The Quest for Predicting Sustained Shunt Response in Normal-Pressure Hydrocephalus: An Analysis of the Callosal Angle's Utility

BACKGROUND: Diagnosing normal-pressure hydrocephalus (NPH) and selecting patients who will experience a sustained benefit from fluid diversion surgery remains challenging. This study seeks to evaluate the association between the callosal angle (CA) and the long-term postoperative response to ventriculoperitoneal shunt surgery in a different subgroup population than previously studied to assess its generalizability. METHODS: We studied 72 patients with idiopathic NPH who underwent ventriculoperitoneal shunt surgery and had at least 18 months of follow-up between 2000 and 2016. We recorded their pre- and postoperative symptoms according to the NPH Eide scale and their comorbidities with the Kiefer index. Their CA, as well as Evans' Index, ventricular height, and transependymal signal were measured. Multivariable statistical models were used to determine which factors were associated with postoperative improvement while we controlled for the presence of the NPH triad. RESULTS: Fifty-nine patients (82%) demonstrated a successful response to surgery at their first postoperative follow-up. However, this declined to 54 patients (75%) at 1 year and 45 (62.5%) patients at their last follow-up. When we controlled for the presence of the triad of symptoms, the CA significantly predicted a good, sustained response to surgery; for every degree decrease in the CA, a patient is 4% more likely to experience benefit from surgery. CONCLUSIONS: The CA is a useful preoperative prognostic tool for predicting which patients will experience a sustained benefit from surgery. Further studies are required to clarify this disease in the context of old age, comorbidity, and possible concomitant neurodegenerative diseases.