The pathophysiology of chronic noncommunicating hydrocephalus: lessons from continuous intracranial pressure monitoring and ventricular infusion testing

J Neurosurg 129:220–233, 2018

The pathophysiology of chronic noncommunicating hydrocephalus (ncHC) is poorly understood. This present study explored whether lessons about the pathophysiology of this clinical entity might be retrieved from results of overnight monitoring of pulsatile and static intracranial pressure (ICP) and ventricular infusion testing.

METHODS The study cohort included adult patients (> 20 years of age) with chronic ncHC due to aqueductal stenosis in whom symptoms had lasted a minimum of 6 months. A reference cohort consisted of age- and sex-matched patients managed for communicating HC (cHC). Information about symptoms and clinical improvement following surgery was retrieved from a quality register, and results of overnight ICP recordings and ventricular infusion testing were retrieved from the hospital ICP database.

RESULTS The cohort with ncHC consisted of 61 patients of whom 6 (10%) were managed conservatively, 34 (56%) by endoscopic third ventriculostomy (ETV), and 21 (34%) using ETV and subsequent shunt surgery. In patients responding to surgery, pulsatile ICP (mean ICP wave amplitude) was significantly increased to a similar magnitude in patients with ncHC and the reference cohort (cHC). Furthermore, intracranial compliance (ICC) was reduced in clinical responders. The results of ventricular infusion testing provided evidence that patients responding to ETV have impaired ventricular CSF absorption, while those requiring shunt placement after ETV present with impaired CSF absorption both in the intraventricular and extraventricular compartments.

CONCLUSIONS The study may provide some lessons about the pathophysiology of chronic ncHC. First, increased pulsatile ICP and impaired ICC characterize patients with chronic ncHC who respond clinically to CSF diversion surgery, even though static ICP is not increased. Second, in patients responding clinically to ETV, impaired ventricular CSF absorption may be a key factor. Patients requiring shunt placement for clinical response appear to have both intraventricular and extraventricular CSF absorption failure. A subgroup of patients with ncHC due to aqueductal stenosis has normal ventricular CSF absorption and normal ICC and may not be in need of surgical CSF diversion.

 

Benign external hydrocephalus: a review, with emphasis on management

Neurosurg Rev. DOI 10.1007/s10143-011-0327-4

Benign external hydrocephalus in infants, characterized by macrocephaly and typical neuroimaging findings, is considered as a self-limiting condition and is therefore rarely treated. This review concerns all aspects of this condition: etiology, neuroimaging, symptoms and clinical findings, treatment, and outcome, with emphasis on management. The review is based on a systematic search in the Pubmed and Web of Science databases. The search covered various forms of hydrocephalus, extracerebral fluid, and macrocephaly. Studies reporting small children with idiopathic external hydrocephalus were included, mostly focusing on the studies reporting a long-term outcome.

A total of 147 studies are included, the majority however with a limited methodological quality. Several theories regarding pathophysiology and various symptoms, signs, and clinical findings underscore the heterogeneity of the condition. Neuroimaging is important in the differentiation between external hydrocephalus and similar conditions. A transient delay of psychomotor development is commonly seen during childhood. A long-term outcome is scarcely reported, and the results are varying.

Although most children with external hydrocephalus seem to do well both initially and in the long term, a substantial number of patients show temporary or permanent psychomotor delay. To verify that this truly is a benign condition, we suggest that future research on external hydrocephalus should focus on the long-term effects of surgical treatment as opposed to conservative management.