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A to Z of neurological topics

In this section we feature information on a number of tests, treatments and conditions, with links for more information either within this website or on external sites where possible. If you can't find what you're looking for, you may wish to speak with one of our Helpline team who may be able to answer your questions. Send an email to [email protected] or call free on 0808 808 1000.

  • A

    Acoustic neuroma

    (also known as a vestiblar schwannoma)


    A type of tumour that occurs in the brain and develops from the lining of the nerve that connects the ear to the brain (vestibulocochlear nerve.)


    Useful links:

    British Acoustic Neuroma Association



    If something is acquired it means that it developed sometime after birth.

    Acquired brain injury (ABI)


    See brain injury for more information.



    A symptom or condition is acute when it has developed fairly rapidly or has not been present for a long time.

    ADEM (Acute Disseminated Encephalomyelitis)


    An inflammatory demyelinating condition that affects the brain and spinal cord. It is an autoimmune condition that often follows on from a minor infection.

    Adrenomyeloneuropathy (AMN)


    A genetic, degenerative condition that can affect the spinal cord and the brain and which damages the fatty tissue in the lining that surrounds and insulates the nerves.

    Alzheimer’s Disease


    A progressive, degenerative condition that can affect multiple functions of the brain, including memory, and is the most common form of dementia.


    Useful links:

    Alzheimer’s Society



    A blood-filled swelling or bulge in a blood vessel. Aneurysms can develop in places where the walls of a blood vessel are typically weaker, such as where they branch, or they can develop as the result of damage or weakening of the walls of a blood vessel following injury or disease.


    You may also be interested in reading about Subarachnoid haemorrhage.



    An investigation that uses X-rays to examine blood vessels and the flow of blood though them. Blood vessels do not usually show up on an X-ray and so a special dye is injected in to the blood in order to make the blood vessels visible.



    See our Angiogram of the brain fact sheet

    Ankylosing spondylitis


    A chronic, inflammatory condition that primarily affects the joints in the spine, but can affect other joints in the body, and which causes back pain, fatigue, and stiffness in the back.



    Anosmia is the absence or loss of the sense of smell.


    Useful links:

    Fifth Sense



    This refers to the front of the body or one of its parts. It is the opposite of posterior.



    Aphasia is an impairment of language that occurs due to injury or damage to the brain. A person with aphasia may have difficulty finding words, problems understanding what is said to them, or they may lose the ability to speak, read, or write altogether.


    Useful links:

    Stroke Association


    Talking Point 
    Information about speech, language and communication in children.


    (also called the arachnoid mater)


    A thin membrane that covers and surrounds the brain and spinal cord. It is the middle layer of the group of three layers that are referred to as the meninges. The other two layers are the pia mater and the dura mater.

    Arachnoid Cyst


    Arachnoid cysts are fluid filled sacs that can form between the brain or spinal cord and the arachnoid layer which covers them, or within the arachnoid layer itself.


    Useful links:

    Arachnoid Cyst Friends 
    Yahoo group supporting people affected by Arachnoid Cyst (you need to join the group in order to read or post messages)

    Arachnoid web


    Arachnoid webs are abnormal ‘bands’ of the arachnoid membrane that can cause symptoms by affecting the flow of fluid around the spinal cord, and by distorting the normal anatomy of the spinal cord.



    A condition that involves inflammation of the arachnoid membrane that surrounds the brain and spinal cord. The cause of inflammation can be an infection, a consequence of surgery or trauma, or due to some other source of irritation to the arachnoid membrane. Scarring and adhesions can develop due to the inflammation and these can cause longer term symptoms and problems.

    Arnold-Chiari malformation


    Arnold-Chiari malformation is a an older term that was generally used to refer to what is now called a type 2 Chiari malformation. 


    For more information see Chiari malformation



    A blood vessel that carries oxygenated blood away from the heart and to the body.

    Astrocytic glioma

    (also known as an astrocytoma)


    A type of tumour that occurs in the brain and spinal cord, and develops from a particular kind of supporting cell in the central nervous system known as astrocytes


    See our Brain tumour booklet



    Ataxia is the loss of the ability to coordinate muscles during voluntary movement, and is also an umbrella term for a group of disorders that can affect balance, coordination and speech.


    Useful links:

    Ataxia UK

    Autonomic nervous system


    The autonomic nervous system is the part of the nervous system that controls involuntary actions such as heart rate, blood pressure, body temperature, and digestion.

    AVM (Arteriovenous malformation)


    An arteriovenous malformation is a tangle of abnormal and poorly formed blood vessels that form a connection between an artery and a vein. This connection can interfere with normal blood circulation and if a bleed develops from this malformation, it can cause severe problems depending on where it is located.


    See our Vascular malformations of the brain booklet