Pitfalls in the treatment of hydrocephalus

This article aims to describe the causes and types of hydrocephalus, as well as explain why treatment options may vary from case to case. Potential complications of treatment are also discussed. What is hydrocephalus? Hydrocephalus is a condition which develops when there is an abnormality in either the production or the removal of cerebrospinal fluid (CSF) from the ventricles within the brain and the spaces that surround the brain. The resulting build-up of fluid within these spaces, usually in the ventricles, causes an increase in intracranial pressure which can cause a variety of symptoms. The majority of patients with hydrocephalus have problems with absorption of the fluid rather than over-production. CSF is made by the choroid plexus, a rich network of blood vessels mostly located in the lateral ventricles of the brain and to a smaller extent within the fourth ventricle. Once secreted into the ventricles, the fluid then travels through small channels, including one particularly important channel known as the cerebral aqueduct, before exiting the ventricular system and entering the space around the outside of the brain. The CSF bathes the brain before coming up to the midline surfaces over the top of the brain where it is re-absorbed by a primarily passive process into the venous sinuses, notably the superior sagittal sinus, and then re-incorporated into the bloodstream. The location of the difficulty in communication between the site of production and the site of absorption distinguishes the two main types of hydrocephalus known as communicating and non-communicating (or obstructive) hydrocephalus. In communicating hydrocephalus, there is free-flow of CSF to the venous sinuses as well as through the subsequent connection to the spinal canal, where the CSF also bathes the spinal cord. The abnormality lies in delayed or reduced absorption at the venous sinus level. Common causes for communicating hydrocephalus include subarachnoid haemorrhage and meningitis. In obstructive hydrocephalus there is a physical barrier to the fluid getting to the venous sinuses and the spinal column, leading to a build-up of fluid within the ventricular system. Common causes for obstructive hydrocephalus include tumours, particularly those that obstruct the cerebral aqueduct, and haemorrhages that lead to a clot being lodged somewhere within the ventricular system (also commonly at the aqueduct or within the cerebellum region). Symptoms and signs of hydrocephalus Patients with hydrocephalus generally present with symptoms of raised intracranial pressure, and may arise in conjunction with symptoms caused by the underlying cause of the hydrocephalus. In broad terms, the hydrocephalus itself causes different sets of symptoms and clinical findings depending on the age of the patient. In babies where the skull has not yet fused, hydrocephalus tends to present with vomiting, drowsiness, listlessness and irritability. If the history is more chronic, i.e. over several weeks, then an increase in head circumference may also be noticed by the parents. Occasionally parents may also comment that the child is unable to look upwards (known as ‘sun-setting’); their neurological development may cease or they may even lose developmental milestones. In older children and adults the primary symptom will be headaches associated with loss of appetite and vomiting, increased sleepiness, lack of concentration or confusion. These symptoms can progress to blurred vision, and the visual deterioration may be severe enough to leave the patient blind. Eventually there may be decreased conscious level, coma and death. Although these last consequences are relatively unusual outside of a very acute setting in developed countries, every year there are deaths or major disabilities as a consequence of undiagnosed or inadequately treated hydrocephalus in the UK. Some neurological symptoms, such as cranial nerve palsies (often leading to double vision) or seizures can occur in any age group.