Biochemistry of Hydrocephalus

ABSTRACT

The treatment of hydrocephalus, over the centuries, underwent three stages of evolution. During antiquity, middle ages and renaissance, hydrocephalus was not understood. Prior to the late 19^th century, treatment for “water on the brain” involved more observation than intervention .Medical treatment was useless; surgery was hopeless. The second stage extends from the 19^th century to the end of the first half of the 20^th century. Cerebrospinal fluid (CFS) circulation was now understood; surgery however, remained inefficient, but some patients survived with arrested hydrocephalus. The third stage begins in the nineteen fifties with the development of silicone shunts with a valve. Surgery transforms the prognosis of hydrocephalus, but the number of post-operative complications creates new problems. The different attempts that have been made during these past two decades to solve these problems are reviewed. They have resulted in a reduction of the mechanical and infectious complications. CSF over drainage has been minimized. Percutaneous ventriculo- cisternostomies have in some cases replaced shunts. In the future, to improve outcome in these hydrocephalics, surgery, when indicated, should be performed as early as possible. Knowledge and prevention of the causes of hydrocephalus should be developed.

CHAPTER ONE

INTRODUCTION

1. History and nomenclature

Hydrocephalus is a condition where an abnormal build-up of cerebrospinal fluid (CSF) fluid causes an increase in pressure in the ventricles or subarachnoid space of the brain. It can be caused by either the blockage of CSF flow (i.e. obstructive/non communicating hydrocephalus) in the ventricular system or by inadequate re-absorption of CSF fluid (i.e. non-obstructive/communicating hydrocephalus). These features result  in enlargement of the ventricles (i.e. ventriculomegaly) or subarachnoid space and  increase intracranial pressure (ICP). The severity of ICP can compress surrounding  brain parenchyma, manifesting into identifiable acute or chronic symptoms depending on the age of onset. Major developments in the treatment of hydrocephalus have occurred since the 20th century, with the use of shunts and neurosurgical interventions being the most successful. Currently, no cure has been found for hydrocephalus. (Drake et al.,1995).

1.1 Types and classification of hydrocephalus

Hydrocephalus can be grouped based on two broad criteria: 1) pathology and 2) etiology. Pathology can be grouped as either obstructive (non-communicating) or non-obstructive (communicating). Etiology can be grouped as congenital or acquired.  Additionally, there is a form of hydrocephalus called normal pressure hydrocephalus  (NPH),  which primarily affects the elderly population. Congenital hydrocephalus is present at birth, and can be caused by Dandy-Walker malformations,  porenchphaly,  spina bifida, Chairi I and II malformations, arachnoid cysts, and most commonly aquaductal stenosis. Very few cases of congenital hydrocephalus are inherited (X-linked  hydrocephalus). Acquired hydrocephalus may be caused by subarachnoid haemorrhage, intraventricular hemorrage, trauma, infection (meningitis),tumour, surgical  complications or severe head injury at any age. Describing hydrocephalus based on type of CSF flow (i.e. communicating/non-obstructive or non communicating/obstructive) is preferred because of the implications for treatment. Communicating hydrocephalus is often treated with shunt surgery while non-communicating hydrocephalus suggests treatment with endoscopic third ventriculostomy (ETV). Regardless of etiology, both groups present with ventriculomegaly and elevated intracranial pressure, which are responsible for the similar symptoms seen in both communicating and non-communicating forms of hydrocephalus (Drake et al., 1995).                                                      

1.2 Obstructive (Non-communicating) hydrocephalus

Obstructive hydrocephalus results from the blockage of CSF circulation, either in the ventriclesor subarachnoid space. This can be caused by cysts, tumours, haemorrhages, infections, congenital malformations and most commonly, aqueductal stenosis or cerebral aqueduct blockage. An MRI or CT scan can be useful to identify the point of blockage. Patients can then be treated by removing the obstructive lesion or diverting   the CSF using ETV or a shunt

(Tisell, M., and Wikkelso, C. 2004).

 1.3 Non-obstructive (Communicating) hydrocephalus

Non-obstructive hydrocephalus may be caused by a disruption of CSF equilibrium.

Hydrocephalus can be caused by an abundance of CSF production, as a result of a choroid plexus papilloma or carcinoma. Hydrocephalus is typically the underlying condition when CSF absorption is impaired, and can be caused by a complication after an infection or by hemorrhagic complications. Patients are often treated using a shunt.

 The causes of  hydrocephalus  is not known with certainty and is probably multifactorial. It may be caused by impaired cerebrospinal fluid (CSF) flow, reabsorption, or excessive CSF production.

• Obstruction to CSF flow hinders the free passenger of cerebrospinal fluid through the ventricular system and subarachnoid space (e.g.,  stenosis of the cerebral aqueduct or obstruction of the interventricular foramina) secondary to tumours, hemorrhages, infections or congenital malformations)and can cause increase in the central nervous system pressure.
• Hydrocephalus can also be caused by overproduction of cerebrospinal fluid (relative obstruction) (e.g., Choroid plexus papilloma, villous hypertrophy)
• Bilateral ureteric obstruction is a rare, but reported, cause of hydrocephalus.
• hydrocephalus can be caused by an abundance of CSF production, as a result  of a choroid plexus papilloma or carcinoma.

Hydrocephalus is typically the underlying condition when CSF absorption is impaired, and can be caused by a complication after an infection or by hemorrhagic complications. Patients are often treated using a shunt (Tisell, M., and Wikkelso, C. 2004).

1.4 Signs and Symptoms of Hydrocephalus

The signs and symptoms of hydrocephalus in infants and children vary depending on their age, the degree of hydrocephalus at presentation, the primary etiology, and the time over which the hydrocephalus develops. Because of the plasticity of the infant brain and the ability of the cranium to expand, ventriculomegaly can progress without obvious signs of increased intracranial pressure. In premature infants, in which hydrocephalus is caused predominately by IVH, there is a general correlation between the severity of hemorrhage and the degree of hydrocephalus . Infants with PHH may have minimal symptoms or may exhibit 50 N. Nielsen and A. Breedt increasing spells of apnea and bradycardia. They may also have hypotonia, sunsetting eyes, ophthalmoplegia, and seizures. As the ventriculomegaly progresses, the fontanel will bulge, become tense and nonpulsatile, and the cranial sutures become splayed. In a healthy premature infant, the head circumference generally increases about 1 cm a week. In premature infants with progressive ventriculomegaly, the head circumference may increase more rapidly than normal (when charted on the head growth chart) but may not accurately reflect the rate of increase in ventricular size. In full-term infants, signs often include macrocephaly and progressively increasing occipital frontal head circumference, crossing percentile curves. Normal head circumference for a full term infant is 33–36 cm at birth. A normal head circumference increases by approximately 2 cm/month during the first 3 months, by 1.5 cm/month

(Brock JW et al., 2011)

       Intracranial pressure and Normal pressure hydrocephalus                                                

Fig 1: Illustration showing different effects of hydrocephalus on the brain and cranium.

The clinical presentation of hydrocephalus varies with chronicity.  Acute dilatation of the ventricular system is more likely to manifest with the nonspecific signs and symptoms of increased intracranial pressure. By contrast chronic dilatation (especially in the elderly population) may have a more insidious onset presenting, for instance, with Hakim’s triad (Adams triad).

Symptoms of increased intracranial pressure may include headaches, vomiting, nausea, papilledema, sleepiness or coma. Elevated intracranial pressure may result in uncal and/or cerebellar tonsil herniation, with resulting life-threatening brain stem compression.

Hakim’s triad of gait instability, urinary incontinence and dementia is a relatively typical manifestation of the distinct entity normal pressure hydrocephalus (NPH). Focal neurological deficits may also occur, such as abducens nerve palsy and vertical gaze palsy (Parinaud syndrome due to compression of the quadrigeminal plate, where the neural centers coordinating the conjugated vertical eye movement are located).The symptoms depend on the cause of the blockage. The person’s age, and how much brain tissue has been damaged by the swelling. (Wilson, R.K. and Williams, M.A. 2006).

In infants with hydrocephalus, CSF builds up in the central nervous system, causing the fontanelle (soft spot) to bulge and the head to be larger than expected. Early symptoms may also include:

• Eyes that appear to gaze downward;
• Irritability;
• Seizures;
• Separated sutures;
• Sleeping;
• Vomitting

Symptoms that may occur in older children can include:

• Brief, shrill, high-pitched cry;
• Changes in personality, memory, or the ability to reason or drink;
• Changes in facial appearance and eye spacing;
• Crossed eyes or uncontrolled eye movement;
• Difficulty feeding;
• Excessive sleepiness;
• Headache;
• Irritability, poor temper control;
• Loss of bladder control (urinary incontinence);
• Loss of coordination and trouble walking;
• Muscle spasticity (spasm);
• Slow growth (child 0-5 years);
• Vomiting

adversely affected.  Learning disabilities including short- term memory loss are common among those with hydrocephalus, who tend to score better on verbal IQ, which is thought to reflect the distribution of nerve damage to the brain. However the severity of hydrocephalus can differ considerably between individuals and some are of average or above-average intelligence. Someone with hydrocephalus may have motion and visual problems, problems with coordination, or may be clumsy. They may reach puberty earlier than the average child.

(Koch-Wiewrodt, D., and Wagner, W. 2006).

Pages:  56

Category: Seminar

Format:  Word & PDF

Chapters: 1-4

Material contains Table of Content, Abstract and References