◊The peritoneum is an efficient site of fluid absorption
Components: ventriculostomy catheter, pressure-sensitive valve + reservoir, barium-integrated silicone peritoneal catheter
- symptoms of increased intracranial pressure: seizures, headache, nausea, vomiting, lethargy, irritability
- persistent bulging of anterior fontanel
- excessive rate of head growth
- slowed refill of shunt reservoir; abdominal pain, fever
Cause: occlusion of catheter by choroid plexus / glial tissue, discontinuity of tubes
- sutural diastasis + increased size of cranial cavity
- increasing ventricular size:
- interval increase since last exam
- enlargement of temporal horns (earliest finding)
- preferential enlargement of temporal horns in infants
N.B.:- no enlargement with scarring of ventricular walls
- marked ventricular dilatation does not necessarily indicate shunt malfunction
- shuntogram (by scintigram / contrast radiography) determines site of obstruction
- brain edema tracking along shunt + within interstices of centrum semiovale (with partial obstruction)
- formation of white matter cyst surrounding ventricular catheter
Obstruction of VP Shunt
Location: ventricular end >peritoneal end
Cause: plugging of the catheter by brain parenchyma / choroid plexus / proteinaceous material / tumor cells; adhesions within peritoneum
NUC: 99mTc-albumin colloid injected into shunt tubing proximal to reservoir:
- no uptake within ventricles + normal peritoneal activity (= proximal obstruction)
Contrast study (injection of nonionic contrast material into shunt reservoir):
- collection of contrast material at peritoneal end of shunt without spillage (= distal obstruction)
Disconnection & Breaks of VP Shunt
Location: connection of tubing to reservoir, at Y-connectors, areas of great mobility (neck)
DDx: pseudo-disconnection ← radiolucent tube components
Migration of VP Shunt
- Proximal catheter: into soft tissues of neck / unusual locations within CNS
- Distal catheter: peritoneal cavity, thorax, abdominal wall, scrotum, perforation into GI tract
Leakage of VP Shunt
= CSF escape without complete break / disconnection
- palpable cystic mass
- contrast verifies leak site
CSF Pseudocyst of VP Shunt
- shunt tubing coiled in an abdominal soft-tissue mass
US / CT:
- cyst surrounding catheter tip
Cx: bowel obstruction
Incidence: 1–5–38%
Time of onset: within 2 months of shunt placement
- intermittent low-grade fever
- anemia, dehydration, hepatosplenomegaly
- stiff neck; swelling + redness over shunting tract; peritonitis
- ventriculitis (= enlarged ventricles with irregular enhancing ventricular wall ± septations)
- meningitis (= enhancement of cerebral cortical sulci)
Abdominal Complications of VP Shunt
- Ascites
- Pseudocyst formation
- Perforation of viscus / abdominal wall
- Intestinal obstruction
- Metastases to peritoneum: germinoma, medulloblastoma, astrocytoma, glioblastoma
Subdural Hematoma / Hygroma of VP Shunt
Cause: precipitous drainage of markedly enlarged ventricles
Age: usually seen in children >3 years of age with relatively fixed head size
Prognosis: small hematomas resolve on their own
Granulomatous Lesion of VP Shunt
= rare granulomatous reaction adjacent to shunt tube within / near ventricle
- irregular contrast-enhancing mass along course of shunt tube
Slit Ventricle Syndrome (0.9–3.3%)
= proximal shunt failure from ventricular collapse
Cause: overdrainage of CSF, intermittent shunt obstruction, decreased intracranial compliance, periventricular fibrosis, intracranial hypotension
Incidence: 0.9–3.3%
- intermittent / chronic headaches, vomiting, malaise
- slowed refill of shunt reservoir
- small / slitlike ventricles