Cerebrospinal Fluid Lumbar Tapping Utilization for Suspected Ventriculoperitoneal Shunt Under-Drainage Malfunctions

OBJECTIVE: The diagnosis of shunt malfunction can be challenging since neuroimaging results are not always correlated with clinical outcomes. The purpose of this study was to evaluate the efficacy of a simple, minimally invasive cerebrospinal fluid (CSF) lumbar tapping test that predicts shunt under-drainage in hydrocephalus patients. METHODS: We retrospectively reviewed the clinical and radiological features of 48 patients who underwent routine CSF lumbar tapping after ventriculoperitoneal shunt (VPS) operation using a programmable shunting device. We compared shunt valve opening pressure and CSF lumbar tapping pressure to check under-drainage. RESULTS: The mean pressure difference between valve opening pressure and CSF lumbar tapping pressure of all patients were 2.21±24.57 mmH₂O. The frequency of CSF lumbar tapping was 2.06±1.26 times. Eighty five times lumbar tapping of 41 patients showed that their VPS function was normal which was consistent with clinical improvement and decreased ventricle size on computed tomography scan. The mean pressure difference in these patients was −3.69±19.20 mmH₂O. The mean frequency of CSF lumbar tapping was 2.07±1.25 times. Fourteen cases of 10 patients revealed suspected VPS malfunction which were consistent with radiological results and clinical symptoms, defined as changes in ventricle size and no clinical improvement. The mean pressure difference was 38.07±23.58 mmH₂O. The mean frequency of CSF lumbar tapping was 1.44±1.01 times. Pressure difference greater than 35 mmH₂O was shown in 2.35% of the normal VPS function group (2 of 85) whereas it was shown in 64.29% of the suspected VPS malfunction group (9 of 14). The difference was statistically significant (p=0.000001). Among 10 patients with under-drainage, 5 patients underwent shunt revision. The causes of the shunt malfunction included 3 cases of proximal occlusion and 2 cases of distal obstruction and valve malfunction. CONCLUSION: Under-drainage of CSF should be suspected if CSF lumbar tapping pressure is 35 mmH₂O higher than the valve opening pressure and shunt malfunction evaluation or adjustment of the valve opening pressure should be made.

Comparison of the CT and Pathologic Findings of Pulmonary Fat Embolism Induced by Triolein and Oleic Acid in Rabbits

PURPOSE: The aim of this study was to evaluate the CT findings of pulmonary fat embolism syndrome that was induced by triolein and oleic acid, along with its pathologic correlation. MATERIALS AND METHODS: 16 rabbits were included in this study. The rabbits in group I (n=8) were embolized with 0.2 mL triolein and the rabbits of group II (n=8) were embolized with 0.2 mL oleic acid through ear veins. HRCT scans were done prior to embolization and at 0.5, 4, 24, 48 and 72 hours post-embolization. The pathologic correlations were determined at 0.5, 24, 48 and 72 hours. RESULTS: At 24 hours, one group I rabbit showed abnormal CT findings that were composed of several 2-3 mm nodules and multiple ill-defined peripheral ground glass opacities. The pathologic finding of this rabbit at 48 hours was mainly intraarveolar edema. All the group II rabbits (n=8/8) showed ill-defined bilateral and peripheral ground glass opacities with (n=6/8) or without consolidations (n=2/8) on the 0.5 hour CT. All the rabbits (n=7/7) showed that the new ground glass opacities and ground glass opacities noted on the 0.5 hour CT were changed into consolidation. The margins of the ground glass opacities and consolidations were more sharpened on the 24 hours CT. All 6 rabbits (n=6/6) showed consolidations without ground glass opacities and the margins of the consolidations were more sharpened on the 48 hours CT. There was no significant interval change on the 72 hours CT. The pathologic findings of ground glass opacities were interstitial edema or mild intraalveolar edema. The pathologic findings of consolidation were intraalveolar edema, hemorrhage and coagulation necrosis. CONCLUSION: The CT findings after fat embolization using triolein and oleic acid were ill-defined peripheral ground glass opacities with/without consolidations. These findings occurred in only one triolein group with the time lag, but these findings were immediately and extensively seen in all group II rabbits. These CT findings may be important for making a diagnosis of pulmonary fat embolism syndrome.