Mechanism for measurement of flow rate of cerebrospinal fluid in hydrocephalus shunts.

The measurement of the flow rate of cerebrospinal fluid (CSF) or existence of CSF flow inside the shunt tube after shunt implant have been reported as tedious process for both patients and doctors; this paper outlines a potential in vitro flow rate measurement method for CSF in the hydrocephalus shunt. The use of implantable titanium elements in the shunt has been proposed to allow for an accurate temperature measurement along the shunt for prediction of CSF flow rate. The CSF flow velocity can be deduced by decoupling the thermal transfer in the measured differential time at a pair of measurement spots of the titanium elements. Finite element analyses on the fluidic and thermal behaviors of the shunt system have been conducted. Preliminary bench-top measurements on a simulated system have been carried out. The measured flow rates, ranging from 0.5 mm/sec to 1.0 mm/sec, which is clinically practical, demonstrate good agreements with the simulation results.

Prenatal diagnosis of herniated Dandy-Walker cysts.

OBJECTIVE: The purpose of this series is to describe the prenatal diagnosis and pregnancy outcome of fetuses affected with Dandy-Walker malformation in which a posterior cyst herniated through a bony defect of the occipital skull, foramen magnum, or both. METHODS: Two- and 3-dimensional sonography were used to examine 2 fetuses with poorly delineated cerebellar structures and a large posterior cystic neck mass. Fetal magnetic resonance imaging (MRI) was added to this evaluation as a complementary diagnostic modality. RESULTS: Three-dimensional sonography helped characterize the precise site of cyst herniation through the occipital skull or foramen magnum. Fetal MRI confirmed the sonographic findings. Neonatal MRI studies identified heterotopic gray matter as evidence of a neuronal migration disorder in both fetuses. The second fetus also had agenesis of the corpus callosum. Retrospective review of the fetal MRI (25.9 weeks' menstrual age) and 3-dimensional sonographic (18.7 weeks' menstrual age) studies confirmed ventricular wall nodularity involving the occipital horns of the second fetus. CONCLUSIONS: The antenatal detection of a large posterior cystic neck mass and a poorly defined or nonvisualized cerebellar vermis suggest Dandy-Walker malformation with a herniated cyst. Three-dimensional sonography and fetal MRI are important adjunctive methods that can be used to evaluate the herniation site and a possible neuronal migrational disorder.