Surgery For Chiari Malformation In Adults
Linda Berens
The most common surgery for Chiari malformation is called posterior fossa decompression. Surgery involves removing a small section of bone in the back of the skull. This relieves pressure by giving the brain more room.
This malformation occurs during fetal development and is characterized by downward displacement by more than four millimeters, of the cerebellar tonsils beneath the foramen magnum into the cervical spinal canal. This displacement may block the normal pulsations of CSF between the spinal canal and the intracranial space. This form of Chiari malformation may be associated with syringomyelia/hydromyelia. It is diagnosed more commonly in adolescents or adults.
Chiari I malformations that are asymptomatic should be left alone (this involves the majority of Chiari malformations). There is no indication for "prophylactic" surgery on these. If the malformation is defined as symptomatic, or is causing a syrinx, treatment is usually recommended.
There are many different types/extent of surgery based on the extent of compression or other anomalies. Chiari I malformations may be treated surgically with only local decompression of the overlying bones, decompression of the bones and release of the dura (a thick membrane covering the brain and spinal cord) or decompression of the bone and dura and some degree of cerebellar tissue resection. Occasionally some patients will also require cervical spinal fusion.
Background: Chiari I malformations are common in adults and a frequent procedure in neurosurgical practice. Despite several studies, there is no consensus about the indications or surgical technique for this common condition. Increasing emphasis on value-based care has emphasized reduction of readmissions and reoperations and is particularly relevant in Chiari, which has traditionally been associated with a high complication rate.
Methods: The American College of Surgeons National Surgical Quality Improvement Program database was queried to determine 30-day outcomes after surgery for Chiari I malformations in adults between 2005 and 2016. Demographics, clinical risk factors, and postoperative events were analyzed, along with reoperation and readmission reasons.
Conclusions: Surgery for Chiari in adults is common and carries a definitive risk profile, including rates of readmission and reoperation higher than other common neurosurgical procedures. This cohort provides a representative sample of contemporary neurosurgical outcomes in surgery for Chiari I malformations.
A recent NIH-funded research study examined the outcomes one year after surgery for Chiari I malformation and syringomyelia in children treated with posterior fossa decompression surgery. The researchers compared the outcomes of study participants who just had bone removed with the outcomes for study participants who also had opening and expansion of the dural membrane (duraplasty) to make more space at the foramen magnum. Patients with duraplasty had fewer and less severe symptoms after surgery, a smaller syrinx, and a lower chance of needing another surgery. Complication rates were greater in the duraplasty group early after surgery, but comparable by six months after surgery.
When it comes to Chiari malformation treatment, there are generally two approaches a surgeon may use: traditional surgery or minimally invasive. Traditional surgical procedures are what you would think of as open surgery and include Chiari decompression surgery and cervical laminectomies, which have been used by many doctors to effectively treat Chiari malformation patients. However, new advances in technology and techniques have made minimally invasive Chiari malformation treatments possible. In a minimally invasive surgery, the surgeon uses specialized instruments that allow him or her to make smaller incisions and disrupt less of the surrounding tissues.
Most patients who are candidates for traditional Chiari malformation surgery are also eligible for minimally invasive approaches. In fact, many Chiari malformation specialists have come to prefer using minimally invasive treatments because they are just as effective as traditional surgery, with increased benefits to patients.
As a patient, minimally invasive treatments means that you can expect to experience less bleeding, less pain and a shorter recovery period. Your hospital stay following a minimally invasive Chiari malformation procedure will typically be shorter than traditional open surgery. You will likely require less pain medication and/or need medication over a shorter duration. You may also be able to return to work and resume your normal activities more quickly, although recovery is a very individual process and varies from patient to patient.
Chiari malformation refers to a structural defect in the cerebellum, in which a part of it, the cerebellar tonsils, protrudes into the spinal canal. When the cerebellar tonsils are pushed down into the foramen magnum and into the spinal canal, pressure is created on the brainstem. This blocks the flow of cerebrospinal fluid, a clear fluid cushioning the brain and spinal cord. The block in the flow of the cerebrospinal fluid disrupts normal functioning of the brain and spinal cord and causes fluid to accumulate in the spinal cord (syringomyelia) or brain (hydrocephalus). Chiari malformation can occur in adults as well as in children.
Chiari malformation is associated with symptoms such as head, neck, chest and general body pain, imbalance, hearing loss, sleep apnea, swallowing difficulty, arm and leg numbness and impaired thinking. Chiari malformation can be managed with regular monitoring and medications. However, severe cases would require surgery.
As a baby, Adelynn was diagnosed with a Chiari malformation that was interfering with her ability to eat, sleep and breathe. She underwent surgery at Johns Hopkins to correct the problem, and today she is a healthier, happier child.
Forty adult patients (average age 40 years), with the clinical and radiological features of the Chiari malformations, were seen at the Toronto Western Hospital between 1967 and 1984. Surgical confirmation of the diagnosis was obtained in 32 cases; of these, 23 were classified as Chiari I malformation while 9 fulfilled the anatomic criteria of Chiari II. The patient population consisted of 22 males and 18 females. Common presenting symptoms included head and neck pain (60%), sensory complaints (60%), upper extremity weakness (42%), and gait disturbance (40%). Neurological findings included signs of central cord dysfunction (73%), long-tract motor and/or sensory findings (58%), brainstem signs (38%), cerebellar dysfunction (18%), and increased intracranial pressure (15%). The majority of patients underwent myelography with or without computed tomography of the cervical-medullary junction. Two recent patients had 0.15T MRI scans which helped demonstrate an intramedullary syrinx. Thirty-three patients underwent 47 operative procedures (discounting spinal fusion and CSF shunt revisions). Open surgical management was performed in 32 patients, with CSF shunting along in one patient. Five patients (15%) incurred surgical complications within a six week postoperative period. Follow-up to date, ranges from one month to 11 years. In the 33 surgically treated patients, 18 are improved (55%), 10 are neurologically stable (30%), and five have worsened clinically (15%), including one death. Based on this study it appears that the Chiari II malformation maybe more common in adults than previously recognized. Surgical intervention has a favourable outcome in the majority of patients but a significant proportion continue to deteriorate.
Chiari I malformation is a condition in which there is crowding of the cerebellar at the base of the skull and the upper spinal area are not formed properly. For most patients, treatment for Chiari I consists of surgery to repair the abnormality and relieve symptoms. However, some patients who do not have symptoms may not need surgery. Instead they are seen routinely by their doctors for follow-up examinations.
At the Pediatric Neurosurgery Center, we have been collecting information for decades to help determine whether opening of the dura mater is a necessary component of surgery for individuals with Chiari I malformation.
The ACS NSQIP database was queried from 2011 to 2020 to identify all patients with a CPT code of 61343 (craniectomy, suboccipital with cervical laminectomy for decompression of medulla and spinal cord, with or without dural draft for Chiari malformation) and the concurrent ICD-9 (348.4) or ICD-10 (G93.5) diagnosis code for CM-I. The ICD-9 code alone was previously validated against institutional records with an excellent positive predictive value in children (97%) and in adults (> 99%).5,24 ACS NSQIP diagnosis/procedure-free text descriptions were manually reviewed to confirm cases of Chiari decompression surgery.
This study demonstrates that increasing frailty, as measured by the RAI-rev, is associated with increasing rates of NHD disposition following suboccipital decompression surgery in adults with CM-I. The adverse outcomes were very low, with a rate of routine HD exceeding 95%, a major postoperative complication rate of only 1.8%, and a single 30-day mortality. Preoperative RAI-rev frailty assessment may help identify CM-I patients at increased risk of postoperative complications, including NHD, and thus allows for more accurate informed consent and preoperative decision-making regarding the risks and benefits of surgical intervention.
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