Normal pressure hydrocephalus in the elderly

Introduction to normal stress hydrocephalus in the elderly Normal-pressure hydrocephalus (SNPH) is a clinical syndrome caused by a variety of causes of chronic hydrocephalus in adults, ventricular enlargement but normal brain pressure [<1.8 kPa (180 mmH2O)]. basic knowledge Sickness ratio: 0.0001% Susceptible people: the elderly Mode of infection: non-infectious Complications: ataxia, optic disc edema, epilepsy

The cause of normal stress hydrocephalus in the elderly

(1) Causes of the disease

Divided into 2 categories according to the presence or absence of a clear cause:

1. Idiopathic SNPH is unknown. It may be caused by occult subarachnoid hemorrhage (SAH) or meningeal infection. Faltz and Ward divide the ventricular enlargement after SAH into 2 phases, immediately after acute (early) bleeding. Ventricular dilatation occurs within 2 weeks, accompanied by rapid deterioration of the condition, but usually there is no clinical manifestation of SNPH, and the chronic phase (late) occurs at any time 2 to 6 weeks after hemorrhage, accompanied by a gradual deterioration of the condition.

2. Secondary SNPH (symptomatic SNPH) can be caused by cerebrospinal fluid circulation disorders caused by cerebrospinal meningitis, SAH, trauma, intracranial and intraspinal operations, or brain tumors, stenosis of the midbrain.

Factors related to the occurrence of SNPH: Due to the different perspectives observed by the authors, different relevant factors are proposed and summarized as:

(1) Location of aneurysm: Some scholars believe that the proportion of early ventricular dilatation after rupture of anterior communicating aneurysm is high, but some people think that it is not related to the location of aneurysm.

(2) ventricular hemorrhage: associated with cerebral ventricular hemorrhage after SAH.

(3) Application of anti-fibrous solvent: After treatment with anti-fibrous solvent, the rate of re-bleeding of SAH decreased, but the incidence of ischemia and hydrocephalus increased.

(4) Cerebral infarction: About half of the cases of chronic ventricular enlargement are complicated by cerebral infarction.

(5) Number of SAH: The more the number of bleeding, the higher the incidence of SNPH, and the secondary incidence rate was 38.1%.

(6) Hemorrhagic degree: The more severe the disease, the higher the incidence of SNPH; the severity of the disease, the more frequent SNPH occurs in patients with more cerebral ventricular hemorrhage and affecting the absorption of cerebrospinal fluid by arachnoid granules.

(two) pathogenesis

The basic pathological changes of SNPH are in the subarachnoid space, especially the meningeal fibrosis in the basal pool. This fibrosis can exist alone, or it can be accompanied by changes in arachnoid granules, and some can be seen in a wide area of the cerebral cortex. Small lacunar infarction with microvascular changes in hypertension; amyloid angiopathy can be seen in the blood vessels of some patients; water canal stenosis due to external compression or internal inflammatory reaction can also be seen.

Some scholars have divided the surgical and autopsy specimens of SAH patients into 5 grades by scanning electron microscopy:

Grade 0: no pathological changes under electron microscopy, grade I: mild atrophy of the arachnoid, fibrous tissue around the blood vessels, grade II: arachnoid thickening subarachnoid fibrosis, grade III: severe obstruction of the subarachnoid space, IV Grade: The subarachnoid space is completely obstructed and there is no gap in the CSF cycle. The authors point out that not all patients have subarachnoid fibrosis, but subarachnoid fibrosis may be related to traffic hydrocephalus. factor.

It is generally believed that SNPH can be caused by any of the ventricular sinus that can block the normal flow of CSF outside the ventricular system, that is, in the basal cistern or the convex surface of the brain.

In 1965, Adams and his colleagues first explained the pathogenesis of SNPH using the hydraulic principle according to Pascal's law: the force of the closed liquid on the inner wall of the container (F) is equal to the hydraulic pressure (P) by the surface area of the inner wall of the container (A): F = P × A, they believe that the initial pressure of CSF is higher than normal, leading to enlargement of the ventricle with the expansion of the ventricular surface area, CSF pressure to normal, but the force is constant, due to the pressure on the ventricular wall is too large, CSF It can be infiltrated into the periventricular tissue, leading to neurological dysfunction. The hypothesis that a small amount of CSF can cause a dramatic improvement in clinical symptoms is supported by the hypothesis. It is also believed that in those cases where CSF channel obstruction is known, the initial increase in CSF pressure is significant; However, in the unexplained SNPH, there is no abnormal CSF pathway before the disease, so the hydraulic principle does not explain the reasons for the expansion of these ventricles.

Another theory is that hypertension, arteriosclerotic vascular disease changes the mechanism of intracranial autoregulation, so that lower cerebral blood flow can produce SNPH. Experiments show that hypoperfusion can produce ischemia and microinfarction, leading to secondary ventricles. Expanding, further, microinfarction of tissue surrounding the ventricles will limit CSF through the ependymal reabsorption.

These two theories can be used as the basis for the pathophysiology of SNPH.

Some people have done animal experiments to prove that the first manifestation of traffic hydrocephalus is the imbalance between CSF secretion and absorption, and then the intraventricular pressure rises. The consequence is that the ventricles expand, and after 15 days, it tends to absorb and secrete CSF. The balance is re-established, and the state of modern repayment is gradually formed. Two different types of hydrocephalus can appear in the future due to adequate compensation: SNPH and high intracranial hydrocephalus.

According to the above experimental inference: the enlargement of the ventricle area itself can reduce the intraventricular pressure of the original increase until the new balance is restored, thus forming the SNPH.

Through animal experiments, it is found that after the formation of SNPH, the pressure of the convex surface of the brain is higher than the pressure of CSF in the ventricle. The two have significant statistical significance. This experiment supports the theory that the CSF pressure of the convex surface of the brain is different from the CSF pressure in the ventricle. The physiology of ventricular dilatation explains why ventricular pressure is normal, and hydrocephalus can still occur and persist.

In fact, in the early stage of hydrocephalus formation, cerebrospinal fluid circulation disorder is caused by some reason, and the intracranial pressure is high. At this time, the ependymal membrane is broken, forming an alternative pathway for the absorption of cerebrospinal fluid from the ependymium to the white matter. The normal circulation of the occluded cerebrospinal fluid is opened, so that the intracranial pressure gradually becomes normal. However, although this alternative pathway reduces the intracranial pressure, it causes changes in the elasticity and extensibility of the ventricular wall. Lowering, the ventricular wall remains in an expanded state. Not only that, but because of the formation of an alternative absorption pathway, the cerebrospinal fluid passes through the brain tissue, which can also cause brain disorders to develop and the symptoms worsen.

In general, most scholars advocate that this problem should be explained by the circulation of cerebrospinal fluid.

Cerebrospinal fluid circulatory disorder is blocked by reabsorption of arachnoid villi, and cerebrospinal fluid secretion, a significant imbalance between circulation and absorption, causes cerebrospinal fluid to accumulate in the ventricles.

Elderly people with normal pressure hydrocephalus prevention

The cause should be clarified, and the disease should be actively treated to prevent complications.

Normal pressure hydrocephalus complications in the elderly Complications, ataxia, optic disc edema, epilepsy

Some patients may have ataxia, optic disc edema, enlarged ventricles, and epilepsy.

Symptoms of normal stress hydrocephalus in the elderly Common symptoms Hydrocephalus psychiatric disorder Dementia Spinal cord compression Forgetful personality Change Urinary incontinence Debilitating Intelligent obstacles Limb stiffness

Mental disorder

The initial symptoms of SNPH are progressive aggravation of forgetfulness, slow mental response and speech impairment, slow development or computational impairment, decreased observation and apathy, and eventually severe mental disorders and dementia.

2. Gait disorder

Patients frequently fall, gradually appearing step base widening, gait drag, limb stiffness, slow movement, lower limbs squat gait, when the disease develops to a peak, gait disorders and motor function are very low, so that all voluntary activities are affected limit.

3. Incontinence

Usually occurs after mental and gait disorders, as the condition worsens and the symptoms persist, incontinence rarely occurs, only in the most severe cases.

In addition to the above three main signs, personality changes, epilepsy, horizontal nystagmus, extrapyramidal symptoms, grasping reflexes, primitive reflexes, and hypothalamic hypopituitarism may occur. In the advanced stage, incomplete paraplegia may occur, and lower extremity tendon reflexes may occur. Pathological reflex positive.

Examination of normal pressure hydrocephalus in the elderly

Cerebrospinal fluid examination, cell number, protein, sugar content is normal.

1.CSF inspection

Lumbar puncture pressure is normal or slightly lower, rarely exceeds 1.8kPa (180mmH20), CSF cell number, protein, sugar content is normal, most cases have improved after lumbar puncture, but the clinical symptoms are not improved, can not rule out SNPH Diagnosis.

2. Cerebroencephalography

It is the main method for diagnosing SNPH in the past. The typical change is that the ventricular system (especially the anterior horn) is enlarged, and the subarachnoid space on the brain surface is poorly inflated. However, because the method has certain damage, it has been replaced by CT in conditional hospitals. .

3. Radionuclide brain angiography

This method provides a method for measuring the kinetics of CSF. When SNPH changes its kinetics due to CSF absorption disorder, radiotracer can be found in the ventricle within 30 to 60 minutes after injection, and stays here for 24-72 hours. Above, and the convex development of the brain is poor, there is no radionuclide concentration in the sagittal sinus after 20-30 hours of injection, or the subarachnoid space above the basal cistern is completely unfilled. It is rare that the radionuclide accumulates in the basal pool. With the slow movement of CSF in the convex surface of the brain, accompanied by radionuclide concentration.

4.CT scan

SNPH showed ventricular enlargement, which is characterized by a spherical shape of the lateral ventricle, with a low-density area around the ventricle (especially the frontal angle), suggesting that CSF undergoes compensatory absorption of the ependymal membrane of the ventricular wall to cause edema around the ventricle, while the sulcus is not Affected, this feature can be distinguished from changes in brain atrophy.

Vassidouthis's ventricle measurement method is more commonly used, that is, the ventricle width (X) of the interventricular hole plane and the width (Y) between the inner plane of the same plane are measured on the CT slice, and the ratio of the two is used to determine the degree of hydrocephalus. In case: X/Y is less than 1:6.4, if X/Y is mild ventricular enlargement between 1:5 and 1:6.4, X/Y is moderate ventricle enlargement between 1:4 and 1:5. X/Y greater than 1:4 is a significant increase.

Diagnosis and differential diagnosis of normal pressure hydrocephalus in the elderly

Diagnostic criteria

It is not necessary to have a triple connection at the time of diagnosis, and the possibility of SNPH should be considered in the following cases:

1 rapid progress and neurasthenia, cerebral arteriosclerosis is more serious mental retardation.

2 no signs of spinal cord compression, showed increased muscle tension on both sides, pathological signs are not very obvious, and severe walking disorders.

3 After the acute attack of cerebrovascular disease, the symptoms such as sputum and other symptoms are significantly improved or restored, and the mental retardation gradually progresses or the original intelligent obstacle is significantly aggravated. In all of the above situations, the possibility of SNPH should be considered and promptly made. Brain CT or MRI scans, radionuclide cerebral angiography or iodine hydrocephalus CT scans are expected to obtain early diagnosis.

Differential diagnosis

Dementia associated with normal intracranial pressure hydrocephalus is characterized by low memory and thought and slow movement, and then manifests as lack of initiative, not interested in the outside world, and illusion, delusion and deviant actions are rare, the course of disease is usually several months.

Alzheimer's disease is caused by the same obstacles in all mental activities including memory. The personality changes are very significant. The course of disease is several years, and there is multiple infarct dementia. Although memory is the main obstacle, the disease is until the late stage. Still able to maintain a high degree of judgment and personality, due to mental imbalance, also known as mottled dementia.

As mentioned above, various dementias have certain characteristics that are helpful for differential diagnosis. However, it is difficult to identify these diseases based only on the type of dementia. The following items can be used as a reference for identification:

1 normal intracranial pressure hydrocephalus occurs in the early stage of walking disorders, the course of disease is only a few months,

2 The course of senile dementia lasts for several years. Although there is a degree of difference between personality changes and multiple infarct dementia, there are many cases of stroke history and the symptoms progress gradually.

Normal intracranial hydrocephalus with walking disorders is characterized by difficulty in maintaining balance, so there is instability and small walking when changing direction. About half of the patients have urinary incontinence, but fecal incontinence is rare, with multiple ages of 50. ~60 years old, mostly male.

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