Cervico-medullary compression ratio: A novel radiological parameter correlating with clinical severity in Chiari type 1 malformation

Validation of PROMIS score as a measure of postoperative success following decompressive surgery for Chiari I malformation

OBJECTIVE

Evaluating postoperative outcomes in Chiari I malformation represents a challenge. Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Health (PH) and Mental Health (MH) metrics are highly reliable measures of patient-reported health status commonly used and validated in spine and stroke populations. We investigate the validity of PROMIS-PH and PROMIS-MH in tracking postoperative success following decompressive surgery for Chiari I malformation.

METHODS

Adult patients undergoing decompressive surgery for Chiari I malformation at our institution were identified. Prospectively administered pre- and postoperative PROMIS-PH and MH scores were of interest, from which postoperative score improvement was calculated. The current standard for discerning surgical success, postoperative physician gestalt, was retrospectively assigned as "improved" or "unimproved" following review of the clinical documentation at a time point coinciding with the postoperative PROMIS score. Univariable logistic regression and receiver operative characteristic (ROC) analyses were performed to validate postoperative PROMIS improvement as a metric for clinical success.

RESULTS

One hundred thirteen patients were identified (mean follow-up: 14.4 months). Seventy-four (65.5 %) patients experienced clinical improvement according to physician gestalt assessment. Postoperative PROMIS-PH score change was superior in the "improved" patients (improved: 8.5, unimproved: -2.5), p < .001. Logistic regression demonstrated PROMIS-PH to be an independent predictor of clinical improvement, with OR of 1.44 (95 % CI: 1.27-1.70). ROC area was 0.852 with mean clinically important difference of 3.0. PROMIS-MH was not a satisfactory predictor of surgical success (ROC area: 0.740).

CONCLUSION

Postoperative PROMIS-PH score improvement serves as a responsive and valid metric for trending postoperative outcomes in the Chiari I population.

The Small Posterior Cranial Fossa Syndrome and Chiari Malformation Type 0

Patients showing typical Chiari malformation type 1 (CM1) signs and symptoms frequently undergo cranial and cervical MRI. In some patients, MRI documents >5 mm of cerebellar tonsillar herniation (TH) and the diagnosis of CM1. Patients with 3−5 mm TH have “borderline” CM1. Patients with less than 3 mm of TH and an associated cervical syrinx are diagnosed with Chiari “zero” malformation (CM0). However, patients reporting CM1 symptoms are usually not diagnosed with CM if MRI shows less than 3−5 mm of TH and no syrinx. Recent MRI morphometric analysis of the posterior fossa and upper cervical spine detected anatomical abnormalities in and around the foramen magnum (FM) that explain these patients’ symptoms. The abnormalities include a reduced size of the posterior fossa, FM, and upper cervical spinal canal and extension of the cerebellar tonsils around the medulla rather than inferior to the foramen magnum, as in CM1. These morphometric findings lead some neurologists and neurosurgeons to diagnose CM0 in patients with typical CM1 signs and symptoms, with or without cervical syringes. This article reviews recent findings and controversies about CM0 diagnosis and updates current thinking about the clinical and radiological relationship between CM0, borderline CM1, and CM1.

Are Two-Dimensional Morphometric Measures Reflective of Disease Severity in Adult Chiari I Malformation?

BACKGROUND

Two-dimensional (2D) morphometric measures have been previously used to diagnose Chiari I malformation (CMI) and distinguish patients from healthy subjects. There is, however, a paucity of literature regarding whether morphometric differences exist across the range of CMI disease severity. We evaluated whether 2D morphometrics demonstrate significant changes across standardized grades of CMI severity in adults.

METHODS

This retrospective observational study comprised 76 patients with symptomatic CMI with or without syringomyelia. Patients matched for age, sex, and body mass index were selected from each of the 3 severity grades of the Chiari Severity Index (CSI). The study used 17 2D craniocervical and posterior fossa morphometric variables that were previously found to differentiate patients with CMI from healthy subjects. The measurements were performed on midsagittal T1-weighted magnetic resonance imaging sequences using 2 custom in-house software tools, MorphPro and CerePro, and compared across CSI grades.

RESULTS

Analysis of variance showed that none of the 17 morphometric variables were significantly different across the 3 CSI grades (P > 0.003). Bayes factor 10 scores ranged from 0.11 to 0.82. Of variables, 9 had Bayes factor 10 scores between 0.10 and 0.30, while 8 had scores between 0.30 and 1. None of the Bayes factor 10 scores provided support for the alternative hypothesis that the morphometric measures differed across the CSI grades.

CONCLUSIONS

Our study indicated that 2D morphometrics are not reflective of CMI disease severity as indicated by the CSI grading system. The findings of our study support the need for further investigation into whether non-2D morphometric variables can be used as markers of disease severity.

Association between craniovertebral junction abnormalities and syringomyelia in patients with chiari malformation type-1

Objectives:

To assess the correlation between craniovertebral junction (CVJ) abnormalities and syringomyelia in patients with Chiari malformation type-1 (CM1).

Methods:

This was a retrospective study including patients with CM1. Identification of cases was done by searching a radiology database at a university hospital from 2012 to 2017. Patients were divided into 2 groups based on whether CVJ abnormalities were present (CVJ+) or absent (CVJ-). The patients’ demographic and clinical data were reviewed. All magnetic resonance imaging studies were examined by a certified neuroradiologist.

Results:

Sixty-four consecutive patients with CM1 were included. The mean age was 24±17 years; 59% were females. The CVJ+ group had more female patients (p = 0.012). The most frequent CVJ abnormality was platybasia (71%), followed by short clivus (44%) and cervical kyphosis (33%). The CVJ abnormalities were more in Syringomyelia cases (p = 0.045). However, the results were not significant when hydrocephalus cases were excluded.

Conclusion:

Among CM1 patients, CVJ abnormalities were found more in patients with syringomyelia. Future studies with larger sample size are required to further study the correlation between CVJ abnormalities and both syringomyelia and hydrocephalus in CM1 patients.