A computational fluid dynamics study to assess the impact of coughing on cerebrospinal fluid dynamics in Chiari type 1 malformation.

Chiari type 1 malformation is a neurological disorder characterized by an obstruction of the cerebrospinal fluid (CSF) circulation between the brain (intracranial) and spinal cord (spinal) compartments. Actions such as coughing might evoke spinal cord complications in patients with Chiari type 1 malformation, but the underlying mechanisms are not well understood. More insight into the impact of the obstruction on local and overall CSF dynamics can help reveal these mechanisms. Therefore, our previously developed computational fluid dynamics framework was used to establish a subject-specific model of the intracranial and upper spinal CSF space of a healthy control. In this model, we emulated a single cough and introduced porous zones to model a posterior (OBS-1), mild (OBS-2), and severe posterior-anterior (OBS-3) obstruction. OBS-1 and OBS-2 induced minor changes to the overall CSF pressures, while OBS-3 caused significantly larger changes with a decoupling between the intracranial and spinal compartment. Coughing led to a peak in overall CSF pressure. During this peak, pressure differences between the lateral ventricles and the spinal compartment were locally amplified for all degrees of obstruction. These results emphasize the effects of coughing and indicate that severe levels of obstruction lead to distinct changes in intracranial pressure.

Combined Cerebrospinal Fluid Hydrodynamics and Fourth Ventricle Outlet Morphology to Improve Predictive Efficiency of Prognosis for Chiari Malformation Type I Decompression.

OBJECTIVE: To identify the morphological characteristics together with cerebrospinal fluid (CSF) hydrodynamics on preoperative magnetic resonance imaging that improve the prediction of foramen magnum decompression (FMD) treatment outcome for Chiari malformations type I (CM-I) patients compared with the CSF hydrodynamics-based model. METHODS: This retrospective study included CM-I patients who underwent FMD, phase-contrast cine magnetic resonance, and static MR between January 2018 and March 2022. The relationships of the preoperative CSF hydrodynamic quantifications derived from phase-contrast cine magnetic resonance and morphological measurements from static magnetic resonance imaging, clinical indicators with different outcomes, were analyzed with logistic regression analysis. The outcomes were determined using the Chicago Chiari Outcome Scale. The predictive performance was evaluated with receiver operating characteristic, calibration, decision curves and area under the receiver operating characteristic curve, net reclassification index, and integrated discrimination improvement and was compared with CSF hydrodynamics-based model. RESULTS: A total of 27 patients were included. 17 (63%) had improved outcomes and 10 (37%) had poor outcomes. The peak diastolic velocity of the aqueduct midportion (odd ratio, 5.17; 95% confidence interval: 1.08, 24.70; P = 0.039) and the fourth ventricle outlet diameter (odd ratio, 7.17; 95% confidence interval: 1.07, 48.16; P = 0.043) were predictors of different prognoses. The predictive performance improved significantly than the CSF hydrodynamics-based model. CONCLUSIONS: Combined CSF hydrodynamic and static morphologic MR measurements can better predict the response to FMD. A higher peak diastolic velocity of the aqueduct midportion and broader fourth ventricle outlet were associated with satisfying outcomes after decompression in CM-I patients.

Cerebrospinal Fluid Hydrodynamics in Chiari I Malformation and Syringomyelia: Modeling Pathophysiology.

Anatomic MRI, MRI flow studies, and intraoperative ultrasonography demonstrate that the Chiari I malformation obstructs CSF pathways at the foramen magnum and prevents normal CSF movement through the foramen magnum. Impaired CSF displacement across the foramen magnum during the cardiac cycle increases pulsatile hindbrain motion, pressure transmission to the spinal subarachnoid space, and the amplitude of CSF subarachnoid pressure waves driving CSF into the spinal cord. Central canal septations in adults prevent syrinx formation by CSF directly transmitting its pressure wave from the fourth ventricle to the central canal.

Postural control in Chiari I malformation: protocol for a paediatric prospective, observational cohort - potential role of posturography for surgical indication.

INTRODUCTION: Chiari I malformation (CM1) is an anatomical abnormality characterised by the cerebellar tonsils descending at least 5 mm below the foramen magnum. CM1 causes obstruction of cerebrospinal fluid (CSF) circulation as well as direct compression on the brainstem, thus causing typical consequences (syringomyelia), and typical clinical features (characteristic headaches and neurological impairment). Surgery is the only available treatment, indicated when symptomatology is present. However, sometimes patients have atypical complaints, which are often suggestive of otolaryngological (ears, nose and throat, ENT) involvement. This may be difficult for a neurosurgeon to explain. Our study aims to investigate the relationship between one of these atypical symptoms, for example, postural instability, in a paediatric population using a Computerised Dynamic Posturography (Equitest, NeuroCom, Clackamas, OR). To our knowledge, there are no previously published studies carried out on children with CM1, using dynamic posturography. METHODS AND ANALYSIS: Forty-five children aged 6-18 years old presenting with radiologically confirmed CM1 and presenting ENT clinical complaints will be included in the study for a duration of 3 years. As primary endpoint, posturographic results will be described in the population study. Second, posturographic results will be compared between patients with and without indication for surgery. Finally, preoperative and postoperative posturographic results, as well as CSF circulation quality at foramen magnum level, syringomyelia, sleep apnoea syndrome, scoliosis and behaviour will be compared in the operated patient group. ETHICS AND DISSEMINATION: This protocol received ethical approval from the Clinical Research Delegation of Nancy University Hospital, in accordance with the National Commission on Informatics and Liberties (Commission Nationale de l'Informatique et des Libertés) (protocol number 2019PI256-107). Our data treatment was in accordance with the Methodology of reference Methodology Reference-004 specification for data policy. The study findings will be disseminated via peer-reviewed publications and conference presentations, especially to the Neurosphynx's rare disease healthcare network. TRIAL REGISTRATION NUMBER: NCT04679792; Pre-results.

In vitro evaluation of cerebrospinal fluid velocity measurement in type I Chiari malformation: repeatability, reproducibility, and agreement using 2D phase contrast and 4D flow MRI.

BACKGROUND: Phase contrast magnetic resonance imaging, PC MRI, is a valuable tool allowing for non-invasive quantification of CSF dynamics, but has lacked adoption in clinical practice for Chiari malformation diagnostics. To improve these diagnostic practices, a better understanding of PC MRI based measurement agreement, repeatability, and reproducibility of CSF dynamics is needed. METHODS: An anatomically realistic in vitro subject specific model of a Chiari malformation patient was scanned three times at five different scanning centers using 2D PC MRI and 4D Flow techniques to quantify intra-scanner repeatability, inter-scanner reproducibility, and agreement between imaging modalities. Peak systolic CSF velocities were measured at nine axial planes using 2D PC MRI, which were then compared to 4D Flow peak systolic velocity measurements extracted at those exact axial positions along the model. RESULTS: Comparison of measurement results showed good overall agreement of CSF velocity detection between 2D PC MRI and 4D Flow (p = 0.86), fair intra-scanner repeatability (confidence intervals ± 1.5 cm/s), and poor inter-scanner reproducibility. On average, 4D Flow measurements had a larger variability than 2D PC MRI measurements (standard deviations 1.83 and 1.04 cm/s, respectively). CONCLUSION: Agreement, repeatability, and reproducibility of 2D PC MRI and 4D Flow detection of peak CSF velocities was quantified using a patient-specific in vitro model of Chiari malformation. In combination, the greatest factor leading to measurement inconsistency was determined to be a lack of reproducibility between different MRI centers. Overall, these findings may help lead to better understanding for application of 2D PC MRI and 4D Flow techniques as diagnostic tools for CSF dynamics quantification in Chiari malformation and related diseases.

Correlation of a new hydrodynamic index with other effective indexes in Chiari I malformation patients with different associations.

This study aimed to find a new CSF hydrodynamic index to assess Chiari type I malformation (CM-I) patients' conditions and examine the relationship of this new index with morphometric and volumetric changes in these patients and their clinical symptoms. To this end, 58 CM-I patients in four groups and 20 healthy subjects underwent PC-MRI. Ten morphometric and three volumetric parameters were calculated. The CSF hydrodynamic parameters were also analyzed through computational fluid dynamic (CFD) simulation. The maximum CSF pressure was identified as a new hydrodynamic parameter to assess the CM-I patients' conditions. This parameter was similar in patients with the same symptoms regardless of the group to which they belonged. The result showed a weak correlation between the maximum CSF pressure and the morphometric parameters in the patients. Among the volumetric parameters, PCF volume had the highest correlation with the maximum CSF pressure, which its value being higher in patients with CM-I/SM/scoliosis (R2 = 65.6%, P = 0.0022) than in the other patients. PCF volume was the more relevant volumetric parameter to assess the patients' symptoms. The values of PCF volume were greater in patients that headache symptom was more obvious than other symptoms, as compared to the other patients.

Cerebrospinal fluid area and syringogenesis in Chiari malformation type I.

OBJECTIVE: Syringogenesis in Chiari malformation type I (CM-I) is thought to occur secondary to impaction of the cerebellar tonsils within the foramen magnum (FM). However, the correlation between the CSF area and syringogenesis has yet to be elucidated. The authors sought to determine whether the diminution in subarachnoid space is associated with syringogenesis. Further, the authors sought to determine if syrinx resolution was associated with the degree of expansion of subarachnoid spaces after surgery. METHODS: The authors performed a retrospective review of all patients undergoing posterior fossa decompression for CM-I from 2004 to 2016 at the University of Virginia Health System. The subarachnoid spaces at the FM and at the level of the most severe stenosis were measured before and after surgery by manual delineation of the canal and neural tissue area on MRI and verified through automated CSF intensity measurements. Imaging and clinical outcomes were then compared. RESULTS: Of 68 patients, 26 had a syrinx at presentation. Syrinx patients had significantly less subarachnoid space at the FM (13% vs 19%, p = 0.0070) compared to those without syrinx. Following matching based on degree of tonsillar herniation and age, the subarachnoid space was significantly smaller in patients with a syrinx (12% vs 19%, p = 0.0015). Syrinx resolution was associated with an increase in patients' subarachnoid space after surgery compared with those patients without resolution (23% vs 10%, p = 0.0323). CONCLUSIONS: Syrinx development in CM-I patients is correlated with the degree to which the subarachnoid CSF spaces are diminished at the cranial outlet. Successful syrinx reduction is associated with the degree to which the subarachnoid spaces are increased following surgery.

Clinicoradiological study of adult Chiari malformation type 1 patients with emphasis on cerebrospinal fluid peak flow velocity at foramen magnum level.

INTRODUCTION: The aim of this study was to determine the peak cerebrospinal fluid (CSF) flow velocity at the foramen magnum level in adult patients with Chiari type 1 malformation (CM1) and to determine the changes in velocity after posterior fossa decompression. An attempt was also made to determine whether or not CSF flow velocity can be a significant predictor in patients who need surgical intervention. MATERIALS AND METHODS: A prospective longitudinal study was conducted in 32 symptomatic patients of CM1 treated with craniocervical decompression. Only adult patients with age ≥18 years and tonsillar herniation ≥5 mm were included in this study. Clinical and radiological assessment of patients with reference to their CSF flow characteristics was done both preoperatively and after suboccipital decompression. RESULTS: Out of the 32 patients, 30 patients underwent a suboccipital decompression and two patients were treated with a venriculoperitoneal shunt procedure due to gross hydrocephalus. The preoperative mean tonsillar herniation was 10.4 ± 4.64 mm that reduced to 7.35 ± 3.10 mm in the follow up period. Postoperatively, there was also a substantial decrease in the peak CSF velocity at the foramen magnum along with reduction in the extent and size of the syrinx. These changes in CSF velocity correlated with a more normal appearing foramen magnum and an improvement in symptoms. CONCLUSION: Although the selection criteria for surgery are based mainly on the degree of tonsillar ectopia and presenting symptoms, the degree of CSF flow obstruction rather than the degree of tonsillar herniation can better select patients who are most responsive to surgery. An improved CSF velocity profile following surgery in such patients is a useful guide to anticipate a symptomatic improvement.

Relationship of Morphologic Changes in the Brain and Spinal Cord and Disease Symptoms with Cerebrospinal Fluid Hydrodynamic Changes in Patients with Chiari Malformation Type I.

BACKGROUND: Morphometric analysis or examination of symptoms in patients with Chiari malformation type I (CM-I) with various associations does not suffice for evaluation of surgical outcome of these patients. We assessed the relationship of morphologic changes in brain and spinal cord and disease symptoms with changes in cerebrospinal fluid (CSF) hydrodynamic parameters in patients with CM-I. METHODS: The study included 41 patients in 3 groups of CM-I, CM-I/occipitoatlantoaxial joint instability, and CM-I/tethered cord syndrome and 18 normal subjects. Phase-contrast magnetic resonance imaging and computational fluid dynamics analysis were done for all samples. RESULTS: Maximum CSF velocities and pressures in patients had an increase of 17.1%-23.2% and 41.5%-56.8%, respectively, compared with normal subjects. The data dispersion of maximum CSF velocity was >3.1 times that of the maximum pressure. Results showed that maximum CSF pressure is a more appropriate hydrodynamic parameter than maximum CSF velocity for assessing the condition of patients. Results also showed that CSF and PCF volumes had declined 57% and 11.3%, respectively, in CM-I. These declines were greater in CM-I than in the other 2 groups. CONCLUSIONS: Maximum CSF pressure regardless of the group the patients belonged to was similar in patients with symptoms of similar intensity. The correlation between maximum CSF pressure with CSF and PCF volumes decreased secondary to the disease. PCF volume was more favorable than CSF volume for assessing intensity of disease symptoms. Furthermore, in a constant pressure change, sensitivity of PCF volume in CM-I/occipitoatlantoaxial joint instability and CM-I/tethered cord syndrome groups was more than in the CM-I group.

Relationship between Cough-Associated Changes in CSF Flow and Disease Severity in Chiari I Malformation: An Exploratory Study Using Real-Time MRI.

BACKGROUND AND PURPOSE: Currently no quantitative objective test exists to determine disease severity in a patient with Chiari I malformation. Our aim was to correlate disease severity in symptomatic patients with Chiari I malformation with cough-associated changes in CSF flow as measured with real-time MR imaging. MATERIALS AND METHODS: Thirteen symptomatic patients with Chiari I malformation (tonsillar herniation of ≥5 mm) were prospectively studied. A real-time, flow-sensitized pencil-beam MR imaging scan was used to measure CSF stroke volume during rest and immediately following coughing and relaxation periods (total scan time, 90 seconds). Multiple posterior fossa and craniocervical anatomic measurements were also obtained. Patients were classified into 2 groups by neurosurgeons blinded to MR imaging measurements: 1) nonspecific Chiari I malformation (5/13)-Chiari I malformation with nonspecific symptoms like non-cough-related or mild occasional cough-related headache, neck pain, dizziness, paresthesias, and/or trouble swallowing; 2) specific Chiari I malformation (8/13)-patients with Chiari I malformation with specific symptoms and/or objective findings like severe cough-related headache, myelopathy, syringomyelia, and muscle atrophy. The Spearman correlation was used to determine correlations between MR imaging measurements and disease severity, and both groups were also compared using a Mann-Whitney U test. RESULTS: There was a significant negative correlation between the percentage change in CSF stroke volume (resting to postcoughing) and Chiari I malformation disease severity (R = 0.59; P = .03). Mann-Whitney comparisons showed the percentage change in CSF stroke volume (resting to postcoughing) to be significantly different between patient groups (P = .04). No other CSF flow measurement or anatomic measure was significantly different between the groups. CONCLUSIONS: Our exploratory study suggests that assessment of CSF flow response to a coughing challenge has the potential to become a valuable objective noninvasive test for clinical assessment of disease severity in patients with Chiari I malformation.

How Should Syringomyelia be Defined and Diagnosed?

OBJECTIVE: Syringomyelia is considered as a fluid-filled cavitation inside the spinal cord. However, there is no agreement whether a dilated central canal should be included under this heading or how glioependymal cysts, myelomalacias, or cystic tumors should be distinguished from syringomyelia. This article provides a definition of syringomyelia and guidelines for its diagnosis. METHODS: Between 1991 and 2015, of 3206 patients with spinal cord pathologies 2276 demonstrated cystic features. All patients underwent magnetic resonance imaging. Syringomyelia was differentiated from cystic intramedullary tumors, glioependymal cysts, myelomalacias, and dilatations of the central canal by clinical and radiologic criteria. RESULTS: A total of 1535 patients were diagnosed with syringomyelia, 635 with dilatations of the central canal, 52 with glioependymal cysts, 52 with mylomalacias, and 2 with cystic intramedullary spinal cord tumors. Additional neuroradiologic studies revealed the causes of syringomyelia. As a result 604 patients showed pathologies at the craniocervical junction leading to disturbances of cerebrospinal fluid (CSF) flow. The commonest was a Chiari I malformation in 543 patients. Nine hundred thirty-one patients presented with pathologies in the spinal canal. The commonest causes were spinal arachnopathies, leading to CSF flow obstructions in 533 patients, intramedullary tumors in 152 patients, and tethered cord syndromes in 69 patients. CONCLUSIONS: The diagnosis of syringomyelia should be reserved for patients with a fluid-filled cavity in the spinal cord related to either a disturbance of CSF flow, spinal cord tethering, or an intramedullary tumor. For patients in whom such a relation cannot be established, the diagnosis of syringomyelia should be withheld.

Novel Assessment of Cerebrospinal Fluid Dynamics by Time-Spatial Labeling Inversion Pulse Magnetic Resonance Imaging in Patients with Chiari Malformation Type I.

OBJECTIVE: We investigated cerebrospinal fluid (CSF) dynamics at the craniocervical junction (CCJ) using Time-SLIP magnetic resonance imaging to demonstrate the significance of ventral and dorsal combined CSF dynamics in assessing CSF flow disturbance in patients with Chiari malformation type I. METHODS: Fifteen examinations were performed in 9 cases of CM-I (3 female patients; mean age, 24.7 years; age range, 11-46 years) before or after craniocervical decompression. The longitudinal maximum movement of the caudal edge of tagged midsagittal CSF at the CCJ was measured as length of motion (LOM), and total on the ventral and dorsal sides was defined as total LOM. RESULTS: In 8 conditions, where it was concluded that no craniocervical decompression was necessary or where symptoms improved following craniocervical decompression based on the clinical symptoms, total LOM was 49.8 ± 13.1 mm. In contrast, in the 7 cases where craniocervical decompression was mandatory, total LOM was 23.2 ± 9.2 mm. Significant differences were identified between the 2 groups. Total LOM <35.0 mm resulted to indicate the insufficiency of CSF dynamics, because it corresponded to the necessity of craniocervical decompression based on patients' symptoms. CONCLUSIONS: Time-SLIP MRI enabled clinicians to use novel dynamic indices, such as CSF motions, in addition to the conventional findings acquired by MRI. In particular, it was essential to examine combined ventral and dorsal CSF dynamics in assessing CSF patency at the CCJ in patients with CM-I.

Chiari malformation may increase perivascular cerebrospinal fluid flow into the spinal cord: A subject-specific computational modelling study.

Syringomyelia is associated with Chiari I malformation, although the mechanistic link is unclear. Studies have suggested that cerebrospinal fluid enters the spinal cord via the perivascular spaces, and that changes in the timing of the subarachnoid pressures may increase flow into the spinal cord. This study aims to determine how Chiari malformation and syringomyelia alter the subarachnoid space pressures and hence perivascular flow. Subject-specific models of healthy controls (N = 9), Chiari patients with (N = 7) and without (N = 8) syringomyelia, were developed from magnetic resonance imaging (MRI), to simulate the subarachnoid pressures. These pressures were input to an idealised model of the perivascular space to evaluate potential differences in perivascular flow. Peak pressures in Chiari patients without a syrinx were higher than in controls (46% increase; p = .029) and arrived earlier in the cardiac cycle than both controls (2.58% earlier; p = .045) and syrinx patients (2.85% earlier; p = .045). The perivascular model predicted Chiari patients without a syrinx would have the greatest flow into the cord (p < .05) if the arterial pulse delay was between 4 and 10% of the cardiac cycle. Using phase-contrast MRI the mean arterial delay for all subjects was similar, and was estimated as 4.7 ±â€¯0.2%. The perivascular pumping rate showed a strong positive correlation (RAdj2=0.85; p < .0001) with extended periods of high pressure that arrived earlier in the cardiac cycle, suggesting these pressure characteristics may play a role in syrinx development.

Direct numerical simulation of transitional hydrodynamics of the cerebrospinal fluid in Chiari I malformation: The role of cranio-vertebral junction.

Obstruction to the cerebrospinal fluid (CSF) outflow caused by the herniation of cerebellar tonsils as a result of Chiari malformation type I leads to altered CSF hydrodynamics. This contribution explores the minutest characteristics of the CSF hydrodynamics in cervical subarachnoid space (SAS) of a healthy subject and 2 Chiari patients by performing highly resolved direct numerical simulation. The lattice Boltzmann method is used for the simulations because of its scalability on modern supercomputers that allow us to simulate up to approximately 109 cells while resolving the Kolmogorov microscales. The results depict that whereas the complex CSF flow remains largely laminar in the SAS of a healthy subject, constriction of the cranio-vertebral junction in Chiari I patients causes manifold fluctuations in the hydrodynamics of the CSF. These fluctuations resemble a flow that is in a transitional regime rather than laminar or fully developed turbulence. The fluctuations confine near the cranio-vertebral junction and are triggered due to the tonsillar herniation, which perturbs the flow as a result of altered anatomy of the SAS.

Computational Investigation of Cerebrospinal Fluid Dynamics in the Posterior Cranial Fossa and Cervical Subarachnoid Space in Patients with Chiari I Malformation.

PURPOSE: Previous computational fluid dynamics (CFD) studies have demonstrated that the Chiari malformation is associated with abnormal cerebrospinal fluid (CSF) flow in the cervical part of the subarachnoid space (SAS), but the flow in the SAS of the posterior cranial fossa has received little attention. This study extends previous modelling efforts by including the cerebellomedullary cistern, pontine cistern, and 4th ventricle in addition to the cervical subarachnoid space. METHODS: The study included one healthy control, Con1, and two patients with Chiari I malformation, P1 and P2. Meshes were constructed by segmenting images obtained from T2-weighted turbo spin-echo sequences. CFD simulations were performed with a previously verified and validated code. Patient-specific flow conditions in the aqueduct and the cervical SAS were used. Two patients with the Chiari malformation and one control were modelled. RESULTS: The results demonstrated increased maximal flow velocities in the Chiari patients, ranging from factor 5 in P1 to 14.8 in P2, when compared to Con1 at the level of Foramen Magnum (FM). Maximal velocities in the cervical SAS varied by a factor 2.3, while the maximal flow in the aqueduct varied by a factor 3.5. The pressure drop from the pontine cistern to the cervical SAS was similar in Con1 and P1, but a factor two higher in P2. The pressure drop between the aqueduct and the cervical SAS varied by a factor 9.4 where P1 was the one with the lowest pressure jump and P2 and Con1 differed only by a factor 1.6. CONCLUSION: This pilot study demonstrates that including the posterior cranial fossa is feasible and suggests that previously found flow differences between Chiari I patients and healthy individuals in the cervical SAS may be present also in the SAS of the posterior cranial fossa.

Cerebrospinal fluid velocity amplitudes within the cerebral aqueduct in healthy children and patients with Chiari I malformation.

PURPOSE: To assess the effects of cerebrospinal fluid (CSF) bidirectional motion in Chiari malformation type I (CMI), we monitored CSF velocity amplitudes on phase contrast MRI (PC-MRI) in patients before and after surgery; and in healthy volunteers. MATERIALS AND METHODS: 10 pediatric volunteers and 10 CMI patients participated in this study. CMI patients underwent PC-MRI scans before and approximately 14 months following surgery. Two parameters-amplitude of mean velocity (AMV) and amplitude of peak velocity (APV) of CSF-were derived from the data. Measurements were made at the mid-portion of the cerebral aqueduct, and anterior and posterior compartments of the spinal canal at the craniovertebral junction (CVJ). RESULTS: AMV and APV within the cerebral aqueduct were greater in preoperative assessments of the CMI patients compared to normal volunteers. Statistical significance was noted when comparing aqueductal AMV between the preoperative values and normal controls (P = 0.03), and before and after surgery in the CMI patients (P = 0.02). Lower values of AMV (P = 0.02) were noted in the anterior CVJ compartment in the patients before and after surgery when compared to the normal volunteers. There were no significant correlations (P = 0.06) noted for the APV at the CVJ between the normal control and patients, before or after surgery. CONCLUSION: In pediatric CMI patients, AMV for CSF within the cerebral aqueduct and anterior CVJ subarachnoid space are significantly elevated preoperatively and normalize following surgery. Given the biphasic CSF motion, measuring amplitude accounts for cranial and caudal flow. It may offer an alternative parameter to assess postsurgical outcome. J. Magn. Reson. Imaging 2016;44:463-470.

Cough-Associated Changes in CSF Flow in Chiari I Malformation Evaluated by Real-Time MRI.

BACKGROUND AND PURPOSE: Invasive pressure studies have suggested that CSF flow across the foramen magnum may transiently decrease after coughing in patients with symptomatic Chiari I malformation. The purpose of this exploratory study was to demonstrate this phenomenon noninvasively by assessing CSF flow response to coughing in symptomatic patients with Chiari I malformation by using MR pencil beam imaging and to compare the response with that in healthy participants. MATERIALS AND METHODS: Eight symptomatic patients with Chiari I malformation and 6 healthy participants were studied by using MR pencil beam imaging with a temporal resolution of ∼50 ms. Patients and healthy participants were scanned for 90 seconds (without cardiac gating) to continuously record cardiac cycle-related CSF flow waveforms in real-time during resting, coughing, and postcoughing periods. CSF flow waveform amplitude, CSF stroke volume, and CSF flow rate (CSF Flow Rate = CSF Stroke Volume × Heart Rate) in the resting and immediate postcoughing periods were determined and compared between patients and healthy participants. RESULTS: There was no significant difference in CSF flow waveform amplitude, CSF stroke volume, and the CSF flow rate between patients with Chiari I malformation and healthy participants during rest. However, immediately after coughing, a significant decrease in CSF flow waveform amplitude (P < .001), CSF stroke volume (P = .001), and CSF flow rate (P = .001) was observed in patients with Chiari I malformation but not in the healthy participants. CONCLUSIONS: Real-time MR imaging noninvasively showed a transient decrease in CSF flow across the foramen magnum after coughing in symptomatic patients with Chiari I malformation, a phenomenon not seen in healthy participants. Our results provide preliminary evidence that the physiology-based imaging method used here has the potential to be an objective clinical test to differentiate symptomatic from asymptomatic patients with Chiari I malformation.

Multimodal evaluation of CSF dynamics following extradural decompression for Chiari malformation Type I.

OBJECT Extradural decompression is a minimally invasive technique for treating Chiari malformation Type I (CM-I) that avoids the complications of dural opening. While there is no agreement on which surgical method is optimal, mounting evidence demonstrates that extradural decompression effectively treats clinical symptoms, with a minimal reoperation rate. Neurological symptoms such as headache may be related to obstructed flow of CSF, and one aspect of successful extradural decompression is improved CSF dynamics. In this series, the authors report on their use of phase-contrast cine flow MRI to assess CSF flow as well as satisfactory decompression. METHODS The authors describe their first surgical series of 18 patients with CM-I undergoing extradural decompression and correlate clinical improvement with radiological changes. Patients were categorized as having complete, partial, or no resolution of their symptoms. Posterior fossa area, cisterna magna area, and tonsillar herniation were assessed on T2-weighted MRI, whereas improvement of CSF flow was evaluated with phase-contrast cine flow MRI. All patients received standard pre- and postoperative MRI studies; 8 (44.4%) patients had pre- and postoperative phase-contrast cine, while the rest underwent cine studies only postoperatively. RESULTS All 18 patients presented with symptomatic CM-I, with imaging studies demonstrating tonsillar herniation ≥ 5 mm, and 2 patients had associated syringomelia. All patients underwent suboccipital decompression and C-1 laminectomy with splitting of the dura. Patients with complete resolution of their symptoms had a greater relative increase in cisterna magna area compared with those with only partial improvement (p = 0.022). In addition, in those with complete improvement the preoperative cisterna magna area was smaller than in those who had either partial (0.020) or no (0.025) improvement. Ten (91%) of the 11 patients with improved flow also had improvement in their symptoms. There was 1 postoperative complication of dysphagia and dysphonia. None of the patients have required a second operation. CONCLUSIONS Extradural decompression has the potential to be the first-line treatment for CM-I but has been lacking an objective measure by which to assess surgical success as well as the need for reoperation. An increase in the CSF spaces and improved CSF dynamics may be associated with resolution of clinical symptoms. Including cine imaging as part of routine pre- and postoperative evaluation can help identify which patients are most likely to benefit from surgery.

Pediatric and adult Chiari malformation Type I surgical series 1965-2013: a review of demographics, operative treatment, and outcomes.

OBJECT: Chiari malformation Type I (CM-I) is a hindbrain disorder associated with elongation of the cerebellar tonsils, which descend below the foramen magnum into the spinal canal. It occurs in children and adults. Clinical symptoms mainly develop from alterations in CSF flow at the foramen magnum and the common subsequent development of syringomyelia. METHODS: The authors reviewed English-language reports of pediatric, adult, and combined (adult and pediatric) surgical series of patients with CM-I published from 1965 through August 31, 2013, to investigate the following: 1) geographical distribution of reports; 2) demographics of patients; 3) follow-up lengths; 4) study durations; 5) spectrum and frequency of surgical techniques; 6) outcomes for neurological status, syrinx, and headache; 7) frequency and scope of complications; 8) mortality rates; and 9) differences between pediatric and adult populations. Research and inclusion criteria were defined, and all series that contained at least 4 cases and all publications with sufficient data for analysis were included. RESULTS: The authors identified 145 operative series of patients with CM-I, primarily from the United States and Europe, and divided patient ages into 1 of 3 categories: adult (>18 years of age; 27% of the cases), pediatric (≤18 years of age; 30%), or unknown (43%). Most series (76%) were published in the previous 21 years. The median number of patients in the series was 31. The mean duration of the studies was 10 years, and the mean follow-up time was 43 months. The peak ages of presentation in the pediatric studies were 8 years, followed by 9 years, and in the adult series, 41 years, followed by 46 years. The incidence of syringomyelia was 65%. Most of the studies (99%) reported the use of posterior fossa/foramen magnum decompression. In 92%, the dura was opened, and in 65% of these cases, the arachnoid was opened and dissected; tonsillar resection was performed in 27% of these patients. Postoperatively, syringomyelia improved or resolved in 78% of the patients. Most series (80%) reported postoperative neurological outcomes as follows: 75% improved, 17% showed no change, and 9% experienced worsening. Postoperative headaches improved or resolved in 81% of the patients, with a statistical difference in favor of the pediatric series. Postoperative complications were reported for 41% of the series, most commonly with CSF leak, pseudomeningocele, aseptic meningitis, wound infection, meningitis, and neurological deficit, with a mean complication rate of 4.5%. Complications were reported for 37% of pediatric, 20% of adult, and 43% of combined series. Mortality was reported for 11% of the series. No difference in mortality rates was seen between the pediatric and adult series. CONCLUSIONS: Before undergoing surgical treatment for CM-I, symptomatic patients and their families should be given clear information about the success of treatment and potential complications. Furthermore, surgeons may benefit from comparing published data with their own. In the future, operative CM-I reports should provide all details of each case for the purpose of comparison.