Good morning. My name is Doug Brockmeyer, and our topic of discussion today is outcomes research and treatment failures as it pertains to Chiari malformations. I have no disclosures. My objectives are to cover the current state of Chiari outcomes research, discuss the known reoperation rates for posterior fossa decompression versus duroplasty, what are the costs involved, how does value enter into the equation, and overall, what is a Chiari treatment failure? Is it lack of symptomatic relief, or is it lack of improvement in some specified patient reported outcome measure, or is it perhaps a return to the operating room, or is there a combination of all of these? There is considerable interest in Chiari outcomes research, and this is built off of success by adult spine and pediatric hydrocephalus registries. However, this interest is hindered by lack of industry support, relatively low patient volumes, few, if any, Chiari-specific validated outcome measures, and lack of standardized definitions. We'll start our discussion in March 2012 when the Chicago Chiari outcome score was published. Most of you are aware of this score. It's a post-operative outcome score used to assist in performing a chart review. It covers four domains, including pain, non-pain, functionality, and complication areas for the patient. Each of these is broken down into four grades from significantly improved, or in fact, resolved versus worse. An excellent Chicago Chiari outcome score is defined as 15 or 16. This outcome score was validated in 2014 by the group at Wash U using a pediatric cohort. They found that the Chicago score versus Gestalt had good agreement. However, functionality and non-pain sub-scores had very poor inter-observer reliability leading to question whether this was a good prognostic tool or not. In 2015, the Chiari Severity Index was published from Wash U. It's a complex study. First off, they defined treatment success as favorable responses to the following questions. How much of an improvement in your general health did you experience after your surgery, and how satisfied are you with your overall outcome? If you answered four or five in a Likert scale to both of those, it was defined as a success. One of the limitations is that this index was created with a pediatric cohort. To begin with, they broke down clinical symptoms into various grades. Grade one was defined as if you had a classic Chiari headache or poorly localized headache. Grade two was a frontotemporal headache or no headache. Grade three was myelopathic symptoms including subjective weakness or numbness or weakness or numbness on examination. Neuroimaging grade was an A if your syrinx was less than six millimeters or you had no syrinx, B if it was greater than six millimeters. Using a process called conjunctive consolidation, they came up with the scale. If you had a clinical grade of one and a neuroimaging grade of A or B, your severity index was one, and your chance of having an improvement or success defined by those questions we talked about before was 83%. The severity index of two defined as clinical grade of two or three with a neuroimaging grade of A gave you a chance of 69% and a severity index of three was 45%. In 2018, Thaker et al. published the points-based algorithm looking at adult patients with syringomyelia in 82 consecutive patients and their outcome measure was using the Chicago Chiari outcome score and syrinx resolution. They found that OBEC's position and a new metric, the M-line force ventricular distance correlated with good Chicago Chiari outcome scores, whereas gait imbalance predicted a poor Chicago score. Motor deficits predicted poor syrinx resolution. 2015, a systematic review was done of outcome methods used in clinical studies of Chiari. The group from Washington University looked at all of the different scales used in previously published articles, and those are listed in table one. As you can see, few, if any, of them were validated with Chiari populations, and none of them were proven to be reliable Chiari populations. Table two showed which scales were disease-specific. Again, there were very few, if any, that were specific to Chiari malformation. In table three showed the six key domains necessary to create good outcome measures and what percentage of the published studies included them. As you can see, clinical impression had 90.5% of the studies used that as their outcome measure as opposed to other lower percentages for quality of life assessed, new symptoms, multidimensional assessment performed, revision surgery, or method of reporting headache. This is a checklist that they put together covering different types of outcome methods and the questions they should answer to be thorough and successful. And these include, does the outcome measure incorporate direct patient reporting? Does it include a specific assessment of quality of life? Does it encounter or does it account for new symptoms? Does it provide sufficient multidimensional assessment? Does it detail the headaches? Does it include revision surgery, and is it valid and reliable? A study soon to be published in Journal of Neurosurgery Spine was performed on a cohort of 149 adult Chiari 1 malformation patients from Johns Hopkins. They calculated the CSI and Thaker point score for each patient and used the Chicago outcome scale as their outcome measure. In their hands, the CSI and Thaker point score failed to provide prediction value that was meaningful for adult Chiari patients. In the pediatric realm, there have been several papers studied. This one included using the PQL, using patient reported outcome measures. This includes the CHIP, the Huey 3, the CSI, and PROMIS scores. And there's much more to be learned in both the adult and pediatric patient population. Let's turn to known reoperation rates for Chiari surgery. And that's not to imply that reoperation is a treatment failure because you could have more than one reoperation, but a year down the road after surgery you may have a very successful outcome. So this is just meant to look at some of the costs involved in these decisions and these clinical scenarios. So here are a number of clinical studies in the literature covering posterior fossa decompression versus duraplasty. You can see the numbers. For posterior fossa decompression failure rate, I took the average of those numbers from the most applicable studies and we assigned them 11% reoperation rate. The duraplasty group was assigned a 3% reoperation rate using an average of those numbers. Based on previously published costs from Chiari surgery from the University of Oregon, in their hands a posterior fossa decompression was $27,000. If you added a duraplasty it went to $30,000. If you did 100 posterior fossa decompressions and had 11% reoperation rate, the total was approximately $3.03 million. If you reversed it and performed 100 posterior fossa decompressions and had three reoperations, the total was again very close to $3 million. If you had a practice where it was split 50-50 with decompression and duraplasty, again if you do the math and you take into account the reoperation rates, again the total comes to approximately $3 million. So it looks like cost would not be a good argument for making decisions in order to provide care for Chiari patients. The overall objective for Chiari surgery is to provide value for patient. Value is defined as a meaningful outcome for the patient divided by the total cost for the patient over the complete arc of care. For adults, it's return to work. That's a very meaningful outcome in pediatrics. It would come down to return to school or other metrics to assess whether it's a successful outcome. You would want to use validated outcome tools in order to assess this. And the total cost would include hospital visits, clinic visits, parental costs, lost wages, transportation, return to the OR, et cetera. And you need to keep all of these into account. Lastly, I wanted to cover the complex Chiari. And this is a patient population that I tend to see a fair amount of. And some of these patients are very challenging to manage. Questions are, what is it? When is it reasonable to perform a fusion or odontoid reduction? How do you perform the procedure? What are the risks? And what are the outlooks for these patients? By definition, a complex Chiari malformation is assessed by our 2012 article in J&S Peds. It was defined as a tonsillar brainstem herniation, which was a Chiari 1.5, anterior brainstem compression by a retroflexed odontoid, a medullary kink, abnormal craniocervical angulation with a craniocervical angle less than 125 degrees, and plus minus syringomyelia and scoliosis. This is our experience from this paper where we had 64 classic or simple Chiari 1s and 37 complex Chiari patients. We had zero reoperations for occipital cervical fusion or other problems in the Chiari 1 patients, where with the complex Chiari patients, 11 of them required upfront OC fusions or transoral odontoid reductions, and eight of those required operations later for occipital cervical fusion. Here's a good example of a patient with Chiari 1, a three-year-old boy with suboccipital headaches and swallowing difficulty. He underwent tonsillar shrinking and duroplasty. Six years later, he comes back with a scan for another reason. His headaches are gone, and he's doing well in school, and you see the typical result. Here's a patient with a complex Chiari, a two-year-old boy with significant descent of the cerebellar tonsils. He had developmental delay. He underwent standard suboccipital decompression, tonsillar shrinking, and duroplasty. Two years later, he's slightly improved but not perfect. Two years after that, he comes back with drooling and snoring and other signs of brainstem symptomatology. You can see a significant compression of the brainstem anteriorly. This would be defined as a Chiari 1.5. Here's his preoperative CT scan showing retroflexed odontoid. We decided to redo his Chiari, perform a posterior occipital C2 fusion with odontoid reduction. Here's the postoperative CT scan showing the significant reduction of the odontoid away from the brainstem. And here's his instrumentation. The indications for such a surgery include the radiographic definition of Chiari that we covered before plus significant bulbar symptomatology, myelopathy, or severe headaches from mechanical factors due to angulation or settling. Progressive or severe unresolved syrinx is a relative indication. Surgical technique is to perform the decompression. You may or may not redo the Chiari decompression. I typically place bilateral C2 PAR screws, hook it up to the occiput using a rod plate construct. Do the odontoid reduction interoperably under fluoro with gentle distraction and then extension of the head. Place rib autograft and then use cable and maxillofacial screw fixation for the rib. I always use BMP, not DBS, actually, at the contact points of the rib against the bone. This is what it looks like postoperatively. Follow-up from these patients show that all have had successful arthrodesis and had minimal complications, that no repeat procedures and successful arthrodesis has been obtained. And then all post-fusion patients have had significant improvement and other preoperative symptoms, oftentimes dramatically. A biomechanical hypothesis is that you have a complex Chiari with upfront risk factors, which includes a Chiari 1.5 and a CXA of less than 125 degrees. If you perform dorsal decompression and release of the posterior tension band, you get cranial settling and or accentuation of the forward bending movement of the clival dense pivot point. Then you get forward folding of the cranial cervical angle and progressive brainstem compression and worsening signs and symptoms. This is one way to look at it where Chiari 1, malformations of the simple type are probably due to mostly imbalance of the volume of the posterior fossa versus the amount of bone available and also hydrodynamic factors probably drive most of the symptomatology and findings. For complex Chiari malformations, probably genetically driven skull base and brainstem morphology set up the initial clinical scenario with abnormal clival cervical relationships, retroflexodontoid and basilar vagination. You add to that biomechanical stress and failure over time and on top of that hydrodynamic factors always come into play. I thank you for your attention.

Chiari outcomes research

validated outcome measures

treatment success

reoperation rates

occipital cervical fusion