Response to journal club: role of endoscopic third ventriculostomy and ventriculoperitoneal shunt in idiopathic normal pressure hydrocephalus: preliminary results of a randomized clinical trial.

R esponding to the invitation, we kindly consider the Journal ClubCritical Analysis and respond to questions raised. We thank Neurosurgery for this particularly amazing forum for discussion and improvement of papers and scientific information. We also thank Drs Ghobrial and Lang for their attention to our work and astounding critical analysis and discussion. Objectively, idiopathic normal pressure hydrocephalus (INPH) is still not fully understood in its physiopathology, and literature pertaining to the surgical management of INPH exists largely in the form of retrospective cohort studies; high level studies are still lacking. Difficult concepts of physiopathology and clinical settings contribute to the heterogeneous samples of patients even in welldesigned studies. Currently, surgical options for treating INPH are ventriculoperitoneal shunt (VPS) and endoscopic third ventriculostomy (ETV). VPS is by far the most commonmethod used to treat INPH worldwide. Once INPH was recognized as a classic communicant hydrocephalus, ETV was somehow not encouraged in its management. Nevertheless, recent use of ETV has been reported in the form of retrospective data, demonstrating neurological improvement in up to 69% of patients. Severe limitations of this study are the less stringent diagnostic criteria, which fail to discriminate secondary normal pressure hydrocephalus (NPH) from INPH. These intriguing facts lead us to enroll patients to compare radiological and clinical patterns of evolution according to the treatment modality adopted (VPS vs ETV). We faced important limitations, which compose almost half of our discussion. However, they were, point-by-point, necessary. The Tap Test was the only preoperative test used for the treatment of patients due to its advantages of applicability, validity, and availability. Prolonged lumbar drain is certainly the gold standard, and it does not require greater technique expertise. However, an availability limitation was also present, considering the Brazilian public health system. We also believe that use of nonprogrammable valves may decrease, but not invalidate, the quality of the data presented by the study. Current evidence clearly points to the superiority of programmable valves over nonprogrammable ones. There are several medical diseases that present with the same symptoms as the classic triad of NPH, and we are unable to control entirely all of those diseases. For example, a large number of patients with dementia-like syndromes have been categorized as having Alzheimer’s disease, and symptoms that are not typical of Alzheimer’s disease may be present in such patients. This contributes to heterogeneity of groups evaluated. Our study sample may be the most questioned point. Indeed, 25 patients in each study arm seem to be a small number; however, we disagree with the need to evaluate 878 patients in each study arm. A larger sample size of patients would surely strengthen the conclusions of this preliminary study, and thus it would not be called preliminary anymore. We calculated our sample size based on the Altman nomogram and the following formula, testing the difference between the means in the Berg Balance Scale (before and after surgery) in both treatment groups.