Reappraisal of intradural findings in Chiari malformation type I.

OBJECTIVE: Management of Chiari malformation type I (CM-I) requires the functional restoration of an obstructed cisterna magna. In posterior fossa decompression with duraplasty (PFDD), various intradural pathologies are suggested to alter CSF flow at the craniocervical junction and require surgical correction. However, reports of the spectrum of intraoperative intradural findings and their nuances are scarce, especially those characterizing rarer findings pertaining to the vascular structures and vascular compression. METHODS: The authors conducted a retrospective cohort analysis of adults and children who underwent first-time PFDD for CM-I (2011-2021), with and without syringomyelia. The surgical reports and intraoperative videos were reviewed, and the frequency and nature of the intradural observations in regard to the tonsils, arachnoid, and vasculature were analyzed along with the clinical findings and surgical outcomes. RESULTS: All 180 patients (age range 1-72 years; median [interquartile range] 24 (14-38) years; 37% of patients were children < 21 years of age) exhibited multiple intradural findings, with a median of 7 distinct concurrent observations in each patient. Novel findings not previously reported included posterior inferior communicating artery (PICA) branches compressing the neural elements at the cervicomedullary junction (26.7%). Other common findings included arachnoid adhesions (92.8%), thickening (90.6%), webs at the obex (52.2%), tonsillar gliosis (57.2%), tonsillar hypertrophy (18.3%), adhesions obstructing the foramen of Magendie (FoM) (62.2%), PICA obstruction of the FoM (17.2%), and dural scarring (87.8%). Tonsillar gliosis and intertonsillar adhesions obstructing the FoM were more common in children than adults. Tonsillar gliosis and arachnoid webs were more common among syringomyelia patients. After multivariable adjustment, none of the observed findings were independently associated with syringomyelia, preoperative symptoms, or postoperative improvement. The vast majority of patients improved postoperatively. The complication rate was low: 1.2% of patients required revision PFDD at > 3 years postoperatively, 3.6% experienced other operative complications, and 0% had CSF leaks. CONCLUSIONS: The diversity of intradural findings and observations revealed in this study suggests that obstructive and compressive structural anomalies may be more common than previously reported among CM-I patients, both those patients with and those without syringomyelia and especially those with obstructive and compressive PICA branches. Although the authors cannot conclude that all these findings are necessarily pathological, further study may determine how they contribute to CM-I pathology and symptomatology in the setting of a compromised cisterna magna.

Compromised Cranio-Spinal Suspension in Chiari Malformation Type 1: A Potential Role as Secondary Pathophysiology.

In Chiari Malformation Type I (CM1), low-lying tonsils obstruct the cisterna magna at the foramen magnum, thereby compromising the essential juncture between the cranial and spinal compartments. The anatomical obstruction of the cisterna magna inhibits bi-directional CSF flow as well as CSF pulse pressure equilibration between the intracranial compartment and the intraspinal compartment in response to instances of increased intracranial pressure. Less understood, however, are the roles of the spinal cord suspension structures at the craniocervical junction which lend viscoelastic support to the spinal cord and tonsils, as well as maintain the anatomical integrity of the cisterna magna and the dura. These include extradural ligaments including the myodural bridges (MDBs), as well as intradural dentate ligaments and the arachnoid framework. We propose that when these elements are disrupted by the cisterna magna obstruction, tonsillar pathology, and altered CSF dynamics, there may arise a secondary pathophysiology of compromised and dysfunctional cranio-spinal suspension in CM1. We present intraoperative images and videos captured during surgical exposure of the craniocervical junction in CM1 to illustrate this proposal.

Incidence, Characteristics, and Outcomes of Pseudomeningocele and Cerebrospinal Fluid Fistula after Posterior Fossa Surgery.

OBJECTIVE: Posterior fossa approaches are common neurosurgical procedures. Rates of postoperative infection, pseudomeningocele, and cerebrospinal fluid (CSF) fistula are high; however, evidence regarding predisposing risk factors and treatment outcomes remain sparse. METHODS: A retrospective cohort study was carried out of all posterior fossa surgeries conducted at a single institution between January 2015 and October 2019. Univariate statistical methods and stepwise logistic regression were used to assess which factors contributed most to risk of development of postoperative complications. RESULTS: A total of 269 patients were included; 18.6% experienced any postoperative complication, 13% developed either pseudomeningocele or CSF fistula, and 9.7% developed an infection. In multivariate analysis, development of a pseudomeningocele was significantly associated with previous cranial surgery (hazard ratio [HR], 3.15; 95% confidence interval [CI], 1.12-9.28; P = 0.0391). Development of a CSF fistula was significantly associated with index surgery for resection of neoplasm (HR, 7.65; 95% CI, 1.86-22.31; P = 0.0174). Development of an infection was significantly associated with concurrent CSF fistula (HR, 7.16; 95% CI, 1.91-23.19; P = 0.0041) and concurrent pseudomeningocele (HR, 3.41; 95% CI, 1.37-5.95; P = 0.0082) and nonsignificantly associated with diabetes requiring treatment (HR, 2.42; 95% CI, 0.69-8.50; P = 0.168). Other hypothesized risk factors for these complications, such as nonmidline approaches to the posterior fossa, watertight duraplasty, use of dural fibrin sealant, and cranioplasty were not associated with these complications on multivariate analysis. Although many patients with pseudomeningocele were successfully managed with observation, only 38% of patients in whom CSF diversion was attempted avoided surgery. CONCLUSIONS: History of diabetes, cranioplasty, revision surgery, and surgery for tumor resection are identified as risk factors for the development of infection, pseudomeningocele, and CSF fistula, respectively.

Early Outcomes After Carotid Endarterectomy and Carotid Artery Stenting: A Propensity-Matched Cohort Analysis.

BACKGROUND: Carotid endarterectomy (CEA) and carotid artery stenting (CAS) represent options to treat many patients with carotid stenosis. Although randomized trial data are plentiful, estimated rates of morbidity and mortality for both CEA and CAS have varied substantially. OBJECTIVE: To evaluate rates of adverse outcomes after CAS and CEA in a large national database. METHODS: We analyzed 84 191 adult patients undergoing elective, nonemergent CAS (n = 81 361) or CEA (n = 2830), from 2011 to 2018, in the American College of Surgeons' National Surgical Quality Improvement Program database. Odds of adverse outcomes (30-d rates of stroke, myocardial infarction (MI), cardiac arrest, prolonged length of stay (LOS), readmission, reoperation, and mortality) were evaluated in propensity-matched (n = 2821) cohorts through logistic regression. RESULTS: In the propensity-matched cohorts, CAS had increased odds of periprocedural stroke (odds ratio [OR] 1.97, 95% CI 1.32-2.95) and decreased odds of cardiac arrest (OR 0.33, 95% CI 0.13-0.84) and 30-d reoperation (OR 0.59, 95% CI 0.44-0.80) compared to CEA. Relative odds of MI, prolonged LOS, discharge to destination other than home, 30-d readmission, or 30-d mortality were statistically similar. In the unmatched patient population, rates of adverse outcomes with CEA were constant over time; however, for CAS, rates of stroke increased over time. In both the matched and unmatched patient cohorts, patients 70 yr and older had lower rates of post-procedural stroke with CEA, but not with CAS, compared to younger patients. CONCLUSION: In a propensity-matched analysis of a large, prospectively collected, national, surgical database, CAS was associated with increased odds of periprocedural stroke, which increased over time. Rates of MI and death were not significantly different between the 2 procedures.