Across all vertebrate animals and the majority of invertebrates, the brain continues to serve as the hub of the nervous system. It is located within the head, typically close to the sensory structures that support senses, such as vision. This is the most intricate organ that is part of a vertebrate. The human brain seems to be the nervous system’s command center, enabling ideas, processing thoughts and feelings, and memory, and it is involved with movement and emotions through a complex function that represents the highest outcome of evolutionary processes and biological responses [1] .

Maintaining robust brain health throughout life is crucial for longevity and overall well-being, especially as the global population ages and the prevalence of neurological disorders rises. The brain, the central command center of the nervous system in vertebrates and most invertebrates, is a complex organ with distinct regions. The forebrain, the largest region, comprises the cerebral hemispheres, corpus callosum, thalamus, hypothalamus, and hippocampus. Located beneath the forebrain is the hindbrain, consisting of the cerebellum, pons, and medulla [2] .

Hydrocephalus is a significant neurological condition that has intrigued physicians for centuries due to its complex presentation and impact on cognitive function. This review aims to provide a comprehensive overview of pediatric hydrocephalus, examining its causes, symptoms, and pathophysiology. The study also highlights the latest research and innovative treatment approaches, addressing the ongoing challenges in managing this condition [3] [4] .

Hydrocephalus has been recognized and studied throughout history, with significant contributions from various medical pioneers. Their work has laid the foundation for our current understanding and treatment of this condition [5] .

The ventricular system develops from the corresponding vesicles of the neural tube. Therefore, the cavity of every telencephalic vesicle has now become the lateral ventricle, and the cavity of the diencephalic vesicle’s cavity becomes the third ventricle. The fourth ventricle is formed by the cavity of the rhombencephalon [8] . The central canal continues into the spinal cord. Thus, every lateral ventricle is a spherical space within the telencephalic vesicle throughout development. The ventricle grows Antero posteriorly as it grows forward and backward. The posterior end tends to grow downward and forward to establish the chronological horns, giving the ventricles a “C” shape. Finally, the occipital horns recede. The convergence of the two emerging telencephalic vesicles causes these same medial walls of the lateral ventricles to collide, forming a septum [9] . Well, this surface develops into the third ventricle’s roof, as well as its lateral invagination creates a choroidal fissure. The tela choroidea is created by extending a mater fold of the pia into this fissure. A collection of capillaries grows in this fold, creating the choroid plexus [4] [10] . Table 2 outlines the stages of ventricular system development and their relationship to hydrocephalus.

The precise site of the CSF flow obstruction can be determined using CT and magnetic resonance imaging (MRI) techniques. Consequently, the following classification is more accurate: One of three things can lead to hydrocephalus:

1) An excessive amount of CSF is produced (a rare condition).

2) The lateral ventricles and foramen of Monroe, the aqueduct of Sylvius, the third and fourth ventricles, or the subarachnoid spaces are blocked from CSF flow.

3) Defects in the absorption.

Hydrocephalus is a complex neurological condition characterized by an abnormal cerebrospinal fluid (CSF) accumulation within the brain’s ventricles [11] - [13] . Hydrocephalus is managed by a buildup of fluid inside the ventricles, which are deep inside the brain. Extra fluid causes the ventricles to expand, increasing the amount of pressure in the brain [14] . Typically, cerebral spinal fluid bathes the spinal column in the brain by passing through into the ventricles. However, the pressure of too much cerebrospinal fluid associated with hydrocephalus can damage brain tissues and cause a variety of cognitive function problems. While the most common types of hydrocephalus are obstructive (noncommunicating) and communicating, other classifications are based on specific criteria. One classification system categorizes hydrocephalus based on the number of ventricles involved. Monoventricular hydrocephalus affects only one lateral ventricle, while biventricular hydrocephalus involves both lateral ventricles. Triventricular hydrocephalus affects both lateral and third ventricles, and panventricular hydrocephalus involves all four ventricles.

Another classification system categorizes hydrocephalus based on its cause. Congenital hydrocephalus is present at birth, while acquired hydrocephalus develops after birth due to various factors such as injury, infection, or tumor. Idiopathic hydrocephalus is diagnosed when the cause cannot be determined.

Other types of hydrocephalus include normal pressure hydrocephalus (NPH), which primarily affects older adults and is characterized by a triad of symptoms: gait disturbance, dementia, and urinary incontinence. Hydrocephalus ex-vacuo occurs when brain tissue is lost, leading to an apparent increase in CSF volume [15] . A secondary classification under one of the following headings may be added, depending on the precise etiology: Neoplastic, traumatic, degenerative, congenital, inflammatory, and other types of hydrocephalus.

Although hydrocephalus can appear at any age, it is more common in infants and people 60 years and older. Since its inception, doctors have been fascinated by hydrocephaly due to its horrifying appearance [16] . Procedures that provide more effective treatment will have to be created once the anatomy and pathophysiology of hydrocephalus, as well as the production and absorption of cerebrospinal fluid, have been clarified.

There are obstructive and non-obstructive subtypes of hydrocephalus [17] . It is known that either a CSF flow obstruction or a decrease in the body’s capacity to store CSF can lead to hydrocephalus. The pressures within the brain then rise by swelling brought on by CSF buildup inside the ventricles and subarachnoid spaces. Despite the likelihood of intracranial hypertension in children over the age of two, infants frequently develop progressive macrocephaly [18] . Traditional methods that incorporate abnormal cerebral pulsations, brain compliance, and unique, fully categorized water transport mechanisms are replacing the conventional theory of hydrocephalus as the result of a blockage inside the bulk flow of the CSF.

Several causes of hydrocephalus develop when the balance between CSF production and absorption is disturbed, leading to dilated ventricles. There seem to be numerous classifications; however, the two most used are obstructive (noncommunicating) and communicating. The obstructive pathway manifests as a block in cerebrospinal fluid (CSF) proximal to arachnoid granulation, whereas the direct pathway method manifests itself as an abnormality in uptake in arachnoid granulation [19] .

Depending on the person’s age, stage of the disease, and level of acceptance of the situation, the hydrocephalus of each person will manifest differently clinically.

Adults may experience loss of function, such as difficulty walking or thinking, while infants and young children may be more susceptible to symptoms of increased intracranial pressure, such as vomiting. An infant’s ability to compensate for increased CSF pressure and ventricle enlargement differs from an adult. The infant skull may enlarge to facilitate the accumulation of CSF because the sutures, the fibrous joints connecting the skull bones, have not yet been forced to close [20] ( Table 3 ).

Hydrocephalus is a complex condition with a multifactorial etiology. While the exact causes of hydrocephalus are not always clear, research suggests a possible link between comorbidities, environmental factors, and the development of hydrocephalus, particularly in pediatric cases. Comorbidities, or coexisting medical conditions, can play a significant role in the development of hydrocephalus. For instance, maternal diabetes has been associated with an increased risk of congenital abnormalities and growth deformities in infants, including hydrocephalus. This may be due to a more permeable blood-brain barrier in mothers with diabetes, potentially leading to increased CSF production and brain disorders such as hydrocephalus.

Similarly, maternal hypertension during pregnancy has been linked to hydrocephalus in some children. This may be due to decreased placental blood flow, resulting in reduced oxygen and nutrient supply to the fetus, potentially contributing to the development of hydrocephalus. Environmental factors can also interact with comorbidities to increase the risk of hydrocephalus. For example, socioeconomic factors, such as poverty and malnutrition during pregnancy, can contribute to fetal growth retardation and central nervous system malformations, including hydrocephalus. Furthermore, exposure to certain environmental toxins or infections during pregnancy can also increase the risk of hydrocephalus in the developing fetus. The complex interplay between comorbidities and environmental factors highlights the multifactorial nature of hydrocephalus. Further research is needed to fully understand these intricate relationships and develop effective prevention and treatment strategies.

The most typical risk factors include: [21] - [23]

An abnormal buildup of cerebrospinal fluid in the cerebral ventricles is known as hydrocephalus, and it is typically caused by a problem with the fluid’s bloodstream absorption. In other words, when the CSF cannot travel adequately from its point of production inside the cerebral ventricles toward its point of absorption into the systemic circulation, it causes hydrocephalus, an active distension of the brain’s ventricular system.

Although patients with this disorder have a less-than-ideal prognosis, the pathophysiology of congenital and neonatal hydrocephalus is not well understood. This could be because the injury mechanisms are numerous and overlap with epidemiology, which is also complex and varied [24] . Mechanical, ischemic, and metabolic-toxic disturbances are their main mediators [25] . iNPH combines several pathogenetic elements, creating a vicious cycle that reinforces itself. Most studies suggest CSF disturbances due to altered hemodynamics [26] . Vascular, hemodynamic, and metabolic factors are all part of the physiopathology of iNPH.

It is generally accepted that the choroid plexuses, which account for 70% to 80% of CSF production, are the primary sites of CSF production. Here, CSF is filtered from across capillaries’ endothelial walls and secreted through the choroidal epithelium. Since CSF formation of CSF is thought to be an active process independent of intracranial pressure, hydrocephalus will result from a blockage of the CSF pathways [27] . The following is the typical pathway for CSF from production to clearance: The cerebral spinal fluid (CSF) leaves the choroid plexus. It travels through the lateral ventricle, interventricular foramen of Monroe, third ventricle, cerebral aqueduct of Sylvius, fourth ventricle, two lateral foramen of Luschka, one medial foramen of Magendie, subarachnoid space, arachnoid granulations, Dural sinus, and ultimately venous drainage. The Dural sinus, the subarachnoid space, the arachnoid granulations, two medial foramina of Luschka, yet another medial foramen of Magendie, and eventually the venous drainage [28] .

The following are the theories that explain the pathogenesis of hydrocephalus:

The International Guidelines have recommended the following key imaging features for the diagnosis of iNPH and the selection of patients shunt-responsive:

The most commonly used radiological criteria in the diagnosis of hydrocephalus is given below:

A high-volume spinal tap (>30 ml) (lumbar tap test) was the earliest method to establish the diagnosis of iNPH and predict the response to shunting and external lumbar drainage (ELD). A lumbar spinal catheter is inserted, and CSF is drained at a rate of 10 to 15 cm³ per hour for 72 hours [45] . Although a commercially available automated gait analysis system can quantify response to ELD walking speed, it can also be measured using a timed 10-meter walk before and after ELD.

These deal with the comorbid conditions that occur during pregnancy; they are ruled out in the following:

The clinical signs of hydrocephalus vary greatly from one person to another, depending on age, disease progression, and individual acceptance of the circumstance. Infants and young children, for instance, seem to be more vulnerable to symptoms of elevated intracranial pressure, such as vomiting, whereas adults may undergo loss of function, such as trying to walk or thinking. The capacity of an infant to compensate for increased CSF pressure and ventricle enlargement differentiates from an adult.

The complex interplay between comorbidities and environmental factors highlights the multifactorial nature of hydrocephalus, particularly in pediatric cases. Maternal diabetes and hypertension during pregnancy have been identified as significant comorbidities that can increase the risk of hydrocephalus in children. Additionally, socioeconomic factors and exposure to environmental toxins or infections during pregnancy can also contribute to the development of hydrocephalus. Further research is needed to fully understand these intricate relationships and develop effective prevention and treatment strategies for hydrocephalus.