Characteristics of patients with idiopathic normal pressure hydrocephalus for whom neurosurgeons hesitate to perform shunt surgery: a nationwide hospital-based survey in Japan

Background: There is a lack of consensus regarding the indications for shunt surgery in patients with idiopathic normal pressure hydrocephalus (iNPH) who present with physical or mental disorders. This study is the first nationwide analysis investigating current approaches of neurosurgeons to iNPH treatment and shunt surgery adaptation for patients with iNPH. Methods: We developed a questionnaire in collaboration with neurosurgeons and dementia specialists. From October 10 to December 11, 2023, the survey was conducted at 1,220 facilities. Results: A total of 656 facilities (53.8%) responded. Of them, 30 (4.6%) had a policy of not performing shunt surgery for patients with iNPH, and 139 (21.2%) did not perform any shunt surgeries in 2022. The most common number of shunt surgeries performed in 2022 was 1–5 surgeries per facility, accounting for 257 facilities (57.1%). Regarding indications for shunt surgery, 159 (35.3%) responded that age was not considered. Among 268 facilities (59.6%) that considered age, 155 (57.8%) responded that patients aged ≥90 years were not indicated for shunt surgery. Among 450 facilities (68.6%) that performed shunt surgery at least once in 2022, the percentages of facilities that hesitated to perform it due to the presence of cerebrovascular disease, orthopedic disease, dialysis, Parkinson’s syndrome, Alzheimer’s disease (AD), schizophrenia, “absence of disproportionately enlarged subarachnoid space hydrocephalus (DESH),” and “not receiving adequate care/institutionalized” were 45 (10.0%), 52 (11.5%), 134 (29.8%), 88 (19.5%), 192 (42.7%), 199 (44.2%), 187 (41.5%), and 252 (56.0%), respectively. To identify factors that influence the indications for shunt surgery, logistic regression analysis was performed. The results showed that the number of shunt surgeries performed in 2022 was significant predictor of age ≥90 years, cerebrovascular disease, Parkinson’s syndrome, AD, no DESH, and “not receiving adequate care/institutionalized.” Significant predictors for dialysis, AD, and schizophrenia included the presence of collaborating internal medicine facilities. For dialysis and AD, the classification of facilities and having a qualified dementia specialist were significant predictors, respectively. Conclusions: Characteristics of patients with iNPH for whom Japanese neurosurgeons hesitate to perform shunt surgery included patients aged ≥90 years; those with comorbid AD and schizophrenia, no DESH; and those “not receiving adequate care/institutionalized.”