Diseases and Disorders

An Endoscopic Nightmare: Hydrocephalus

Avikgna Linganathan


Abstract

Hydrocephalus often arises due to a number of causes including genetic abnormalities, trauma or injury and often affects patients at infancy or over the age of 60. The disease involves a dilation of the cerebral ventricular system with a following compression of the brain’s parenchyma thus leading to increased intracranial pressure.It can be both communicative and obstructive and the current forefront of treatment is the insertion of a shunt. Recently, endoscopic third ventriculostomy has gained popularity as an alternative form of treatment. Recent studies show that the disease has  an estimated incidence of 1 in 1500 births [1].  Have modern research studies come far enough to accurately explain the pathology and treatment of such a disease?

 

Overview and Etiology

The disease hydrocephalus is described to be caused by an accumulation of cerebrospinal fluid (CSF) in the ventricles of the brain which are located within the brain’s parenchyma. The parenchyma consists of several ventricles, two lateral ventricles and the Sylvius aqueduct. The disease affects a wide age range, however it is most prevalent after fetal development and in the infancy stage as well as in people above 60 years of age.. The accumulation of CSF is the main contributing factor towards hydrocephalus, and its accumulation causes a blockage in its circulation pathway which begins in the lateral ventricles and passes through the subarachnoid space before finally being absorbed in the bloodstream [2], causing the ventricles to expand and to exert intracranial pressure, thus causing hydrocephalus. 

There are multiple types of hydrocephalus including, normal pressure hydrocephalus (NPH), obstructive hydrocephalus, congenital hydrocephalus, and hydrocephalus ex-vacuo. The first and possibly the most common is communicating hydrocephalus. It occurs when the blockage or restriction in flow occurs once the CSF exits the ventricle; the term ‘communicating’ essentially means that it will still be able to flow between open ventricles. Normal pressure Hydrocephalus is a form of hydrocephalus where CSF abnormally builds up in the ventricle, as opposed to outside the ventricle due to complications following surgery, head trauma, or some form of injury. Obstructive hydrocephalus arises when the flow of CSF is blocked before it can enter the ventricle. This is often linked to aqueductal stenosis, in particular, the stenosis of the aqueduct Sylvius (the aqueduct leading to the third and fourth ventricle) which narrows and obstructs the flow of CSF into the ventricle [4]. Congenital hydrocephalus often develops in the fetal stages of development due to genetic abnormalities. Congenital hydrocephalus has been specifically linked to genes regulating brain growth and development [5]. Although we don’t fully understand the origins of congenital hydrocephalus, it is believed to develop during a specific embryonic time period of neural stem cell proliferation and brain differentiation [6]. Finally, hydrocephalus ex-vacuo emerges when neurodegenerative diseases, such as dementia, cause a reduction in brain tissue rather than a buildup in CSF, thus increasing intracranial pressure and causing hydrocephalus. 

 

Pathology

The development of hydrocephalus in an individual is often credited to genetic abnormalities, trauma, injury, or diseases such as meningitis. Congenital hydrocephalus in particular occurs in the fetal development stage and is caused by a genetic abnormality that contributes towards brain growth and development [5]. A genetic abnormality contributing towards the narrowing of the aqueduct Sylvius or towards the narrowing of the brain’s ventricles is likely to cause hydrocephalus as it allows pressure to more easily build up in the brain due to CSF accumulation. Trauma and injury often also contribute towards a CSF accumulation by causing a subarachnoid hemorrhage. This form of stroke or hemorrhage causes the blood to block the exit of CSF from the ventricles to the cisterns or to block the passageway for CSF within the cisterns. Furthermore, the hemorrhage can block arachnoid granulations via scarring. Arachnoid granulations act as one-way valves that allow CSF to exit the subarachnoid space and enter the bloodstream by allowing  CSF to diffuse across the granulations and into the superior sagittal sinus and enter venous circulation [7]. This essentially means that subarachnoid hemorrhage further contributes to CSF accumulation by damaging the arachnoid granulations. Additionally, meningitis has often been linked to increased intracranial pressure (ICP) and hydrocephalus. Pathogens linked to meningitis often reach the subarachnoid space through the bloodstream and are able to penetrate the blood-brain barrier (BBB). As it enters the subarachnoid space, it influences and imbalances the water content of the brain parenchyma, CSF volume, and cerebral blood flow, thus increasing ICP and contributing towards hydrocephalus [8].

Extra-cranial processes within the neck, heart, and mediastinum are primary CSF disturbances which are exacerbated by an increased venous pressure, reduce the rate of CSF absorption and therefore contribute towards increased ICP and hydrocephalus. Studies regarding hydrocephalus and its effects often link the majority of its damage to the periventricular white matter as well as the area surrounding the subarachnoid space in terms of neuropathological changes. The cerebral blood vessels are distorted and the capillaries often collapse while the myelin and axons suffer damage within the periventricular white matter [10]. This damage is attributed to continuous increased ICP and an overall distortion of the brain’s structure.    

 

Treatment and Diagnosis

Increased ICP and hydrocephalus often exhibit a specific triad of symptoms. Hydrocephalus often induces a gait disturbance in which the patient has difficulty walking, some form of mild dementia along with impaired control of the bladder. NPH in particular exhibits potentially reversible dementia, frequent falls as a result of gait disturbance, and recurrent urinary tract infections in the elderly [11]. It is this triad of symptoms that is often viewed as a major indicator for Hydrocephalus. Gait disturbance is often the first observed symptom as the expansion of the lateral ventricles affects the corticospinal tract motor fibres which disturbs motor function and gait.  Bladder incontinence arises as hydrocephalus causes absent central brain inhibition which leads to a hyperactive detrusor muscle thus releasing an increased amount of urine with decreased control.

The diagnosis for hydrocephalus is often performed for two reasons: to identify if the patient is indeed suffering from hydrocephalus, and to identify the patient’s candidacy for shunt treatment (Shunt treatment  is the insertion of a hollow tube into the brain via a surgical procedure which drains and redirects cerebrospinal fluid). A doctor will often begin with a physical and neurological exam, and a short interview to assess the severity of symptoms and agony. To assess the severity of the ventricle enlargement and the location of the CSF accumulation, a doctor may conduct either an MRI (Magnetic Resonance Imaging) or a CT scan (Computed Tomography). Finally, before treatment may commence, the patient’s candidacy for shunt treatment must be assessed. Therefore, a doctor may perform a lumbar spinal tap, external lumbar drainage or measure CSF outflow resistance in order to help predict shunt pressure and responsiveness. 

A patient that is a likely candidate for shunt treatment often displays the following characteristics:

The foremost treatment for a neurological disorder such as hydrocephalus is the insertion of a shunt to perform shunt treatment. Symptomatic hydrocephalus patients are likely to improve due to shunt treatment, especially patients suffering from post-traumatic hydrocephalus (PTH). [12]. The main function of a shunt is to drain the excess CSF into another part of the body where it can be easily drained. The first part of a shunt is the collection catheter which is placed within the enlarged ventricle. In the case of an enlarged ventricle with multiple septations, a neuroendoscopy can be specifically used to place a collection catheter in a location where it may be connected to an Ommaya reservoir to drain the CSF or to administer medicinal drugs [13]. There is also a valve mechanism which ensures the rate of CSF flow is controlled. Finally, a shunt is latched to an exit catheter which may be linked to an Ommaya reservoir to drain the CSF away.

A rare form of treatment for obstructive hydrocephalus is an endoscopic third ventriculostomy. This form of treatment is often performed on patients who have a CSF accumulation in the third ventricle of the brain’s parenchyma. The neuroendoscopy allows the doctor to view the ventricular system and make a small hole on the base of the third ventricle, thus allowing the CSF to bypass the obstruction and flow on its normal path around the brain surface. This technique is viewed as a valid treatment for obstructive hydrocephalus, and is an alternative to cerebrofluid shunt application [15]. Complicated cases of hydrocephalus have now improved management, and advances in technology have improved our opportunities for minimally invasive techniques [16]. Alternatively, in the case of congenital hydrocephalus, where the baby suffers from increased ICP, cephalocentesis (hollow needle inserted for drainage) without ultrasound may be performed in conjunction with fetal delivery with a baby that has massive cranial enlargement. This process has a high risk of foetal morbidity and is often only selected when cranial dimensions preclude uncomplicated vaginal delivery [17]. 

 

Conclusion

Modern medicine has been observed to have an ever-evolving nature that has pivoted over the years. With the study of medicine, our understanding of anatomy and disease has developed rapidly where we have manufactured classifications and treatments for a number of diseases that once served an undeniable threat to humanity. Although our knowledge of the pathology, origin and treatment of Hydrocephalus has evolved through a number of sources, it is apparent that a clearer, more apparent method for classifying this condition in particular should be developed due to its complex etiology. Developing a medicinal unanimity on the classification and treatment of the disease will create a manner of structure in the medical community in terms of pursuing medical trials for the disease and the development of further technologies to decrease the invasiveness of surgical procedures to treat hydrocephalus.


References


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Avikgna Linganathan

Avikgna Linganathan


I'm a student at Marlborough College Malaysia with an interest in neurosurgery and neuroscience