A small vessel stroke occurs when a small artery that branches from a large artery in the brain becomes blocked or leaks. This deprives the brain of oxygen and nutrients, which kills brain cells.
Because small-vessel strokes occur in the subcortical region — an area deep in the brain made up of multiple structures — they are also known as subcortical strokes.
Although the affected area of a subcortical stroke is usually small, it can cause obvious signs and symptoms, such as weakness or numbness on one side of the body. That said, a small-vessel stroke is less likely to lead to life-threatening consequences, such as seizures or brain swelling.
Read on to learn how and where small vessel strokes occur, as well as some of their possible symptoms.
Types and Causes of Small Vessel Stroke
There are two main types of small vessel stroke:
- boat ischemic Stroke: When small arteries deep in the brain become narrowed or blocked.
- boat hemorrhagic Stroke: When a small artery deep in the brain leaks or bursts.
Both of these conditions can lead to decreased blood flow to the brain. Brain cells immediately start dying because they cannot get the oxygen and nutrients they need to survive. This response to insufficient blood flow is called an infarction.
High blood pressure (hypertension) is a major risk factor for all small vessel strokes. Elevated blood pressure can damage the walls of tiny arteries, causing them to narrow or rupture.
Atherosclerosis can also lead to small vessel ischemic stroke, a condition in which fatty deposits (plaques) block arteries.
They can also develop from blood clots that enter the brain from other parts of the body. A flowing blood clot is called an embolus.
Which arteries are affected?
Arteries are blood vessels that carry oxygen-rich blood to vital organs throughout the body, including the brain.
Small vessel strokes affect small branches of three large arteries – the middle cerebral artery, the anterior cerebral artery, and the posterior cerebral artery.
These small branches are called penetrating terminal arteries because they have no branches and stop within the brain tissue.
The anterior and posterior cerebral arteries are part of the Circle of Willis, a network of arteries located at the base of the brain.
The middle cerebral artery is not part of the circle of Willis, but it runs nearby, branching off from the internal carotid artery, which runs along the side of your neck
Which brain structures are affected?
Small vessel strokes occur in structures deep in the brain, such as the thalamus, basal ganglia, internal capsule, and brain stem.
The thalamus is a key hub region that collects and integrates sensory signals (eg, taste, vision, and hearing) before delivering them to the outermost layer of the brain, called the cerebral cortex.
Specifically, the right side of the thalamus transmits sensation from the left side of the body, and the left side of the thalamus transmits sensation from the right side of the body.
A small-vessel thalamic stroke can cause numbness, tingling, and even complete loss of sensation in the face, arms, and legs.
The thalamus also plays a key role in transmitting motor (motor) signals, regulating mood and sleep-wake cycles, and managing various cognitive processes such as attention and memory processing.
That said, larger vessel thalamic strokes, but not smaller vessel strokes, typically result in impairment of one or more of these higher-order functions.
This basal ganglia is a group of subcortical nerve cells that are highly connected to multiple brain regions, including the thalamus, brain stem, and cerebral cortex. The basal ganglia contains multiple structures. One, the massive substantia nigra, is affected in Parkinson’s disease.
The basal ganglia control complex functions requiring coordination and muscle movement. Strokes in small blood vessels affecting the basal ganglia can cause symptoms such as writhing, writhing, muscle twitching, and/or tremors.
The internal capsule is located deep in the brain. Its white appearance is the result of myelin, a special type of fat that coats the brain and nerve cells to protect and insulate them, allowing electrical signals to travel quickly and efficiently.
The internal capsule is mainly involved in regulating movement. Therefore, symptoms of a small vessel stroke in this area may include mild weakness, severe weakness, or complete paralysis of the opposite, arms and legs.
In addition, the internal capsule is involved in transmitting nerve signals related to sensation. Numbness on the other side of the body can occur with a stroke in the small blood vessels in that area.
Although the internal capsule also transmits visual and verbal information, these functions are rarely affected by small vessel stroke.
The brainstem connects your brain to the spinal cord and has many functions, such as helping to control your breathing, heartbeat, and blood pressure. It also helps control your eye movements and swallowing. Motor and sensory pathways also run through the brainstem.
Symptoms of a brainstem small vessel stroke may include weakness or loss of sensation on the side of the body opposite the stroke.eye movement problems or swallowing problems (hard to swallow) may also occur.
Small vessel strokes, also known as subcortical strokes, are caused by blockage or leakage of the small, deep branches of the larger arteries in the brain. High blood pressure is the leading cause of small vessel stroke.
Symptoms of these strokes often include movement and/or sensory problems on one side of the body. More complex functions, such as language, vision, and cognitive processes, are usually not affected.
Small vessel strokes are often the first sign of stroke risk factors, such as high blood pressure, diabetes or high cholesterol.
This means that, in addition to recovering from the stroke itself, you will need a medical examination to understand the cause of your stroke.
With rehabilitation and risk factor management, you can maximize recovery and prevent additional strokes.