Significance of pathognomonic features of normal-pressure hydrocephalus on computerized tomography

White matter changes should not exclude patients with idiopathic normal pressure hydrocephalus from shunt surgery

Introduction

White matter changes (WMC) on brain imaging can be classified as deep white matter hyperintensities (DWMH) or periventricular hyperintensities (PVH) and are frequently seen in patients with idiopathic normal pressure hydrocephalus (iNPH). Contradictory results have been reported on whether preoperative WMC are associated with outcome after shunt surgery in iNPH patients. The aim of this study was to investigate any association between DWMH and PVH and shunt outcome in patients with iNPH, using magnetic resonance volumetry.

Methods

A total of 253 iNPH patients operated with shunt surgery and clinically assessed before and 12 months after surgery were included. All patients were investigated preoperatively with magnetic resonance imaging of the brain. The volumes of DWMH and PVH were quantified on fluid-attenuated inversion recovery images using an in-house semi-automatic volumetric segmentation software (SmartPaint). Shunt outcome was defined as the difference in symptom score between post- and preoperative investigations, measured on the iNPH scale, and shunt response was defined as improvement with ≥ 5 points.

Results

One year after shunt surgery, 51% of the patients were improved on the iNPH scale. When defining improvement as ≥ 5 points on the iNPH scale, there was no significant difference in preoperative volume of WMC between shunt responders and non-responders. If outcome was determined by a continuous variable, a larger volume of PVH was negatively associated with postoperative change in the total iNPH scale (p < 0.05) and negatively associated with improvement in gait (p < 0.01) after adjusting for age, sex, waiting time for surgery, preoperative level of symptoms, Evans’ index, and disproportionately enlarged subarachnoid space hydrocephalus. The volume of DWMH was not associated with shunt outcome.

Conclusions

An association between outcome after shunt surgery and volume of PVH was seen, but there was no difference between shunt responders and non-responders in the volumes of DWMH and PVH. We conclude that preoperative assessment of WMC should not be used to exclude patients with iNPH from shunt surgery.

Revisiting secondary normal pressure hydrocephalus: does it exist? A review

OBJECTIVE There are several etiologies that can lead to the development of secondary normal pressure hydrocephalus (sNPH). The aim of this study was to evaluate the etiology, diagnosis, treatment, and outcome in patients with sNPH and to highlight important differences between the separate etiologies. METHODS A comprehensive review of the literature was performed to identify studies conducted between 1965 and 2015 that included data regarding the etiology, treatment, diagnosis, and outcome in patients with sNPH. Sixty-four studies with a total of 1309 patients were included. The inclusion criteria of this study were articles that were written in English, included more than 2 patients with the diagnosis of sNPH, and contained data regarding the etiology, diagnosis, treatment, or outcome of NPH. The most common assessment of clinical improvement was based on the Stein and Langfitt grading scale or equivalent improvement on other alternative ordinal grading scales. RESULTS The main etiologies of sNPH were subarachnoid hemorrhage (SAH) in 46.5%, head trauma in 29%, intracranial malignancies in 6.2%, meningoencephalitis in 5%, and cerebrovascular disease in 4.5% of patients. In 71.9% of patients the sNPH was treated with ventriculoperitoneal shunt placement, and 24.4% had placement of a ventriculoatrial shunt. Clinical improvement after shunt placement was reported in 74.4% and excellent clinical improvement in 58% of patients with sNPH. The mean follow-up period after shunt placement was 13 months. Improvement was seen in 84.2% of patients with SAH, 83% of patients with head trauma, 86.4% of patients with brain tumors, 75% of patients with meningoencephalitis, and 64.7% of patients with NPH secondary to stroke. CONCLUSIONS Secondary NPH encompasses a diverse group of clinical manifestations associated with a subset of patients with acquired hydrocephalus. The most common etiologies of sNPH include SAH and traumatic brain injury. Secondary NPH does indeed exist, and should be differentiated from idiopathic NPH based on outcome and on clinical, pathophysiological, and epidemiological characteristics, but should not be considered as a separate entity.

Ongoing search for diagnostic biomarkers in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus is a syndrome, which typically has a clinical presentation of gait/balance disturbance, often accompanied by cognitive decline and/or urinary incontinence. Its diagnosis is based on relevant history and clinical examination, appropriate imaging findings and physiological testing. The clinical picture of idiopathic normal pressure hydrocephalus may occasionally be difficult to distinguish from that of Alzheimer’s dementia, subcortical ischemic vascular dementia and Parkinson’s disease. The aim of this article is to systematically review the literature from the last 29 years in order to identify cerebrospinal fluid (CSF) or imaging biomarkers that may aid in the diagnosis of the syndrome. The authors concluded that no CSF or imaging biomarker is currently fulfilling the criteria required to aid in the diagnosis of the condition. However, a few studies have revealed promising CSF and imaging markers that need to be verified by independent groups. The reasons that the progress in this field has been slow so far is also commented on, as well as steps required to apply the current evidence in the design of future studies within the field.

Noninvasive biomarkers in normal pressure hydrocephalus: evidence for the role of neuroimaging

Object

Normal pressure hydrocephalus (NPH) represents a treatable form of dementia. Recent estimates of the incidence of this condition are in the region of 5% of patients with dementia. The symptoms of NPH can vary among individuals and may be confused with those of patients with multi-infarct dementia, dementia of the Alzheimer type, or even Parkinson disease. Traditionally the diagnosis of NPH could only be confirmed postoperatively by a favorable outcome to surgical diversion of CSF. The object of this literature review was to examine the role of structural and functional imaging in providing biomarkers of favorable surgical outcome.

Methods

A Medline search was undertaken for the years 1980–2006, using the following terms: normal pressure hydrocephalus, adult hydrocephalus, chronic hydrocephalus, imaging, neuroimaging, imaging studies, outcomes, surgical outcomes, prognosis, prognostic value, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.

Results

The query revealed 16 studies that correlated imaging with surgical outcomes offering accuracy results. Three studies fulfilled the statistical criteria of a biomarker. A dementia Alzheimer-type pattern on SPECT in patients with idiopathic NPH, the presence of CSF flow void on MR imaging, and the N-acetylaspartate/choline ratio in patients with the secondary form are able to predict surgical outcomes with high accuracy.

Conclusions

There is at present Level A evidence for using MR spectroscopy in patients with secondary NPH, and Level B evidence for using SPECT and phase-contrast MR imaging to select patients with idiopathic NPH for shunt placement. The studies, however, need to be repeated by other groups. The current work should act as a platform to design further studies with larger sample sizes.

Correlation between ventricular enlargement and white matter changes

The clinical significance of white matter changes including periventricular hyperintensity (PVH) and deep white matter hyperintensity (DWMH) on MRI in patients with normal pressure hydrocephalus is unclear. We investigated the correlation between ventricular size and white matter changes in healthy individuals. We performed MRI in 683 (mean age 59; 55% men) neurologically normal adults without a history or radiological findings of brain disease or trauma, who were undergoing brain health screening. The correlation between Evans' index and severity of white matter changes was analyzed. Multiple linear regression analysis was used to identify the main clinical factors influencing ventricular enlargement and white matter changes. Evans' index was 0.248+/-0.026 (mean+/-SD). Incidence of PVH was 40% and DWMH was 29%. Evans' index was weakly correlated with PVH grading (rho=0.24; P<.01) and DWMH grading (rho=0.24; P<.01). Multiple linear regression analysis showed that age (beta=0.034; SE=0.003) diastolic blood pressure (0.004; 0.002), Evans' index (0.019; 0.009), and a history of hypertension (0.173; 0.053) had a significant impact on PVH grade, whereas age (0.030; 0.003) and history of hypertension (0.224; 0.049) were related to DWMH grade. It was suggested that there is an independent correlation between ventricular enlargement and PVH in normal adults. This finding in a normal population could be due to the presence of preclinical disease, but its bearing on the changes that occur in normal pressure hydrocephalus remain uncertain at the present time.

Quantitative SPECT cisternography in normal pressure hydrocephalus

Twenty-one patients with normal pressure hydrocephalus (NPH), 8 patients with various brain diseases with an element of hydrocephalus, and 7 patients with miscellaneous dementia disorders were investigated with quantitative radionuclide cisternography (RC) using single photon emission computerized tomography (SPECT). The total intracranial counts as well as the counts in the lateral and third ventricles were measured. All 15 NPH patients accessible for postoperative examination were improved after shunt surgery. In all groups the ventricular and total intracranial counts level increased during the measurement period but remained constant in distribution in each group. The NPH patients had a higher relative count value in the lateral and third ventricles compared to the patients with miscellaneous dementia disorders. The relative values in the third and lateral ventricles were predictive for the outcome of shunt surgery. Quantitative SPECT RC appears to be a useful diagnostic procedure in NPH investigations.

Idiopathic normal pressure hydrocephalus: the CSF tap-test may predict the clinical response to shunting

A follow-up study was performed in nine patients with idiopathic normal pressure hydrocephalus (NPH) 37 months (mean) after shunting and 10 non-operated controls with comparable degrees of ventricular enlargement, gait disorder, and dementia. Five operated patients vs. no controls reported sustained general improvement (p < 0.02). Objectively improved gait at follow-up (compared with preoperative status) was found in five of the six tested NPH-patients vs. none of the controls (p < 0.005). Improved gait and/or psychometric function was found in four of six NPH vs. none of eight control patients (p < 0.02) after drainage of 40 ml cerebrospinal fluid (CSF tap-test). Improved gait during the CSF tap-test predicted continued improvement at follow-up. Temporal horn size was the only radiological variable which showed a (moderate) positive correlation with resistance to CSF absorption and rate of pressure increase. The size of the third ventricle diminished in parallel with clinical improvement.

Binswanger's encephalopathy: a review

Binswanger's encephalopathy is reviewed in respect to history, computed tomography, magnetic resonance imaging, epidemiology, pathology, clinical picture, laboratory findings, differential diagnosis, and treatment. The various viewpoints on the pathogenesis of the process are discussed, in particular the role of ischemia, vascular disease, high blood pressure, lacunar infarction, hypoxia, edema, and hydrocephalus. The white matter hypomyelination of congophilic angiopathy and Alzheimer's disease should provide clues. A unifying hypothesis has not been attained.

Computed tomography of the brain in the diagnosis of and prognosis in normal pressure hydrocephalus

Thirty-eight patients with normal pressure hydrocephalus were examined by CT before and after a ventriculo-peritoneal shunt operation. Evans ratio, periventricular hypodensity and width of hemispheric sulci, sylvian fissures, cella media, temporal horns and third and fourth ventricle were examined. Twenty-eight patients improved after the operation while 10 were unchanged (non responders). Those patients who improved had more often enlarged third ventricle, enlarged temporal horns and normal sylvian fissures than those who did not improve. No single CT parameter or combination of CT parameters alone could identify responders and non-responders. The ventriculo-peritoneal shunt operation reduced ventricular size (Evans ratio, cella media width), abolished periventricular hypodensity and reduced width of the temporal horns and third ventricle in both responders and non-responders. Reduction of the width of the third ventricle correlated to clinical improvement.

CSF hydrodynamics after subarachnoid hemorrhage

Recent reports have shown that despite an apparently satisfactory recovery from previous subarachnoid hemorrhage (SAH), many patients still have minor sequelae when specifically looked for. The cause of this so-called post-SAH-encephalopathy is uncertain. This prospective study comprises 54 patients who underwent aneurysmal surgery after SAH between September 1978 and March 1985. One patient died, and 6 patients were non-biased drop-outs. CSF hydrodynamics, determined by infusion test and isotope cisternography, were evaluated on the remaining 47 patients in the recovery stage. Five patients (11%) were found to have typical clinical, CSF dynamic and radiological manifestations of normal pressure hydrocephalus (NPH), and all were shunted with good results. Twelve (26%) had abnormal results consistent with disturbed CSF-hydrodynamics, although there were no clinical or radiological findings supporting the diagnosis of shunt-demanding NPH. Disturbed CSF-hydrodynamics as one of the possible etiological factors of post-SAH-encephalopathy is discussed.

Normal pressure hydrocephalus: correlation between CT and measurements of cerebrospinal fluid dynamics

Twenty-nine patients consecutively admitted for consideration of CSF diversion surgery for suspected communicating ("normal pressure") hydrocephalus underwent cranial computerized tomography (CT) and study of cerebrospinal fluid (CSF) absorption, the latter determined as resistance to outflow of CSF (Ro). From the CT the size of the ventricular system was determined by various linear measurements and ratios and the presence of periventricular lucencies (PVL) and the size of cortical sulci was noted. Except for absence of cortical sulci greater than 3 mm no CT feature was suggestive of compromised CSF absorption. On the other hand, cortical atrophy did not rule out increased resistance to CSF-outflow. Features thought of as characteristic for normal pressure hydrocephalus on CT: large ventricles as compared with the amount of cortical atrophy and presence of PVL, correlated poorly with measured high resistance values. There was no correlation between the size of the ventricular system and resistance to CSF outflow. In the diagnostic distinction between communicating ("normal pressure") hydrocephalus and cerebral atrophy (hydrocephalus ex vacuo) static CT cannot replace an actual determination of CSF outflow resistance.

Experiences with intrathecally enhanced computed tomography

Computed tomographic cisternography (CTC) shows small normal and pathological structures in the extracerebral CSF spaces in an excellent way and is able to differentiate communicating from non-communicating CSF-containing cysts in congenital malformations and acquired lesions. The main value of the CTC is in the examination of CSF dynamics. A report is given about our experiences with 121 patients. The dynamic flow patterns are divided into eight groups. The results are discussed in detail with suggestions as to the treatment.