Hydrocephalus

Overview

The symptomatic buildup of cerebrospinal fluid (CSF) inside the brain ventricles is known as hydrocephalus. This buildup might be due to a blockage in the normal flow of CSF, issues with absorption into the venous system by arachnoid granulations, or excessive CSF production. Dandy defined hydrocephalus as communicative and noncommunicating (obstructive), and several other categories have subsequently been offered.

There are four forms of hydrocephalus in adults: obstructive, communicative, hypersecretory, and normal pressure hydrocephalus (NPH). Congenital or developmental hydrocephalus is common at birth and is frequently associated with a genetic abnormality or spinal dysraphism.

Hydrocephalus definition

Hydrocephalus is described generically as a disruption in the creation, flow, or absorption of cerebrospinal fluid (CSF), resulting in an increase in the volume occupied by this fluid in the central nervous system (CNS). This illness is also known as a hydrodynamic CSF abnormality.

Cute hydrocephalus lasts a few days, subacute hydrocephalus lasts a few weeks, and chronic hydrocephalus lasts months or years. Cerebral atrophy and isolated destructive lesions can potentially cause an aberrant rise in CSF in the CNS.

In some cases, the loss of brain tissue creates a void that is passively filled with CSF. Because these disorders are not caused by a hydrodynamic problem, they are not classed as hydrocephalus. Hydrocephalus ex vacuo was an earlier term used to characterize these diseases.

Benign external hydrocephalus (infant enlargement of the subarachnoid spaces) is a self-limiting absorption defect of infancy and early childhood characterized by modestly elevated intracranial pressure (ICP) and expanded subarachnoid spaces. The ventricles are normally not greatly enlarged, and the condition usually resolves within a year.

Normal-pressure hydrocephalus (NPH) is an uncommon illness that affects people under the age of 60. The name NPH was coined due to enlarged ventricles and normal CSF pressure upon lumbar puncture (LP) in the absence of papilledema. However, sporadic intracranial hypertension has been seen during surveillance of individuals suspected of having NPH, generally at night. Gait apraxia, incontinence, and dementia are the typical Hakim trio of symptoms. Headache is not a common symptom of NPH.

When the ventricles and subarachnoid space communicate fully, this is referred to as communicating hydrocephalus. It is caused by overproduction of CSF, poor absorption of CSF or venous drainage insufficiency 

Noncommunicating hydrocephalus occurs when CSF flow is impeded inside the ventricular system or in its outputs to the arachnoid space, resulting in impaired CSF flow from the ventricular to the subarachnoid area. The most prevalent kind of noncommunicating hydrocephalus is obstructive, which is characterized by intraventricular or extraventricular mass-occupying lesions that disturb the ventricular structure.

Epidemiology

Infancy is the most likely time for hydrocephalus to develop as a result of congenital abnormalities and intraventricular bleeding in preterm newborns. It reaches a new high later in life as a result of NPH instances. The general global prevalence of hydrocephalus is around 85 per 100,000 people, with a notable disparity across age groups; 88 per 100,000 for the pediatric population and 11 per 100,000 for adults.

Due to the high frequency of NPH later in life, the prevalence in the senior population is substantially greater, about 175 per 100,000, and more than 400 per 100,000 for those over 80 years old. Hydrocephalus is more common in Africa and South America. The prevalence of infantile hydrocephalus ranges between 1 and 32 per 10,000 babies. In general, both genders are equally impacted.

Hydrocephalus causes

Obstructive hydrocephalus is caused by a blockage in the CSF channels. The foramina Monro, the aqueduct of Sylvius, the fourth ventricle, and the foramen magnum are the most usually obstructed CSF channels, however most tumors of substantial size can block at any point in the CSF pathways. Ependymoma, subependymal giant cell astrocytoma, choroid plexus papilloma, craniopharyngioma, pituitary adenoma, hypothalamic or optic nerve glioma, hamartoma, and metastatic cancers are among the most common tumors linked with hydrocephalus. Hydrocephalus is frequently related to malignancies of the posterior fossa.

The reason for communicating hydrocephalus is poor CSF absorption. Post-hemorrhagic or post-inflammatory alterations are the most typical causes. One-third of these instances are caused by subarachnoid hemorrhage, which prevents CSF absorption at the arachnoid granulations. Meningitis, particularly bacterial meningitis, can be worsened by hydrocephalus. Head trauma in the industrial environment is a major factor to adult hydrocephalus.

Hypersecretory hydrocephalus is caused by an increase in CSF production, which is most likely caused by a plexus papilloma or, in rare cases, a carcinoma. Children are more likely to get these tumors.

Normal-pressure hydrocephalus (NPH) is a kind of communicating hydrocephalus that is more common in elderly people and has an unknown cause. It is caused by impaired CSF dynamics with little or no rise in intracranial pressure (ICP)

Hydrocephalus can be caused by prenatal bleeding or infection. Some hereditary variants of hydrocephalus may be undetectable at birth. Almost 10% of all occurrences of hydrocephalus in infants are caused by brainstem abnormality with cerebral aqueduct stenosis. In this age range, Dandy-Walker deformity will be the source of 2-4 percent of hydrocephalus. Arnold-Chiari types 1 and 2, foramen of Monro agenesis, and Bickers-Adams syndrome are all prevalent in babies with hydrocephalus.

Pathophysiology

The choroid plexus, which is found in the lateral, third, and fourth ventricles, is the primary producer of CSF. It goes through the ventricular system via the foramen of Monro from the lateral ventricle to the third ventricle, and from the third to the fourth ventricle via the cerebral aqueduct or aqueduct of Sylvius. It exits the fourth ventricle via the two lateral foramina of Luschka and the median foramen of Magendie to reach basal cisterns, and a portion of it continues to circulate around the spinal cord and in the spinal canal.

Arachnoid granulations that develop into dural venous sinuses, particularly the superior sagittal sinus, are the primary sources of CSF absorption. CSF enters the systemic circulation after being absorbed into the venous sinuses. The typical CSF volume is about 150 mL, with a daily output of roughly 500mL. This implies that the whole volume of CSF is changed three times every 24 hours.

CFS moves slowly from sites of production to sites of absorption. Hydrocephalus can be caused by any physical or functional restriction within the ventricular system, subarachnoid space, or venous sinuses. CSF flow inside the ventricular system might be blocked by an obstructive lesion or gliosis. Inflammation or scarring of the subarachnoid space, as well as high venous pressure inside the venous sinuses, can all reduce CSF absorption into the systemic circulation. 

The total volume of the brain, CSF, and blood within the skull is constant. An increase in one compartment must be accompanied by a reduction in another; otherwise, the pressure within the skull would rise, as in hydrocephalus. Increased ICP causes transependymal CSF extravasation into brain tissue, resulting in brain injury and pressure-induced atrophy.

Hydrocephalus symptoms

Hydrocephalus is often diagnosed using a combination of clinical symptoms, radiological imaging, and CSF pressure measures. The patient's age, origin, location of the blockage, length, and quickness of start all have an impact on the clinical symptoms of hydrocephalus.

Acute hydrocephalus is a potentially fatal disorder that can cause brain herniation, transtentorial herniation of the temporal lobe, or cerebellar herniation into the foramen magnum, with a dilated and nonreactive ipsilateral pupil, autonomic dysfunction, loss of brain stem reflexes, and coma. To alleviate the pressure, rapid neurosurgical intervention is required.

Congenital hydrocephalus is a condition that occurs at birth. A big head at birth is a telltale indicator of congenital hydrocephalus. Many other symptoms of congenital hydrocephalus include tense and bulging fontanelle, suture disjunction, thin and shiny scalp with prominently visible veins, stiff arms and legs prone to contractions, "the setting sun" outlook (pupils of the eyes may be close to the lower eyelid), breathing difficulties, poor feeding, the infant's unwillingness to bend or move their neck or head, and delayed developmental stages.

Patients may exhibit delayed development and sexual maturity, high-pitched crying, irritation, sleepiness, or both, as well as vomiting and convulsions. The failure of upward gaze is caused by supranuclear pressure on the tectal plate. Other components of dorsal midbrain syndrome (Parinaud syndrome) may be present in severe untreated types of hydrocephalus.

Hydrocephalus can develop at any age. Headache, neck pain, nausea, explosive vomiting, sleepiness, lethargy, irritability, seizures, confusion, disorientation, blurred vision, diplopia, urine and bowel incontinence, gait instability, balance issues, loss of appetite, personality changes, and memory problems are some of the symptoms.

Gait difficulties, dementia, and urine incontinence are the typical Hakim trio of NPH. NPH signs and symptoms might take months or years to appear. A wide-based gait is the most common type of gait disability. As the condition progresses, individuals may develop apraxia, or the inability to take steps. Muscle strength is normally normal, however reflexes may be heightened with or without the Babinski reaction. Sucking and clutching reflexes, as well as frontal release indications, may be present in the late stages.

Diagnosis

In the case of congenital hydrocephalus, genetic testing and counseling may be advised. CSF analysis might be performed to aid in the diagnosis and to rule out any remaining infection.

X-rays of the skull may show erosion of the sella turcica, or the look of a "beaten copper cranium," however they are seldom helpful or suggested given the advent of better imaging tools.

In babies, ultrasound via the anterior fontanelle may be utilized to assess the ventricular system and the course of hydrocephalus.

Neuroimaging is crucial in verifying a suspected diagnosis, determining the etiology, and considering therapy options. An emergency head computed tomographic (CT) scan is the primary option in situations of acute hydrocephalus to measure ventricular size. On a brain CT scan, transependymal exudate can be seen as periventricular hypoattenuation. The "Mickey Mouse" sign is formed by ballooning the frontal horns of the lateral ventricle and third ventricle. It might be an aqueductal occlusion.

The research of choice is magnetic resonance imaging (MRI) of the brain, which displays the posterior fossa structures better, can discriminate between brain tumors and degenerative disorders, and can distinguish NPH from cerebral atrophy. Transependymal exudate can be seen on T2 and FLAIR sequences as periventricular hyperintensity.

CSF extravasation must be distinguished from periventricular white matter alterations caused by aging. On axial cross-sectional scans, such alterations are typically smaller than 10mm in diameter, and their thickness decreases from anterior to posterior. The corpus callosum can be pushed up in sagittal images.

Temporal horns may be less pronounced in situations of persistent hydrocephalus. The corpus callosum may also be atrophied in these circumstances, although the neurodegenerative illness should be ruled out. The MRI cine method may be used to evaluate CSF stroke volume in the cerebral aqueduct, however these findings do not appear to be effective in predicting response to shunting.

Radionuclide cisternography is a technique for determining NPH and the likelihood of shunting. This test has a limited sensitivity and is rarely used.

Hydrocephalus treatment 

If left untreated, hydrocephalus can result in lifelong brain damage, physical and mental incapacity, and death. The initial therapy focuses on the cause. Surgical evacuation may be used to treat hydrocephalus caused by intraparenchymal bleeding or tumors. When hydrocephalus continues, it is treated surgically by inserting a ventricular shunt. CSF is shunted to another portion of the body where it can be absorbed. Many people enjoy healthy lives with little restrictions after receiving therapy.

The most frequent form of shunt is a ventriculoperitoneal (VP) shunt. It normally drains CSF from the lateral ventricle to the peritoneal cavity; in children, the distal peritoneal section can be left long and does not need to be changed as the kid grows. A ventriculoatrial shunt (VA) shunt is another prevalent form. CSF is shunted into the right atrium via the jugular vein and superior vena cava.

It is most commonly utilized in patients with abdominal anomalies such as peritonitis, following significant abdominal surgery, or in people who are very obese. If the above-mentioned therapies fail, a ventriculo-pleural shunt is a last resort. In situations of pseudotumor cerebri, a lumboperitoneal shunt is recommended.

There are alternatives to shunting to consider. Endoscopic third ventriculostomy (ETV) is a procedure that opens the floor of the third ventricle, allowing CSF from the third ventricle to enter the prepontine basal cistern. ETV is often utilized to prevent a permanent shunt in situations with aqueductal stenosis; however, the outcome in very young newborns is poor.

In addition, individuals with long-standing shunted obstructive hydrocephalus had poor outcomes because the arachnoid granulations had lost their absorptive ability. Choroid plexus coagulation can be utilized to treat situations of excessive CSF generation. Repeat lumbar punctures can be performed in patients of communicating hydrocephalus if spontaneous resorption is suspected.

Acute hydrocephalus is considered a medical emergency. In neonates, an anterior fontanelle ventricular tap may be done if a shunt cannot be implanted immediately. The most common operation performed in these circumstances in adults and children is the insertion of an external ventricular drain. Lumbar puncture is an option in post hemorrhagic and post meningitic hydrocephalus.

Serial fontanelle taps may help premature babies with post hemorrhagic hydrocephalus. The vast majority of individuals with hydrocephalus caused by a posterior fossa tumor do not require a permanent shunt. A ventriculostomy may be inserted briefly preoperatively or intraoperatively to aid in tumor removal and then withdrawn when no longer required.

Acetazolamide, a carbonic anhydrase inhibitor, reduces CSF production by the choroid plexus and is thus used to treat hydrocephalus. It is most commonly used in the treatment of pseudotumor cerebri.

Differential Diagnosis

Because the appearance of hydrocephalus is similar to that of many other disorders, the following differential diagnoses should be considered when examining a patient with hydrocephalus.

• Idiopathic intracranial hypertension (IIH) (pseudotumor cerebri): There is an increase in intracranial pressure but no identified disease.
• Age-related changes 
• Secondary atrophy: Autoimmune diseases, HIV infection, chemotherapy 
• Brainstem gliomas
• Frontal lobe epilepsy
• Frontal lobe syndromes
• Intracranial hemorrhage
• Migraine headache
• Primary CNS lymphoma
• Pituitary tumors
• Acute subdural hematoma
• Subdural empyema

Prognosis

The prognosis is primarily determined by the source of the hydrocephalus. Half of the patients with severe intraventricular hemorrhage may necessitate immediate treatment. After posterior fossa surgery, around 20% of children will require permanent shunting.

There are various, often contentious, factors used to predict the success of shunting in NPH patients. It is believed that if a gait impairment precedes a mental disturbance, shunting has a greater than 77 percent probability of improving the condition. The response to a single lumbar puncture or external lumbar drain is another criterion.

Improvement in symptoms following a single lumbar puncture with 40-50 ml of CSF extracted or after the lumbar drain is seen as a favorable predictor of shunt success. Persistent ventricular activity 48 to 72 hours after isotope cisternography increases the likelihood of symptom relief with shunt installation by more than 75%.

Complications

The extent of brain damage produced by hydrocephalus varies depending on a number of factors. At delivery, newborns with severe advanced hydrocephalus will most certainly have brain impairment as well as physical problems. Patients with less severe hydrocephalus who receive appropriate therapy may live a largely normal life. Complications are connected with the advancement of hydrocephalus, medical therapy, and surgical surgery.

• Visual changes
• Temporal lobe herniation
• Cognitive dysfunction
• Incontinence
• Gait problems
• Electrolyte imbalance
• Metabolic acidosis
• Shunt obstruction
• Shunt disconnection
• Under shunting
• Over shunting
• Subdural hematoma
• Subdural hygroma
• Seizures
• Extraneural metastases
• Hardware erosion
• Peritonitis
• Inguinal hernia
• Perforation of abdominal organs
• Intestinal obstruction
• Volvulus
• Ascites 
• Septicemia
• Endocarditis
• Pulmonary hypertension
• Radiculopathy and arachnoiditis (lumboperitoneal shunts)

Conclusion 

Hydrocephalus is a disorder in which cerebrospinal fluid (CSF) accumulates within the brain. This usually results in increased pressure inside the skull. Headaches, double vision, poor balance, urine incontinence, behavioral changes, and mental impairment are all common among the elderly.

In the treatment of hydrocephalus, especially in children, a multidisciplinary team approach is critical. Their health-care requirements persist into childhood and youth. Health care transition is the process of leaving the childhood health care system and entering the adult health care system, however many families and patients are unprepared for this era. 

Best practices have been discovered, and consensus suggestions have been made to help with this difficult moment. A multidisciplinary team comprised of a pediatrician, neurosurgeon, ophthalmologist, and rehabilitation expert provides the patient with integrated treatment for a positive outcome.