Treatment for secondary deterioration in idiopathic normal pressure hydrocephalus in the later course of the disease: a retrospective analysis.

Background: Cerebrospinal fluid (CSF) shunting is a highly effective treatment for idiopathic normal pressure hydrocephalus (iNPH). However, secondary deterioration can occur at a later time. Thus, the current study aimed to evaluate the incidence rate and causes of secondary deterioration.

Methods: A retrospective analysis was conducted on all patients with iNPH who were treated with implantation of a CSF shunt since 1993. A meticulous shunt workup was recommended to all patients who presented to our department with secondary deterioration during their follow-up visits. Data about the proportion of patients with such deterioration and its causes, subsequent treatment, and clinical outcome were obtained.

Results: A total of 169 patients were included, and the mean follow-up time was 69.2 months. In total, 119 (70.4%) patients presented with a total of 153 secondary deteriorations. In 9 cases (5.9%), the deterioration was caused by delayed subdural hematoma and in 27 (22.1%) cases, by shunt dysfunction. Invasive shunt testing was commonly required to validate shunt failure. Moreover, 19 of 27 patients experienced a satisfactory improvement after revision surgery. In total, 86 deteriorations were attributed to nonsurgical causes, and the valve pressure was decreased in 79 patients, with only 16.5% presenting with a satisfactory improvement after lowering of valve pressure.

Conclusions: Most patients with shunted iNPH presented with deterioration in the later course of the disease. Shunt dysfunction was considered a cause of secondary deterioration. Moreover, shunt revision surgery was a highly effective treatment, and patients with deterioration should undergo screening procedures for shunt dysfunction, including invasive shunt testing.