Types of shunt

Description

Receded VP shunts historically but are now infrequently placed due to risks of endocarditis, cor pulmonale, shunt nephritis, and the potential for propagation into the heart or pulmonary artery of a blood clot on the distal catheter (pulmonary embolus) or the distal catheter itself in the event of a disconnection. Another significant liability of VA shunts is the predictable failure that accompanies natural growth of the child as the fixed-length distal (atrial) catheter is gradually pulled out of the heart. In a VA shunt the distal end of the catheter resides at the junction of the superior vena cava and the right atrium. The primary indication for a VA shunt in contemporary practice is peritoneal insufficiency in a child who is not a candidate for or who has failed ETV. Peritoneal insufficiency may result from a variety of conditions, such as necrotizing enterocolitis of infancy, multiple VP shunt infections, omphalocele, or intraperitoneal infections, which may arise from bowel perforation or because of intra-abdominal surgery such as bladder augmentation in the spina bifida population.

Second or third line treatment due to limited/variable capacity of the pleural cavity to reabsorb fluid, particularly in infants and small children. It can be a useful temporizing intervention if intra-abdominal infection or peritoneal insufficiency prevents distal catheter. Contraindications to implantation of the catheter in the chest include active chest infection, compromised pulmonary reserve, and a history of thoracic surgery, which would increase the risk for adhesions. A preoperative chest radiograph is important in ruling out pneumonia, pleural effusion, or congenital anomalies, which may have an impact on patient risk and hence candidacy for VPI shunt implantation.

VP shunts are the most commonly placed and most versatile shunts for long-term management of hydrocephalus. Peritoneal location overtook atrium pronounced absorptive capacity of the (even injured or diseased) peritoneum to absorb fluid and the universally observed decreased severity of complications in comparison to atrial shunts (e.g. endocarditis, shunt nephritis). VP shunts simply represent the best available treatment for patients with hydrocephalus who are not candidates for ETV.

CSF is diverted from the lateral ventricle to a small pocket that is gently dissected beneath the galea. From this location, CSF enters the cervical lymphatics and can be absorbed gradually for several weeks or months. The function of the distal slits in the subgaleal shunt is to ensure unidirectional flow into a subgaleal fluid collection. VSG shunts offer a unique advantage over the alternative shunt system widely used for posthemorrhagic hydrocephalus of the neonate (the ventricular reservoir shunt): the VSG shunt drains continuously and does not have to be serially tapped. Another significant advantage of the VSG shunt is that its simple valve design does not appear to be sensitive to the presence of considerable amounts of blood or protein. Wound failure is a common problem with these procedures because of the delicate quality and inherent fragility of neonatal skin. In practical terms, last about 8-12 weeks and play a very valuable role in temporizing until more definitive treatment with a VP shunt can be accomplished (and has more acceptable anesthetic risks and less risk for hydrocephalus).

Indicated where serial taps of CSF or cysts fluid will be required over an extended period of time when symptomatic, e.g. in posthemorrhagic hydrocephalus of the newborn, aggressive CNS neoplasm that requires intrathecal delivery of chemotherapy, or craniopharyngioma cyst.