Hydrocephalus--revision of its definition and classification with special reference to "intractable infantile hydrocephalus"

Management of cerebrospinal-fluid-related intracranial abnormalities in frontoethmoidal encephalocele using "Shunt algorithm for frontoethmoidal encephalocele" (SAFE)

A cerebrospinal-fluid-related (CSF-related) problem occurred in 25-30% of frontoethmoidal encephalocele (FEE) cases. Since there was no algorithm or guideline, the judgment to treat the CSF-related problem often relies upon the surgeon's experience. In our institution, the early shunt was preferable to treat the problem, but it added risks to the children. We developed an algorithm, "Shunt Algorithm for Frontoethmoidal Encephalocele" (SAFE), to guide the surgeon in making the most reasonable decision. To evaluate the SAFE's efficacy in reducing unnecessary early shunting for FEE with CSF-related intracranial abnormality. Medical records of FEE patients with CSF-related abnormalities treated from January 2007 to December 2019 were reviewed. The patients were divided into two groups: before the SAFE group as group 1 (2007 - 2011) and after the SAFE group as group 2 (2012 - 2019). We excluded FEE patients without CSF-related abnormalities. We compared the number of shunts and the complications between the two groups. One hundred and twenty-nine patient's medical records were reviewed. The males were predominating (79 versus 50 patients) with an average age of 58.2±7.1 months old (6 to 276 months old). Ventriculomegaly was found in 18 cases, arachnoid cysts in 46 cases, porencephalic cysts in 19 cases, and ventricular malformation in 46 cases. Group 1, with a score of 4 to 7 (19 cases), received an early shunt along with the FEE repair. Complications occurred in 7 patients of this group. Group 2, with a score of 4-7, received shunts only after the complication occurred in 3 cases (pseudomeningocele unresponsive with conservative treatment and re-operation in 2 cases; a sign of intracranial hypertension in 1 case). No complication occurred in this group. Groups 1 and 2, with scores of 8 or higher (6 and 8 cases, respectively), underwent direct shunt, with one complication (exposed shunt) in each group. The SAFE decision algorithm for FEE with CSF-related intracranial abnormalities has proven effective in reducing unnecessary shunting and the rate of shunt complications.

Multimodal Sensing Capabilities for the Detection of Shunt Failure

Hydrocephalus is a medical condition characterized by the abnormal accumulation of cerebrospinal fluid (CSF) within the cavities of the brain called ventricles. It frequently follows pediatric and adult congenital malformations, stroke, meningitis, aneurysmal rupture, brain tumors, and traumatic brain injury. CSF diversion devices, or shunts, have become the primary therapy for hydrocephalus treatment for nearly 60 years. However, routine treatment complications associated with a shunt device are infection, obstruction, and over drainage. Although some (regrettably, the minority) patients with shunts can go for years without complications, even those lucky few may potentially experience one shunt malfunction; a shunt complication can require emergency intervention. Here, we present a soft, wireless device that monitors distal terminal fluid flow and transmits measurements to a smartphone via a low-power Bluetooth communication when requested. The proposed multimodal sensing device enabled by flow sensors, for measurements of flow rate and electrodes for measurements of resistance in a fluidic chamber, allows precision measurement of CSF flow rate over a long time and under any circumstances caused by unexpected or abnormal events. A universal design compatible with any modern commercial spinal fluid shunt system would enable the widespread use of this technology.

Morphological and morphometric analysis of the hippocampus in Wistar rats with experimental hydrocephalus

BACKGROUND

The present study aims at better establishing the alterations caused by the usual enlargement of brain ventricles in this structure.

METHODS

Hydrocephalus was induced in 7-day-old Wistar rats by the injection of kaolin into the cisterna magna. Morphological studies were performed on the hippocampus 7, 14 and 21 days after injection. The total number of neurons in each hippocampus subarea as well as that of pyknotic neurons were counted. Then we calculated the pyknotic index (PI) by hippocampal subarea, taking into account the level of ventricular dilatation and time of induction of hydrocephalus.

RESULTS

PI was statistically larger in the CA1 subarea of the experimental group after 1 week of hydrocephalus induction as compared to the corresponding control as well as in animals that had developed mild hydrocephalus in groups G1, G2 and G3.

CONCLUSION

Hydrocephalus caused morphological alterations in the hippocampus, leading to important changes in its shape.

Is all "communicating" hydrocephalus really communicating? Prospective study on the value of 3D-constructive interference in steady state sequence at 3T

BACKGROUND AND PURPOSE

3D-constructive interference in steady state (3D-CISS) sequence has been used to assess the CSF pathways. The aim of this study was to investigate the additive value of 3D-CISS compared with conventional sequences in the diagnosis of obstructive membranes in hydrocephalus.

MATERIALS AND METHODS

A total of 134 patients with hydrocephalus underwent MR imaging examination with a 3T unit consisting of turbo spin-echo, 3D-CISS, and cine phase-contrast (cine PC) sequences. 3D-CISS was used to assess obstructive membranes in CSF pathways compared with other sequences. Cine PC, follow-up imaging, and surgical findings were used to confirm obstructive membranes.

RESULTS

Comparing the number of noncommunicating cases by using the conventional and 3D-CISS images, we found 26 new cases (19.4%) of 134 cases that were previously misdiagnosed as communicating hydrocephalus by conventional images. 3D-CISS sequence identified obstructive membranes invisible in other sequences, which facilitated selection of neuroendoscopy in the treatment of 31 patients (23.1%) in total who would have been otherwise treated with shunt insertion. These patients included 26 newly diagnosed noncommunicating cases after demonstration of intraventricular and/or fourth ventricular outlet membranes and 5 cases of communicating hydrocephalus with obstructing cisternal membranes. There were obstructions of the foramina of Luschka in 22 of 26 newly found noncommunicating cases.

CONCLUSIONS

Conventional sequences are insensitive to obstructive membranes in CSF pathways, especially in the fourth ventricular exit foramina and the basal cisterns. 3D-CISS sequence, revealing these obstructive membranes, can alter patient treatment and prognosis.

A contemporary definition and classification of hydrocephalus

This review focuses on the problems related to defining hydrocephalus and on the development of a consensus on the classification of this common problem. Such a consensus is needed so that diverse research efforts and plans of treatment can be understood in the same context. The literature was searched to determine the definition of hydrocephalus and to identify previously proposed classification schemes. The historic perspective, purpose, and result of these classifications are reviewed and analyzed. The concept of the hydrodynamics of cerebrospinal fluid (CSF) as a hydraulic circuit is presented to serve as a template for a contemporary classification scheme. Finally, a definition and classification that include all clinical causes and forms of hydrocephalus are suggested. The currently accepted classification of hydrocephalus into "communicating" and "noncommunicating" varieties is almost 90 years old and has not been modified despite major advances in neuroimaging, neurosciences, and treatment outcomes. Despite a thorough search of the literature using computerized search engines and bibliographies from review articles and book chapters, I identified only 6 previous attempts to define and classify different forms of hydrocephalus. This review proposes the following definition for hydrocephalus: hydrocephalus is an active distension of the ventricular system of the brain related to inadequate passage of CSF from its point of production within the ventricular system to its point of absorption into the systemic circulation. Based on this definition (potential points of flow restriction) and on the view of the CSF system as a hydraulic circuit, a classification system is proposed. The acceptance of this proposed definition and classification schema would allow clinicians and basic scientists to communicate effectively, to share information and results, and to develop testable hypotheses.

The definition and classification of hydrocephalus: a personal recommendation to stimulate debate

The aim of this review is to refine the definition and classification of hydrocephalus as a preview to developing an international consensus on the nomenclature of this complex condition. This proposed definition and classification is based on my own work in this area and is intended to promote a debate on the concepts presented.

A literature review of contemporary definitions and classifications of hydrocephalus, and of the historic context in which these concepts developed, is presented. Based on new technology and understanding of hydrocephalus, the rationale for nomenclature is also discussed.

Currently, there is no recognized definition of hydrocephalus. The failure to agree on a working definition impedes progress in understanding the pathophysiology and treatment of hydrocephalus. There are many proposed classifications, each with its own starting point in terms of the definition of the condition. This author recommends that the following definition be used as a starting point to develop a consensus statement defining hydrocephalus: "Hydrocephalus is an active distension of the ventricular system of the brain resulting from inadequate passage of cerebrospinal fluid from its point of production within the cerebral ventricles to its point of absorption into the systemic circulation." Such a definition can be used to develop a rational classification consistent with observations from contemporary neuroimaging and can lead to testable hypotheses. It is concluded that hydrocephalus is a complicated neurologic disorder with many causes and methods of treatment. Clinicians and basic scientists must agree on a working definition of the condition to be able to interpret results from different investigators. Reaching a consensus on a working definition and functional classification should be a high priority for researchers in this field.

Genetics of human hydrocephalus

Human hydrocephalus is a common medical condition that is characterized by abnormalities in the flow or resorption of cerebrospinal fluid (CSF), resulting in ventricular dilatation. Human hydrocephalus can be classified into two clinical forms, congenital and acquired. Hydrocephalus is one of the complex and multifactorial neurological disorders.

A growing body of evidence indicates that genetic factors play a major role in the pathogenesis of hydrocephalus. An understanding of the genetic components and mechanism of this complex disorder may offer us significant insights into the molecular etiology of impaired brain development and an accumulation of the cerebrospinal fluid in cerebral compartments during the pathogenesis of hydrocephalus. Genetic studies in animal models have started to open the way for understanding the underlying pathology of hydrocephalus. At least 43 mutants/loci linked to hereditary hydrocephalus have been identified in animal models and humans. Up to date, 9 genes associated with hydrocephalus have been identified in animal models. In contrast, only one such gene has been identified in humans. Most of known hydrocephalus gene products are the important cytokines, growth factors or related molecules in the cellular signal pathways during early brain development. The current molecular genetic evidence from animal models indicate that in the early development stage, impaired and abnormal brain development caused by abnormal cellular signaling and functioning, all these cellular and developmental events would eventually lead to the congenital hydrocephalus.

Owing to our very primitive knowledge of the genetics and molecular pathogenesis of human hydrocephalus, it is difficult to evaluate whether data gained from animal models can be extrapolated to humans. Initiation of a large population genetics study in humans will certainly provide invaluable information about the molecular and cellular etiology and the developmental mechanisms of human hydrocephalus.

This review summarizes the recent findings on this issue among human and animal models, especially with reference to the molecular genetics, pathological, physiological and cellular studies, and identifies future research directions.

Predictors of outcome in patients with normal-pressure hydrocephalus

From 1982 until 2000 we examined 200 patients diagnosed with normal-pressure hydrocephalus (NPH) in a prospective study. From the patients who were surgically treated by a shunt implantation we could re-examine 155 (78%) at a mean time interval of 7 months after the operation. NPH differed in severity according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In our study, we focused on the possible predictors: patient age; length of disease; clinical signs including gait ataxia, dementia, and bladder incontinence; idiopathic vs. secondary origin; implanted valve type and the resistance of the valve to cerebrospinal fluid outflow. In 80 patients without cerebral atrophy and a short course of disease (< 1 year), a slight amount of dementia and an implanted Miethke Dualswitch-Valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only minimal relevance for outcome. Seventy-five patients with cerebral atrophy had a better outcome when dementia was not present, outflow resistance was above 20 mmHg/mL/min, the CSF tap-test was positive, and a Miethke Dualswitch-Valve was implanted.

Predictors of outcome in patients with normal-pressure hydrocephalus

Despite knowledge emerging over the last 40 years, the postoperative results after shunt implantation in patients diagnosed with normal-pressure hydrocephalus (NPH) have not improved significantly over the last decade. For that reason predictors have to be identified in order to preoperatively predict outcome. From 1982 to 2000 we prospectively studied 200 patients diagnosed with NPH. From the patients, who were surgically treated by a shunt implantation we reexamined 155 (78%) postoperatively a mean time interval of 7 months. The NPH was graded according to the results of the intrathecal infusion test in an early stage NPH (without brain atrophy) and late stage NPH (with brain atrophy). In our study, we focussed attention on the possible predictors: patients age, length of disease, clinical signs (gait ataxia, dementia and bladder incontinence), aetiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH recovery rate and as the statistical test the chi(2) according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy), a short course of disease (<1 year), a slight degree of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance to outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20mm Hg/min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.

Current concept of hydrocephalus: evolution of new classifications

Since hydrocephalus is a multifactorial disease with a diverse pathogenesis, no single, truly ideal classification of its exists. Hydrocephalus has been classified from various standpoints, each classification reflecting the current level of knowledge about hydrocephalus. Hydrocephalus needs to be classified according to the purpose of the study. There are two major categories of classification of hydrocephalus: academic and practical. Untreatable hydrocephalus still occurs. We propose a practical clinical classification based on the time of onset and the etiology for use in the clinico-epidemiologic study of intractable hydrocephalus and its future management.

Classification of hydrocephalus and outcome of treatment

PURPOSE

Retrospective analysis in cooperative study of hydrocephalus at institutions of members of the Research Committee on Intractable Hydrocephalus sponsored by the Ministry of Health and Welfare of Japan was performed to determine the functional prognosis for all types of hydrocephalus and thus to clarify the outcome.

METHODS

In preparation of this study, we have proposed the definition, clinical classification and diagnostic criteria of hydrocephalus. We have classified non-tumoral hydrocephalus into eight types based on its etiology and the time of onset. To establish the diagnosis in each type of hydrocephalus, we have set up inclusion and exclusion criteria, as well as supplementary criteria which are useful for its diagnosis.

RESULTS

Analysis of the 1450 cases of hydrocephalus of various etiologies stored in the data base obtained from the study for each type of hydrocephalus revealed that following types and conditions were associated with a neurologic deficit: (1) early fetal hydrocephalus, (2) overt neonatal hydrocephalus, (3) hydrocephalus associated with such severe brain malformations as hydranencephaly, holoprosencephaly and lissencephaly, (4) hydrocephalus associated with severe brain damage, (5) hydrocephalus associated with epilepsy, (6) hydrocephalus shunted late after detection, and (7) hydrocephalus complicated by a shunting operation.

CONCLUSION

The postnatal functional outcome was significantly poor in fetal hydrocephalus diagnosed in the early gestation. Childhood onset hydrocephalus showed a poorer outcome than adult hydrocephalus.

Consensus: nosographic identification

Since hydrocephalus cannot be regarded as a single entity but is a group of illnesses whose pathophysiology remains unexplained in many aspects, its classification is particularly important. Various types of hydrocephalus are discussed with special reference to their etiology. The need for more research work is stressed.

Subarachnoid fluid collection in infants complicated by subdural hematoma

In the natural history of infantile extracerebral fluid collections, subarachnoid fluid collection itself is regarded as a benign lesion, and surgical treatment is not indicated. As this condition is age-related and self-limiting, spontaneous resolution can be expected in most cases by 2-3 years of age. However, out of 20 cases of infantile subarachnoid fluid collection in an 8-year period, 3 infants developed subdural hematoma. Infantile subarachnoid fluid collection seems to be prone to complicate subdural hematoma. Surgical treatment should be considered when subarachnoid fluid collection is complicated by subdural hematoma due to arachnoid ruptures or tearing of the bridging veins. Therefore, all patients should be observed closely and measures should be taken to prevent head trauma since it may precipitate subdural hematoma.

Giant interhemispheric cysts associated with agenesis of the corpus callosum

Interhemispheric cysts, often associated with agenesis of the corpus callosum, are rare lesions demonstrating little uniformity of pathogenesis. Four large interhemispheric cystic lesions with several unique features are reviewed. Magnetic resonance imaging clearly showed agenesis of the corpus callosum and was useful in the diagnosis of interhemispheric cysts. The differential diagnosis of these lesions is discussed, along with therapeutic considerations.