Ventricular Anatomy and Shunt Catheters

Abstract

A functioning shunt must have a patent proximal catheter within the cerebrospinal fluid space. Occlusion with choroid plexus or ependymal tissue might be expected if these tissues are in contact with the proximal inlets. This study was undertaken to define the intraventricular distances available for a standard-placement shunt cather and to compare the available distances with actual ventricular catheter inlets. In 52 normal subjects (age range from 1 month to 20 years; median 7.7 years) magnetic resonance imaging was used to measure the dimensions of the anterior horn in planes typically used for cather placement. For anterior placements, the intraventricular length (ventricle entry to the foramen of Monro) was measured for a standardized catheter route ('As') and for a route yielding a maximum lenght ('Amax'). For posterior placements, the length (ventricle tip to foramen of Monro) was obtained for a standardized catheter placement to the ipsilateral ('Pi') and the contralateral ventricle ('Pc') as well as measuring a maximum length in a curved trajectory ('Pmax'). The average length (and range) in centimeters for the various trajectories was: As = 1.5 (1.1-1.9), Amax = 1.7 (1.2-2.2), Pi = 1.6 (1.2-2.1), Pc = 2.0 (1.4-2.9), and Pmax = 2.8/3.1 (2.1-3.6). Minor variations from a standard shunt insertion site did not affect the length of catheter within the ventricle. Current ventricular catheters have proximal inlets extending 1.6-2.4 cm from the catheter tip. Variations in standard ventricular catheter placement should have no measurable effect on how much ventricle is available for the proximal catheter. It may not be possible to place a standard ventricular catheter and keep the inlets within the ventricle and placed consistently away from choroid plexus and ependyma, regardless of approach. This may contribute to the similar proximal occlusion rates reported for the differing placements. Subsequent studies of shunt placement should correlate proximal occlusion rates with ventricular size. To prevent ventricular size from directly affecting proximal conclusion, consideration should be given to altering the design of ventricular catheters by placing inlets over a shorter distance (1.0 cm) from the tip.

Dorsal Bony Septum: A Split Cord Malformation Variant

“…In other words, the lesions in our patients were consistent with SCM. Our cases are similar to the cases reported by Erşahin [4]and Chandra and Mahapatra [3]. These lesions could not be classified as type I or type II SCMs according to the unified theory.…”

“…Chandra and Mahapatra [3]reported a different case of dorsally situated bony spur in 1999 which could not be explained by the unified theory, and they proposed a slight modification of the unified theory. They hypothesized two mechanisms responsible for the occurrence of that rare lesion: (1) passage of an abnormal cell population dorsally and subsequent loss of contact with the ventrally situated cell population; (2) migration of cells first around the hemicords and then passing between them in a dorsoventral direction.…”

“…Thus, we need a new hypothesis to explain these entities. Although Chandra and Mahapatra [3]and Ersahin [4]tried to explain this situation with different hypotheses, in our opinion, further embryological studies must be conducted to evaluate such hypotheses.…”

“…dural investment of the hemicords and the nature of the midline mesenchymal derivates. Although this classification covers almost all types of SCMs, there are a few cases that cannot be classified according to this system [3, 4]. …”

What We Should Know About the Cellular and Tissue Response Causing Catheter Obstruction in the Treatment of Hydrocephalus

“…Acceptable CSF hydrodynamics have been generated from a catheter with only 1 patent hole, 136 and other ongoing work has implied that fewer holes or holes with a shorter distance to the tip may decrease the risk of tissue infiltration. 127,137 The role of shear stress may also play a role in how the number of holes alters adhesion since fewer holes are likely to increase shear stress through the remaining holes. Another consideration is whether the holes should be replaced by an open-ended lumen, with research efforts focused on methods to inhibit tissue infiltration during surgery (Kehler's peel-away sheath may help in this case).…”