In this presentation, we are going to discuss adult KR1 malformation, including its demographics, the anatomy of the craniocervical junction, and the results of the microsurgical decompression of craniocervical junction and subarachnoid spaces. I do not have any commercial disclosures. I am officer of various national and international neurosurgical associations, as listed. KR1 malformation is congenital or acquired hindbrain deformity, and it was first described by Dr. Chiari, who was Austrian pathologist in 1891. In essence, it is caudal displacement of posterior fossa structures below the plane of foramen magnum, 3-5 mm. It usually has peg-like elongation of tonsils and may be associated with syringomyelia or hydrocephalus. Average presentation is at age 41, and this caudal displacement of hindbrain can cause obliteration of cisterna magna. In general population, its prevalence varies. Some authors listed it at 0.56%, and some authors go all the way up to 3% of all patients with KR1 malformation that had family member with same diagnosis. At any rate, we can say that prevalence ranges between 0.5% and 1%, and several percent of patients with KR1 malformation have a family member. In those, there is autosomally dominant pattern of inheritance, according to different authors. In KR1 malformation, there is impairment of spinal fluid circulation at the cranio-cervical junction between cranial and spinal compartment. As you can see, the egress of spinal fluid from the fourth ventricle may be obstructed at the level of majendi foramen or lusca foramina on the sides, and there is impairment of transmission of the pressure between cranial compartment and spinal compartment. The etiology of this malformation is unknown. In pathogenesis, there is embryological defect in development of occipital bone, and subsequently there is proportionally smaller posterior cranial fossa, and there is disproportion between the size of the posterior cranial fossa and cerebellum. The cerebellar tonsils descend caudally towards the spinal canal and they compromise the cisterna magna, the cerebrospinal fluid flow at the foramen magnum area, there is compression of the brainstem in many cases, and also dysfunction of lower cranial nerves. There is approximately 12 to 100 percent of association of syrinx in Kiari 1 malformation patients, and this syrinx may be associated with pain, temperature, sensory dissociation. There have been several theories of syrinx pathogenesis, but the most common and most commonly discussed are three theories, hydrodynamic theory posted by Gardner in 1965, cranial spinal pressure dissociation theory by Williams in 1969, and obstruction of rapid to and from CSF movement theory by Heiss in Oldfield in 1999. Syringomyelia is most commonly associated with Kiari 1 malformation, but syringomyelia can also be associated with other conditions such as choleosis, trauma, inflammation, or compressive lesions. Those compressive lesions may be spinal cord tumors, disc osteophyte complexes in the cervical or thoracic spine, hemorrhage, or infections and abscesses. In etiology, there is a distal, which means rostral or cranial obstruction of the central canal of the spinal cord, which can be complete, near complete, or partial. The incidence of syringomyelia has been calculated to be approximately 8 on 100,000 population in USA. Milhara did a large series autopsy study on stenosis of the central canal, and he postulated that this central canal serves as a sinkhole for drainage or clearing of substances from spinal cord, and age-related problems associated with aging of central canal stenosis may cause erection disorder, constipation, orthostatic hypotension, and other conditions. This stenosis has been present in autopsy material in 0% of fetuses and can go above 100% in more than 70 years old. Pediatric and adult Kiari 1 malformation have certain differences. The main differences are that lower cranial nerve deficits are more common in pediatric population, as is hydrocephalus. Also, pediatric population is most commonly associated with spinal deformities such as scoliosis, and there is fairly significant dural vascularization at cranio-cervical junction in pediatric patients, which creates potential for significant blood loss. As the individual ages, the dural vascularization somewhat decreases over time. There are different presenting signs and symptoms associated with Kiari 1 malformation. They include foramen magnum compression with ataxia, sensory deficits, lower cranial nerve pulses, downbeat nystagmus, dizziness, central cord syndrome, which presents with loss of pain and temperature, and preserved touch and joint position sense, long triangle signs or hyperreflexia. 10% of patients may have a normal neurological exam, and most common symptom is suboccipital pain and headaches that are aggravated by elevation of intracranial pressure, such as with defecation, sex, coughing, sneezing, laughing, lifting, and bending. Other signs and symptoms are present as well, such as blurred vision, dizziness, aggravated migraine, headaches, etc. The symptom frequency is most commonly weakness of upper and lower extremities, severe suboccipital headaches that worsen with valsalva maneuvers, as mentioned above, sensory dissociation of pain and temperature, gait instability, extremity numbness. Other symptoms are less frequent and have a whole range of them. Less common symptoms that are presented in certain cases may be pseudotumor-like symptoms with papilledema, Meniere disease-like syndrome, decreased hearing or loss of hearing, dizziness. There have been cases reported of trigeminal neuralgia, a couple of cases have been described by Dendi, and of obstructive sleep apnea and central sleep apnea. The adolescent idiopathic scoliosis may be associated in 25% of cases with KR1 malformation. Approximately 38-62% of cases stabilize or improve after suboccipital decompression, as reported by Sengupta, Brockmeier, and Farley. Better outcomes are with the younger age. There are two types of headaches associated with KR1 malformation. One of them is suboccipital pain, again exacerbated significantly with increased intracranial pressure with valsalva maneuvers. The other one is aggravated migraine headaches that failed after 3-6 months of conservative treatment. There are also factors that can precipitate symptoms in previously asymptomatic patients, as 10% of patients may be asymptomatic at presentation and present after MRI has been done for other reasons. 30% of patients with tonsillar descent of 5 mm may be asymptomatic as per VAN. But trauma, even minor trauma with whiplash c-spine injuries may be a precipitating factor, chiropractic manipulations, contact spores, fall, even causing accidental death. McKella has suggested that military surface needs to be modified. Increasing BMI has been described to precipitate symptoms and lumbar puncture. Radiological diagnoses include MRI of the brain and cervical spine. Especially T2 sequences are helpful. They show degree of foramen magnum obstruction, position of tonsils, presence of hydrocephalus, presence of searings, etc. CT scan bone windows with sagittal reconstruction can show presence of bony abnormalities. Sine MRI has been used to evaluate CSF dynamics. And of course, dynamics x-rays of cervical spine with flexion and extension component can show evidence of spinal instability at cranial-cervical junction. Most books quote 5 mm descent of cerebellar tonsils as a cut-off for diagnosis of Chiari 1 malformation. However, it has been described as little as 2 mm descent of tonsils as Chiari. Any tonsillar herniation in Chiari 1 malformation is in essence Cushing herniation and can cause sudden onset of medullary dysfunction or respiratory arrest. Flexion of spine pushes CT downwards to spinal canal in Chiari 1 malformation and further decreases range of motion of cerebral spine. As you can see of this sample in one of my patients, there has been minimal or no descent of cerebellar tonsils below the level of foramen magnum, yet there was still obstruction of cranial spinal subarachnoid spaces causing severe spinal searings and myelopathy. And you can see how the searings almost completely resolved after decompression. We have found that there is association of increased body mass index with Chiari 1 malformation in adults as well as in searings formation and we have published this work. In essence, we have noticed on number of our patients that increasing BMI creates symptomatic Chiari 1 malformation as is seen in this patient. You can see this sagittal T2-weighted MRI on the same patient when her BMI was 28.5. After she gained significant weight and her BMI increased to 41, she developed symptomatic Chiari 1 malformation with significant searings, as you can see on this picture. And then subsequently after decompression, you can see that there is complete resolution of the searings. Here is another example, also female patient, BMI of 21. There was a borderline Chiari 1 malformation, but increasing BMI to 32, you can see that there is descent of cerebellar tonsils into the spinal canal and creation of symptomatic Chiari 1 malformation. Here is another patient that showed similar findings in reverse order. You can see that she had significant searings with minimal Chiari 1 malformation. At that time, she was 50 years old. Her BMI was 45. In this picture, you can see after decompression, her searings continued to grow and her BMI at that time was 46. After decompression, further increased BMI, searings continued to grow. And then when she lost weight and dropped BMI 10 points to 36, which was approximately 60 pounds of weight loss, her searings significantly improved. It's true that both gaining weight may precipitate findings and symptoms in Chiari 1 malformation, including searings formation, but also losing weight can improve searings and symptoms of Chiari 1 malformation. This was essentially conclusion of our paper. I find there are certain instruments that help us in microsurgical decompression of KRN1 malformation. They include Yashagil forceps with progressive working length and different size of tips, as you can see here on the left side. Also, bionetted micro-scissors with blunted and sharp points, pointing tips. We also like Yashagil control suction system with different calibers of suctions, depending on the age and size of patients. And also, pot scissors are extremely helpful in my hands for opening of the dura. In any surgery, and in particular, the compression surgery. We also use harvesting of fat before the patient is positioned in the prone position. While the patient is still in supine position, we harvest fat through horizontal incision. Surgery, we place patient in prone position with head affixed in three-point Mayfield head holder. We create incision between external occipital protuberance to C2 spinous process approximately three inches long. We dissect the cervical and suboccipital muscles through the nuhal ligament. You can see here how there is a plane between two leaflets of nuhal ligament that's completely avascular. And this, we dissect through this plane to be able to have completely avascular surgery. We also recently described in detail suboccipital ligament. That is the ligament that stretches between both occipital condyles and atlas condyles between both sides. This suboccipital ligament, as you can see here, is covered partially with suboccipital bone. And once we remove the bone in suboccipital decompression, it completely uncovers this ligament. This ligament has been described previously that it's thicker and more pronounced in Chiari patients, but we have disputed that fact because we have not yet discovered but we have disputed that fact because comparing Chiari 1 malformation patients and the patient with other pathologies with suboccipital ligament, we found that the sizes are absolutely the same. The difference is only in a certain ultra structure of those ligaments in Chiari 1 malformation, including presence of healing bodies, which cannot be found in a non-Chiari patient. Surgery includes a resection of the C1 lamina as seen here, creating the plan of a horseshoe style drilling at the suboccipital bone. You can see here the drilling to create the trough in the bone. And then basically using kerosene to take the inner table of the bone and elevate the free bone flap. You can see here bone flap prior to elevation and then eventually elevated. Now you can see nicely suboccipital ligament, which we resect and excise and then do decompression laterally to do wider lateral decompression because it's more important to do lateral decompression than the vertical decompression in our experience. Opening, here you can see still suboccipital ligament and then here is the whole picture of the exposed cranial suboccipital dura and spinal dura removed suboccipital ligament coagulated venous lakes and the dura is ready for opening. Dural incision is done with number 15 blade and then we use tuck-up stitches to retract the dura laterally trying to preserve arachnoid membrane until the dura is completely open. You can see here the dura is open in the form of letter Y and dural edge is tucked up to the surrounding stitches with four neural sutures. We then use the small blunted hook to elevate the arachnoid membrane and open it first vertically. We then open the arachnoid membrane laterally thus opening the majandi and subsequently the lusca foramina. After we do that, we go laterally and open subarachnoid spaces in left and right cerebellar medullary cistern showing origin of the pica from the vertebral artery thus decompressing circumferentially the cranial cervical junction. Here is the example of one patient with Chiari 1 malformation and severe myelopathy. Here is, as I mentioned, opening arachnoid membrane first vertically and then opening arachnoid membrane laterally in the right and left cerebellar medullary cistern. You can see here both pica arteries in view. Here is the right pica artery, left pica artery. You can see here cranial nerve 11 spinal accessory. Here is left pica, cranial nerve 11 and 12, opening lateral cerebellar medullary cistern. Here showing the origin of the fourth ventricle and majandi foramen. And then coagulation of cerebellar tonsil tips to shrivel them up. Here is the final view after the compression of cranial cervical junction and the compression of subarachnoid spaces. We use bovine pericardial malograft which we pre-cut in roughly triangular shape as you can see. And then we suture them with three-stage stitches at the angles of the opening and then suture them with running stitches. We then use tooth seal to obliterate any potential openings and very thin layer of fat tissue to prevent formation of pseudo-meningoseal and spinal fluid leak. Here is a post-operative condition of the same patient. And here you can see pre-operative gait of the patient. Then immediate post-operative follow-up visit gait and then gait at two months after surgery, how it almost completely resolved. We have also did systematic review of all pediatric and adult KR1 malformation series between 1965 and 2013 and published. We have found over the course of 48 years, 145 series, which at least four cases. Majority of these patients were published in the last 20 years, approximately 78% with 8,605 patients, roughly equal distribution between adult and pediatric patients. Interesting finding that majority of patients has been reported from North America. Second were, second common were patients from Europe and then about 10% of patients from Asia. There were only a few percent of patients from South America, Africa, and Australia. The reason for this remains unknown, maybe because there is some continental or racial differences between KR1 malformation incidents, or it's only because they were not reported from these areas. At any rate, this needs to be further looked. There is, we found approximately 1,600 patients in adult only series with prevalence of women, whereas in pediatric series, there were 2,300 patients, almost equal distribution between boys and girls. In total, there were more commonly, women were more commonly represented by approximately 10%. If we look the series by adult and pediatric population, we can see that there is exactly equal distribution of adult and pediatric series. If we look by number of cases, there is slightly more pediatric cases described in those series, whereas there is still a large number of patients where the gender has not been described, and that should be addressed with future publication. We found that there are two peak ages in adult population. One peak age is 41 years, and the second peak age is 46 years. These are the two most common ages where patients become symptomatic and present in this huge number of patients that we did systematic review on. The incidence of syringomyelia has been 69% in adult series, 40% in pediatric series, 78% in combined series, and averagely 65% of patient had syringomyelia present. When we looked into the distribution of operative techniques in QRA1 malformations, we found that operative technique was being described, performed operative technique in 93% in adult series, 97% in combined series, in pediatric series, and 100% in combined series. Posterior fossa decompression has been done in all adult series and almost all pediatric and combined series, that means removal of the bone. Dural opening has been done in almost all adult cases, and a vast majority of pediatric and combined series. Arachnoid opening has been done in more than two thirds of adult and combined series, and roughly 50% of pediatric series. Tonsillar resection has been done in approximately quarter of adult and combined series, and approximately 40% of pediatric series. And then shunt has been used sporadically. Outcomes of cranioscervical decompression for QRA1 malformation has been excellent. If we look only headache outcomes, there has been improvement or resolution in 73% of adults, 88% of pediatric patients. In combined series, 79% showed improvement overall, 80% show improvement, which is very good. Syringomyelia outcomes showed 78% improvement in adult series, 79% improvement in pediatric series, 78% improvement in combined series, and average improvement of 78%, again, very good outcome. Improvement of neurological outcomes has been shown 73% in adults, 84% in pediatric, slightly better outcome in pediatric than in adult, 72% in combined, and overall, 75% of cases. In other words, three quarters of patients had significant improvement in neurological condition. Distribution of operative complication has been presented in 20% of adult and 37% of pediatric cases. Most commonly, it included pseudomeningocele, both in pediatric and combined series, and to a lesser extent, adult series. Aseptic meningitis was next in order of occurrence, and then CSF leak, followed by meningitis and wound infection, as you can see here. Mortality has been reported in 11% of cases, total of 65 patients. There has been no difference in mortality rates between adult and pediatric cases, and the reason for death was, in descending order, pneumonia, respiratory failure, sepsis, postoperative bleeding, and sleep apnea. In conclusions, we can say that there has been a constant increase in KR1 malformation operative series in publication over the past 21 years. Most commonly, series were published in USA and Europe. Mean duration of studies in 10 years and mean follow-up is 3.5 years. Mean age in all studies was 27 years, and median age, 36 years. There are peak ages at surgery, 41 years of, and then 46 years in adult operative series. Two-thirds of all patients harbor syringomyelia, but it's more commonly represented in adults. In adult series, almost all patients, or overwhelmingly, has used posterior cranial fossa decompression, dural opening with duraplasty, and arachnoid open, including this dissection of arachnoid membrane. In pediatric population, arachnoid opening versus arachnoid preservation is split evenly. Overall, there is 78% rate of improvement and resolution of syringomyelia, 75% rate of improvement or resolution of neurological deficit, and 81% rate of headache improvement or resolution. Postoperative headache improvements are slightly better in pediatric population. Postoperative worsening of neurological function is more common in adult population. Postoperative complications are more commonly reported in pediatric population, and mortality is rare, but most commonly caused by pneumonia, respiratory failure, infection, sepsis, postoperative bleeding, and sleep apnea. Thank you very much for your attention.

adult KR1 malformation

cranio-cervical junction

syringomyelia

decompression surgery

headache symptoms

neurological deficits

surgical management