Emergency department management of ventriculoperitoneal cerebrospinal fluid shunts

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

BACKGROUND AND PURPOSE

Imaging evaluation of ventriculostomy tubes, despite the frequency of malfunction, has remained inadequate due to the absence of a systematic way of assessing the catheter itself. In this retrospective review, we assessed the utility of high-resolution 3D MR imaging techniques, including CISS and volumetric interpolated breath-hold examination sequences, in the evaluation of ventriculostomy catheters.

MATERIALS AND METHODS

We performed a retrospective review of 23 clinical MR imaging cases of shunted hydrocephalus spanning a 3-year period, all depicting ventriculostomy catheters. The MR imaging examinations included isotropic CISS and volumetric interpolated breath-hold examination sequences performed with and without contrast. These were independently evaluated by 2 neuroradiologists with respect to the catheter course, side hole position, relationship of the side holes to the ventricles, patency, and the presence or absence of intraluminal debris.

RESULTS

The catheter tip was best seen on isotropic CISS sequences reformatted in an oblique plane, and side holes were visualized as CSF signal defects along the catheter wall in 10/23 (43%) cases. The relationship of the catheter side holes to the ventricles was seen in 47% of cases and was best visualized on the coronal CISS sequences. Catheter patency was confirmed in 12/23 (52%) cases, while the other 48% were notable for T2 hypointense filling defects compatible with luminal obstruction. Enhancement of some of these filling defects on imaging is suggestive of choroid plexus ingrowth rather than debris.

CONCLUSIONS

High-resolution 3D MR imaging using isotropic CISS sequences allows systematic evaluation of catheter positioning, patency, and potential etiologic differentiation of filling defects when shunt dysfunction is suspected.

Test characteristics of neuroimaging in the emergency department evaluation of children for cerebrospinal fluid shunt malfunction

Objective:

Cerebrospinal fluid (CSF) shunt malfunction is one of the most common life-threatening neurosurgical conditions. In the emergency department (ED), imaging techniques to identify shunt malfunction include the shunt series (SS) and CT scanning of the head. We sought to determine the test characteristics of the SS and CT scan for identifying children with shunt malfunction.

Methods:

We retrospectively reviewed the medical records of children with a CSF shunt who presented to our tertiary care pediatric emergency department and received an SS during a 2-year period from Jan. 1, 2001, to Dec. 31, 2002. A pediatric neuroradiologist reviewed all SS and CT scans. We defined shunt malfunction as present if the child underwent operative shunt revision.

Results:

We identified 437 ED visits by 280 children. Forty-seven SS were read as abnormal. A CT scan was performed in 386 (88.3%) cases and 80 were abnormal. Shunt malfunction was identified in 131 (30.0%) children. Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio of the SS for identifying cases of shunt malfunction were 30.0%, 95.8%, 72.3%, 75.1%, 7.1 and 0.7, respectively; for the CT scan, they were 61.0%, 82.7%, 64.5%, 80.5%, 3.5 and 0.5, respectively.

Conclusion:

Neuroimaging has a low sensitivity for identifying shunt malfunction. Neurosurgical consultation should be sought if shunt malfunction is clinically suspected, despite normal imaging.

Comparison of rapid cranial MRI to CT for ventricular shunt malfunction

OBJECTIVES

To compare the accuracy of rapid cranial magnetic resonance imaging (MRI) with that of computed tomography (CT) for diagnosing ventricular shunt malfunction.

METHODS

We performed a single-center, retrospective cohort study of children ≤21 years of age who underwent either rapid cranial MRI or cranial CT in the emergency department (ED) for evaluation of possible ventricular shunt malfunction. Each neuroimaging study was classified as "normal" (unchanged or decreased ventricle size) or "abnormal" (increased ventricle size). We classified a patient as having a ventricular shunt malfunction if operative revision for relief of mechanical causes of altered shunt flow was needed within 72 hours of initial ED evaluation. Our primary analysis tested noninferiority of the accuracy of rapid cranial MRI to CT for diagnosing shunt malfunction (noninferiority margin 10%).

RESULTS

We included 698 ED visits for 286 unique patients, with a median age at visit of 10.0 years (interquartile range 5.9-15.5 years). Patients underwent CT in 336 (48%) or rapid cranial MRI in 362 (52%) of ED visits for evaluation of possible shunt malfunction. Patients had operative revision for ventricular shunt malfunction in 140 ED visits (20%). The accuracy of rapid cranial MRI was not inferior to that of CT scan for diagnosing ventricular shunt malfunction (81.8% MRI vs 82.4% CT; risk difference 2.0%; 95% confidence interval, -4.2% to 8.2%).

CONCLUSIONS

Rapid cranial MRI was not inferior to CT for diagnosing ventricular shunt malfunction and offers the advantage of sparing a child ionizing radiation exposure.

Additive value of nuclear medicine shuntograms to computed tomography for suspected cerebrospinal fluid shunt obstruction in the pediatric emergency department

OBJECTIVE

To measure the predictive value of nuclear medicine studies (cerebrospinal fluid [CSF] shuntograms) and radiographic studies (computed tomographic [CT] scans) in a cohort of children undergoing evaluation for suspected shunt obstruction in a tertiary care pediatric emergency department (ED).

METHODS

A retrospective chart review was conducted on patients younger than 18 years who presented to the pediatric ED of the Children's Hospital of Western Ontario and had both CT of the head and a CSF shuntogram ordered by the attending pediatric emergency medicine physician between December 1998 and April 2003 because of suspected shunt obstruction.

RESULTS

A total of 69 patients were evaluated for suspected shunt obstruction in the ED during this period with both a CT and a CSF shuntogram. Twenty-seven patients (39.1%) subsequently required corrective surgery for suspected shunt obstruction that was confirmed intraoperatively. The CT scans showed abnormalities suggestive of CSF shunt obstruction in 21 of the patients who required surgery (sensitivity, 77.8%; negative predictive value, 82.4%), whereas the CSF shuntograms showed abnormalities suggestive of CSF obstruction in 25 of the patients who required surgery (sensitivity, 92.6%; negative predictive value, 92.6%). The CT scans and the shuntograms combined revealed abnormalities suggestive of CSF shunt obstruction in 26 of the 27 patients who required surgery (sensitivity, 96.3%; negative predictive value, 97.4%).

CONCLUSIONS

Over one third of pediatric ED patients evaluated with CT and CSF shuntograms required surgical management. Sensitivity was increased with CT and CSF shuntogram compared with CT alone. Prospective studies are required to assess the use of radiographic and nuclear medicine tests for the shunt evaluation in conjunction with the development of a clinical prediction rule for the pediatric emergency physician.

Radiographic evaluation for suspected cerebrospinal fluid shunt obstruction

OBJECTIVE

To measure the predictive value of plain radiographs (shunt series) and computed tomography (CT) scans in a group of children undergoing evaluation for suspected shunt obstruction in a tertiary care pediatric emergency department (ED).

METHODS

Radiology reports were reviewed for all ED patients who underwent a shunt series over an 18-month period. Two investigators categorized all reports as normal, possibly abnormal (eg, kink in shunt tubing, no prior CT scan for comparison), or abnormal (with definite evidence of shunt dysfunction, such as shunt tubing disconnection and increase in ventricular size since prior CT scan). Studies for which there was disagreement were re-read independently by a pediatric radiologist. Medical records were reviewed to determine outcomes.

RESULTS

A total of 233 patients had shunt series and CT scans ordered. Of these, 60 patients subsequently required surgery for shunt obstruction. The shunt series revealed abnormalities in 12 patients (sensitivity, 20%; negative predictive value, 22%), whereas CT scans showed definite or possible abnormalities in 50 patients (sensitivity, 83%; negative predictive value, 93%). Combined, the two tests detected 53 shunt obstructions (sensitivity, 88%; negative predictive value, 95%). Two obstructed patients had abnormalities on shunt series that would not have been suspected after physical examination or CT scan.

CONCLUSIONS

Over one quarter of pediatric ED patients evaluated radiographically for suspected shunt obstruction required surgical management. One in eight obstructed patients had normal radiographic studies. Routine performance of shunt series had a low overall yield but on rare occasions detected abnormalities that were missed by CT. Prospective studies are needed to improve the use of radiographic tests for shunt evaluation and determine clinical indications for further workup when studies are normal.