Patient's question:
At nine months of pregnancy, the child was born with hydrocephalus. From birth to over four years old, no abnormalities were found. Is this normal?Doctor's answer:
Hydrocephalus is classified into congenital and acquired types, each of which can be further divided into communicating and non-communicating. The obstruction in non-communicating hydrocephalus occurs in the ventricular system, while in communicating hydrocephalus, it occurs in the subarachnoid space. The etiologies can be summarized as follows:(I) Congenital Hydrocephalus
It is primarily caused by malformations. Common types include:
1. Aqueductal malformations, which are further classified as:
- Aqueductal duplication
- Aqueductal stenosis or atresia
- Aqueductal membrane
2. Cerebellar tonsil herniation, where the tonsils, medulla, and fourth ventricle herniate into the spinal canal, causing the fourth ventricle to become (narrow and elongated), and the foramen of Magendie and lateral apertures to shift downward, obstructing CSF circulation. This malformation can occur alone but is often associated with spinal meningocele or basilar invagination.
3. Congenital atresia of the foramen of Magendie and lateral apertures is rare and should be differentiated from post-infectious adhesions.
4. A significant portion of congenital hydrocephalus can be caused by posterior fossa tumors in infants and children.
5. Other congenital diseases, such as achondroplasia, craniovertebral junction anomalies, spina bifida, neurocutaneous melanosis, Dandy-Walker syndrome, corpus callosum agenesis, and cerebellar cortical malformations, can also be associated with hydrocephalus.
(II) Acquired Hydrocephalus
The main causes include:
1. Intracranial infections: Bacterial, fungal, or viral infections in infants during gestation or after birth can lead to inflammatory adhesions, causing CSF circulation obstruction and resulting in hydrocephalus. Inflammatory adhesions most commonly occur in the subarachnoid space or at the outlet of the fourth ventricle.
2. Subarachnoid hemorrhage: Hemorrhage in the subarachnoid space due to various causes can obstruct CSF circulation by blocking arachnoid granulations or by organized blood clots, leading to hydrocephalus. Hydrocephalus caused by infection and hemorrhage is typically communicating.
(I) Surgical Treatment
Surgery is required for progressive hydrocephalus in children. Early surgery yields better results; however, in cases of severe cerebral atrophy and functional impairment, surgical outcomes are poorer. Various surgical procedures are available, including those that reduce CSF formation, intracranial and extracranial CSF shunts, bypass surgeries at the proximal and distal ends of ventricular obstruction, and surgeries to remove the underlying cause of obstruction. The choice of surgery depends on the etiology, nature, and location of the obstruction. For non-communicating hydrocephalus, the principle is to identify the cause and relieve the obstruction as much as possible. For communicating hydrocephalus, shunt surgery can be performed, with ventriculocardiac (V-AS) and ventriculoperitoneal (V-PS) shunts being commonly used. When hydrocephalus is accompanied by non-communicating arachnoid cysts, both ventricular and cyst shunts should be performed. Similarly, if a Dandy-Walker malformation is associated with aqueductal stenosis, both ventricular and Dandy-Walker cyst shunts are necessary. Both V-AS and V-PS require 13-type reservoirs and CSF shunt devices. Common shunt devices include domestic NJS-4 shunts, Pudez-Heyer tubes, and Holter-Spitz tubes. Each shunt device has a specially designed valve to allow unidirectional fluid flow and maintain intracranial pressure within the normal range. The short-term outcomes of V-AS and V-PS are similar. In terms of postoperative complications, V-AS is mainly associated with infection, often persistent sepsis and meningitis, and if the shunt tube becomes blocked, it is usually at the ventricular end. V-PS’s main complication is shunt tube obstruction, typically occurring at the abdominal end, and if infection occurs, it is usually abdominal. Most literature suggests that V-PS is superior to V-AS. However, long-term follow-up by George et al. indicates that post-shunt infection is not related to the surgical method but to the surgeon’s technique. Persistent sepsis after V-AS can be prevented by strict adherence to sterile techniques and avoiding insertion of the heart end tube too deeply. Moreover, V-AS has better long-term outcomes than V-PS. Based on clinical experience, the author believes V-AS is superior to V-PS. However, V-AS is contraindicated in cases of right heart failure, recent craniotomy, or incomplete absorption of intracranial gas after pneumoencephalography. Patients who have undergone V-AS should not undergo brain gas imaging.
(II) Non-Surgical Treatment
Non-surgical treatment is suitable for cases that cannot be surgically treated or as preoperative preparation to improve the child’s condition and gain surgical timing. This includes Chinese and Western diuretics and dehydration agents. For hydrocephalus secondary to subarachnoid hemorrhage, multiple lumbar punctures can also be performed.
(III) Post-Shunt Complications and Management
1. Infection: The overall infection rate after shunt surgery is 2.7–22%, with infants under one year having the highest infection rate. Children with other congenital abnormalities also have a higher infection rate. External shunt infections can cause wound or subcutaneous infection, while internal shunt infections can lead to ventriculitis, bacteremia (in V-AS), and peritonitis (in V-PS). Sometimes, shunt dysfunction (see below) is the only manifestation of infection. In some cases, infections are asymptomatic and only detected during shunt revision with routine cultures. Once infection is confirmed post-shunt, the shunt should be removed or replaced, and appropriate antibiotics should be administered intrathecally and intravenously based on bacterial culture and sensitivity results. For patients with increased intracranial pressure symptoms after shunt removal, external ventricular drainage should be performed.
2. Shunt Dysfunction: Initially, dysfunction is not apparent but may only be detected during repeated CT scans showing progressive ventricular enlargement. This can progress to persistent bulging of the anterior fontanelle, excessive head circumference growth in older children, and intracranial hypertension symptoms and signs. Management involves first determining the specific location of the obstruction and then considering shunt revision or alternative shunt procedures. Diagnostic methods include:
- If CSF cannot be aspirated from the reservoir or the valve cannot be refilled after being compressed, it indicates obstruction at the ventricular end, often due to choroid plexus or blood clot blockage.
- Difficulty compressing the valve suggests obstruction at the valve itself or the distal shunt, commonly caused by blood clots (in V-AS), omentum, or fibrin clots (in V-PS).
- Fluid accumulation in the subcutaneous tunnel suggests adhesion or pseudocyst formation at the abdominal end, or the distal tube may have been displaced from the abdomen due to growth.
3. Intracranial Hematomas: This complication is more common in children over 3 years with large head circumference and significant ventricular enlargement, resulting from rapid drainage. Subdural hematomas occur in 0.4% of cases, while epidural hematomas are rare. This can be reduced and prevented by minimizing CSF release during surgery and using high-pressure valves (0.93–1.23 kPa).
4. Premature Sutural Closure: In some children with significantly enlarged ventricles, premature suture closure can occur after ventricular shunt with low- or medium-pressure valves, leading to overlapping cranial bones. High-pressure valves (0.93–1.23 kPa) can prevent this complication.
Differential Diagnoses
1. Infantile Subdural Hematoma or Effusion: Often caused by birth trauma or other bleeding factors, it can be unilateral or bilateral, most commonly in the frontal and parietal regions. Chronic cases can also cause head enlargement and thinning of the skull. Puncture of the anterior fontanelle can differentiate it, as blood-stained or pale yellow fluid can be aspirated from the subdural space.
2. Rickets: Characterized by irregular skull thickening, leading to (prominent) frontal and occipital bones and a square skull appearance, resembling macrocephaly. However, this condition does not cause intracranial hypertension and has other rickets symptoms, distinguishing it from hydrocephalus.
3. Cerebral Dysgenesis: While ventricles may be enlarged, there is no abnormal head circumference increase. The main feature is intellectual disability without intracranial hypertension.
4. Hydrocephalus Ex Vacuo: Can be differentiated with CT scans. In hydrocephalus ex vacuo, there is no cerebral cortex in the occipital region on CT, and basal ganglia prominence is visible.
5. Macrocephaly: Caused by abnormal increases in brain weight and volume due to various factors. Some primary macrocephalies may be familial with or without cellular structural abnormalities. Although the head is large, there is no intracranial hypertension, and CT shows normal-sized ventricles.