Intraventricular fat from retrograde flow through a lumboperitoneal shunt.

We present a case of intraventricular fat deposits discovered on magnetic resonance imaging and computed tomography in the absence of a ruptured dermoid cyst. The patient is a 25-year-old right-handed African-American female who previously had lumboperitoneal (LP) shunt placement for pseudotumor cerebri. She had multiple shunt-related complications that required two revisions as well as an incisional hernia repair. We suggest that the presence of fat in her ventricles is due to retrograde flow from abdominal fat during the time when the shunt tip was located in the anterior abdominal wall as opposed to her peritoneum. Unlike ventriculoperitoneal shunts, LP shunts do not contain valves, making retrograde passage of fat possible when abdominal pressures exceed lumbar subarachnoid pressures. The presence of these small amounts of fat in the ventricles is unlikely to cause any further symptoms in this patient, but monitoring for any blockage of cerebrospinal fluid flow or neurologic deterioration would be advisable.