It is common to evaluate children with suspected CSF shunt malfunctions using CT of the head or, more recently, “quick brain” MRI. However, the reliability of using ventricular behavior, as assessed on cranial imaging during previous presentations with shunt obstructions, is not well defined. The authors conducted a study to determine if CT or MRI of ventricular morphology added useful clinical information in the evaluation of shunt malfunctions.
A retrospective chart review of children operated on at Texas Children's Hospital from February 20, 2011, to June 18, 2013, for shunt obstruction was conducted. Inclusion criteria involved age 3 years or older in patients who had undergone two or more shunt revisions for intraoperatively confirmed obstructions. Patients with shunt infection but without shunt obstruction and patients with fourth ventricular shunt failure were excluded from the study. Preoperative CT or MRI results were dichotomized into two distinct categories, as determined by a radiologist's report: either dilation of the ventricular system in comparison with prior scans at points the shunt was deemed functional, or no dilation of the ventricular system in comparison such scans. Determination of the presence of shunt obstruction was assessed by findings documented by the surgeon in the operative report. Each case was then analyzed to see if the patient has a reliable pattern of ventricular dilation, or no dilation, at times of shunt obstruction.
Forty-two patients (25 males and 17 females) were included in the study. There were a total of 117 patient encounters analyzed and an average of 2.79 encounters per patient. The mean age at shunt failure presentation was 10.8 years (range 3–23 years). In 4 encounters, patients presented with a CSF leak or pseudomeningocele. Twenty-seven patients (64%) consistently demonstrated dilation of the ventricular system during episodes of shunt obstruction. Four patients (10%) consistently demonstrated no dilation during episodes of shunt obstruction. Eleven patients (26%) demonstrated inconsistent changes in ventricular size at times of shunt obstruction. In those first patient encounters with shunt obstruction presenting with ventricular dilation, 92% (49 of 53) of subsequent encounters demonstrated ventricular dilation with shunt obstruction presentations.
Historical CT or MRI data regarding ventricular morphology patterns seen during prior examinations of shunt obstructions may inform a clinician's judgment of shunt obstruction on subsequent presentations, but they are not conclusive. In the present series, the authors found that changes in the morphology of a given patient's ventricular system when shunt obstruction occurs were often consistent and predictable, but not always. It remains imperative, however, that cranial images obtained to rule out shunt malfunction be compared with prior studies.