Eye Conditions

Medical Information on Hydrocephalus and Spina Bifida

For whom is this information intended?

The information contained in this document is intended for use primarily by parents, other members of the family and older children with visual impairment. The information will also be of use to interested health professionals, carers and teachers.

The purpose of each information document

The purpose of the information is to explain:

• The way the eyes and brain normally work to make 'vision'
• The reason why vision may become impaired by a specific condition
• The cause of the condition
• The effects of the condition on the child's vision
• How the condition is diagnosed
• What can be done to help

This document is written with the minimum use of medical terms and jargon. It is impossible to avoid all medical terms but where we have used them we have attempted to explain them as clearly as we can. Although the information is intended to describe most aspects of the condition each child is different and there will always be exceptions to the rule. As far as we can determine these pages are true and accurate and have been written in good faith. Inevitably there will be some mistakes. We apologise for this.

What this information is not for

This document is not a substitute for a consultation with a Health Professional and should not to be used as a means of diagnosing a condition.

We hope the information will help you

After reading the information we hope you will:

• Have a better understanding of the condition
• Know what tests and treatments are normally available
• Know when to seek professional advice
• Be able to discuss the condition in a more informed way
• Make the most of consultations with carers, teachers and health professionals
• Be reassured and more able to cope

Authors

These pages represent the consensus of opinion of many different people who include Parents of Visually Impaired Children, Visually Impaired Children themselves, Community Paediatricians, Ophthalmologists, Educationalists and Psychologists.

The main author and person responsible for their content is Dr Andrew Blaikie who is an Ophthalmology Research Fellow with Visual Impairment Scotland and a member of the Royal College of Ophthalmologists. We are very keen that parents and children feedback to VI Scotland about these information documents. If you have any questions or comments regarding the information please contact:

Visual Impairment Scotland
Scottish Sensory Centre
The University of Edinburgh
Holyrood Road
Edinburgh EH8 8AQ

Telephone Number : 0131 651 6078
Fax Number : 0131 651 6502
Textphone : 0131 651 6067

Email : viscotland@ed.ac.uk
Website : www.viscotland.org.uk

Medical Information on Hydrocephalus and Spina Bifida

What we see is made in the brain from signals given to it by the eyes.

What we see is in fact made in the brain. The brain makes sight from signals given to it by the eyes.

What is the normal structure of the eye?

The eye is made of three parts.

• A light focussing bit at the front (cornea and lens).
• A light sensitive film at the back of the eye (retina).
• A large collection of communication wires to the brain (optic nerve).

A curved window called the cornea first focuses the light. The light then passes through a hole called the pupil. A circle of muscle called the iris surrounds the pupil. The iris is the coloured part of the eye. The light is then focused onto the back of the eye by a lens. Tiny light sensitive patches (photoreceptors) cover the back of the eye. These photoreceptors collect information about the visual world. The covering of photoreceptors at the back of the eye forms a thin film known as the retina. Each photoreceptor sends its signals down very fine wires to the brain. The wires joining each eye to the brain are called the optic nerves. The information then travels to many different special ‘vision’ parts of the brain. All parts of the brain and eye need to be present and working for us to see normally.

What is Hydrocephalus?

The brain is surrounded by special water called cerebrospinal fluid (CSF). The CSF is made in a part of the brain called the choroid plexus. From there it flows in and around the brain through pipes and water tanks called aqueducts and ventricles. It leaves the brain through drains called the arachnoid villi. The CSF carries, amongst many other things, sugars and salt that helps the brain work. It is always being made and always draining out. This means there is always a constant flow of CSF in and around the brain. If a pipe (aqueduct) or tank (ventricle) becomes blocked the water pressure behind it builds up. Hydrocephalus is a condition where this happens. This leads to high pressure in the head.

Children with Spina Bifida are prone to developing Hydrocephalus

Children with Spina Bifida are prone to developing Hydrocephalus. Spina Bifida is a condition where the bones and nerves of the spine do not develop fully while the unborn child is in the womb. Most children do not have any symptoms from Spina Bifida. However some children may have difficulty with bladder and bowel control. Sometimes children also have difficulty controlling and feeling the lower parts of their body.

Why are children with Spina Bifida prone to developing Hydrocephalus?

Children with Spina Bifida often have a part of the brain that is a bit bigger than usual. It is found low down near the back of the brain and is called the cerebellum. This is diagnosed by looking at the pictures of a head scan. This finding is called the Chiari or Arnold Chiari Malformation, after the Doctors who first reported it. In children with Spina Bifida the large cerebellum may press on and squeeze bits of the brain near by. This can cause them to stop working. This may lead to problems with headaches, stiff neck, difficulty swallowing and weakness of the arms and legs. There is also an important ventricle near the cerebellum. It may also be squeezed and become blocked. This will stop the flow of CSF and lead to raised pressure in the head. This is why children with Spina Bifida are prone to developing Hydrocephalus.

What symptoms might a child with Hydrocephalus complain of?

The symptoms and signs that a child with Hydrocephalus might complain of can vary. High pressure in the head can often cause headaches. A child might also feel sick and tired.

How is Hydrocephalus diagnosed?

If Hydrocephalus is suspected then the pressure of CSF can be measured. A small needle is placed into the fluid around the brain. It is connected to a gauge that measures the pressure. A scan of the head is often also done. This will show if there is any obvious cause for the raised pressure.

How is Hydrocephalus treated?

With most children a drain can be placed that overcomes the blockage. This can help reduce the pressure and improve some of the symptoms. The drains can sometimes become blocked and need to be fixed or replaced.

When Hydrocephalus is caused by an enlarged cerebellum (Arnold Chiari Malformation) then a small operation may help. More space (for the large cerebellum) can be made, by taking away small bits of bone and muscle from nearby. This relieves the pressure and may help unblock the ventricle.

Many children may still need a shunt, even if they undergo an operation.

How does Hydrocephalus affect the eyes and vision?

Different children will be affected in different ways by hydrocephalus. Many children with hydrocephalus will not have any visual impairment. Others may develop several different conditions of the eyes and vision. These might include:

• Cerebral Visual Impairment (CVI)
• Visual Field Loss
• Optic Atrophy
• Nystagmus
• Squint

What is Cerebral Visual Impairment?

Cerebral Visual Impairment (CVI also sometimes known as cortical visual impairment) is a condition where some of the special ‘vision’ parts of the brain are damaged and not working properly. ‘Cerebral’ is another word for the brain. This causes reduced vision, even though the eyes are normal. In most cases, once the damage has happened it does not get worse. As the child grows the vision may slowly improve.

How does Cerebral Visual Impairment affect the way a child sees?

Most young children with Cerebral Visual Impairment feel their vision to be ‘normal’ as they have never known anything else but their own visual world. At first they assume that everyone else has vision the same as their own and do not realise that other people see things differently.

Cerebral Visual Impairment can affect vision in many ways. All or only one of the special ‘vision’ parts of the brain can be damaged to different degrees. If there has been lots of damage to many parts of the brain the vision can be very poor. However the child may still see movement and bright lights. Complete blindness due to brain damage is rare.

If there has been only a small amount of damage in only one part of the brain the visual problem can be a lot less impairing.

Children with CVI may have problems Getting Around and Recognising Objects

The many different ‘vision’ parts of the brain combine together to make two visual ‘systems’.

1. The ‘dorsal stream’ helps children get around safely and quickly

One system helps the child to get around safely and quickly. It also helps the child pick objects up and avoid bumping into things and falling over. This visual system that tells the body how to get around is called the ‘dorsal stream’. It is called a ‘stream’ because it is a flow of information about the visual world from one place to another like water flowing in a stream. ‘Dorsal’ describes the part of the brain where the system is.

When the dorsal stream is damaged it is difficult to know precisely where things are in three dimensions. It can be difficult to:

• Use stairs without falling.
• Step onto pavements without tripping.
• Reach forward and grab a cup or handle.

Damage to the dorsal stream can also make it difficult to see a lot of different things at the same time. This means it can be difficult to find a toy on a patterned carpet or to see something that is pointed out in the distance amongst other things.

2. The ‘ventral stream’ helps a child recognise objects

The other system, called the ‘ventral stream’ helps us to recognise faces, objects and places. Damage to this system leads to problems:

• Recognising familiar faces.
• Knowing what common everyday objects are.
• Losing the way in places that should be well known to the child.

There are a number of other problems that can occur in children with CVI who still appear to have good vision. These include:

• Difficulty remembering things they have seen.
• Difficulty imagining ‘seeing’ things in their minds.
• Some children’s vision can become ‘tired’ more quickly than others. This means that their ability to see can vary from one time to another.
• Difficulty reading. This can be due to lots of different reasons.

What is Visual Field Loss?

Visual field is the medical word for the full area that we can see: our visual world. If an area of our visual world is blurred or missing with the rest clear then visual field loss is present. It is due to damage to some of the special vision parts of the brain. The relationship between brain damage and visual field loss is all opposite to what you might think.

The right side of the brain is responsible for seeing the left side of the visual world. The left side of the brain sees the right side of the visual world. If the right side of the brain is damaged the left side of the visual world may not be seen. In the same way the upper part of the back of the brain is responsible for seeing the lower part of the visual world. A child with damage in this area will not see the ground when looking straight ahead. The child may then tend to trip over things.

What is Optic Atrophy?

The optic nerve contains thousands of communication wires from the eye to the brain. The wires may become damaged by high CSF (brain fluid) pressure. Some of the wires will then wear out and disappear. This may cause blurred vision and ‘washed’ out colour vision.

What is Nystagmus?

Our eyes move quickly when we watch something that is moving quickly. Our eyes are still when we look at something that is still. This is so the eyes can focus sharply on an object. The eye can then give clear signals to the brain to make clear vision. In some children the eyes are always moving ‘to and fro’ even though the object that they are looking at is still.

This ‘to and fro’ movement is called Nystagmus. Children do not know that they are doing it. Because the eye is shaking the vision is usually a bit blurred. This is like if a camera moves during a photograph. The photograph is also usually blurred. Surprisingly most children do not see the visual world shaking or moving. Often the Nystagmus slows down and sometimes stops when a child looks in a certain directions. Vision may be sharper when the Nystagmus movement slows. Children with Nystagmus often adopt a head turn to see more clearly.

What is Squint?

Squint is when a child’s eyes do not appear to be looking in the same direction. One eye may be looking too far out (divergent squint) or too far in (convergent squint). Sometimes spectacles or an operation may help the eyes to look straighter.

What can be done to help improve vision?

There are no medicines or surgical treatments that will fix or improve brain damage. There are however lots of things that can be done to help children with Hydrocephalus see better.

We use our vision to get around, learn new things and to meet other people and make friends. It is important to consider what your child’s particular problems with vision might be.

If your child has been prescribed spectacles, contact lenses or a Low Visual Aid (LVA) it is important that they are encouraged to wear and use them. This will help your child see more clearly and help the vision parts of the brain grow and develop.

Problems at school may be due to some of the reading books being hard to see. This often means it takes longer and more effort to do the work. If the size of print is increased and letters and words spaced more widely most children will find schoolwork easier. Good bright lighting and crisp black print on a clean white background will also make things easier. Sometimes placing reading books on a slope, which tilts the print towards the child, will improve reading speed as well.

When reading it can be helpful to read one line at a time through a ‘letter box’ placed over the page. Placing a piece of blue tack below the line they are reading, at the beginning of the next sentence, can help some children find their way back to the start of the next line more quickly.

A child with Nystagmus, who chooses to use a head turn or to move the head to and fro, to improve vision should not be made to stop doing this. They are trying to see more clearly and are often doing it without knowing it.

Some children may also benefit from using a computer software programme while reading. The programme only shows one word of a sentence at a time. It is in the middle of the computer screen. This reduces the need for fast eye movements. It can increase reading speed and reduce tiredness. The programme is called ACE READER. A demonstration can be downloaded from www.acereader.com. If you need any help with this please let us know.

It is also worth watching carefully to find out what the smallest toys are that a child can see and play with. Then try to only play with toys that are the same size or bigger. If the child has visual field loss try to place toys in the part of the child’s vision that is working. Placing one toy on a plain background will often help children see it more readily. Placing lots of toys of different size and colour close together on a patterned background can make them ‘invisible’ to many children with CVI.

Recognising facial expressions can often be difficult. It is worth trying to find out at what distance facial expressions can be seen and responded to. Then always try to talk and smile from within this distance. This helps a child to learn what facial expressions mean and to copy them. There is a special part of the brain that helps children ‘make sense’ of faces. Sometimes this part is also damaged. These children may have difficulty responding to smiling even if their vision is clear enough.

Infants and young children need to learn about the world around them. Home visiting teachers, physiotherapists and occupational and speech therapists may all add to the child’s care and education. It is important to continue the programmes that they recommend. If the child is involved in family activities vision can improve and new skills can develop.

Even if a child has very poor vision many useful and practical things can be done to improve the ability of the child to get around, interact with other children and learn. See the Advice section on the VI Scotland Website.