What is agnosia?

Agnosia is a condition that affects the nervous system. It causes an inability to recognise familiar objects, people, smells, flavours, tastes, or sounds. If you have signs of agnosia, you should see your doctor for advice.

What are the types and symptoms of agnosia?

If you have agnosia, you will find it difficult or impossible to recognise certain things that should be familiar, even though your senses such as vision or hearing are working normally.

There are 5 main types of agnosia, each causing different symptoms. Each type affects a different sense:

• Sight (visual agnosia) — difficulty recognising familiar faces and objects. For example, identifying a photo of family or the right items of clothing when getting dressed.
• Smell (olfactory agnosia) — difficulty recognising familiar smells, such as the fresh smell of soap.
• Taste (gustatory agnosia) — difficulty recognising familiar tastes, such as the difference between sweet and salty.
• Hearing (auditory agnosia) — difficulty recognising familiar sounds. For example, people’s voices, or a phone ringing.
• Touch (somatosensory agnosia) — difficulty recognising familiar objects by touch. For example, identifying a key or safety pin without looking at the object, or sensations related to pain, pressure, and temperature.

What causes agnosia?

Agnosia occurs when specific parts of the brain responsible for processing sight, smell, taste, hearing, memory, and recognition are suddenly damaged or deteriorate over time.

It can occur suddenly due to causes such as:

• stroke
• brain infection
• brain injury

It can develop over time, due to causes such as:

• a brain tumour
• dementia
• Parkinson's disease

When should I see my doctor?

You should see your doctor if you have trouble recognising familiar things or people.

How is agnosia diagnosed?

Agnosia is usually diagnosed by a specialist such as a neurologist or a neuropsychologist, who will:

• ask you to identify some common objects using sight, touch and smell
• check for other possible reasons for your symptoms, for example, by checking your hearing and vision
• test your brain function and memory
• refer you for imaging tests of your brain, such as a CT scan or MRI scan

How is agnosia treated?

Whether agnosia can be treated will depend on what has caused it. Your doctor will talk to you about the options available to treat whatever is causing your agnosia. For example, if you have a brain tumour, it might be possible to treat it with radiation or surgery.

A speech therapist or occupational therapist can help you to learn to cope with the effects of agnosia. Therapy usually involves:

• learning how to use other senses to compensate for an affected sense. For example, if you have visual agnosia, you can learn to close your eyes and rely more on other senses such as touch, hearing, and smell.
• relearning skills by practicing a specific task repeatedly — for example, drawing an object, while receiving feedback.
• changing your environment to make tasks easier. For example, you might label things so you can identify what they are or rearrange furniture at home for easier movement.

Resources and support

If you, or your family or carers need help living with agnosia, you might find it useful to talk to your doctor. You can also find information and support online.

• If you're experiencing symptoms and want advice on what to do next, call healthdirect on 1800 022 222 to speak with a registered nurse, 24 hours, 7 days a week (known as NURSE-ON-CALL in Victoria).
• Synapse — for people impacted by brain injury
• Stroke Foundation — for people affected by stroke