Cervical compressive myelopathy: flow analysis of cerebrospinal fluid using phase-contrast magnetic resonance imaging

Magnetic Resonance Imaging-CCCFLS Scoring System: Toward Predicting Clinical Symptoms and C5 Paralysis

STUDY DESIGN

A retrospective study.

OBJECTIVE

To develop a new MRI scoring system to assess patients' clinical characteristics, outcomes and complications.

METHODS

A retrospective 1-year follow-up study of 366 patients with cervical spondylosis from 2017 to 2021. The CCCFLS scores (cervical curvature and balance (CC), spinal cord curvature (SC), spinal cord compression ratio (CR), cerebrospinal fluid space (CFS). Spinal cord and lesion location (SL). Increased Signal Intensity (ISI) were divided into Mild group (0-6), Moderate group (6-12), and Severe group (12-18) for comparison, and the Japanese Orthopaedic Association (JOA) scores, visual analog scale (VAS), numerical rating scale (NRS), Neck Disability Index (NDI) and Nurick scores were evaluated. Correlation and regression analyses were performed between each variable and the total model in relation to clinical symptoms and C5 palsy.

RESULTS

The CCCFLS scoring system was linearly correlated with JOA, NRS, Nurick and NDI scores, with significant differences in JOA scores among patients with different CC, CR, CFS, ISI scores, with a predictive model (R2 = 69.3%), and significant differences in preoperative and final follow-up clinical scores among the 3 groups, with a higher rate of improvement in JOA in the severe group (P < .05), while patients with and without C5 paralysis had significant differences in preoperative SC and SL (P < .05).

CONCLUSION

CCCFLS scoring system can be divided into mild (0-6). moderate (6-12), severe (12-18) groups. It can effectively reflect the severity of clinical symptoms, and the improvement rate of JOA is better in the severe group, while the preoperative SC and SL scores are closely related to C5 palsy.

LEVEL OF EVIDENCE

III.

Epidural pressure measurement using a fiber-optic sensor (proof-of-principle in vivo animal trial)

BACKGROUND

An increase in epidural pressure around the stenosis has been observed in patients with lumbar spinal stenosis (LSS) with positive signs of sedimentation or redundant nerve roots. Further analysis of the pressure conditions in the stenotic area would be of great interest. We hypothesized that it would be possible to determine the physiological parameters of the epidural pulse wave and its course in pathological stenosis as a basis for objective identification of LSS based on pressure using a new measuring method with continuous spatial and temporal resolution.

METHODS

We performed a single-case proof-of-principle in vivo animal trial and used a newly developed hybrid pressure-measurement probe with a fiber-tip Fabry-Pérot interferometer and several fiber Bragg gratings (FBG).

RESULTS

With reproducible precision, we determined the mean epidural pressure to be 7.5 mmHg and the peak-to-peak value to be 4-5 mmHg. When analyzing the pressure measured by an FBG array, both the heart and respiratory rates can be precisely determined. This study was the first to measure the pulse wave velocity of the cerebrospinal fluid pressure wave as 0.97 m/s using the newly developed pressure probe. A simulated LSS was detected in real time and located exactly.

CONCLUSIONS

The developed fiber-optic pressure sensor probe enables a new objective measurement of epidural pressure. We confirmed our hypothesis that physiological parameters of the epidural pulse wave can be determined and that it is possible to identify an LSS.

Radiological Analysis of Cerebrospinal Fluid Dynamics at the Craniovertebral Junction Using Time-Spatial Labeling Inversion Pulse Magnetic Resonance Imaging in Patients with Cervical Spinal Canal Stenosis

OBJECTIVE

Spondylotic changes in the cervical spine cause degeneration, leading to cervical spinal canal stenosis. This stenotic change can affect cerebrospinal fluid (CSF) dynamics by compressing the dural sac and reducing space in the subarachnoid space. We examined CSF dynamics at the craniovertebral junction (CVJ) using time-spatial labeling inversion pulse magnetic resonance imaging (Time-SLIP MRI) in patients with cervical spinal canal stenosis.

METHODS

The maximum longitudinal movement of the CSF at the CVJ was measured as length of motion (LOM) in the Time-SLIP MRI of 56 patients. The sum of ventral and dorsal LOM was defined as the total LOM. Patients were classified into 3 groups depending on their spinal sagittal magnetic resonance imaging findings: control (n = 27, Kang classification grades 0 and 1), stenosis (n = 14, Kang classification grade 2), and severe stenosis (n = 15, Kang classification grade 3).

RESULTS

Time-SLIP MRI revealed pulsatile movement of the CSF at the CVJ. The mean total, ventral, and dorsal LOM was 14.2 ± 9, 8.1 ± 5.7, and 3.8 ± 2.9 mm, respectively. The ventral LOM was significantly larger than the dorsal LOM. The total LOM was significantly smaller in the severe stenosis group (6.1 ± 3.4 mm) than in the control (16.0 ± 8.4 mm) or stenosis (11 ± 5.4 mm) groups (P < 0.001, Kruskal-Wallis H-test). In 5 patients, postoperative total LOM was improved after adequate decompression surgery.

CONCLUSIONS

This study demonstrates that CSF dynamics at the CVJ are influenced by cervical spinal canal stenosis. Time-SLIP MRI is useful for evaluating CSF dynamics at the CVJ in patients with spinal canal stenosis.

Characterising spinal cerebrospinal fluid flow in the pig with phase-contrast magnetic resonance imaging

BACKGROUND

Detecting changes in pulsatile cerebrospinal fluid (CSF) flow may assist clinical management decisions, but spinal CSF flow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF flow changes. Pigs are emerging as a favoured large animal SCI model; therefore, the aim of this study was to characterise CSF flow along the healthy pig spine.

METHODS

Phase-contrast magnetic resonance images (PC-MRI), retrospectively cardiac gated, were acquired for fourteen laterally recumbent, anaesthetised and ventilated, female domestic pigs (22-29 kg). Axial images were obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Dorsal and ventral SAS regions of interest (ROI) were manually segmented. CSF flow and velocity were determined throughout a cardiac cycle. Linear mixed-effects models, with post-hoc comparisons, were used to identify differences in peak systolic/diastolic flow, and maximum velocity (cranial/caudal), across spinal levels and dorsal/ventral SAS. Velocity wave speed from C2/C3 to L1/L2 was calculated.

RESULTS

PC-MRI data were obtained for 11/14 animals. Pulsatile CSF flow was observed at all spinal levels. Peak systolic flow was greater at C2/C3 (dorsal: - 0.32 ± 0.14 mL/s, ventral: - 0.15 ± 0.13 mL/s) than T8/T9 dorsally (- 0.04 ± 0.03 mL/s; p < 0.001), but not different ventrally (- 0.08 ± 0.08 mL/s; p = 0.275), and no difference between thoracolumbar levels (p > 0.05). Peak diastolic flow was greater at C2/C3 (0.29 ± 0.08 mL/s) compared to T8/T9 (0.03 ± 0.03 mL/s, p < 0.001) dorsally, but not different ventrally (p = 1.000). Cranial and caudal maximum velocity at C2/C3 were greater than thoracolumbar levels dorsally (p < 0.001), and T8/T9 and L1/L2 ventrally (p = 0.022). Diastolic velocity wave speed was 1.41 ± 0.39 m/s dorsally and 1.22 ± 0.21 m/s ventrally, and systolic velocity wave speed was 1.02 ± 0.25 m/s dorsally and 0.91 ± 0.22 m/s ventrally.

CONCLUSIONS

In anaesthetised and ventilated domestic pigs, spinal CSF has lower pulsatile flow and slower velocity wave propagation, compared to humans. This study provides baseline CSF flow at spinal levels relevant for future SCI research in this animal model.

Revisiting Cerebrospinal Fluid Flow Direction and Rate in Physiologically Based Pharmacokinetic Model

The bidirectional pulsatile movement of cerebrospinal fluid (CSF), instead of the traditionally believed unidirectional and constant CSF circulation, has been demonstrated. In the present study, the structure and parameters of the CSF compartments were revisited in our comprehensive and validated central nervous system (CNS)-specific, physiologically based pharmacokinetic (PBPK) model of healthy rats (LeiCNS-PK3.0). The bidirectional and site-dependent CSF movement was incorporated into LeiCNS-PK3.0 to create the new LeiCNS-PK“3.1” model. The physiological CSF movement rates in healthy rats that are unavailable from the literature were estimated by fitting the PK data of sucrose, a CSF flow marker, after intra-CSF administration. The capability of LeiCNS-PK3.1 to describe the PK profiles of other molecules was compared with that of the original LeiCNS-PK3.0 model. LeiCNS-PK3.1 demonstrated superior description of the CSF PK profiles of a range of small molecules after intra-CSF administration over LeiCNS-PK3.0. LeiCNS-PK3.1 also retained the same level of predictability of CSF PK profiles in cisterna magna after intravenous administration. These results support the theory of bidirectional and site-dependent CSF movement across the entire CSF space over unidirectional and constant CSF circulation in healthy rats, pointing out the need to revisit the structures and parameters of CSF compartments in CNS-PBPK models.

Anterior Canal Reconstruction and Fusion for Myelopathy Caused by Degenerative Cervical Kyphosis and Stenosis With or Without Ossification of the Posterior Longitudinal Ligament

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

To introduce an anterior surgical technique for myelopathy caused by degenerative cervical kyphosis and stenosis (DCKS) with or without ossification of the posterior longitudinal ligament (OPLL).

SUMMARY OF BACKGROUND DATA

The optimal approach in the treatment of DCKS remains a controversy because each anterior or posterior route surgery has advantages and disadvantages.

MATERIALS AND METHODS

In the period from June 2017 through June 2019, a consecutive cohort of adults diagnosed with DCKS underwent anterior canal reconstruction and fusion (ACRF). All patients underwent x-ray, computed tomography, and magnetic resonance imaging of the cervical spine. Radiologic assessment included kyphosis, canal area, canal reconstruction, OPLL, and spinal cord curvature and morphology. The Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the neurological status. Surgery-related and implant-related complications were all recorded. Follow-up was carried out at 3, 6, 12, 24, and 36 months postoperation.

RESULTS

Fourty-one patients were included in the study, of which 19 presented with OPLL. Postoperatively, the canal area were significantly greater at last follow-up compared with preoperation (208.4 vs. 123.2 mm2; P=0.001). There was significant kyphosis correction (-17.6 vs. 8.5 degrees, P=0.001) at last follow-up. Ninety-six segmental canal reconstruction were performed, 89 (92.7%) reached bone fusion at both grooves with a mean time of 7.9 months. On sagittal magnetic resonance imaging, 33 (80.5%) patients presented with lordosis in the spinal cord curvature, 8 (19.5%) with straight. The mean JOA score at last follow-up was significantly better than preoperation (15.0 vs. 9.3 points; P<0.01). One patient presented with cerebrospinal fluid leakage, 1 with screw displacement and 2 with dysphagia.

CONCLUSION

ACRF, receiving good correction of kyphosis, amplified canal area, solid instrumented fusion and circumferential decompression, is an effective and safe surgical technique for cervical myelopathy caused by DCKS with or without OPLL.

LEVEL OF EVIDENCE

Level III-a retrospective analysis.

Advanced magnetic resonance imaging of chronic whiplash patients: a clinical practice-based feasibility study

BACKGROUND

Whiplash injury is common following road traffic crashes affecting millions worldwide, with up to 50% of the injured developing chronic symptoms and 15% having a reduced working capability due to ongoing disability. Many of these patients receive treatment in primary care settings based upon clinical and diagnostic imaging findings. Despite the identification of different types of injuries in the whiplash patients, clinically significant relationships between injuries and chronic symptoms remains to be fully established. This study investigated the feasibility of magnetic resonance imaging (MRI) techniques including quantitative diffusion weighted imaging and measurements of cerebrospinal fluid (CSF) flow as novel non-invasive biomarkers in a population of healthy volunteers and chronic whiplash patients recruited from a chiropractic clinic for the purpose of improving our understanding of whiplash injury.

METHODS

Twenty chronic whiplash patients and 18 healthy age- and gender matched control subjects were included [mean age ± SD (sex ratio; females/males), case group: 37.8 years ± 9.1 (1.22), control group: 35.1 years ± 9.2 (1.25)]. Data was collected from May 2019 to July 2020. Data from questionnaires pertaining to the car crash, acute and current symptoms were retrieved and findings from clinical examination and MRI including morphologic, diffusion weighted and phase-contrast images were recorded. The apparent diffusion coefficient and fractional anisotropy were calculated, and measurement and analysis of CSF flow was conducted. Statistical analyses included Fisher's exact test, Mann Whitney U test and analysis of variance between groups.

RESULTS

The studied population was described in detail using readily available clinical tools. No statistically significant differences were found between the groups on MRI.

CONCLUSIONS

This study did not show that MRI-based measures of morphology, spinal cord and nerve root diffusion or cerebrospinal fluid flow are sensitive biomarkers to distinguish between chronic whiplash patients and healthy controls. The detailed description of the chronic whiplash patients using readily available clinical tools may be of great relevance to the clinician. In the context of feasibility, clinical practice-based advanced imaging studies with a technical setup similar to the presented can be expected to have a high likelihood of successful completion.

Severe altered mentation due to cervicothoracic intrathecal pump after correction of cervical stenosis: a case report

BACKGROUND

Cerebral spinal fluid (CSF) dynamics are complex and changes in spinal anatomy may influence the rostrocaudal movement of intrathecal medications. We present the first reported case demonstrating that acute cervical spinal stenosis may impede the distribution of adjacent intrathecal medications, and that correction of such stenosis and the resulting changes in CSF flow may necessitate significant adjustments in the intrathecal infusates.

CASE PRESENTATION

We present a case of a 60-year-old male patient with a cervicothoracic intrathecal pump (ITP) infusing morphine, bupivacaine, and baclofen for chronic neck pain. The alert and oriented patient had a recent fall resulting in an acute severe cervical stenosis and cord compression which required urgent surgical decompression. Postoperatively, after the cervical decompression, the patient had significant altered mental status requiring a naloxone infusion. Multiple attempts to reduce the naloxone infusion were initially not successful due to worsened somnolence. The previously tolerated ITP medications were continuously reduced over the next 14 days, allowing concomitant decrease and eventual cessation of the naloxone infusion while maintaining patient mental status. The only opioids the patient received during this period were from the ITP.

CONCLUSIONS

This case presents clinical evidence that severe spinal stenosis may impede the rostral CSF distribution of intrathecal medications. Intrathecal medications previously tolerated by patients prior to decompression may need to be significantly reduced in the postoperative period.

Risk factors for persistent coronal imbalance or revision surgery following L3 LIV selection in adolescent idiopathic scoliosis (AIS)

STUDY DESIGN

Retrospective case-control.

OBJECTIVE

To identify a cohort of patients with persistent coronal imbalance (CIB) or revision surgery 5 years following fusion to an L3 lowest-instrumented-vertebra (LIV) and determine factors that make an L3 LIV high-risk. In surgical planning for AIS, L3 is chosen over L4 whenever possible to maximize motion segments below the LIV. Though fusion to an L3 LIV is common, the rate of failure and its risk factors have not been described.

METHODS

In this analysis of prospectively-collected multi-center data of AIS patients who underwent posterior spinal fusion (PSF) to an L3 LIV, we identified patients with CIB at 5 years and/or those who required revision surgery attributable to LIV selection. Patients who were balanced at 5 years and did not require revision surgery served as controls. Pre-operative patient and radiographic variables were compared between cases and controls to identify risk factors for CIB/revision surgery.

RESULTS

We identified 646 patients with 2-year follow-up and 225 patients with 5-year follow-up, of which 11 were found to have CIB and/or revision surgery attributable to selecting L3 as the LIV. There were statistically significant differences between cases and controls with respect to several pre-operative factors, including BMI (24.5 in cases vs. 20.1 in controls; p = 0.01), Lenke curve type (81.8% Lenke 5/6 vs. 44.4%; p = 0.03), lumbar curve magnitude (56 vs. 45°; p < 0.01), TL/L apical vertebral translation (AVT) (6.2 vs. 4.1 cm; p < 0.01), L3 angulation (30° vs. 22°; p < 0.01), L3 translation (4.3 vs. 2.9 cm; p < 0.01), thoracic rib hump (7° vs. 12°; p = 0.02), lumbar rib hump (16° vs. 10°; p < 0.01), and thoracolumbar (T10-L2) kyphosis (10.5° vs. 2°; p = 0.006). Multivariate logistic regression showed that pre-operative BMI, TL/L AVT, L3 angulation, L3 translation, lumbar rib hump, and thoracolumbar kyphosis were independent predictors of CIB/revision surgery.

CONCLUSIONS

An L3 LIV is frequently successful at 5 years post-operatively. Consider an L4 LIV when: pre-operative BMI ≥ 28, L3 angulation ≥ 25°, L3 translation ≥ 4 cm, TL/L AVT ≥ 6 cm, or the lumbar curve is large (≥ 55°) and rotated (≥ 10°).

LEVEL OF EVIDENCE

Level III.

Safety and Feasibility of Lumbar Cerebrospinal Fluid Pressure and Intraspinal Pressure Studies in Cervical Stenosis: A Case Series

INTRODUCTION

Degenerative cervical myelopathy (DCM) leads to functional impairment by compression of the spinal cord and nerve roots. In DCM, the dynamics of cerebrospinal fluid pressure (CSFP) and intraspinal pressure (ISP), as well as spinal cord perfusion pressure (SCPP) remain not investigated yet. Recent technical advances have enabled investigation of these parameters in acute spinal cord injury (SCI). We aim to investigate the properties of CSFP/ISP and spinal cord hemodynamics during and after decompressive surgery in DCM.

MATERIALS AND METHODS

Four patients with DCM were enrolled; during surgery and 24 h postoperative, ISP at level was measured in one patient, and CSFP was measured in two patients. In one patient, CSFP was recorded at bedside before surgery.

RESULTS

All measurements were conducted without adverse events and were well tolerated. With CSFP analysis, post-decompression Queckenstedt's test was responsive in two patients (i.e., jugular vein compression resulted in an elevation of CSFP pressure). In the patient whose CSFP was tested at bedside, Queckenstedt's test was not responsive before decompression. Individual optimum SCPPs were calculated to be between 70 and 75 mmHg.

CONCLUSION

ISP and CSFP can reflect spinal compression and sufficient decompression. A better understanding and systematic monitoring possibly lead to improved hemodynamic management and may allow early recognition of postoperative complications such as swelling and bleeding.

Quantification of cerebrospinal fluid flow in dogs by cardiac-gated phase-contrast magnetic resonance imaging

BACKGROUND

Cerebrospinal fluid (CSF) flow in disease has been investigated with two-dimensional (2D) phase-contrast magnetic resonance imaging (PC-MRI) in humans. Despite similar diseases occurring in dogs, PC-MRI is not routinely performed and CSF flow and its association with diseases is poorly understood.

OBJECTIVES

To adapt 2D and four-dimensional (4D) PC-MRI to dogs and to apply them in a group of neurologically healthy dogs.

ANIMALS

Six adult Beagle dogs of a research colony.

METHODS

Prospective, experimental study. Sequences were first optimized on a phantom mimicking small CSF spaces and low velocity flow. Then, 4D PC-MRI and 2D PC-MRI at the level of the mesencephalic aqueduct, foramen magnum (FM), and cervical spine were performed.

RESULTS

CSF displayed a bidirectional flow pattern on 2D PC-MRI at each location. Mean peak velocity (and range) in cm/s was 0.92 (0.51-2.08) within the mesencephalic aqueduct, 1.84 (0.89-2.73) and 1.17 (0.75-1.8) in the ventral and dorsal subarachnoid space (SAS) at the FM, and 2.03 (range 1.1-3.0) and 1.27 (range 0.96-1.82) within the ventral and dorsal SAS of the cervical spine. With 4D PC-MRI, flow velocities of >3 cm/s were visualized in the phantom, but no flow data were obtained in dogs.

CONCLUSION

Peak flow velocities were measured with 2D PC-MRI at all 3 locations and slower velocities were recorded in healthy Beagle dogs compared to humans. These values serve as baseline for future applications. The current technical settings did not allow measurement of CSF flow in Beagle dogs by 4D PC-MRI.

Study protocol for an observational study of cerebrospinal fluid pressure in patients with degenerative cervical myelopathy undergoing surgical deCOMPression of the spinal CORD: the COMP-CORD study

INTRODUCTION

Degenerative cervical myelopathy (DCM) is a disabling spinal disorder characterised by sensorimotor deficits of upper and lower limbs, neurogenic bladder dysfunction and neuropathic pain. When suspected, cervical MRI helps to reveal spinal cord compression and rules out alternative diagnoses. However, the correlation between radiological findings and symptoms is weak. Cerebrospinal fluid pressure (CSFP) analysis may complement the appreciation of cord compression and be used for intraoperative and postoperative monitorings in patients undergoing surgical decompression.

METHODS AND ANALYSIS

Twenty patients diagnosed with DCM undergoing surgical decompression will receive standardised lumbar CSFP monitoring immediately before, during and 24 hours after operation. Rest (ie, opening pressure, CSF pulsation) and stimulated (ie, Valsalva, Queckenstedt's) CSFP-findings in DCM will be compared with 20 controls and results from CSFP monitoring will be related to clinical and neurophysiological findings. Arterial blood pressure will be recorded perioperatively and postoperatively to calculate spinal cord perfusion pressure and spinal vascular reactivity index. Furthermore, measures of CSFP will be compared with markers of spinal cord compression by means of MR imaging.

ETHICS AND DISSEMINATION

The study protocol conformed to the latest revision of the Declaration of Helsinki and was approved by the local Ethics Committee of the University Hospital of Zurich (KEK-ZH number PB-2016-00623). The main publications from this study will cover the CSFP fluid dynamics and pressure analysis preoperative, perioperative and postoperative correlated with imaging, clinical scores and neurophysiology. Other publications will deal with preoperative and postoperative spinal perfusion. Furthermore, we will disseminate an analysis on waveform morphology and the correlation with blood pressure and ECG. Parts of the data will be used for computational modelling of cervical stenosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT02170155).

The possible impact of cervical stenosis on cephalad neuronal dysfunction

Earlier observers have speculated on the causal relationships between abnormal CSF circulation and a variety of neurological dysfunctions. Such speculations have been at least partially validated by recent evidence and inquiries contravening the traditional static viewpoint of CSF circulation. More contemporary inquiries establish a number of factors which influence both CSF production and absorption (sleep disturbance, neck position, cerebral metabolism, brain atrophy, medications, etc.). Thus, transient periods of abnormality are possibly mingled with periods of normality. Such episodic alterations suggest that the physiological arrangements which underpin CSF circulation may be in some ways likened to blood pressure alterations, in that long-standing CSF abnormalities may be both unappreciated and gradual, though virulent enough to cause substantial neurological injury. We suggest that cervical stenosis (blocking an important CSF decompressive pathway into the vertebral canal) is among the largely unappreciated causes of abnormal CSF circulation and may play a role in cephalad neuronal dysfunction. Such a blockage is correlated with age and easily assessed by cine MRI study. Indeed, episodic disturbances can diminish CSF cerebral flow circulation increasing deposition in cerebral parenchyma of contrary metabolic products (e.g. beta Amyloid), possibly having a causal influence on senile dementia. Additionally, cervical stenosis, by increasing posterior fossa cerebral pressure, could play a causal role in a number of afflictions, among them sleep apnea, concomitant respiratory and circulatory dysfunction, hypertension, chronic occipital headaches, tinnitus, etc. We further suggest that among those patients with substantial cervical stenosis (extensive enough to block CSF circulation in the cervical area as identified by cine MRI) appropriate comparative clinical studies could be undertaken to demarcate associations with presenile dementia, sleep disturbance and posterior fossa dysfunction. Additionally, we suggest that an intracranial monitoring implant be perfected to chronically monitor both intracranial pressure and CSF flow - a monitoring device comparable to the rather less invasive sphygmometric evaluation of blood pressure. If such speculations prove correct, different therapeutic regimens which might improve outcome could be imagined. Among them better sleep hygiene (to by position maximize CSF flow) and possibly more aggressive operative decompressive intervention to diminish cervical obstruction.

Immediate improvement of intraoperative monitoring signals following CSF release for cervical spine stenosis: Case report

Cervical spondylotic myelopathy (CSM) is a degenerative pathology characterized by partial or complete conduction block on intraoperative neuromonitoring. We describe a case treated using osseoligamentous decompression and durotomy for cerebrospinal fluid (CSF) release. Intraoperative monitoring demonstrated immediate signal improvement with CSF release, suggesting that clinical improvement in CSM may result from resolution of CSF flow anomalies.