The Additive Value of Radionuclide Shuntogram to Computed Tomography in Evaluation of CSF Shunts

Background: Placement of cerebrospinal fluid diversions or shunts, is a common neurosurgical procedure indicated for a wide spectrum of conditions impeding the normal flow of cerebrospinal fluid (CSF). The most common systems employed are ventriculoperitoneal, ventriculoatrial and lumboperitoneal shunts. Management of patients with surgically treated hydrocephalus may be challenging, as the clinical presentation of a malfunctioning shunt is often nonspecific, especially in young children. Moreover, conventional radiological examinations, such as shunt series, cerebral ultrasound or CT scans, are sometimes equivocal in diagnosing cases of shunt malfunction, also in determining the site of obstruction. Thus, numerous procedures have been proposed to ascertain shunt function, and localize site of obstruction. Injection of contrast media and radionuclide directly into the shunt device into the lateral ventricles is one of the most common techniques employed, to assist in evaluating shunt function. Patients and methods: A prospective study of 20 patients with suspected shunt malfunction. Their age, sex distribution, clinical presentations, and causes of hydrocephalus were recorded. We evaluated shunt function using CT brain and Radionuclide shuntogram. Shunt malfunction was evaluated by using CT-Brain only, Shuntogram only, and by combining both techniques. We evaluated these techniques regarding their results, dividing them into positive and negative cases, and establishing true and false results by following clinical progression and operative findings. After calculating sensitivity, specificity, predictive values and accuracy of the individual techniques, we determined the added value of combining shuntogram to CT-Brain in diagnosing shunt malfunction. Results: Patients were verified into 15 males (75%) and 5 females (25%), the average age was 5.8 years. In evaluation using CT brain only, the results were 19 true positive results (95%), one case with false positive result (5%) and no negative cases (100% sensitivity and 95% accuracy). In Radionuclide shuntogram, results were: 18 true positive studies (90%); one true negative study (5%), one false negative study (5%) and no false positive results (94.73% sensitivity and 95% accuracy). The combined results of CT brain and Radionuclide shuntogram were 18 true positive cases (where both tests showed positive obstruction), no negative cases, and 2 cases with conflicting results (100% sensitivity and 100% accuracy). The sites of true positive cases verified into 13 distal blocks (65%), 5 proximal blocks (25%) and one case with combined proximal and distal blocks (5%). Conclusion: In adding shuntogram to CT-Brain, the sensitivity and accuracy for diagnosis of shunt obstruction increased. Its advantage over other methods lies in not only diagnosing shunt malfunction but also localizing and qualifying the malfunction, thus aiding the neurosurgeon in targeting the part of the shunt requiring revision. Because of its limitation (time and costs involved in shuntogram technique), it's not used routinely in clinical practice. But, when used in selected cases, it can help avoid unnecessary surgical intervention.