What Are Brain Lesions? Understanding Their Causes and Symptoms

The brain is the most vital organ in the body, playing a key role in judgment, thinking, learning and memory. It also controls all movements, coordinating them throughout the body. The brain controls many essential functions required to sustain life. Every process in the body, whether directly or indirectly, is influenced by the brain. Brain lesions can disrupt all of these vital processes.

Symptoms

Different regions of the brain are responsible for various functions, so the symptoms of brain lesions can differ based on their location. A neurologist or healthcare provider will use your symptoms to pinpoint the affected area of your brain. The brain is composed of three primary sections: Cerebrum, cerebellum and brainstem.

Cerebrum: The cerebrum is the largest part of the brain and is divided into two halves: The left and the right hemispheres. Each hemisphere of the brain comprises four regions (called lobes): Frontal, temporal, parietal and occipital lobes. Additionally, there is a concealed internal region, known as the insula, located beneath the frontal lobe.

Frontal lobe: It is located at the front of the brain. Lesions in this area can result in various symptoms or conditions, such as:

• Difficulty with learning
• Issues with visual-motor coordination
• Executive dysfunction, including problems with attention, planning, focus and inhibition
• Agitation and mood fluctuations
• Aphasia (Broca’s type) (difficulty expressing words)
• Weakness or paralysis in a particular area or side of the body
• Loss of the sense of smell (anosmia)

Temporal lobe: These are located on the sides of the head. Lesions in this region of the brain may lead to:

• Aphasia (Wernicke’s type) (difficulty understanding words)
• Challenges with auditory processing
• Parietal lobe: It is located at the top of the head. Lesions in this area may lead to:
• Numbness or tingling (typically caused by nerve issues in the limbs rather than the brain)
• Agraphia (inability to write)
• Acalculia (difficulty with math)
• Finger agnosia (inability to recognise your own hands or fingers)
• Confusion between left and right

Insular lobe: It is also known as the insula. It is located just beneath the frontal lobe. Lesions in this area may lead to:

• Loss of taste sensation (ageusia)
• Disruptions in the sympathetic (fight or flight) and parasympathetic (rest and digest) nervous systems
• Occipital lobe: It is located at the back of the head. Lesions in this area may lead to:
• Cortical blindness (loss of vision due to a brain issue rather than an eye problem)
• Complete colour blindness (achromatopsia)
• Face blindness (prosopagnosia)
• Difficulty recognising objects (visual agnosia)

Cerebellum: It is a compact region of brain tissue located at the lower back of the skull. Lesions in the cerebellum can cause the following symptoms:

• Dysarthria (difficulty coordinating the muscles needed for speech)
• Dizziness
• Paralysis
• Shaking and tremors
• Difficulty controlling eye movements, resulting in vision issues such as double vision (diplopia)

Brainstem: The brainstem is a stalk-like structure that links the brain to the spinal cord. Lesions in the brainstem can lead to issues with heart rhythm, breathing, blood pressure, eye alignment and other vital functions.

Causes  

Brain lesions can occur in any condition or situation that causes damage to the brain.

Medical conditions that cause brain lesions include:

• Brain tumours (including cancer)
• Birth defects (conditions present at birth) and metabolic disorders
• Degenerative brain disorders, particularly those related to ageing, such as Alzheimer’s disease, Lewy body dementia, multiple system atrophy and Parkinson’s disease
• Immune and inflammatory disorders, like multiple sclerosis or lupus
• Infections from microorganisms such as bacteria, fungi, parasites or amoebas
• Genetic conditions like Huntington’s disease or Wilson’s disease
• Progressive supranuclear palsy
• Seizures and epilepsy
• Strokes or transient ischemic attacks (TIAs)

Injuries, trauma and non-medical factors that can lead to brain lesions include:

• Concussions and other types of traumatic brain injuries
• Medical treatments like surgery, radiation therapy or chemotherapy
• Exposure to radiation
• Poisoning from heavy metals or other toxins

Diagnosis

A healthcare provider may begin to suspect a brain lesion after conducting a neurological exam. During this exam, they assess muscle strength in the limbs, check the reflexes and evaluate the functioning of the senses. Following a neurological exam, the next step in detecting a brain lesion is through imaging scans.  

Some of the most common imaging techniques used to identify these lesions include:

Computed tomography (CT) scan: CT scans detect varying tissue densities, with denser structures appearing brighter. During brain imaging, hyper-dense lesions in the brain are brighter due to higher density, while hypo-dense lesions in the brain appear darker due to lower density. Lesions with similar density to surrounding tissue are called iso dense. Ring-enhancing lesions in the brain are abnormal neuroimaging findings characterised by a region of reduced density encircled by a bright rim caused by the enhancing contrast dye.

• Magnetic resonance imaging (MRI) scans
• Positron emission tomography (PET) scans

Other tests may also be used, usually to identify or exclude other conditions that could produce similar symptoms. Your healthcare provider is the best person to explain which tests they recommend and the reasons behind their choices.

Treatment

Brain lesion treatment depends on the underlying cause. Mild conditions, like concussions, often heal on their own with rest and reduced activity. Infections may be treated with antibiotics, and accessible growths or tumours can sometimes be removed through surgery. Small, symptom-free lesions typically require no treatment. However, some lesions cause severe, untreatable damage, especially in conditions like Alzheimer’s disease. As treatment options vary, it’s important to consult with your healthcare provider, who will assess your condition and recommend the most appropriate treatment based on the lesion’s cause and severity.

Conclusion

Brain lesions can occur for various reasons and are common indicators of brain-related conditions. Some lesions are mild and may require little or no treatment, while others can be more severe and need medical intervention, such as surgery. Unfortunately, some lesions are permanent or result from conditions that cannot be treated. Advances in medical imaging have greatly improved the ability to detect and assess brain lesions, aiding in treatment planning and predicting outcomes. Additionally, progress in understanding the brain offers new potential treatments and recovery options for brain lesions and their underlying causes.