Letter: Prepontine Shunting for Pseudotumor Cerebri in Previously Failed Shunt Patients: A 5-Year Analysis.

Abstract

To the Editor: We read the article by White et al1 with great enthusiasm and interest. Pseudotumor cerebri (PTC) is an enigmatic neurological disease that has puzzled neurologists and neurosurgeons for the past few decades. PTC is a condition of raised intracranial pressure for obscure reasons. It has a complex pathophysiological mechanism that has not yet been completely comprehended and may indeed have various etiologies. Surgical intervention is indicated when conservative treatment fails, and there is a progressive visual deterioration. Cerebrospinal fluid (CSF) diversion and optic nerve sheath fenestration (ONSF) are the 2 routinely utilized surgical options to treat PTC. The interesting article of White et al1 highlights an important issue of shunt malfunction in PTC and shares important findings on prepontine shunting in PTC shunts with previous shunt malfunction. The authors present a retrospective series of a cisterno-peritoneal shunt (CPS) in 49 PTC patients with previous 2 shunt malfunctions when followed up for a period of 3 yr.1 The authors have reported a body mass index (BMI) range from 29 to 58 with a mean BMI of 48 in these patients. This finding is in line with other studies proposing that higher shunt failure rates in patients with PTC might be related to higher BMI.2 We congratulate authors for presenting a technically demanding procedure of prepontine-peritoneal shunt placement in slit-like ventricles and the unfavorable anatomy of the third ventricle floor. It is interesting to note that shunt failure rates were higher for lumboperitoneal shunt (70.8% at 2 yr) as compared to ventriculoperitoneal shunt (50% at 2 yr). This is in contrast with other studies in which failure rates were reported to be higher for ventriculoperitoneal shunt than lumboperitoneal shunt or almost similar.3,4 It is interesting to know if the stereotaxy guided placement of ventriculoperitoneal shunt resulted in longer functioning of shunt than lumboperitoneal shunt. The study should be interpreted in light of certain limitations as mentioned by the authors. Shunt series is not found to be a reliable screening tool to assess shunt patency, as it found shunt-related pathology only 3.9% times in a series of 25 patients.5 Programmable and pressure-regulated devices are reported to have lower failure rates in idiopathic intracranial hypertension (IIH) and can confound the results in a comparative study.6 The technique described by authors for prepontine shunt placement includes perforation of the third ventricle floor similar to endoscopic third ventriculostomy (ETV).1 ETV has been described as feasible, safe, and effective in symptom resolution in IIH patients with favorable ventricular anatomy.7 Though authors have mentioned ETV having low success scores, it is one of the important limitations and very difficult to answer whether the working status of CPS shunt is a result of third ventriculostomy created during shunt insertion. The authors in the present study have followed up the patients for 3 yr, but the time to shunt failure in IIH patients, though less than non-IIH hydrocephalus, is reported to be up to 57 mo. Hence, a longer follow-up period of these patients will shed light on the longevity of prepontine shunt placement in IIH patients. Papilledema is identified as an independent risk factor predicting shunt revisions.8 It is important to stress that many IIH patients have spontaneous CSF leak, and these patients have raised intracranial pressure in the absence of visual symptoms and papilledema.9,10 Accordingly, some patients might have been left out from the study because of the inclusion criteria, as authors have only included patients with visual symptoms and papilledema. A recent study has found that CSF shunting was successful in maintaining an improved or stable visual capacity during follow-up.11 Complications of shunt placement include shunt obstruction, shunt infections, abdominal complications, and shunt migration. Because shunt failure happens quite frequently, shunt modifications are often required.12 Karsy et al13 reported that stereotactic biventricular shunt placement is safe in IIH patients with 2.9% complications of proximal shunt catheter at 41.9 mo with no case of proximal catheter onstruction.11 Furthermore, ONSF and dural venous sinus stenting address different pathological mechanisms in patients with PTC.14 This is an interesting field for further studies as the incidence of PTC is increasing alongside the increase in obesity globally. Despite some limitations, the findings of this study are important and notable, as they add value to a technique in the neurosurgeon's armamentarium for managing IIH. More studies with larger cohorts and longer time to follow-up would shed more light on the longevity of CPS shunts in IIH patients. Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.