High-Resolution MRI for Evaluation of Ventriculostomy Tubes: Assessment of Positioning and Proximal Patency

Measuring CSF shunt flow with MRI using flow enhancement of signal intensity (FENSI)

PURPOSE

To develop and validate a noninvasive imaging technique for accurately assessing very slow CSF flow within shunt tubes in pediatric patients with hydrocephalus, aiming to identify obstructions that might impede CSF drainage.

THEORY AND METHODS

A simulation of shunt flow enhancement of signal intensity (shunt-FENSI) signal is used to establish the relationship between signal change and flow rate. The quantification of flow enhancement of signal intensity data involves normalization, curve fitting, and calibration to match simulated data. Additionally, a phase sweep method is introduced to accommodate the impact of magnetic field inhomogeneity on the flow measurement. The method is tested in flow phantoms, healthy adults, intensive care unit patients with external ventricular drains (EVD), and shunt patients. EVDs enable shunt-flow measurements to be acquired with a ground truth measure of CSF drainage.

RESULTS

The flow-rate-to-signal simulation establishes signal-flow relationships and takes into account the T1 of draining fluid. The phase sweep method accurately accounts for phase accumulation due to frequency offsets at the shunt. Results in phantom and healthy human participants reveal reliable quantification of flow rates using controlled flows and agreement with the flow simulation. EVD patients display reliable measures of flow rates. Shunt patient results demonstrate feasibility of the method and consistent flow rates for functional shunts.

CONCLUSION

The results demonstrate the technique's applicability, accuracy, and potential for diagnosing and noninvasively monitoring hydrocephalus. Limitations of the current approach include a high sensitivity to motion and strict requirement of imaging slice prescription.

MRI as a one-stop destination for evaluation of CSF shunt malfunction

Background

Despite the high-frequency rate of cerebrospinal fluid shunt malfunction, radiological evaluation of CSF shunts has remained deficient, focusing mainly on demonstrating secondary signs of shunt failure rather than evaluating the shunt tube itself. We aimed to study the utility of different MR pulse sequences in evaluating the cranial and abdominal ends of CSF shunts in order to identify the potential cause of shunt failure and its impact on patient management.

Results

Twenty-five patients (18 males, 7 females, median age 2.5 years, IQR 0.75–15) were enrolled in the study, having 28 ventriculo-peritoneal shunts and single ventriculo-gallbladder shunt. The catheter lumen and fine intraventricular septae were only demonstrated in 3D-DRIVE sequences (p < 0.001). Except for three patients (having cranial end-related complications), all patients with cranial and/or abdominal end-related complications received surgery (p < 0.001, positive likelihood and negative likelihood ratios = 7.27, 0.3, respectively, sensitivity = 0.7 and specificity = 0.9). MRI findings (luminal occlusion, disconnection, CSF collection, or migration) were consistent with operative data. There is no significant difference between patients who underwent surgery and those with conservative management, or symptomatic and asymptomatic patients in terms of the prevalence of ventricular dilatation or white matter signal abnormality. The results of the abdomino-pelvic fat-suppressed T2-WI showed excellent agreement with ultrasound findings (Cohen’s Kappa 0.9). Quantitative PC could give insights into CSF dynamics, which depend on the site and cause of shunt malfunction.

Conclusions

MRI could be a one-stop destination for evaluating patients with suspected non-acute shunt malfunction. It was found to have clinical relevance in terms of accurately locating the exact site and possible cause of shunt-related complications.

High-Resolution MRI to Evaluate Benefit of Middle Cerebral Artery Stenosis in Secondary Prevention in Patients with Acute Cerebral Infarction

High-resolution magnetic resonance (HRMRI) combined with magnetic resonance angiography (MRA) was used to analyze the correlation between the degree of infarction and the degree of cerebral vascular stenosis, and these patients are all have the trend to contain acute infarction. All patients were examined by CT cerebral angiography, which was analysed by conventional magnetic resonance imaging (MRI), high-Resolution (HRMRI) imaging, and cerebral vascular (MRA) imaging. The infarct size of each patient with cerebral infarction was calculated. The degree of middle cerebral artery stenosis was evaluated. Moreover, agnosis of acute cerebral infarction in middle cerebral artery region was calculated, and the correlation between acute cerebral infarction in middle cerebral artery region and the degree of cerebral vascular stenosis was analyzed. The specificity, sensitivity, and accuracy of magnetic resonance angiography (MRA) in the diagnosis of acute cerebral infarction in the blood supply area of the middle cerebral artery were 90.48%, 94.87%, and 93.94%. The coincidence rates for the degree of middle cerebral artery stenosis were 90.91% for mild stenosis, 92.31% for moderate stenosis, 93.75% for severe stenosis, and 85.71% for vascular occlusion, respectively. The K value was in good agreement with the results of CTA diagnosis (≥0.75). In conclusion, HRMRI can clearly indicated that the location of lesions with acute cerebral infarction, and MRA can show the degree of vascular stenosis, there is a close relationship between them.

Shunt Testing In Vivo: Illustration of Partially Obstructed Ventricular Catheter by In-Growing Choroid Plexus

Assessing shunt function in vivo presents a diagnostic challenge. Infusion studies can be a cost-effective and minimally invasive aid in the assessment of shunt function in vivo. We describe a case of a patient who after a foramen magnum decompression for type I Chiari malformation developed bilateral posterior fossa subdural hygromas and mild hydrocephalus, eventually necessitating insertion of a ventriculoperitoneal shunt. The patient returned with symptoms that were concerning for infection of the shunt. A bedside infusion study helped confirm that the ventricular catheter was partially obstructed by in-growing choroid plexus, but also that the shunt was no longer necessary. Partial blockage due to in-growing choroid plexus was confirmed during surgery to remove the shunt. We discuss the behaviour of in-growing choroid plexus and how partial obstruction can be detected with the use of an infusion study, as well as how this compares to the pattern observed in complete shunt obstruction. The benefits of using infusion studies in the assessment of shunt function are also explored.