Cystoperitoneal Shunt Malfunction in Setting of Rifampin Allergy Presenting as Cerebrospinal Fluid Eosinophilia

Background: Cerebral spinal fluid eosinophilia (CSFe) is correlated with increased risk of cranial shunt malfunctions. Although antibiotics coated shunt catheters have significantly reduced the incidence of infections and associated shunt malfunction, on rare occasion they may contribute to a shunt allergy and become the source of subsequent malfunction. Objective: We present a very rare case of a patient with an arachnoid cyst treated with cysto-peritoneal shunt (CPS), complicated by rifampin allergy manifesting as sterile CSFe and subsequent shunt malfunction. Case Report: A 17-months-old-male with symptomatic arachnoid cyst underwent uneventful craniotomy for cyst fenestration and CPS placement. At 2-month follow up he was neurologically stable; however, he developed an expanding pseudomeningocele that was palpable at the site of the prior craniotomy. Although shunt and pseudomeningocele taps were both negative for infectious etiology, the CSF analysis was notable for isolated CSFe. Given the persistence of symptoms, and well as subsequent emergency room visits for abdominal swelling, low-grade fevers, and intermittent presence of pseudomeningocele, patient was admitted for further workup. Radio-Allergosorbent testing (RAST) was performed and revealed newly diagnosed rifampin allergy. CPS was then removed and patient was treated with a course of steroids until resolution of CSFe, and underwent placemen of a new CPS with non-antibiotics coated catheter. One week after discharge, patient returned with Staphylococcus Aureus related shunt malfunction, for which the shunt was externalized. He underwent a course of antibiotics treatment and was subsequently trialed to be weaned off the CPS, in light of recent cyst fenestration. A ventriculogram revealed complete occlusion of the prior cyst fenestration, thus patient underwent repeat craniotomy for more aggressive cyst fenestration. He was eventually weaned off the shunt and did not require further catheter placement. Discussion: CSFe is associated with underlying infection, inflammatory changes, and hypersensitivity. This can be seen in up to 30% of shunt malfunctions. In the above case, the Rifampin allergy contributed to elevated levels of CSFe and secondary shunt failure. The inflammatory response may have contributed to the closure of initial fenestration, shunt failure, and granulomatous response. Conclusion: Classic presentations of the allergy to the shunt catheter or its associated antibiotic coating are nonspecific and difficult to distinguish from primary infection. In complex cases, where an underlying cause is undetermined, particularly in the setting of isolated elevated CSFe and persistent non-specific shunt related symptoms, further workup is warranted. This case also highlights the need for improved biocompatibility of shunt hardware to avoid conditions leading to shunt malfunction.