Stroke – brain areas and the effects of brain damage.

The brain is the source of our identity, intellect and emotions. Its intricate network of neural connections allows us to think, feel, create and communicate. But what happens when it is damaged? Here is a short guide to the different areas of the brain and the deficits that can arise when they are damaged by an ischaemic stroke — the very difficulties addressed by stroke rehabilitation.

The frontal lobes – effects of damage

The frontal lobe plays a key role in many advanced cognitive and behavioural functions that are unique to each person. This is why damage to this area can lead to specific deficits:

• Behaviour regulation and impulse control: the front part of the frontal lobe, known as the prefrontal cortex, plays a central role in controlling our behaviour. Damage to this area can lead to impulsivity, socially inappropriate behaviour and difficulty controlling anger.
• Cognitive functions: the frontal lobe plays a key role in planning, organising, problem-solving and decision-making. People with damage to the frontal lobe may struggle to carry out complex tasks that require multi-step planning, which is why cognitive rehabilitation can be helpful.
• Motor functions: the primary motor cortex is located in the upper part of the frontal lobe and is responsible for initiating and controlling purposeful movements. Damage to this area can lead to difficulties with motor coordination, paresis of the hand and upper limb or even paralysis.
• Motivation and initiative: people with damage to the frontal lobe often find it difficult to initiate actions on their own. They may become apathetic or lack the motivation to take up any activity.
• Emotional processing: although emotions are complex and involve many areas of the brain, the frontal lobe also plays a role in regulating them. Damage to this area can lead to emotional disturbances, such as emotional lability or difficulty reading other people’s emotions.

All of these functions are inseparably linked to the frontal lobe, which is why damage to it can have wide-ranging and varied effects on how a patient functions.

The parietal lobe – effects of damage

The parietal lobe is central to integrating many kinds of sensory information and coordinating that information with movement. This is why damage to this area of the brain can lead to the deficits described below:

• Sensory processing: the somatosensory cortex, located in the parietal lobe, processes information about touch, temperature and pain from different parts of the body. Damage to this area can lead to problems recognising sensory stimuli.
• Spatial orientation: the parietal lobe plays a key role in our ability to understand spatial relationships, both in relation to our own body and to our surroundings. Damage to this area can lead to difficulties judging distances, locating objects in space and manipulating them.
• Mathematical and language abilities: certain regions of the parietal lobe are linked to numeracy and to understanding certain aspects of language, such as grammar.
• Agnosia: a condition in which a patient is unable to recognise objects, even though their eyesight is intact. It is caused by a disturbance in the processing of visual information in the parietal lobe.
• Attention disorders: the parietal lobe is important for directing attention. People with damage to this area may find it difficult to concentrate on a particular task or object.
• Apraxia: difficulty in performing imitative movements on request, even though there are no motor deficits. Damage to the parietal lobe can lead to this form of apraxia.

Because the parietal lobe is an important hub in the brain’s information-processing network, damage to it can have a range of consequences, affecting a person’s ability to interact with the world in a fully functional way.

The temporal lobe – effects of damage

The temporal lobe plays an important role in a variety of functions related to processing auditory information, memory and certain aspects of language and object recognition. This is why damage to the temporal lobe can lead to deficits:

• Auditory processing: the cortex located in the temporal lobe is responsible for receiving and processing sounds. Damage to this part of the brain can lead to difficulty understanding speech or other sounds.
• Face recognition (prosopagnosia): certain areas of the temporal lobe are specialised in recognising faces. Injury to these areas can lead to difficulty recognising people’s faces, even those of close relatives.
• Memory: the temporal lobe contains important structures such as the hippocampus, which are crucial for forming and storing memories. Damage to this part of the brain can lead to problems with short-term memory and, in some cases, difficulty forming new memories — in other words, memory loss after a stroke.
• Language abilities: the main areas responsible for language are located in the temporal lobe, and damage to them can lead to aphasia, that is, loss of speech after a stroke, including difficulties with speaking, understanding, reading or writing.
• Object recognition: the temporal lobe is important for recognising objects and their properties. Damage can lead to difficulty identifying objects by touch or sight.
• Emotional disturbances: certain areas of the temporal lobe are involved in processing emotions, and damage to them can lead to emotional disturbances or an altered perception of emotional stimuli.

Given the variety of its functions, the temporal lobe is essential to many aspects of everyday experience. Damage to this area can lead to significant difficulties with communication, social interaction and everyday activities.

The occipital lobe – effects of damage

The occipital lobe is a key area responsible for processing visual information. This is why damage to the occipital lobe can lead to specific deficits:

• Visual disturbances: the main area of the visual cortex is located in the occipital lobe. Damage to this area can lead to various forms of impaired vision or even blindness in certain parts of the visual field, for example hemianopia.
• Visual agnosia: difficulty recognising objects despite intact eyesight. A person with visual agnosia may see an object but be unable to recognise or name it.
• Colour perception disorders: damage to certain areas of the occipital lobe can lead to difficulty distinguishing colours.
• Spatial disturbances: the occipital lobe is also involved in understanding spatial relationships and orientation. Damage to this area can lead to difficulty judging distance, depth and the position of objects in space.
• Alexia (word blindness): difficulty reading despite a preserved ability to understand speech. It is caused by damage to the connections between the visual cortex and the language areas of the brain.
• Complex visual hallucinations: in some cases, damage to the occipital lobe can lead to visual hallucinations, in which the patient sees images that do not exist in reality.

The occipital lobe is crucial to our ability to interpret the visual world. Any deficits in this area have a direct impact on the ability to process and respond to visual stimuli, which can affect many aspects of everyday life.

The cerebellum – effects of damage

The cerebellum plays a key role in motor coordination, balance and the precise control of movement. It is not responsible for initiating movement, but for fine-tuning movements so that they are smooth and precise. This is why damage to the cerebellum leads to characteristic deficits:

• Ataxia: the main symptom of cerebellar damage. It manifests as a lack of coordination, and patients may have difficulty walking, reaching for objects or performing precise hand movements.
• Dysmetria: difficulty judging distance while performing movements. For example, when a patient tries to touch their nose with their index finger, they may overshoot or fall short of the target.
• Dysdiadochokinesia: the inability to perform rapid alternating movements, for example when a patient tries to turn their hand up and down repeatedly.
• Intention tremor: unlike a resting tremor, an intention tremor appears during purposeful movement, for example when a person tries to touch something.
• Balance disorders: the cerebellum plays an important role in maintaining balance, so damage to it can lead to instability and falls, as well as gait and balance disorders.
• Speech disorders: cerebellar damage can lead to scanning speech, in which syllables are clearly separated and speech is slow and hesitant.
• Nystagmus (eye-movement disorders): the cerebellum is involved in controlling eye movements. Damage can lead to difficulty tracking moving objects or maintaining a steady gaze.

Although the cerebellum makes up a relatively small part of the brain’s volume, its importance for precise coordination and control of movement is enormous. Any problem with cerebellar function will affect the patient’s ability to carry out everyday activities that require motor coordination.

The brainstem – effects of damage

The brainstem is a key neurological structure that performs many fundamental life functions and acts as a bridge between the brain and the spinal cord. It is an area containing clusters of neurons — the nuclei of the cranial nerves — responsible for many functions, including the control of certain vital processes and the conduction of nerve impulses.

This is why damage to the brainstem leads to characteristic deficits:

• Disturbances of vital functions: the brainstem contains the centres responsible for controlling breathing, circulation and swallowing. Damage to these centres can be immediately life-threatening.
• Movement and sensation disorders: the pyramidal and sensory pathways, which carry impulses to and from the brain, run through the brainstem. Damage to these pathways leads to motor and sensory deficits.
• Cranial nerve disorders: the nuclei of many cranial nerves are located in the brainstem. Damage to these nuclei can lead to paralysis of the facial muscles and problems with hearing, taste, balance, vision and many other difficulties.
• Balance and coordination disorders: the brainstem, together with the cerebellum, plays a key role in maintaining balance and motor coordination.
• Horner’s syndrome: damage to certain parts of the brainstem can lead to symptoms such as a constricted pupil, a drooping eyelid and an absence of sweating (anhidrosis) on one side of the face.
• Autonomic function disorders: the brainstem plays a role in regulating autonomic functions such as heart rate and blood pressure.
• Nystagmus (eye-movement disorders): the brainstem is involved in regulating eye movements. Damage can lead to uncontrolled movements of the eyeballs or difficulty focusing the gaze.
• Disturbances of consciousness: injury or disease affecting the brainstem can lead to a coma or disturbances of consciousness.

Because of the brainstem’s crucial role in so many basic bodily functions, damage to it can lead to permanent deficits or pose an immediate threat to life.

References

1. Gajko K., Prusiński A. „Podstawy neurologii klinicznej”. Wydawnictwo Lekarskie PZWL, Warszawa.
2. Jaskólski D.J. „Neurologia praktyczna”. Wydawnictwo Lekarskie PZWL, Warszawa.
3. Zaborski J. „Atlas obrazów neurologicznych”. Wydawnictwo Lekarskie PZWL, Warszawa.
4. Sienkiewicz-Jarosz H. „Neurologia i neurochirurgia. Podręcznik dla studiów medycznych”. Wydawnictwo Lekarskie PZWL, Warszawa.
5. Niewiadomska M., Waliszewska-Prosół M. „Neurorehabilitacja w praktyce”. Wydawnictwo Lekarskie PZWL, Warszawa.