What Are Brain Lesions?

A brain lesion is a type of abnormality in the brain, usually caused by a disease or injury. There are several kinds of brain lesions, and they can be distinguished by their symptoms, physical examination findings, and diagnostic tests.

If you have neurological symptoms, it is important that your healthcare providers determine whether you have a brain lesion, how many you have, and the type because the treatment and prognosis of each type of brain lesion differs. 

Brain Lesion Symptoms

The effects of brain lesions correspond to the area of the brain where they are located. Usually, the region of the brain where a lesion is located will not function as it normally would. 

Symptoms can be gradual or sudden and may be intermittent or constant. Each type of lesion has an emblematic pattern when it comes to the timing of symptoms.

Common symptoms of brain lesions may include a combination of general and focal symptoms.

General Symptoms 

General symptoms include:

• Head pain 
• Fatigue 
• Dizziness 
• Behavioral changes 
• Cognitive impairment 

Focal Neurological Deficits 

Focal neurological deficits include:

• Weakness of one side of the face, arm, and/or leg 
• Diminished sensation and/or paresthesias (unusual sensations) on one side of the face, arm, and/or leg
• Vision changes
• Impaired balance 
• Neck stiffness 
• Ear pressure 
• Seizures

Causes and Types 

The different types of brain lesions are each associated with certain causes and risk factors.

Stroke

An interruption in blood flow within the brain can cause a stroke, which is a small or large area of brain damage. Risk factors include heart disease, high blood pressure, uncontrolled diabetes, and high cholesterol. This lesion usually consists of a central area of ischemia (death of cells due to deficient blood supply).

Right after a stroke occurs, the lesion may be surrounded by swelling and inflammation, which subside within a few weeks. The ischemic part of the lesion remains, with permanent damage to the affected area of the brain.

Demyelination

Some conditions, such as multiple sclerosis (MS), are caused by temporary or lasting demyelination—loss of the protective myelin coating that surrounds nerves in the brain. This causes one or more demyelinating brain lesions. The condition is usually idiopathic (without a known cause).

A more serious condition, progressive multifocal leukoencephalopathy (PML), is considered a demyelinating inflammatory response to a virus that is usually harmless. PML generally affects people who are severely immunocompromised, and it has a high mortality rate.

Infection

Bacterial, fungal, viral, or parasitic brain infections can cause one or more areas of damage and inflammation. Many types of brain infections can resolve with appropriate treatment.

Inflammation

Inflammatory lesions in the brain can develop due to conditions like lupus, sarcoidosis, therapeutic brain radiation, and more. 

Cancer

Brain tumors and metastatic tumors from elsewhere in the body can cause one or more lesions throughout the brain. The cause of brain tumors is usually unknown. Tumors that metastasize and cause lesions in the brain may have known risk factors. For example, smoking increases the risk of lung cancer, which can spread to the brain.

Vascular Malformations

Vascular malformations such as brain aneurysms and arteriovenous malformations (AVMs) are usually idiopathic. They can be congenital (present from birth) or develop later in life.

These lesions can cause focal neurological deficits when they are small, but they may cause rapid bleeding and severe swelling in the brain if the malformed blood vessels bleed—and could lead to death.

Contusion

Head trauma can lead to a bruise in the brain, which may cause a combination of generalized and focal effects. Contusions in the brain usually partially or fully heal over time. However, repeated blows to the head with multiple lesions can cause chronic traumatic encephalopathy (CTE), with persistent changes.

Hemorrhage

Bleeding in the brain can cause a hemorrhagic lesion. These lesions are more life-threatening than non-hemorrhagic lesions. A number of problems can lead to hemorrhagic lesions, including a bleeding vascular malformation, hemorrhagic conversion of an ischemic stroke, brain tumors that bleed, and head trauma.

Atrophy and Ventricular Dilatation

Sometimes the brain can shrink in size due to damage or dying of the brain cells. This is usually a result of dementia or extensive strokes. This can lead to enlarged spaces within the skull, often noted as atrophic lesions.

Congenital Malformation

Developmental compromise during fetal development can lead to lesions in which areas of the brain are shaped differently than they would be in a healthy brain. Sometimes these malformations lead to impaired physical and cognitive deficits and seizures.

Congenital malformation of the brain can result from genetics or issues such as toxins or insufficient oxygen supply during fetal growth.

Diagnosis 

The diagnosis of brain lesions is based on the history and pattern of symptoms, family history, physical examination, neurological examination, and brain imaging.

There are several types of diagnostic brain studies and brain imaging studies, and some can detect certain brain lesions, while others are better at detecting other brain lesions.

For example:

• Brain computerized tomography (CT) is traditionally considered a good test for detecting hemorrhage.
• Brain magnetic resonance imaging (MRI) is considered a good test for detecting demyelination.
• Vascular malformations are often well visualized with diagnostic studies that examine the blood vessels, such as magnetic resonance angiography (MRA).
• Contrast dye helps to define certain lesions, such as tumors and infections.
• Electroencephalogram (EEG) is often used to detect seizure activity caused by brain lesions, some of which cannot be seen on brain imaging studies.

Some lesions, such as demyelinating lesions in MS, can come and go on brain imaging, despite persistent symptoms and physical examination findings. But the condition must be controlled even when lesions are not visibly present. Lesions due to trauma may cause symptoms and physical examination changes with minimal imaging changes.

Brain aneurysms and AVMs might not be visible except with vascular studies focused on the specific area of the lesion. Your healthcare provider would order your imaging study based on the findings of your physical examination—which can consist of very subtle changes in the context of vascular malformations.  

Treatment 

Brain lesion treatment depends on the cause. Some lesions, such as infections and cancer, can be treated with medication with the goal of a complete cure. Vascular malformations may need to be surgically treated to prevent a rupture. Other lesions, such as demyelination and chronic inflammation, are managed and controlled with medication, but they are not typically curable.

And lesions that cause permanent damage, such as brain contusions, infarct, and hemorrhage, are not curable—but the effects should be managed with rehabilitation. Various types of therapy—physical therapy, speech therapy, cognitive therapy, and more—can help in the recovery and maximizing abilities.

A Word From Verywell

Lesions in the brain usually cause symptoms and can cause lasting damage unless they are treated. Brain lesions can occur for a variety of reasons, and once you know which type of brain lesion you have, you will know what to expect for the short term and the long term.