Hydrocephalus in aqueductal stenosis--a retrospective outcome analysis and proposal of subtype classification

Treatment of aqueductal stenosis (AQS) has undergone several paradigm shifts during the past decades. Currently, endoscopic ventriculostomy (ETV) is recommended as treatment of choice. Several authors have addressed the issue of variable ETV success rates depending on age and pathogenetic factors. However, success rates have usually been defined as "ETV non-failure." The aim of the study was a retrospective analysis of radiological and neurological treatment response after ETV or VP-shunting (VPS) in age-dependent subtypes of AQS.

Eighty patients (median age 12.0 years, range 0-79 years) have been treated for MRI-proven aqueductal stenosis. Neurological treatment success was defined by neurological improvement and, in childhood, head circumference. Radiological response was measured as Evan's index in follow-up MRI. Initial signs and symptoms, type of surgery, and complications were analyzed.

Four types of AQS have been defined with distinct age ranges and symptomatology: congenital type I (n = 24), chronic progressive (tectal tumor-like) type II (n = 23), acute type III (n = 10), and adult chronic (normal-pressure hydrocephalus-like) type IV (n = 23). Retrospective analysis of neurological and radiological outcome suggested that congenital type I (<1 years of age) may be more successfully treated with VPS than with ETV (81 vs. 50 %). Treatment of chronic juvenile type II (age 2-15) by ETV 19 % compared to 57 % after VP-shunt, but similar neurological improvement (>80 %). There has been no influence of persistent ventriculomegaly in type II after ETV in contrast to VPS therapy for neurological outcome. Adult acute type III (age > 15 years) responded excellent to ETV. Chronic type IV (iNPH-like) patients (age > 21) responded neurologically in 70 % after ETV and VPS, but radiological response was low (5 %).

AQS can be divided into four distinct age groups and types in regards of clinical course and symptomatology. Depending on the AQS type, ETV cannot be unequivocally recommended. Congenital type I AQS may have a better neurological outcome with VP-shunt whereas acute type III offers excellent ETV results. Chronic progressive type II still requires prospective investigation of long-term ETV outcome, especially when ventriculomegaly persists. Late chronic type IV seems to result in similar outcome after VP-shunt and ETV.