Introduction

Stroke is one of the leading causes of death or disability in the UK with around 100,000 strokes occurring each year.¹ During a stroke, part of the brain is starved of oxygen, creating a lesion – an area of damaged or dead neurons. Depending on the area affected, patients may present with a range of symptoms caused by neurological damage that stretch from physical disability to cognitive impairment.

One such impairment is agnosia, a rare condition which may occur following a stroke in which a person is unable to identify people, items, voices, or sounds despite having healthily functioning senses.² Agnosia generally presents in one of two forms: associative and apperceptive, which are discussed in further detail later in the article.

What is a stroke?

During a stroke, the brain's usual blood supply is cut off by either a blockage (ischaemic stroke) or bleeding (haemorrhagic stroke) in the brain. This means that the affected area of the brain has little to no oxygen supply.¹ When part of the brain is starved of oxygen for prolonged periods, the neurons become damaged or die, causing a lesion in the brain. The size of the lesion depends on the amount of time taken to restore blood flow, and therefore restore the oxygen supply, to that area of the brain.

Immediate signs of a stroke

• Sudden onset weakness on one side of the body
• Drooping of one side of the face
• Loss of balance
• Difficulty swallowing
• Dizziness or loss of consciousness
• Memory loss and confusion
• Speech difficulties – i.e. unable to form sentences or speak clearly
• Sudden onset headache or migraine that feels different to usual headaches
• Nausea and vomiting
• Loss or blurring of vision^3,4

Think ‘FAST’ and call for help if you notice one or more of the following symptoms:

F – FACE - is the person's face drooping?

A – ARMS - do they have arm weakness?

S – SPEECH - are they having difficulty speaking?

T – TIME to call for an ambulance

Long-term effects of stroke

Stroke is the leading cause of disability in the UK, and its effects can vary massively depending on several factors.¹ This includes the length of time taken to restore blood flow, the extent of damage to the brain, and the specific area of the brain that has been damaged.⁴ As different areas of the brain play different roles in specific cognitive and physical functions, it is perhaps not surprising that there is a huge diversity in the short- and long-term impairments caused by stroke.

Most often, rehabilitation will begin in hospital before patients can be treated as an outpatient at home or at their local clinic.⁵ Agnosia is a neurological condition which can result from stroke and is closely associated with damage to the brain in specific areas which are important for sensory processing, i.e. the parietal, temporal. and occipital lobes.²

Agnosia

Agnosia describes a neurological disorder where a person is unable to identify people, objects, voices, or sounds despite having healthily functioning senses. There are two main forms of agnosia which are categorised by the stage of processing disrupted: apperceptive agnosia and associative agnosia.

Apperceptive agnosia describes a disruption to early perceptual processing, in the absence of any identifiable issues with vision. Individuals with apperceptive agnosia retain their knowledge of objects, items or people, but are unable to process their perceptual features.² For example, a person with apperceptive agnosia would be unable to match an object to a picture of that same object and cannot draw or copy a drawing of that object. They would also be unable to describe the shape, colour, or size of the object.

Associative agnosia, on the other hand, describes a disruption to later processing. An individual with associative agnosia struggles to recognise objects, items, or people, despite having no problems with their vision or perceptual processing.² This means that they can describe perceptual features of an object such as its colour and shape, and can draw, copy or match objects to their photos, unlike in apperceptive agnosia. However, the individual is still unable to name the object or describe its use.

For example, when presented with a mug, an individual with associative agnosia could describe its colour or shape and match it to other mugs or photos of mugs. However, they would be unable to tell you that it is used to hold hot drinks, or describe that one holds the mug by its handle.

There are also several sub-types of agnosia which are categorised by the sensory system which is associated with the agnosia. This includes visual agnosia, tactile agnosia, and auditory agnosia. Each sub-type of agnosia can take either the associative or apperceptive form. Importantly, the introduction of sensory information from other senses which are not associated with that agnosia sub-type can minimise the effects of agnosia.

Types of agnosia stretch far beyond the three listed above and can be extremely specific to skills such as facial recognition (prosopagnosia), topographical organisation – i.e. the ability to orient oneself in one’s surroundings (topographagnosia), and motion perception (akinetopsia).^6,7

A case study for understanding agnosia forms and sub-types:

The following example presents a made-up case of agnosia:

Sarah has no problems with her eyesight. When presented with an apple, Sarah can describe the shape and colour of the apple but cannot name it. Sarah can also match the apple to a picture of an apple and distinguish it from pictures of a pear or a banana. This indicates that she has no issues with perception or early perceptual processing. Additionally, Sarah cannot describe the meaning or use of the apple – i.e. that it is a fruit, and that you can eat it. However, after being allowed to touch the apple, Sarah is now able to name the apple and describe the apple as an edible fruit.

Sarah encounters problems at a later processing stage, preventing her from identifying and naming the apple. This means that their agnosia is associative. Furthermore, Sarah’s difficulty in naming the object occurs when presented with the object visually but disappears when she is allowed to touch the apple – facilitating her to process the tactile sensory information to aid recognition. This means that Sarah has visual agnosia, the most common type of agnosia, and that her processing of tactile sensation is unaffected.

Living with agnosia

Agnosia can create many challenges in the day-to-day life of individuals who have it. Someone living with apperceptive visual agnosia may be unable to distinguish their home from their neighbours’ homes as they cannot process perceptual differences which would usually differentiate them. On the other hand, someone with akinetopsia may be unable to cross a busy road without aid, as their perception of motion is impaired, and their judgement of their speed and direction could put them at risk.⁷ This can have a major impact on the independence of someone living with agnosia and puts significant strain on families and carers to assist them with daily tasks. It is also important to note that in the context of stroke, the onset of agnosia is very sudden and is likely to be accompanied by other effects of stroke such as full or partial paralysis, memory loss, fatigue, and mental health decline.⁸ This can make the care needs of individuals with agnosia, following stroke, more complex.

Treatment for agnosia

There is no cure for agnosia following stroke as it is caused by irreversible damage to important areas in the brain. Agnosia can also have other causes such as traumatic brain injury or brain tumour.² In some cases, treatment of the cause such as shrinking of a brain tumour using radiation therapy may lessen the symptoms of agnosia.

Treatment for agnosia often focuses on therapies which encourage and train patients to make full use of their unaffected senses.² This is sometimes referred to as ‘alternative cue’ therapy. For example, a patient with prosopagnosia (inability to recognise faces) may be encouraged to focus on the sound of others' voices to aid recognition. Other therapies may instead focus on training the senses which are impaired in an attempt to improve the functioning of the damaged brain area through repetition, although improvements may be very limited.⁹

Other adjustments may be recommended to aid the patient’s daily routine. This can include putting labels on household items, making sure that the patient’s home is well-lit, and encouraging routines with all important items (e.g. medications, house keys and mobile phone) kept in the same place between use.⁹

Finally, services may be available in your local area which aim to support patients and their families in adjusting to changes to their lives caused by stroke, including the cognitive impairments caused by agnosia. Contact your local healthcare provider to find out more about the resources specific to your area.

Summary

To conclude, when agnosia occurs due to brain damage caused by stroke, it can present in a range of ways with varying degrees of severity. Hence, there are many forms and sub-types of agnosia which reflect the damaged brain area. The sudden onset of agnosia in the context of stroke, alongside the management of other long-term disabilities caused by stroke, can present many challenges in daily life for both patients and their carers. There is no cure for agnosia, but there are therapies that train patients to fully utilise their intact senses and improve recognition rates.