performed, but they are often performed together during one operation. In addition to complications associated with any major surgery, a surgeon’s indiscretion as to which procedure to use in a certain situation can itself cause serious side effects.
All major surgeries carry risks. The most common risks are side effects or complications due to anesthesia, blood loss and shock, heart and lung complications and infection. Chiari decompression surgeries carry these and other more isolated risks. While most complications during decompression occur because of duraplasty, the necessity for reoperation and the complication known as cerebellar slump are both possible.
A study of surgical technique and success rates published in 2003 cited four factors that may lead to the necessity of reoperation. Sixteen of the 100 patients with ACM Type I, compared to only two of the twenty-three patients over five years of age, were undergoing surgery for the second time. Two of the four trends found in the reoperative cases occurred at the discretion of the neurosurgeon: “a young age at initial surgery… and failure of the surgeon at the initial operation either to assess patency of the foramen of Magendie or correctly place a fourth ventricular stent” (Sacco 172). The study found that children who underwent their first surgery under the age of five years were often judged inadequately during surgery (Sacco 173). This misjudgment itself was also found to lead to reoperation. The foramen of Magendie is the structure that connects the brain’s fourth ventricle with the subarachnoid space, the area most affected by a Chiari Malformation. If a surgeon judges this structure to be satisfactory, or miscalculates the amount of bone that should be removed, problems could occur post-operatively requiring a second surgery.
Cerebellar slumping occurs when “too much bone is removed” (Lazareff) allowing the brain to slide back into its former position. The resulting slump can cause pressure on the spinal cord and skull similar to that experienced before the initial surgery. A second surgery may be performed to compensate for this loss. Despite the risks, neurosurgeons continue performing decompression surgeries on patients with symptomatic Chiari Malformation because it is, in most cases, successful.
Allison J. Green, author of the article “Update on Chiari Malformation: Clinical Manifestations, Diagnosis, and Treatments”, cites a 2002 study showing that “of the 22 pediatric subjects followed postoperatively, 12 reported complete resolution of symptoms, 11 had improvement, and 2 stated the clinical manifestations were unchanged… [In addition] none of the pediatric clients had worsening of symptoms after surgical repair” (Green). A study cited in “What is Chiari, Arnold Chiari, ACM, CM1” stated that “up to 50% become symptom free after surgery, with another 10%-30% improving significantly. On the flip side, for 10%-20%, the surgery will be a failure and they will likely require additional surgeries” (“What is”). Despite this fact, many people who choose to undergo the operation are satisfied with the outcome despite the traumatic experience.
Adam Hulse was first diagnosed with ACM in sixth grade when he lost his hearing in one ear because of a severe case of shingles. An MRI showed that the malformation was not severe enough to warrant surgery at that time; however, two years later a second brain scan was taken because of severe headaches, dizziness and vertigo. Hulse underwent a “conservative” (Hulse) operation that only lessened his symptoms for a short period of time. A few years later, worsening symptoms were misdiagnosed as an inner-ear disease, but later found to be a recurrence of his ACM. A second operation involved removal of the first and second vertebra and duraplasty. Though he still experiences minor symptoms, Hulse says, “Was it worth it? Totally” (Hulse). Surgeons and researchers are hoping that more patients will share Hulse’s response to the surgery with the continuing development of new surgical techniques and methods even though they continue to argue amongst themselves over the current techniques.
In 1998, a group of surgeons from Johns Hopkins Hospital surveyed 234 members of the Pediatric Section of the American Association of Neurological Surgeons. The 77 returned surveys showed that though surgery was favored, “there was no consensus on the optimal procedure” (Haroun). For patients with ACM type I, 25% surveyed bony decompression alone, 32% bony decompression and dural patch grafting, 24% bony decompression, dural patch grafting and intradural dissection, and 31% favored bony decompression, dural patch grafting, intradural dissection and tonsillar manipulation (Haroun). 95% total “recommended a dural patch graft” (Haroun), the cause of most ACM decompression complications. The fact that “30% of pediatric neurosurgeons [who] favor some type of tonsillar manipulation” (Lazareff) spurred the development of a less traumatic surgical technique.
Jorge A. Lazareff, the director of Pediatric Neurosurgery at UCLA Medical School, led a group of UCLA surgeons in developing “a new surgical technique which focuses only on the malformation itself” (Lazareff), in turn reducing trauma to the patient. The surgeons performed 15 decompressions by removing only the cerebellar tonsils, “the bottom portion of the cerebellum”, which were shown upon examination to be made up of “abnormal” tissue (Lazareff). Lazareff comments that “in Chiari patients, the tonsils may not be as important because they are abnormal… [And] they may not be working for the Chiari patient” (Lazareff). Though it is criticized and has yet to be proven on a large scale, Lazareff maintains confidence in his technique which was published in 2002.
Another method of leaving the dura and/or “the underlying arachnoid [space] intact” (“Study Shows”) has worked especially well in children. According to an article published by the organization Opening Minds to Arnold Chiari Malformation, many of the complications experienced during ACM decompressions are caused by the opening of the dura. “There is a risk of infection and sometimes the patch that is sewn in leaks or becomes scarred” (“What is”). However, the use of that technique in adult patients was not popular until an Italian study showed great success. In this study, 87.5% of the patients showed improvement of at least one symptom and, out of the 24 patients, none of the 20 “whose arachnoid was intact experienced any complications” (“Study Shows”). One study shows that this success may have to do with the simplicity of the operation. A Chinese research group found that 95% of simple Chiari operations showed good results compared to 74% of complex operations (“Complex Chiari”). Yet another Chinese study focuses on these reported success rates.
According to Rick Labuda, of the Conquer Chiari Organization, research and study methods make it difficult to determine the success rates themselves; instead, doctors and patients must rely on general studies which show a success rate of 80% for Chiari decompressions (“Large Study”). Labuda cites a Chinese study which was meant to provide more reliable statistics. The study consisted of 316 patients whose post-operative symptoms were labeled Very Good, Good, Fair and Poor. Of the 316, 56% were Very Good, 29% Good, 15% Fair and 4% Poor (“Large Study”). The neurosurgeon’s dedication to his or her technique can also affect a patient’s chance of success.
The Chiari Institute, located in New York, specializes in the diagnosis and treatment of Chiari Malformation and syringomyelia, a condition often associated with ACM. “The complication rate for Chiari-related surgeries at The Chiari Institute is the lowest in the nation (“Surgeries”), possibly attributed to the fact that there are two experienced neurosurgeons on every case, 49% of which are reoperations, and because the entire staff has extensive experience with the condition. The institute has started using the aforementioned technique avoiding duraplasty and reports a 0.2% complication rate, compared to the 8% reported nationwide. This decrease in complication rates is especially impressive since the number of surgeries performed at The Chiari Institute in 2007 is more than triple the number performed in 2002.
Many patients remain hesitant to undergo ACM decompression despite these overwhelming statistics illustrating success in the majority of cases. Their primary reason not to undergo decompression is the possibility of complications. Also, because of the occurrence of misdiagnoses many doctors and patients alike are hesitant to react to a diagnosis. The current popular decompression technique is often successful in eliminating or reducing symptoms. In cases where re-operation is necessary, the second decompression is most often successful. Given the decrease in complication rates with new techniques, the success rate is gradually increasing. With an increase in awareness among doctors and neurosurgeons, research and development of new surgical techniques will also increase. These new methods will make surgery an even more viable option for patients suffering from all four types of Chiari Malformation, especially symptomatic type I.
Chiari Type I Malformation. Neurosurgerytoday.org. June 2001. 14 Oct. 2008.
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“Surgeries”. Chiariinstitute.com. 9 Dec. 2008.
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