What is hydrocephalus?
Excessive retention of cerebrospinal fluid in the ventricles or subarachnoid space due to impaired circulation of cerebrospinal fluid, resulting in enlargement of the ventricles and a corresponding decrease in brain parenchyma, is called hydrocephalus and is often associated with increased intracranial pressure in clinical practice. Zheng Jiaping, Department of Neurosurgery, Aviation General Hospital of China Medical University
Causes of hydrocephalus.
There are 3 causes of hydrocephalus. (1) Poor cerebrospinal fluid circulation pathway. (2) Impaired absorption of cerebrospinal fluid. (3) Excessive production of cerebrospinal fluid. The most common cause of hydrocephalus is poor cerebrospinal fluid circulation, and there is a significant increase in pressure in the venous sinuses due to venous sinus thrombosis and dural arteriovenous fistulas, resulting in impaired absorption of cerebrospinal fluid. Excessive production of cerebrospinal fluid is caused by choroid plexus papilloma, etc.
Diagnostic methods for different types of hydrocephalus
Based on the typical clinical manifestations described above, it is not difficult to diagnose this disease. The following tests are helpful to further understand the cause, type, group blockage site and severity of hydrocephalus.
1.Dynamic observation of head circumference. (For children). The normal neonatal head circumference diameter (frontal and occipital) is 33-35 cm, and it grows faster in the first 6 months after birth, increasing 1.2-1.3 cm per month, up to 8-10 cm in the first 6 months and 2-4 cm in the second 6 months, and the average head circumference is about 46 cm at 1 year old, increasing 2 cm in the second year and 2 cm in the third year, reaching 50 cm at 5 years old and approaching adult head circumference at 15 years old, about 54-58 At 15 years of age, the head circumference approaches that of an adult, about 54-58 cm. The head circumference of children with hydrocephalus can be 2 to 3 times the normal value.
In infants, the skull enlargement, thinning of the skull, scarcity or even complete disappearance of the plate barrier structure, shallowing or disappearance of the vascular sulcus, separation of the cranial suture, enlargement of the fontanelle and disproportion of the craniofacial bones can be seen on the cranial X-ray. In children, intracranial hypertension such as enlargement of pterygma, absorption of posterior bed prominence and deepening of cerebral gyrus pressure traces can be seen, and in some children, frontal foramen can be seen. At present, it is less used.
3.CT and MRI are the main and reliable methods to diagnose hydrocephalus. It helps to clarify the etiology, classify and distinguish the ventricular enlargement caused by other reasons, and can observe the ventricular changes after shunt surgery to track the effect of shunt surgery. In particular, Cine-MRI is decisive in distinguishing obstructive and traffic hydrocephalus, and also distinguishes normal pressure hydrocephalus from ventricular enlargement caused by brain atrophy.
4.Ventriculography, brain pool imaging and radionuclide scan. It is mainly used for the diagnosis and treatment of normal pressure hydrocephalus.
Diagnosis of normal pressure hydrocephalus.
Since normal pressure hydrocephalus is easily confused with ventricular enlargement caused by dementia and cerebral atrophy in terms of clinical symptoms and imaging manifestations, and the etiology is different and the treatment methods used are completely different, it is very important to make a correct diagnosis of normal pressure hydrocephalus.
1.CT: It can show the size of the ventricles, the degree of cortical atrophy and the associated lesions. In normal pressure hydrocephalus, the ventricles are obviously enlarged and the sulci are deepened at the same time, but the two are not proportional
In normal pressure hydrocephalus, enlargement of the ventricles is evident along with deepening of the sulci, but the two are not proportional. In some patients, periventricular hypodensity is an important manifestation.
MRI: It is possible to distinguish flowing cerebrospinal fluid from resting cerebrospinal fluid. By measuring the flow rate of cerebrospinal fluid through the conduit, it is possible to distinguish conduit obstruction or traffic, atrophic ventricular enlargement or hydrocephalic ventricular enlargement, etc.
3.Isotope brain pool scan: Through lumbar puncture, radionuclide is injected into the subarachnoid space and brain scans are performed at 4, 24, 48 and 72 hours. Normally the isotope flows on the convex surface of the brain without entering the ventricles, and the isotope disappears completely from the surface of the brain after 48 hours. In patients with primary normal pressure hydrocephalus, isotopes enter the ventricles and remain there for up to 72 hours without accumulation on the convex surface of the brain. Or the isotope enters the ventricle and also accumulates on the convex surface of the brain.
4.Lumbar puncture: The cerebrospinal fluid pressure is lower than 180 mmH2O in the lateral position, and the patient’s symptoms and signs often improve temporarily after lumbar puncture.
5.Continuous intracranial pressure tracer: continuous monitoring of intracranial pressure for 48 to 72 hours can reveal two kinds of pressure changes. One kind of pressure is basically stable with little fluctuation, and the average intracranial pressure is within the normal range; the other kind of intracranial pressure is seen to have paroxysmal elevation in the form of jagged high waves or plateau waves, accounting for about 10% of the time of pressure measurement, and the intracranial pressure of the rest of the time is often at the upper boundary of normal or mildly elevated. The latter is clinically effective for surgical treatment.
Lumbar puncture cerebrospinal fluid perfusion test: After successful lumbar puncture, the lumbar puncture needle is connected to a tee tube. The other two ends of the tube are connected to a manometer and syringe, respectively, and saline is injected into the subarachnoid space through the syringe at a rate of approximately 1.5 mL per minute, and changes in the manometer are observed. The rise in pressure does not exceed 20 mmH2O per minute when normal, but it is higher than this value in normal pressure hydrocephalus.
Differential diagnosis
1. subdural hematoma or effusion in infants Although infants with subdural hematoma or effusion also have cranial enlargement and cranial thinning, they are often accompanied by optic nerve papillary edema, but lack the sunset sign. ct scan can be differentiated.
2, rickets rickets cranial irregular thickening, resulting in frontal bone and occipital bone protrusion, square cranium, seemingly skull enlargement, but no symptoms of increased intracranial pressure and ventricular enlargement, but there are systemic skeletal abnormalities.
3.Brain dysplasia although the ventricles are also enlarged, but the head is not large without intracranial pressure increase performance, but there are neurological function and intellectual development disorders.
4.Hydrocephalic anencephaly has no cerebral cortex except in the occipital region on CT film, and a prominent basal ganglion is also visible.
5.Megalencephaly has no symptoms of increased intracranial pressure although the head is large, and CT shows normal size of the ventricles.
6, cerebral atrophy is mainly distinguished from normal pressure hydrocephalus. The symptoms of both are similar, but cerebral atrophy usually develops after the age of 50, and the symptoms develop slowly for several years. ct examination is characterized by mild enlargement of the ventricles, but not cumulative fourth ventricle, and significant widening of the sulcus gyrus. mri shows enlargement of both ventricles and subarachnoid space.
Treatment of hydrocephalus
Regardless of the cause of hypertensive hydrocephalus, it must be treated promptly. Pharmacological treatment is mainly aimed at reducing cerebrospinal fluid secretion and increasing the body’s water drainage. It is important to note that pharmacological treatment is mainly used for lighter patients and as temporary preoperative medication. The treatment of hydrocephalus should be mainly surgical. Surgery can be divided into three types: etiologic treatment, reduction of cerebrospinal fluid production, and cerebrospinal fluid shunt. Surgery should be performed as early as possible after hydrocephalus is detected. Surgery is less effective in late stages because of cortical atrophy or severe neurological dysfunction.
Before the 1980s, the treatment of hydrocephalus was a very difficult problem, and patients with hydrocephalus had a very high mortality and disability rate, and early shunt surgery, too, had extremely high complications. In recent years, with the development of technology, many new methods of hydrocephalus treatment have emerged, the emergence of different mechanisms of shunt valves, and the development of neuroendoscopic technology, many patients have been cured through effective treatment and resumed normal life and work.
1.Etiology treatment (radical method)
Etiological treatment should become the preferred method for treating hydrocephalus. For obstructive hydrocephalus, lifting the obstruction is the most ideal method. Such as interventricular foramen perforation, conduit reconstruction, fourth ventricular cyst fistula, intracerebroventricular tumor resection, third ventricular floor fistula, occipital foramen decompression, etc. Using etiologic treatment methods, once the surgery is successful, patients can benefit from it for the rest of their lives. In recent years, neuroendoscopic interventricular foramen perforation, neuroendoscopic conduit reconstruction and neuroendoscopic third ventriculostomy for hydrocephalus treatment have become the most effective and safest minimally invasive methods for hydrocephalus treatment, and the complications of the surgery are less than 5%, and it is the only unit in China and one of the few units in the world that can carry out conduit angioplasty and stent implantation for obstructive hydrocephalus.
2.Reducing cerebrospinal fluid formation
If choroid plexus resection or electrocautery is used. It is mainly used for traffic hydrocephalus, especially in patients who have failed bypass surgery or are not suitable for bypass. Currently, electrocautery is performed endoscopically, which can significantly reduce the occurrence of surgical complications.
3.Cerebrospinal fluid shunt
In the early days, a variety of shunt procedures were performed to treat hydrocephalus, including ventricular and ventricular pool shunts, such as: lateral ventricular and occipital pool shunts. Ventricular body shunts, such as: ventricular (or ventricular pool) ventral shunt, ventriculothoracic shunt, etc. Drainage of cerebrospinal fluid out of the body, e.g., lateral ventricular bulbar shunt. Ventricular and ureteral shunts, etc. Introduction of cerebrospinal fluid onto the cardiovascular system, such as ventriculo-atrial shunt, ventriculo-internal jugular vein shunt, etc.
Many of the above cerebrospinal fluid shunts have been eliminated due to poor efficacy or the tendency to cause more complications. The most commonly used shunts are ventriculoperitoneal shunts and other shunts. However, the main complications that currently plague the outcome of shunt surgery are complications.
These include: 1. Blockage of the shunt system. The most common, generally in the range of 50 to 70%.
2, infection. The incidence is 7-10%, and in children it is more than 30%. Mainly for ventriculitis or peritonitis.
3. Excessive or insufficient shunting.