Cerebrospinal Fluid Flow Velocity Research Articles

Cerebrospinal fluid dynamics at the lumbosacral level in patients with spinal stenosis: A pilot study

Spinal stenosis is a common degenerative condition. However, how neurogenic claudication develops has not been clearly elucidated. Moreover, cerebrospinal fluid physiology at the lumbosacral level has not received adequate attention. This study was conducted to compare cerebrospinal fluid hydrodynamics at the lumbosacral spinal level between patients with spinal stenosis and healthy controls. Twelve subjects (four patients and eight healthy controls; 25-77 years old; seven males) underwent phase-contrast magnetic resonance imaging to quantify cerebrospinal fluid dynamics. The cerebrospinal fluid flow velocities were measured at the L2 and S1 levels. All subjects were evaluated at rest and after walking (to provoke neurogenic claudication in the patients). The caudal peak flow velocity in the sacral spine (-0.25 ± 0.28 cm/s) was attenuated compared to that in the lumbar spine (-0.93 ± 0.46 cm/s) in both patients and controls. The lumbar caudal peak flow velocity was slower in patients (-0.65 ± 0.22 cm/s) than controls (-1.07 ± 0.49 cm/s) and this difference became more pronounced after walking (-0.66 ± 0.37 cm/s in patients, -1.35 ± 0.52 cm/s in controls; p = 0.028). The sacral cerebrospinal fluid flow after walking was barely detectable in patients (caudal peak flow velocity: -0.09 ± 0.03 cm/s). Cerebrospinal fluid dynamics in the lumbosacral spine were more attenuated in patients with spinal stenosis than healthy controls. After walking, the patients experiencing claudication did not exhibit an increase in the cerebrospinal fluid flow rate as the controls did. Altered cerebrospinal fluid dynamics may partially explain the pathophysiology of spinal stenosis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:104-112, 2017.

Visualization of CSF Flow with Time-resolved 3D MR Velocity Mapping in Aqueductal Stenosis Before and After Endoscopic Third Ventriculostomy : AFeasibility Study.

The aim of this study was to evaluate timed-resolved three-dimensional (3D) magnetic resonance (MR) velocity mapping as amethod for investigation of cerebrospinal fluid (CSF) flow changes in patients with aqueductal stenosis (AS) treated by endoscopic third ventriculostomy (ETV). The MR velocity mapping was performed in 12AS patients before and after ETV and in 10 healthy volunteers by using a3-Tesla MR system. Time-resolved 3D MR velocity mapping data were acquired with astandard 3D phase contrast (PC) sequence with cardiac triggering. Values of mean (vmean) and maximum (vpeak) velocity were measured at several ventricular structures using dedicated software. Of the patients 11 showed asatisfactory clinical improvement after ETV, whereas one patient needed subsequent shunt implantation. All AS patients showed significant hypomotile CSF flow dynamics in the third ventricle when compared to healthy subjects before surgery (p< 0.05). In contrast, CSF flow velocity was increased within the Foramen of Monro in AS patients. After ETV, all AS patients showed adecrease of CSF flow dynamics within the third ventricle. Mean and peak CSF flow velocities through the ventriculostomy were 1.72± 0.59cm/s (vmean) and 3.53± 0.79cm/s (vpeak), respectively after ETV. The patient who needed shunt implantation after ETV had the lowest flow velocities through the ventriculostomy. This study demonstrates that timed-resolved 3D MR velocity mapping is auseful imaging investigation for diagnostics and follow-up in patients with AS. This new technique provides an insight into the physiological CSF flow changes related with AS and its treatment.

Is there a pulse wave encephalopathy component to multiple sclerosis?

The dominant hypothesis in multiple sclerosis is that it is an autoimmune disease; however, there is considerable evidence that the immune attack on myelin may be secondary to a cytodegenerative event. Furthermore, the immune modulating therapies longest in clinical use, although modulating the frequency and severity of exacerbation, do not affect long-term progression towards disability. Clearly alternative perspectives on the etiology of multiple sclerosis are warranted. In this paper I outline the commonalities between idiopathic normal pressure hydrocephalus and multiple sclerosis. These include decreased intracranial compliance as evidenced by increased cerebrospinal fluid volume and velocity of cerebrospinal fluid flow through the cerebral aqueduct; increased ventricular volume; periventricular demyelination lesions; increase in size of Virchow-Robin spaces; presence of Hakim's triad comprised of locomotory disabilities, cognitive problems and bladder control problems. Furthermore, multiple sclerosis is associated with decreased arterial compliance. These are all suggestive that there is a pulse wave encephalopathy component to multiple sclerosis. There are enough resemblances between normal pressure hydrocephalus and multiple sclerosis to warrant further investigation. Whether decreases in intracranial compliance is a consequence of multiple sclerosis or is a causal factor is unknown. Effective therapies can only be developed when the etiology of the disease is understood.

Cerebrospinal fluid dynamics at the lumbosacral level in patients with spinal stenosis

The hydrodynamics of the cerebrospinal fluid (CSF) is well-known to contribute to neurological disorders of the brain. However, little attention has been paid to the CSF dynamics in the lumbosacral spine. Meanwhile, the pathomechanism of neurogenic claudication, a characteristic symptom of spinal stenosis, has not been clearly elucidated. In this study, we suspected that spinal stenosis may be associated with altered CSF dynamics and compared CSF flow velocities at the lumbosacral spinal level between patients with spinal stenosis and healthy controls, at rest and at claudication.

Mechanism for measurement of flow rate of cerebrospinal fluid in hydrocephalus shunts.

The measurement of the flow rate of cerebrospinal fluid (CSF) or existence of CSF flow inside the shunt tube after shunt implant have been reported as tedious process for both patients and doctors; this paper outlines a potential in vitro flow rate measurement method for CSF in the hydrocephalus shunt. The use of implantable titanium elements in the shunt has been proposed to allow for an accurate temperature measurement along the shunt for prediction of CSF flow rate. The CSF flow velocity can be deduced by decoupling the thermal transfer in the measured differential time at a pair of measurement spots of the titanium elements. Finite element analyses on the fluidic and thermal behaviors of the shunt system have been conducted. Preliminary bench-top measurements on a simulated system have been carried out. The measured flow rates, ranging from 0.5 mm/sec to 1.0 mm/sec, which is clinically practical, demonstrate good agreements with the simulation results.

Phase contrast magnetic resonance imaging of cerebrospinal fluid flow through the aqueduct of sylvius in chronic tension-type headache

To study the cerebrospinal fluid (CSF) flow through the aqueduct of sylvius in chronic tension-type headache patients with phase contrast magnetic resonance imaging. Phase contrast magnetic resonance imaging (MRI) of the CSF flow through the aqueduct was obtained from 17 patients with chronic tension-type headache and 26 control subjects. A software for CSF flow was applied for MRI data analysis both qualitatively and quantitatively. The CSF through the aqueduct flew in the caudal and cranial directions with the rhythm of the heartbeat in both groups. There were 2 types of flow curves: the smooth "U" and the wave, which were 25 vs 1 in the controls and 11 vs 6 in the patients (P<0.05), respectively. The mean caudocranial flow rate through the aqueduct was (0.235±0.157) mL/s vs (0.133±0.106) mL/s (P<0.05) and the velocity was (6.023±2.654) cm/s vs (3.479±2.364) cm/s (P<0.05), and the mean craniocaudal flow rate was (-0.358±0.201) mL/s vs (-0.190±0.141) mL/s (P<0.05) and the velocity was (-8.263±3.020) cm/s vs (-4.788±2.862) cm/s (P<0.05), respectively. The CSF flow curve, rate and velocity through the aqueduct in the patients with chronic tension-type headache is anomalous in comparison with the controls.

Arterial, Venous, and Cerebrospinal Fluid Flow: Simultaneous Assessment with Bayesian Multipoint Velocity-encoded MR Imaging

To measure arterial, venous, and cerebrospinal fluid (CSF) velocities simultaneously by using Bayesian multipoint velocity-encoded magnetic resonance (MR) imaging and to compare interacquisition reproducibility relative to that of standard phase-contrast MR imaging for sequential measurements of arterial, venous, and CSF velocities. This study was approved by the local ethics committee, and informed consent was obtained from all subjects. Simultaneous measurement of blood and CSF flow was performed at the C1-C2 level in 10 healthy subjects (mean age, 24.4 years ± 2.7; five men, five women) by using accelerated Bayesian multipoint velocity-encoded MR imaging. Data were compared with those obtained from two separate conventional phase-contrast MR imaging acquisitions, one optimized for arterial and venous blood flow (velocity encoding range, ±50 cm/sec) and the other optimized for CSF flow (velocity encoding range, ±10 cm/sec), with an imaging time of approximately 2 minutes each. Data acquisition was repeated six times. Intraclass correlation coefficient (ICC) and linear regression were used to quantify interacquisition reproducibility. There was no significant difference in arterial blood flow measured with Bayesian multipoint velocity-encoded MR imaging and that measured with phase-contrast MR imaging (mean ICC, 0.96 ± 0.03 vs 0.97 ± 0.02, respectively). Likewise, there was no significant difference between CSF flow measured with Bayesian multipoint velocity-encoded MR imaging and that measured with phase-contrast MR imaging (mean ICC, 0.97 ± 0.02 vs 0.96 ± 0.05, respectively). For venous blood flow, the ICC with Bayesian multipoint MR imaging was significantly larger than that with conventional phase-contrast MR imaging (mean, 0.75 ± 0.23 vs 0.65 ± 0.26, respectively; P = .016). Bayesian multipoint velocity-encoded MR imaging allows for simultaneous assessment of fast and slow flows in arterial, venous, and CSF lumina in a single acquisition. It eliminates the need for vessel-dependent adjustment of the velocity-encoding range, as required for conventional sequential phase-contrast MR imaging measurements.

Application of phase-contrast cine magnetic resonance imaging in endoscopic aqueductoplasty

The aim of this study was to evaluate the application of phase-contrast cine magnetic resonance imaging (MRI) in endoscopic aqueductoplasty (EA) for patients with obstructive hydrocephalus. The clinical diagnosis of hydrocephalus caused by aqueduct obstruction in 23 patients was confirmed by phase-contrast cine MRI examination. The patients were treated with EA and MRI was repeated during the follow-up. The cerebrospinal fluid (CSF) flow velocity in the aqueduct was measured to determine whether the aqueduct was obstructed. The results of phase-contrast cine MRI examinations indicated that there was no CSF flow in the aqueduct for all patients prior to surgery. Aqueductoplasty was successfully performed in all patients. The results of phase-contrast cine MRI examinations performed a week after surgery demonstrated an average CSF flow velocity of 4.74±1.77 cm/sec. During the follow-up, intracranial hypertension recurred in two patients in whom CSF flow was not observed in the aqueduct by the phase-contrast cine MRI scan. Aqueduct re-occlusion was revealed by an endoscopic exploration. By measuring the CSF flow velocity, phase-contrast cine MRI accurately identifies aqueduct obstruction. Cine MRI is a nontraumatic, simple and reliable method for determining whether the aqueduct is successfully opened following aqueductoplasty.

Quantitative analysis of intraspinal cerebrospinal fluid flow in normal adults.

The present study quantitatively analyzed intraspinal cerebrospinal fluid flow patterns in 19 normal adults using fast cine phase-contrast magnetic resonance imaging. Results showed increased downward flow velocity and volume compared with upward flow, and the average downward flow volume of intraspinal cerebrospinal fluid decreased from top to bottom at different intervertebral disc levels. Upward and downward cerebrospinal fluid flow velocity reached a peak at the thoracic intraspinal anterior region, and velocity reached a minimum at the posterior region. Overall measurements revealed that mean upward and downward flow volume positively correlated with the subarachnoid area. Upward peak flow velocity and volume positively correlated with spinal anteroposterior diameter. However, downward peak flow velocity and volume exhibited a negative correlation with spinal anteroposterior diameter. Further flow measurements showed that flow velocity in upward and downward directions was associated with subarachnoid anteroposterior diameter, respectively. The present experimental results showed that cerebrospinal fluid flow velocity and volume varied at different intraspinal regions and were affected by subarachnoid space area and anteroposterior diameter size.

The Frequency and Magnitude of Cerebrospinal Fluid Pulsations Influence Intrathecal Drug Distribution

Intrathecal drug delivery is an efficient method to administer therapeutic molecules to the central nervous system. However, even with identical drug dosage and administration mode, the extent of drug distribution in vivo is highly variable and difficult to control. Different cerebrospinal fluid (CSF) pulsatility from patient to patient may lead to different drug distribution. Medical image-based computational fluid dynamics (miCFD) is used to construct a patient-specific model to quantify drug transport as a function of a spectrum of physiological CSF pulsations. Magnetic resonance imaging (MRI) and CINE MRI were performed to capture the patient's central nervous system anatomy and CSF pulsatile flow velocities. An miCFD model was reconstructed from these MRIs and the patient's CSF flow velocities were computed. The effect of CSF pulsatility (frequency and stroke volume) was investigated for a bolus injection of a model drug at the L2 vertebral level. Drug distribution profiles along the entire spine were computed for different heart rates: 43, 60, and 120 bpm, and varied CSF stroke volumes: 1, 2, and 3 mL. To assess toxicity risk for patients with different physiological variables, therapeutic and toxic concentration thresholds for a common anesthetic were derived from experimental studies. Toxicity risk analysis was performed for an injection of a spinal anesthetic for patients with different heart rates and CSF stroke volumes. Both heart rate and CSF stroke volume of the patient strongly influence drug distribution administered intrathecally. Doubling the heart rate (from 60 to 120 bpm) caused a 26.4% decrease in peak concentration in CSF after injection. Doubling the CSF stroke volume diminished the peak concentration after injection by 38.1%. Computations show that potentially toxic peak concentrations due to injection can be avoided by changing the infusion rate. Using slower infusion rates could avoid high peak concentrations in CSF while maintaining drug concentrations above the therapeutic threshold. Our computations identify key variables for patient to patient variability in drug distribution in the spine observed clinically. The speed of drug transport is strongly affected by the frequency and magnitude of CSF pulsations. Toxicity risks associated with an injection can be reduced for a particular patient by adjusting the infusion variables with our rigorous miCFD model.

Application of phase - contrast cine magnetic resonance imaging (MRI) in endoscopic aqueductoplasty

Objective To evaluate the application of phase-contrast cine magnetic resonance imaging (MRI) in endoscopic aqueductoplasty for patients with obstructive hydrocephalus.Methods The clinical diagnosis of hydrocephalus due to aqueduct obstruction in 23 patients was confirmed by phase -contrast cine MRI examination.The patients were treated with endoscopic aqueductoplasty.MRI was repeated during follow- up period.The cerebrospinal fluid (CSF) flow velocity in aqueduct was measured to determine whether the aqueduct was obstructed.Results The Results of phase - contrast cine MRI examinations indicated that there was no CSF flow in aqueduct in any patient.Aqueductoplasty was successfully performed in all patients.after one week,the Results of phase - contrast cine MRI examinations showed an average CSF flow velocity of ( 4.74 ± 1.77 ) cm/s.During follow - up period,intracranial hypertension recurred in two patients in whom CSF flow was not seen inside the aqueduct by phase - contrast cine MRI scan and the aqueduct re - occlusion was revealed by endoscopic exploration.Conclusions By measuring CSF flow velocity,phase - contrast cine MRI could accurately identify whether the aqueduct is obstructed.It should play an important role in the diagnosis of obstructive hydrocephalus and evaluation of the effectiveness of aqueductoplasty,and it could be used for follow -up evaluation as well. Key words: Neuroendoscope ; Hydrocephalus ; Aqueductoplasty ; Phase - contrast eine MRI ; Cerebrospinal fluid flow ; Dynamics ;

Assessment of anatomic morphology of the connective structures among brain ventricles and cerebrospinal fluid movement in them by cerebrospinal fluid spin-labeling MRI

Objective To assess the anatomic morphology of the connective structures among brain ventricles and cerebrospinal fluid (CSF) movement in them by CSF spin-labeling MR imaging. Methods According to the order of registration, 50 healthy volunteers were randomly selected and received cerebrospinal fluid spin-labeling MR scan with time-spatial labeling inversion recovery single-shot fast spin echo sequence (SLIR-SSFSE). The tagged CSF was used as an endogenous tracer. The anatomic morphology of the connective structures of brain ventricles and the flow direction of CSF were observed. The longitudinal diameter and transverse diameter of bilateral foramina of monro, midbrain aqueduct, and the central and bilateral lateral apertures of the fourth ventricle of each subject were measured and calculated based on multiple measurements. The flow rate of CSF was calculated based on the flow distance of CSF in the connective structures between brain ventricles during different TI time. The mean value of each indicator was acquired. Results Two-way flow state of CSF was observed in all connective structures, including bilateral foramina of monro, midbrain aqueduct, and the central and bilateral lateral apertures of the fourth ventricle. On the coronal planes, foramen of monro appears as a Y-type tubular structure locating among the both sides of the anteriomedial thalamus and fornix, which connect upward with bilateral lateral ventricles and downward with the third ventricle. The longitudinal diameter and transverse diameter of the left side of foramen of monro were 3.50-5.50 mm[mean (4.37 ±0.47)mm]and 1.00-1.40 mm[mean(1.21 ±0. 13) mm], respectively. The longitudinal diameter and transverse diameter of the right side of foramen of monro were 4. 20-4. 80 mm[mean(4.42 ± 0.20) mm]and 1.00-1.60 mm[mean (1.21 ±0. 19) mm], respectively. On the sagittal planes, foramen of monro appeared as an oblique fine tubular structure with the angle of 55°-58° between the both sides. CSF flow velocity towards the foot was 1.61-2. 52 mm/s[mean (2. 00 ± 0. 17) mm/s]in the left side of foramen of monro and 1.93-2. 20 mm/s [mean (2.03 ±0.09) mm/s]in the right side of foramen of monro. On the sagittal planes, midbrain aqueduct appeared as a curved tubular structure through diencephalon, with the longitudinal diameter of 9.90-17.30 mm[mean(15.51 ± 1.70) mm]and the transverse diameter of 1.70-2.30 mm[mean (1.92 ± 0. 17)mm]. In midbrain aqueduct, CSF flow velocity towards the foot was about 5.00-8.74 mm/s[mean (7.84 ±0.86) mm/s]and towards the head was about 3.84-6.71 mm/s[mean (6. 01 ±0. 66) mm/s]. On the sagittal plane, the central apertures of the fourth ventricle appeared as a fork-like tubular structure, with a small bifurcation forward to the central canal of the medulla oblongata and a posterior branch downward to cerebellomedullary cistern. On the coronal plane, lateral apertures of the fourth ventricle appeaed as curved tubular structures connecting the lateral horn of the fourth ventricle and cerebellomedullary cistern. The longitudinal diameter and transverse diameter of the left lateral aperture were 6.30-14. 60 mm[mean (10.42 ±2.88) mm]and 1.00-1.50 mm[mean (1.24 ±0.18) mm],respectively; of the right lateral aperture, they were 6. 20-15.50 mm[mean (12. 13 ± 3.05) mm]and 1.00-1.40 mm[mean(1.19 ±0. 13) mm], respectively. The angle range between the left and right lateral aperture was from 87° to 114°. CSF flow velocity towards the foot was about 2. 89-6. 70 mm/s[mean (4. 78 ± 1.32) mm/s]in the left lateral aperture and 2. 84-7.11 mm/s[mean (5.56 ±1.40) mm/s]in the right lateral aperture. Conclusions CSF spin-labeling MR imaging could display the anatomic morphology of the connective structure among brain ventricles and could be used for noninvasively assessing CSF movement. Key words: Cerebrospinal fluid; Cerebral ventricles; Magnetic resonance imaging; Dissection

Monitoring of cerebrospinal fluid flow by intraoperative ultrasound in patients with Chiari I malformation

Objective To investigate the feasibility of intraoperative ultrasound (IOUS) for monitoring cerebrospinal fluid (CSF) flow in patients with Chiari I malformation. Methods Twenty patients with Chiari I were scanned by IOUS with color Doppler flow imaging (CDFI). CSF flow status and flow velocity were monitored at different times during the surgery. Results CSF flow was detected in all 20 cases by IOUS-CDFI in real time. CSF flow was extremely slow or even ceased following bony decompression (craniectomy + laminectomy) in 19 patients; however, bi-directional flow was observed in the systolic phase and cranially directed flow in the diastolic phase. The maximum flow rate ranged from 4 to 13 cm/s after duraplasty, and this varied with respiratory rhythm. Only 1 patient showed typical CSF flow after craniectomy, suggesting sufficient decompression, and without further duraplasty. All surgeries were terminated when bi-directional CSF flow was observed using IOUS-CDFI. With the exception of 1 patient, all the patients’ symptoms were significantly relieved. Conclusion IOUS-CDFI can monitor CSF flow during posterior fossa decompression, provide information about the re-circulation of CSF flow, and objectively evaluate the efficacy of surgery.

Insight into the patterns of cerebrospinal fluid flow in the human ventricular system using MR velocity mapping

The patterns of cerebrospinal fluid (CSF) flow within the human ventricular system are still not fully understood in all their complexity. Knowledge is based on either the interpretation of CSF flow curves or computational simulations. Both approaches only provide an incomplete insight into the spatial and temporal dynamics of CSF flow. Time-resolved three-dimensional magnetic resonance velocity mapping has previously been used to investigate normal and pathologic blood flow patterns in the human vascular system. Here we used this technique to study the spatial and temporal dynamics of CSF flow in the ventricular system of 40 normal volunteers. Classification of the patterns of CSF flow based on calculation of three-dimensional particle path lines over the cardiac cycle revealed one uniform flow pattern for the lateral ventricles, three categories for the third and two categories for the fourth ventricle. We found no significant aging effects on either the presence of a specific CSF flow pattern or on CSF flow velocities. Our results provide the first detailed demonstration of the patterns of CSF flow within the human ventricular system.

Mathematical Modeling of CSF Pulsatile Hydrodynamics Based on Fluid–Solid Interaction

Intracranial pressure (ICP) is derived from cerebral blood pressure and cerebrospinal fluid (CSF) circulatory dynamics and can be affected in the course of many diseases. Computer analysis of the ICP time pattern plays a crucial role in the diagnosis and treatment of those diseases. This study proposes the application of Linninger et al.'s [IEEE Trans. Biomed. Eng., vol. 52, no. 4, pp. 557-565, Apr. 2005] fluid-solid interaction model of CSF hydrodynamic in ventricular system based on our clinical data from a group of patients with brain parenchyma tumor. The clinical experiments include the arterial blood pressure (ABP), venous blood pressure, and ICP in the subarachnoid space (SAS). These data were used as inputs to the model that predicts the intracranial dynamic phenomena. In addition, the model has been modified by considering CSF pulsatile production rate as the major factor of CSF motion. The approximations of ventricle enlargement, CSF pressure distribution in the ventricular system and CSF velocity magnitude in the aqueduct and foramina were obtained in this study. The observation of reversal flow in the CSF flow pattern due to brain tissue compression is another finding in our investigation. Based on the experimental results, no existence of large transmural pressure differences were found in the brain system. The measured pressure drop in the ventricular system was less than 5 Pa. Moreover, the CSF flow pattern, ICP distribution, and velocity magnitude were in good agreement with the published models and CINE (phase-contrast magnetic resonance imaging) experiments, respectively.

CHARACTERISTICS OF CEREBROSPINAL FLUID FLOW IN CAVALIER KING CHARLES SPANIELS ANALYZED USING PHASE VELOCITY CINE MAGNETIC RESONANCE IMAGING

Syringomyelia is an important morbidity source in Cavalier King Charles Spaniels. Although abnormal cerebrospinal fluid (CSF) flow secondary to Chiari malformations is thought to cause syringomyelia in humans, this relationship is unknown in dogs. We used phase-contrast magnetic resonance (MR) imaging to evaluate CSF flow in dogs. Fifty-nine Cavalier King Charles Spaniels were assigned a neurologic grade reflecting their neurologic status. Five normal control dogs of other breeding were imaged for comparison. The presence of syringomyelia was noted from sagittal MR images. The pattern and velocity of CSF flow were assessed using phase-contrast cine MRI at the foramen magnum, C2-C3 disc space, and within syrinxes. Flow was measured most easily with the neck flexed to mimic standing. CSF flow velocity in the dorsal aspect of the subarachnoid space at the foramen magnum was significantly higher in control dogs than Cavalier King Charles Spaniels (P = 0.035). Flow was obstructed at the foramen magnum in 41 of 59 Cavalier King Charles Spaniels. Turbulent flow and jets were associated with syringomyelia presence and severity, and CSF flow velocity at C2/3 dorsally was inversely related to the presence of syringomyelia (P = 0.0197). Peak dorsal subarachnoid space CSF flow velocity at the foramen magnum and C2-C3 were together highly predictive of syringomyelia. CSF flow can be assessed in dogs using phase-contrast cine MRI. Obstruction to flow at the foramen magnum is common in Cavalier King Charles Spaniels and CSF flow pattern and velocity are related to the presence of syringomyelia.

Time‐resolved three‐dimensional (3D) phase‐contrast (PC) balanced steady‐state free precession (bSSFP)

In this study the feasibility of a time-resolved, three-dimensional (3D), three-directional flow-sensitive balanced steady-state free precession (bSSFP) sequence is demonstrated. Due to its high signal-to-noise ratio (SNR) in blood and cerebrospinal fluid (CSF) this type of sequence is particularly effective for acquisition of blood and CSF flow velocities. Flow sensitivity was achieved with the phase-contrast (PC) technique, implementing a custom algorithm for calculation of optimal gradient parameters. Techniques to avoid the most important sources of bSSFP-related artifacts (including distortion due to eddy currents and signal voids due to flow-related steady-state disruption) are also presented. The technique was validated by means of a custom flow phantom, and in vivo experiments on blood and CSF were performed to demonstrate the suitability of this sequence for human studies. Accurate depiction of blood flow in the cerebral veins and of CSF flow in the cervical portion of the neck was obtained. Possible applications of this technique might include the study of CSF flow patterns, direct in vivo study of pathologies such as hydrocephalus and Chiari malformation, and validation for the existing CSF circulation model.

Idiopathic Syringomyelia: Phase-Contrast MR of Cerebrospinal Fluid Flow Dynamics at Level of Foramen Magnum

To measure cerebrospinal fluid (CSF) flow velocities in the foramen magnum in patients with idiopathic syringomyelia (IS). Patient consent for this retrospective study was waived by the institutional review board within the guidelines of HIPAA. The authors reviewed the medical records of a neurosurgery specialty clinic to identify patients with IS-that is, syringomyelia without evidence of Chiari malformation, tumor, or substantial spine trauma. Patients without syringomyelia or Chiari malformation identified from the review served as control subjects. The data of patients and control subjects who had undergone phase-contrast magnetic resonance (MR) imaging were included in the study. MR flow images were inspected for evidence of synchronous bidirectional CSF flow and heterogeneous spatial and temporal flow patterns. Peak CSF flow velocities in the IS and control groups were calculated, and differences were tested for statistical significance by using the Wilcoxon rank sum test. Eight patients who met the criteria for IS and six who met the criteria to serve as control subjects were identified. The phase-contrast MR images obtained in five of the eight patients with IS and in none of the control subjects depicted synchronous bidirectional flow and/or large flow jets. Mean peak systolic (caudal) CSF flow velocities were 6.7 cm/sec in the IS group and 3.6 cm/sec in the control group; the difference was significant (P < .01). Mean peak diastolic (cephalic) velocities were 3.9 and 3.4 cm/sec in the IS and control groups, respectively; the difference was not significant (P = .36). Some patients with IS have increased peak systolic CSF flow velocities.

Endoscopic aqueductoplasty in the treatment of aqueductal obstructive hydrocephalus

Objective To study the application of endoscopic aqueductoplasty for the treatment of aqueductal obstructive hydrocephalus. Methods 16 cases of aqueductal obstructive hydrocephalus were treated with endoscopic aqueductoplasty under flexible neuron-endoscope in trans-frontal or stiboccipital approach respectively from Febrary 2007 to April 2008. Results All 16 patients had a sucessful aqueductoplasty with no complications related to aqueductoplasty such as disturbance of consciousness or oculomotor nerve paresis. The symptom of intracranial hypertension disappeared postoperatively. The maximal velocity of cerebrospinal fluid flow through aqueduct increased (2.18±0.34) cm/s and the maximal flux increased (0. 22±0. 07) ml/s detected by using cine phase-contrast magnetic resonance imaging 6 months postoperation in 12 cases. Conclusion Endoscopic aqueductoplasty with flexible neuron-endoscope is a safe and effective method for the treatment of obstructive hydrocephalus due to aqueductal stenosis or aqueductal membranous obstruction, but the operative indication should be obeyed strictly. Key words: Neuron-endoscope; Obstructive hydrocephalus; Aqueductal stenosis; Aqueductal membranous obstruction; Aqueductoplasty

Apparent Diffusion Coefficient and Cerebrospinal Fluid Flow Measurements in Patients With Hydrocephalus

To evaluate the efficacy of diffusion magnetic resonance imaging and compare with cerebrospinal fluid (CSF) flow imaging in patients with hydrocephalus before and after treatment. Twenty patients with hydrocephalus (group 1, pediatric, with primary aqueductal stenosis, n = 10; group 2, adult, with normal-pressure hydrocephalus, n = 10) and 20 age-matched healthy subjects that served as controls were examined. Cerebrospinal fluid flow velocity interval was calculated as the mean absolute values of the peak craniocaudal velocity and caudocranial velocity on CSF flow measurements. On diffusion magnetic resonance imaging, apparent diffusion coefficient (ADC) values from 8 regions were evaluated. The decrease in ADC values after treatment was significant in both groups (P < 0.001 for both). Preoperative mean CSF flow velocity interval value was significantly lower in group 1 and significantly higher than postoperative and control group values in group 2 (P < 0.001 for all). The ADC values increase in hydrocephalus and decrease significantly after treatment. Preoperative ADC value may serve as baseline, and the change in ADC may be an indicator of response to treatment and CSF flow measurements.