Cine magnetic resonance imaging of aqueductal stenosis

Phase-contrast and three-dimensional driven equilibrium (3D-DRIVE) sequences in the assessment of paediatric obstructive hydrocephalus

BACKGROUND

Recently, most cases of hydrocephalus are related to obstruction. Accurate localization of the site of obstruction is crucial in determination of the treatment strategy.

PURPOSE

To describe the phase-contrast and 3D-DRIVE findings in cases of obstructive hydrocephalus in paediatric patients and to determine their functional and anatomical correlates.

MATERIAL AND METHODS

Brain MRIs of 25 patients (2 months to 11 years) with obstructive hydrocephalus were retrospectively reviewed. Phase-contrast and 3D-DRIVE were performed to assess cerebrospinal (CSF) pathways through the aqueduct of Sylvius and subarachnoid spaces. In addition to flow velocity measurement at the aqueduct of Sylvius, functional and anatomical correlation was analysed at the level of aqueduct of Sylvius, infracerebellar CSF space and at the third ventriculostomy using Spearman's rank test.

RESULTS

Aqueduct of Sylvius was the most common site of obstruction (19 patients) either secondary to focal, multifocal or tubular stenosis, adhesions, or secondary to extrinsic compression. Functional and anatomical correlation was analysed in 58 regions revealing strong correlation (ro = 0.8, p < .001). Functional anatomical mismatch was found in nine regions. Flow velocity measurements revealed diminished flow in most of the cases with obstruction at the aqueduct and normal velocity in cases with obstruction proximal to aqueductal level, while accelerated flow was seen in cases with infra-aqeuductal obstruction.

CONCLUSION

Phase-contrast and 3D-DRIVE sequences are essential sequences in the diagnosis of hydrocephalus enabling perfect localization of the site of obstruction. Both sequences should be interpreted in conjunction to avoid false results. Velocity measurements through the aqueduct can help understand CSF hydrodynamics.

Hydrocephalus presenting as idiopathic aqueductal stenosis with subsequent development of obstructive tumor: report of 2 cases demonstrating the importance of serial imaging

The authors describe 2 cases of triventricular hydrocephalus initially presenting as aqueductal stenosis that subsequently developed tumors of the pineal and tectal region. The first case resembled late-onset idiopathic aqueductal stenosis on serial imaging. Subsequent imaging revealed a new tumor in the pineal region causing mass effect on the midbrain. The second case presented in a more typical pattern of aqueductal stenosis during infancy. On delayed follow-up imaging, an enlarging tectal mass was discovered. In both cases hydrocephalus was successfully treated by cerebrospinal fluid diversion prior to tumor presentation. The differential diagnoses, diagnostic testing, and treatment course for these unusual cases are discussed. The importance of follow-up MRI in cases of idiopathic aqueductal stenosis is emphasized by these exemplar cases.

Phase-contrast MRI and 3D-CISS versus contrast-enhanced MR cisternography on the evaluation of the aqueductal stenosis

INTRODUCTION

In the current study, we aimed to compare the diagnostic efficacies of phase-contrast magnetic resonance imaging (PC-MRI) and three-dimensional constructive interference in steady-state (3D-CISS) sequence over detection of aqueductal stenosis (AS) on the basis of contrast-enhanced magnetic resonance cisternography (MRC).

METHODS

Twenty-five patients with clinically and radiologically suspected AS were examined by PC-MRI, 3D-CISS, and MRC. Axial-sagittal PC-MRI and sagittal 3D-CISS were applied to view the cerebral aqueduct. Following injection of 0.5-1 ml intrathecal gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) injection, postcontrast MRC images were obtained in three planes in early and late phases. Aqueductal patency was scored as follows: grade 0, normal; grade 1, partial narrowing; and grade 2, complete obstruction. Results of PC-MRI and 3D-CISS were compared with the findings of MRC.

RESULTS

In PC-MRI, seven cases were assessed as grade 0, 16 cases grade 1, and two cases grade 2. As a result of 3D-CISS sequence, eight cases were evaluated as grade 0, 12 cases grade 1, and five cases grade 2. Based on MRC, nine cases were assessed as grade 0, whereas nine and seven cases were evaluated to be grades 1 and 2, respectively. Five cases that demonstrated partial patency in PC-MRI or 3D-CISS showed complete obstruction by MRC.

CONCLUSION

PC-MRI is helpful in confirming the AS. However, positive flow does not necessarily exclude the existence of AS. 3D-CISS sequence provides excellent cerebrospinal fluid-to-aqueduct contrast, allowing detailed study of the anatomic features of the aqueduct. MRC should be performed on patients who demonstrate suspected AS findings on PC-MRI and/or 3D-CISS sequences.

Phase-contrast cine MRI versus MR cisternography on the evaluation of the communication between intraventricular arachnoid cysts and neighbouring cerebrospinal fluid spaces

INTRODUCTION

The objective of this study was to evaluate the role of phase-contrast cine magnetic resonance imaging (PC-MRI) in detecting possible communications between intraventricular arachnoid cysts (IV-ACs) and cerebrospinal fluid (CSF) spaces based on MR cisternography (MRC) comparison.

MATERIALS AND METHODS

Twenty-one patients with IV-AC were examined by PC-MRI and MRC. In order to determine the communication of IVAC with its neighbouring CSF spaces, PC-MRI was employed. The communication of IV-ACs with the ventricular system was examined on at least two anatomic planes. Precontrast images and PC-MRI were followed by the intrathecal administration of 0.5-1 ml gadopentetate dimeglumine. Early and delayed MRC were then carried out. Results of PC-MRI were compared with findings of MRC (McNemar's test).

RESULTS

In seven IV-ACs, no communication was detected by PC-MRI. In 14 IVACs, a pulsatile CSF flow into the IV-ACs was observed. All the IV-ACs, which have been determined as non-communicating (NC) on the PC-MRI, showed NC character on MRC as well. Six cases suggesting a communication on PC-MRI showed no communication on MRC. MRC revealed eight communicating (38%) and 13 NC (62%) IV-ACs among a total of 21 cases. The sensitivity and specificity of PC-MRI imaging in demonstrating the communication between the IV-ACs and the CSF were 100% and 54%, respectively.

CONCLUSION

PC-MRI is an effective method for evaluating NC IV-ACs. In order to decide about the management of IV-ACs, which are communicating according to the PC-MRI, the results should be confirmed with MRC if suspected jet flow is depicted.

Evaluation of CSF flow patterns of posterior fossa cystic malformations using CSF flow MR imaging

INTRODUCTION

Differential radiologic diagnosis of cystic malformations of the posterior fossa is often difficult with conventional imaging techniques because of overlapping features of these entities. Posterior fossa cystic malformations occupy the cerebrospinal fluid (CSF) spaces. They may create secondary dynamic effects on the movements of CSF. The aim of this study was to investigate CSF flow alterations in posterior fossa cystic malformations with CSF flow MR imaging.

METHODS

The study included 40 patients with cystic malformations of the posterior fossa. The patients underwent cardiac-gated phase-contrast cine MR imaging. CSF flow was qualitatively evaluated using an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format.

RESULTS

Twelve of the patients had communicating arachnoid cyst, seven had non-communicating arachnoid cyst, ten had mega cisterna magna, six had Dandy-Walker malformation, two had Dandy-Walker variant, and three had Blake's pouch cyst. CSF flow MR imaging indicated the regions of no, slow or higher flow, direction of flow, and abnormal cystic fluid motion. Each malformation displayed a distinct CSF flow pattern.

CONCLUSION

Phase-contrast cine MR imaging for CSF flow evaluation may be a useful adjunct to routine MR imaging in the evaluation of the cystic malformations of the posterior fossa because it can improve the specificity in differentiating such malformations.

How should primary aqueductal stenosis in adults be treated? A review

In 10% of adult patients with hydrocephalus, the cause is because of aqueductal stenosis (AS), causing enlargement of the lateral and third ventricles. There are currently two alternate forms of surgical treatment for AS; shunt surgery and ventriculostomy. Shunt surgery is associated with high complication rates and many patients need revisions, but the effectiveness is high. Endoscopic third ventriculostomy (ETV), re-establishing a physiological route of CSF dynamics, has become the treatment of choice for AS in most neurosurgical centers. ETV has fewer complications and revisions are rare, but some patients need shunt surgery to improve despite a patent ventriculostomy. There are today no common criteria for patient selection to either ETV or ventriculo-peritoneal shunt surgery.

Endoscopic aqueductoplasty in the treatment of aqueductal stenosis

OBJECTIVE

Endoscopic aqueductoplasty is an option in the treatment of obstructive hydrocephalus caused by aqueductal stenoses. We report on our experience with this endoscopic technique, focussing on indications, operative technique, and results.

METHODS

A series of 39 endoscopic aqueductoplasties was performed in 33 patients harbouring a hydrocephalus caused by aqueductal stenosis. In 13 patients, a third ventriculostomy was simultaneously performed. There was no endoscopy-related mortality. One aqueductoplasty had to be abandoned. In 7 patients, reclosure of the restored aqueduct required an endoscopic revision. In 25 patients (76%), the hydrocephalus-related symptoms resolved or improved. The condition was unchanged in 8 patients. Four patients needed to be shunted. The ventricles decreased in size in 22 patients (67%), were larger in 2, and unchanged in the remaining 9 patients.

CONCLUSION

Endoscopic aqueductoplasty is a treatment option in patients with hydrocephalus caused by membranous aqueductal stenosis. Unfortunately, the reclosure rate is higher than initially expected. More experience and longer follow-up are necessary to determine the value of endoscopic aqueductoplasty in the treatment of hydrocephalus caused by aqueductal stenosis.

CSF flow quantification of the cerebral aqueduct in normal volunteers using phase contrast cine MR imaging

Objective

To evaluate whether the results of cerebrospinal fluid (CSF) flow quantification differ according to the anatomical location of the cerebral aqueduct that is used and the background baseline region that is selected.

Materials and Methods

The CSF hydrodynamics of eleven healthy volunteers (mean age = 29.6 years) were investigated on a 1.5T MRI system. Velocity maps were acquired perpendicular to the cerebral aqueduct at three different anatomical levels: the inlet, ampulla and pars posterior. The pulse sequence was a prospectively triggered cardiac-gated flow compensated gradient-echo technique. Region-of-interest (ROI) analysis was performed for the CSF hydrodynamics, including the peak systolic velocity and mean flow on the phase images. The selection of the background baseline regions was done based on measurements made in two different areas, namely the anterior midbrain and temporal lobe, for 10 subjects.

Results

The mean peak systolic velocities showed a tendency to increase from the superior to the inferior aqueduct, irrespective of the background baseline region, with the range being from 3.30 cm/sec to 4.08 cm/sec. However, these differences were not statistically significant. In the case of the mean flow, the highest mean value was observed at the mid-portion of the ampulla (0.03 cm³/sec) in conjunction with the baseline ROI at the anterior midbrain. However, no other differences were observed among the mean flows according to the location of the cerebral aqueduct or the baseline ROI.

Conclusion

We obtained a set of reference data of the CSF peak velocity and mean flow through the cerebral aqueduct in young healthy volunteers. Although the peak systolic velocity and mean flow of the CSF differed somewhat according to the level of the cerebral aqueduct at which the measurement was made, this difference was not statistically significant.

Differences in cerebrospinal fluid dynamics do not affect the levels of biochemical markers in ventricular CSF from patients with aqueductal stenosis and idiopathic normal pressure hydrocephalus

To compare levels of biochemical markers in ventricular cerebrospinal fluid (vCSF) between patients with aqueductal stenosis (AS) and idiopathic normal pressure hydrocephalus (INPH) and relate these results to clinical outcome after surgery. Neurofilament light protein, tau protein, sulfatide, vasoactive intestinal peptide (VIP), neuropeptide PYY (NPY) and CSF/serum albumin ratio were measured in vCSF from 18 consecutive AS and 19 consecutive INPH patients. Clinical outcome was evaluated after surgery by standardized indices. The levels of markers were related to clinical outcome. No differences in any of the markers were found between AS and INPH patients. The concentration of sulfatide and albumin ratio correlated inversely with psychometric improvement, whilst VIP and NPY correlated inversely with improvement in alertness. The similar levels of biochemical markers in vCSF from AS and INPH patients indicate similarities in pathophysiology and turnover rate of vCSF despite differences in CSF dynamics. High albumin ratio and sulfatide concentrations in vCSF in hydrocephalus patients have negative implications for surgical outcome and might indicate concomitant cerebrovascular disorder.

Neurological symptoms and signs in adult aqueductal stenosis

OBJECTIVE

To comprehensively describe and compare prospectively (pre/postoperatively) the symptomatology in aqueductal stenosis (AS) vs idiopathic normal pressure hydrocephalus (INPH).

METHODS

Twenty-seven patients with AS and 39 patients with INPH were consecutively included. Postural functions, gait, wakefulness, cognitive functions, urinary continence and headache were examined before and 3 months after treatment with shunt operation or endoscopic ventriculostomy.

RESULTS

The AS patients had better postural functions, walked faster, performed better cognitively and had a higher wakefulness than INPH patients, but these differences were explained by age differences between groups. The frequency of incontinence was similar in the two patients groups. Headache occurred more frequently in AS, but independently of the other symptoms. Most symptoms and signs improved after surgery.

CONCLUSION

Patients with AS had a higher frequency of headaches than INPH patients, but otherwise the symptomology of the two groups was not found to differ after correcting for age differences.

Validation of the coupling of magnetic resonance imaging velocity measurements with computational fluid dynamics in a U bend

Magnetic resonance imaging (MRI) can be used in vivo in combination with computational fluid dynamics (CFD) to derive velocity profiles in space and time and accordingly, pressure drop and wall shear stress distribution in natural or artificial vessel segments. These hemodynamic data are difficult or impossible to acquire directly in vivo. Therefore, research has been performed combining MRI and CFD for flow simulations in flow phantoms, such as bends or anastomoses, and even in human vessels such as the aorta, the carotid, and the abdominal bifurcation. There is, however, no unanimity concerning the use of MRI velocity measurements as input for the inflow boundary condition of a CFD simulation. In this study, different input possibilities for the inflow boundary conditions are compared. MRI measurements of steady and pulsatile flow were performed on a U bend phantom, representing the aorta geometry. PAMFLOW (ESI Software, Krimpen aan den Ussel, The Netherlands), an industrial CFD software package, was used to solve the Navier-Stokes equations for incompressible flow. Three main parameters were found to influence the choice of an inflow boundary condition type. First, the flow rate through a vessel should be exact, since it proves to be a determining factor for the accuracy of the velocity profile. The other decisive parameters are the physiology of the flow profile and the required computer processing unit time. Our comparative study indicates that the best way to handle an inflow boundary condition is to use the velocities measured by MRI at the inflow plane as being fixed velocities. However, before using these MRI velocity data, they first should be corrected for the partial volume effect by filtering and second scaled in order to obtain the correct flow rate. This implies that a reliable flow rate measurement absolutely is needed for CFD calculations based on MRI velocity measurements.

Resolving obstructive hydrocephalus from AVM

Obstructive hydrocephalus with deterioration of consciousness from a ruptured arteriovenous malformation (AVM) requires urgent decompression, but also vigilance during the preoperative stage in case of rare spontaneous resolution.

SPAMM, cine phase contrast imaging and fast spin-echo T2-weighted imaging in the study of intracranial cerebrospinal fluid (CSF) flow

AIM

To compare the qualitative assessment of cerebrospinal fluid (CSF) flow using a SPAMM (spatial modulation of magnetization) technique with cine phase contrast images (cine PC) and fast spin echo (FSE) T2-weighted images.

MATERIALS AND METHODS

SPAMM, PC and T2-weighted sequences were performed on 22 occasions in 19 patients. Eleven of the studies were performed following a neuroendoscopic third ventriculostomy (NTV), and in these cases, the success of the NTV was determined by clinical follow-up. Two observers used consensus to grade the presence of CSF flow at nine different sites for each study.

RESULTS

At 14 of the 178 matched sites, which could be assessed by both SPAMM and cine PC, SPAMM CSF flow grade was higher than that of cine PC. At a further 14/178 matched sites, the cine PC grade was higher than that of SPAMM. There was definite CSF flow at 113/182 (62%) of all the cine PC sites assessed, and 110/181 (61%) of all SPAMM sites assessed whilst 108/198 (54%) of FSE T2-weighted image sites demonstrated flow voids. Cine PC grades were higher than SPAMM at the cerebral aqueduct (P < 0.05, Wilcoxon sign rank test). Definite CSF flow within the anterior third ventricle was present in 4/5 (SPAMM) and 3/5 (cine PC) successful NTVs, 0/2 (SPAMM and cine PC) unsuccessful NTVs and 1/10 (SPAMM and cine PC) patients without NTV.

CONCLUSION

SPAMM provides a comparable assessment of intracranial CSF flow to that of cine phase contrast imaging at all CSF sites except the cerebral aqueduct.

Analysis of aqueductal cerebrospinal fluid flow after endoscopic aqueductoplasty by using cine phase-contrast magnetic resonance imaging

OBJECT

The purpose of this prospective study was to evaluate aqueductal cerebrospinal fluid (CSF) flow after endoscopic aqueductoplasty. In all patients, preoperative magnetic resonance (MR) imaging revealed hydrocephalus caused by aqueductal stenosis and lack of aqueductal CSF flow.

METHODS

In 14 healthy volunteers and in eight patients with aqueductal stenosis who had undergone endoscopic aqueductoplasty, aqueductal CSF flow was investigated using cine cardiac-gated phase-contrast MR imaging. For qualitative evaluation of CSF flow, the authors used an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format. Quantitative through-plane measurements were performed in the axial plane perpendicular to the aqueduct. Evaluation revealed no significant difference in aqueductal CSF flow between healthy volunteers and patients with regard to temporal parameters, CSF peak and mean velocities, mean flow, and stroke volume. All restored aqueducts have remained patent 7 to 31 months after surgery.

CONCLUSIONS

Aqueductal CSF flow after endoscopic aqueductoplasty is similar to aqueductal CSF flow in healthy volunteers. The data indicate that endoscopic aqueductoplasty seems to restore physiological aqueductal CSF flow.

Analysis of aqueductal cerebrospinal fluid flow after endoscopic aqueductoplasty by using cine phase-contrast magnetic resonance imaging

Object

The purpose of this prospective study was to evaluate aqueductal cerebrospinal fluid (CSF) flow after endoscopic aqueductoplasty. In all patients, preoperative magnetic resonance (MR) imaging revealed hydrocephalus caused by aqueductal stenosis and lack of aqueductal CSF flow.

Methods

In 14 healthy volunteers and in eight patients with aqueductal stenosis who had undergone endoscopic aqueductoplasty, aqueductal CSF flow was investigated using cine cardiac-gated phase-contrast MR imaging. For qualitative evaluation of CSF flow, the authors used an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format. Quantitative through-plane measurements were performed in the axial plane perpendicular to the aqueduct. Evaluation revealed no significant difference in aqueductal CSF flow between healthy volunteers and patients with regard to temporal parameters, CSF peak and mean velocities, mean flow, and stroke volume. All restored aqueducts have remained patent 7 to 31 months after surgery.

Conclusions

Aqueductal CSF flow after endoscopic aqueductoplasty is similar to aqueductal CSF flow in healthy volunteers. The data indicate that endoscopic aqueductoplasty seems to restore physiological aqueductal CSF flow.

Risk factors for failure of endoscopic third ventriculostomy for obstructive hydrocephalus

OBJECTIVE

This is a retrospective study to identify risk factors for failure in the treatment of obstructive hydrocephalus with endoscopic third ventriculostomy (ETV).

METHODS

The records for 89 patients, including 32 with ventriculoperitoneal or ventriculoatrial shunt malfunctions or infections, who underwent ETVs between 1993 and 1998, at our institution, were examined. Multiple variables possibly related to failure were considered. These included age, sex, cause of hydrocephalus, presence and function of ventriculoperitoneal/ventriculoatrial shunts, history of shunt revisions or infections, symptoms, preoperative imaging results, presence of retained shunt catheters, postoperative meningitis, and postoperative ventricular size.

RESULTS

Twenty-nine patients (32.6%) required subsequent shunt replacement and/or ETV revision. Of these 29 reoperations, 12 procedures (41.4%) were performed within 2 weeks and only 3 were performed more than 10 months after the initial ETV procedure. The ventricular size remained unchanged in 75% of the cases on the day after ETV, in 57.4% at 3 months, in 48.2% at 6 months, and in 41.8% at 1 year. Cine phase-contrast magnetic resonance imaging findings were consistent with postoperative symptomatic resolution in 96.3% of the cases. Seven patients (7.9%) experienced complications related to ETV, all of which were transient. Significant risk factors in univariate analyses were as follows: presence of Chiari Type I malformation (P = 0.003), shunt infection at presentation (P = 0.014), history of shunt infections (P = 0.0004), three or more previous shunt revisions (P = 0.0018), and postoperative meningitis (P = 0.0001). Late-onset idiopathic aqueductal stenosis was a significant predictor of good outcomes (P = 0.044). These factors were reanalyzed in a multivariate analysis, which confirmed a history of shunt infections and postoperative meningitis as independent risk factors.

CONCLUSION

The risk of failure increases with intracerebral infection, likely because of obliteration of cerebrospinal fluid pathways.

Endoscopic aqueductoplasty: technique and results

OBJECTIVE

The purpose of this study was to determine the safety and efficacy of endoscopic aqueductoplasty in patients with hydrocephalus caused by aqueductal stenosis. The controversy of third ventriculostomy and aqueductoplasty is discussed.

METHODS

A series of 17 patients who underwent endoscopic aqueductoplasty is reported. Rigid rod-lens scopes were used for inspecting the aqueductal entry and performing balloon aqueductoplasty. With the aid of a 2.5-mm flexible endoscope, the aqueduct and fourth ventricle were explored and aqueductal membranous obstructions were perforated. Third ventriculostomies were performed simultaneously in nine patients. One aqueductal stent was inserted. In six patients, frameless computerized neuronavigation was used for an accurate approach to the aqueduct. The average duration of the endoscopic procedures was 59 minutes (range, 25-100 min).

RESULTS

There was no endoscopy-related mortality. Surgical complications included an asymptomatic fornix contusion and two injuries to the aqueductal roof, which resulted in permanent diplopia due to dysconjugate eye movement (one patient) and transient trochlear palsy (one patient). In addition, two patients developed transient dysconjugate eye movements, and one patient had an asymptomatic epidural hematoma. Eleven patients showed improvement in their symptoms. The conditions of five patients were unchanged. One patient died of stroke 1 month after the operation. No patient required shunting. The ventricles decreased in size in nine patients and were unchanged in the remaining eight patients.

CONCLUSION

Endoscopic aqueductoplasty is an effective alternative to third ventriculostomy for the treatment of hydrocephalus caused by short aqueductal stenosis. However, longer follow-up periods are necessary to evaluate long-term aqueductal patency after aqueductoplasty.

Transient hydrocephalus due to movement of a clot plugging the aqueduct

A rare case of transient hydrocephalus is reported. A 64-year-old woman presented with headache. Computerized tomography (CT) scan revealed hydrocephalus with tiny blood clots in the left foramen of Monro and in the aqueduct. Six hours after the onset, the signs and symptoms disappeared spontaneously. The second CT showed improvement of the hydrocephalus with migration of the clot into the i.v. ventricle. Aqueductal trapping and releasing of the clot formed by bleeding from the choroid plexus located in the left foramen of Monro was suspected for the origin of the transient hydrocephalus.