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Genetics and molecular pathophysiology of normal pressure hydrocephalus.

Idiopathic normal pressure hydrocephalus (iNPH) is characterized by dilation of the cerebral ventricles without increased cerebral pressure. Patients typically present with cognitive impairment, gait abnormalities, and urinary incontinence. Despite current guidelines for diagnosis and surgical intervention, there is little consensus on the pathophysiology of iNPH. Familial cases and genomic studies of iNPH have recently suggested an underappreciated role of genetics in disease pathogenesis, implicating mechanisms ranging from dysregulated CSF dynamics to underlying neurodegenerative or neuroinflammatory processes. In this paper, the authors provide a brief review of genetic insights and candidate genes for iNPH, highlighting the continued importance of integrated genetic analysis and clinical studies to advance iNPH management.

Humans

Relationship of new-onset systemic hypertension and normal pressure hydrocephalus.

Communicating normal pressure hydrocephalus (NPH) is an important remote complication of traumatic brain injury (TBI). The diagnosis of this hydrocephalus depends largely on clinical signs and symptoms, including cognitive deterioration, gait changes and incontinence. However, many of these signs are also seen during post-traumatic amnesia, making early recognition of this syndrome difficult. A case study of one man post-TBI, who presented with new-onset hypertension as a sign of NPH, prompted a retrospective chart review of all patients admitted over a 2-year period with a diagnosis of NPH. Ninety per cent of patients had one or more of the classic triad of NPH and 25% of patients had symptoms suggestive of raised intracranial pressure (unexplained nausea, headache and visual disturbance). Mean systolic and diastolic blood pressures among the 20 subjects for six consecutive days pre-operatively compared with those for days 8-14 and 15-21 post-operatively showed no significant differences; a subgroup of five patients (25%), however, demonstrated a significant change in blood pressure temporally related to shunting. We suggest that demonstration of new-onset systemic hypertension may also be a clinical sign suggestive of NPH useful in the evaluation of the TBI patient.

Adolescent

The physics of the cranial cavity, hydrocephalus and normal pressure hydrocephalus: mechanical interpretation and mathematical model.

It is intended for this research, to provide some basis for the understanding of the rational mechanics of the cranial content. There are many interesting and controversial facts derived from the experimental and clinical-pathological observations of hydrocephalus and increased intracranial pressure. For instance, in some patients a moderate increase of intracranial pressure is accompanied by hydrocephalus and mental changes, while in others, with high intracranial pressure, the ventricles and mental functions remain unaltered. What then is the parameter that changes the size of the ventricles and impairs brain function? It is shown how the transmission of intraventricular pressure throughout the brain parenchyma creates a stress distribution that varies in magnitude; how during the production, maintenance, and reversal of hydrocephalus, and normal pressure hydrocephalus the stress is distributed throughout the brain; and how in the presence of a sudden increase of intracranial pressure nature has arranged additional mechanisms for protecting the brain. It is important to recognize that some aspects of intracranial physiopathology can be explained through classical concepts of physics, prior to attempting to interpret such processes solely in terms of biological or auto-regulatory phenomena.

Adult

CSF monoamine metabolites, cholinesterases and lactate in the adult hydrocephalus syndrome (normal pressure hydrocephalus) related to CSF hydrodynamic parameters.

Monoamine metabolites, cholinesterases and lactic acid in lumbar cerebrospinal fluid (CSF) were investigated on patients with the adult hydrocephalus syndrome (idiopathic normal pressure syndrome; AHS, n = 15), Alzheimer's disease (AD, n = 14), multi-infarct dementia (MID, n = 13) and controls (n = 21). Patients had clinical and CSF hydrodynamic investigations. Monoamine concentrations were determined by reversed-phase liquid chromatography, cholinesterases and lactate were determined photometrically. In the AHS patients, CSF monoamine concentrations were not significantly different compared with controls, AD or MID patients. AHS and AD patients showed a similar reduction of CSF acetylcholinesterase activity compared with controls. Positive correlations were found in concentrations of CSF homovanillic acid, CSF 5-hydroxyindoleacetic acid and CSF lactic acid versus CSF outflow conductance (that is, resistance against CSF outflow) in the AHS patients. A similar pattern was observed in a subgroup of MID patients characterised by dilated ventricles and disturbed CSF hydrodynamics. These data suggest that a low CSF outflow conductance may facilitate the clearance of acidic substances from the arachnoid space at the probenecid sensitive active transport site. Alternative explanations would be that a pathologically low CSF outflow conductance is accompanied by an inverse caudorostral flow of CSF or a compromised trans-ependymal diffusion.

Aged

[Normal pressure hydrocephalus. Part 1. Dynamic study of CSF circulation in patients with normal pressure hydrocephalus (author's transl)].

To clarify the pathogenesis of normal pressure hydrocephalus (NPH), quantitative measurement of CSF dynamics was attempted using RI techniques. In this study results concerning RI ventriculography and RI transfer test from CSF to plasma were reported. "Barrier ratio" and regional cerebral blood flow study in NPH will be reported elsewhere. Fifty-three patients with chronic communicating hydrocephalus wer devided into two groups. Thus, twenty-seven cases were diagnosed as NPH according to clinical symptoms and signs, and others were considered as mere chronic communicating hydrocephalus without any NPH characteristics. Results are as follows: 1) 169Yb--DTPA ventriculography; In NPH group, there was longer retention of RI injected into lateral ventricle, and RI activity was not detected in the cisterna magna 60 minutes after the injection. These findings show remarkable delay of CSF flow in NPH patients. 2) Transfer test of 169Yb--DTPA from CSF to plasma; Immediately after the RI injection, Transfer ratio of RI activity from CSF to plasma was measured. It was revealed that intraventricular RI was more rapidly transfered to plasma in NPH group compared with in the control group, suggesting accelerated trans-ependymal absorption of RI in NPH group.

Aged

Does the shunt opening pressure influence the effect of shunt surgery in normal pressure hydrocephalus?

Thirteen patients with normal pressure hydrocephalus were operated upon with an externally maneuverable shunt system (Sophy SU8) in order to investigate its influence on clinical outcome, intracranial pressure and cranial CT parameters. The opening pressure was set at high at surgery and lowered stepwise at intervals of three months to medium and low. The clinical condition, intracranial pressure and cranial CT parameters were examined at the end of the 3 months interval on each pressure level. The patients improved within the first 3 months inspite of an unchanged mean intracranial pressure and remained in a stable clinical condition during the rest of the study period. The intracranial pressure was significantly reduced at 9 months. The ventricular index, Evans index, temporal horn and third ventricle width were reduced 3 months post-operatively and did not change significantly during the rest of the study. The pre-operative third ventricle width was correlated to high psychometric test results after shunt surgery. Reduction in ventricular index, Evans index and third ventricle width after surgery correlated to improvement in psychometric scoring. The clinical improvement after shunt surgery for normal pressure hydrocephalus is seen within 3 months and is independent of the adjusted valve pressure.

Aged

Computerized axial transverse tomography in normal pressure hydrocephalus.

Twenty patients with normal pressure hydrocephalus were examined by computerized axial transverse tomographic (CT) scanning and the results were compared with pneumoencephalographic findings and clinical responses to ventricular shunting. The CT scan revealed significant cortical atrophy, not demonstrated by pneumoencephalogram in seven patients. The cortical atrophy was confirmed by autopsy in one case. This examination also revealed greatly enlarged ventricles (25 to 40 per cent of intracranial volume) in eight patients up to 4 years after ventricular shunting. There was no relationship between the presence or absence of cortical atrophy, or the postoperative ventricular size, and the clinical responses to ventricular shunting. Current concepts of normal pressure hydrocephalus must be revised in view of these findings.

Adult

Angiotensin converting enzyme inhibition, CBF autoregulation, and ICP in patients with normal-pressure hydrocephalus.

Fourteen patients with normal pressure hydrocephalus had the autoregulation of cerebral blood flow (CBF) and intracranial pressure (ICP) investigated. In 8 of the patients the effect of Captopril on ICP and CBF was also investigated. The mean arterial blood pressure (MABP) was 109 mmHg (intra-arterially), and ICP was 11 mmHg (intraventricularly). Changes in global CBF were estimated by the arterio-venous oxygen difference method. The autoregulation of CBF was present in 13 of the patients (p less than 0.01). The lower limit of CBF autoregulation was 86% of the baseline perfusion pressure. One hour after 50 mg of captopril perorally, MABP was reduced 16 mmHg, and ICP and CBF were unchanged. The autoregulation was maintained and the lower limit was decreased 19 mmHg. Thus patients would be expected to benefit from captopril treatment in hypotensive anaesthesia.

Administration, Oral

Cerebral hemodynamics in patients with normal pressure hydrocephalus: correlation between cerebral circulation time and dementia.

Regional cerebral blood flow and regional cerebral circulation time were measured in 13 demented patients with chronic hydrocephalus, mostly normal pressure hydrocephalus. The average hemispheric, frontal, and temporal cerebral blood flows were significantly reduced. The average regional cerebral circulation time values were significantly prolonged in the frontal, temporal, and thalamic regions, most markedly in the frontal white matter, where periventricular lucency was observed on computed tomography. Clinical improvement was obtained in all patients after operation. While postoperative regional cerebral blood flow values did not change compared with preoperative ones, postoperative regional cerebral circulation time values were significantly reduced in all the regions measured, and most markedly in the frontal white matter. The present results suggest that microcirculation in the frontal lobe is closely correlated with dementia in association with pressure exerted on the nerve fibers in the frontal white matter in patients with normal pressure hydrocephalus.

Aged

The effect of nimodipine on ICP and CBF in patients with normal-pressure hydrocephalus.

Eight patients with normal-pressure hydrocephalus (NPH) were studied. The resting mean arterial blood pressure (MABP) was 100 (90-125) mmHg and the mean intracranial pressure (ICP) was 11 (5-17) mmHg. ICP and MABP were continuously measured intraventricularly and intra-arterially, respectively. Changes in global cerebral blood flow (CBF) were estimated by the arteriovenous oxygen difference method. Intravenous nimodipine (15 microgram/kg/hour) was given in the first 2 hours and 30 microgram/kg/hour in the next 2 hours. MABP was reduced 23 (4-47) mmHg (p less than 0.05). ICP was increased 3 (0-10) mmHg (p less than 0.05). CBF was unchanged in the group on the whole, but in 4 of patients a major drop in perfusion pressure was seen, and CBF decreased 6, 11, 23 and 34%, respectively. Thus these findings underline the importance of maintaining the perfusion pressure under treatment with nimodipine.

Aged

Spontaneous improvement in "normal" pressure hydrocephalus.

A patient is presented with "normal" pressure hydrocephalus including dementia, incontinence, and apraxic gait. He had a normal lumbar CSF pressure, hydrocephalus with lack of air over the convexities on pneumoencephalography, and ventricular filling with prolonged retention on cisternography. He did not receive a shunt and, nevertheless, showed spontaneous improvement in his mental function over the next few years. This cases emphasizes the necessity for a controlled study of shunting for "normal" pressure hydrocephalus.

Aged

Association of deep white matter infarction with chronic communicating hydrocephalus: implications regarding the possible origin of normal-pressure hydrocephalus.

The coexistence of cerebrovascular disease leading to deep white matter infarction and normal-pressure hydrocephalus has been noted previously in clinical studies, as both diseases can present with the triad of gait disturbance, dementia, and incontinence. The purpose of this MR study was to determine if the two diseases demonstrated a statistical association. Evidence of patchy periventricular hyperintensity representing presumed deep white matter infarction was sought in 20 patients shunted for normal-pressure hydrocephalus and in 35 additional consecutive patients with clinical symptoms and MR findings consistent with normal-pressure hydrocephalus. Deep white matter infarction was also sought in 62 consecutive age-matched control subjects. There was a statistically significant (p less than .001) higher association (58%) of marked infarction in the 55 patients with normal-pressure hydrocephalus than in the age-matched controls (24%). MR findings of communicating hydrocephalus (ventriculomegaly and increased aqueductal CSF flow void) were sought in 78 consecutive patients with presumed deep white matter infarction, and the degree of severity of the two diseases was also found to be statistically significant (p less than .05). In view of this association, the possibility that the two diseases are related was considered. A potential mechanism is discussed whereby deep white matter infarction leading to decreased periventricular tensile strength could result in communicating hydrocephalus. It is plausible that normal-pressure hydrocephalus may result from a number of different insults to the brain.

Aged

Normal-pressure hydrocephalus due to tentorial meningioma.

Normal-pressure hydrocephalus and the associated triad of dementia, apraxic gait and urinary incontinence may be casued by various, sometimes unsuspected, lesions, usually those that block the flow of cerebrospinal fluid (CSF) around the tentorium. A 58-year-old woman with insidious onset of behaviour and gait problems had occult, normal-pressure hydrocephalus and a tentorial meningioma, resection of which produced complete recovery. This case demonstrates that a distinction must be made between the syndrome of normal-pressure hydrocephalus resulting from disturbance in CSF dynamics and the pathophysiologic features of the underlying lesion.

Brain Neoplasms

[Cerebral cortex in normal pressure hydrocephalus: an electron microscopy study (author's transl)].

A cortical biopsy was taken at the time when ventricular pressure was measured, or a ventriculo-atrial shunt placed, in 11 patients with Normal Pressure Hydrocephalus (N.P.H.), and was studied with the electron microscope. In 9 cases, a rather typical electron microscopic picture with marked increase of extracellular space in an otherwise normal cortical neuropil was observed. 2 patients did not exhibit this pattern and, coincendentally, did not benefit from the placing of the shunt. As a control, about 600 cortical biopsies that had been taken for other reasons were reviewed. In the group, there were only 3 cortices that had a pattern of increased extracellular space similar to the described in N.P.H. On review of the clinico-pathologic data of these cases, it was felt that all 3 probably represented cases of normal pressure hydrocephalus. It is concluded that the ultrastructure of the cerebral cortex is of at least nosological interest in the study of N.P.H.

Cerebral Cortex

The association of normal-pressure hydrocephalus with obstructive sleep apnea.

This report describes a 70-year-old man with obstructive sleep apnea who deteriorated rapidly when nasal continuous positive airway pressure was begun. The patient was found to have normal-pressure hydrocephalus, which was possibly exacerbated by the nasal continuous positive airway pressure. A review of the literature indicates several significant associations between apnea, normal-pressure hydrocephalus, and increased intracranial pressure and suggests that the association of obstructive sleep apnea and hydrocephalus might not be rare. Implications for diagnosis and treatment are discussed.

Aged

[Changes in CSF pressure induced by acetazolamide administration test--as an indicator of shunt operation for so-called normal pressure hydrocephalus].

Lumber subarachnoid pressure was monitored via intrathecally introduced catheter in 9 patients, who showed ventricular dilatation on brain CT and were suspected of normal pressure hydrocephalus. During the pressure measurement, 500 mg of acetazolamide was rapidly injected intravenously and changes of CSF pressure were recorded. The results of the study were compared to clinical signs, brain CT findings and results of continuous pressure monitoring. The types of response of CSF pressure induced by acetazolamide administration were classified into 2 groups. In 5 cases (Group A), more than 50 percent increase of CSF pressure compared to the resting value was noted. On the contrary, in the remaining 4 cases (Group B), CSF pressure showed only slight increase (less than 25 percent or none). VP shunt was performed in 4 cases in Group A. Definite improvement of clinical symptoms was observed in all of these surgically treated cases. Correlation was found between the response to Acetazolamide administration and the appearance of B wave in the continuous spinal pressure monitoring. This study suggests that Acetazolamide test may be useful diagnostic test to select the patients for shunt operation.

Acetazolamide

Diabetes mellitus in normal pressure hydrocephalus.

Seventeen of 33 patients (51.5%) with normal pressure hydrocephalus were discovered to have diabetes mellitus. This was significantly greater than the 12.1% incidence found in age-matched control subjects. The diabetes was not accounted for either by the patients' ages nor by their physical inactivity due to hospitalisation. Diabetes mellitus concurrent with normal pressure hydrocephalus may result from involvement of hypothalamic and brainstem autonomic structures by the expanding ventricles during the evolution of hydrocephalus.

Age Factors