Strokes can affect any part of the brain. A stroke in the deeper structures of the brain (thalamus, basal ganglia or pons) is called a lacunar stroke. These deep structures have a very unique blood supply – very small arteries that lead directly off much larger arteries.
Most arteries gradually taper down, getting smaller and smaller as they go. In the deep structure of the brain, tiny arteries branch directly off the main arteries, making these tiny arteries very vulnerable to high blood pressure. The larger arteries can tolerate the pressure, but the tiny arteries can’t. The sudden increase in pressure can cause breaks in these tiny vessels and bleeds in the brain. High blood pressure also causes arteriosclerosis (fatty deposits build up on the inside walls of the arteries) and a clots form. Because these arteries are tiny, they are easily blocked, leading to loss of blood flow to this area of the brain, or a lacunar stroke.
Symptoms of lacunar stroke
Symptoms related to lacunar stroke can come on suddenly, or evolve over time, either fluctuating, or getting progressively worse. Severity of symptoms can vary hugely, and depends on the area of the brain affected, and the size of the stroke.
There are 5 classic lacunar syndromes, with a distinct set of symptoms depending on which part of the brain was affected.
Pure motor stroke/ Hemipareisis
This is the most common form of lacunar stroke, representing 33-50% of cases. It occurs when the stroke has occurred in the posterior limb of the internal capsule, basis pontis and/or corona radiata.
It is defined by weakness (hemiparesis) or paralysis (hemiplegia) down one side of the body, usually affecting the face, arm and leg of the opposite side of the body to the side of the brain that the stroke occurred in. Patients may have difficulty speaking (dysarthria) and have difficulty swallowing (dysphasia).
Pure sensory stroke
Occurs when the stroke occurred in the thalamus, internal capsule, corona radiata, midbrain.
The typical symptoms are persistent or transient numbness, tingling, and burning pain usually down one side of the body (the opposite side to which the stroke occurred in the brain).
The second most common form of lacunar stroke. Occurs with strokes in the posterior limb of the internal capsule, basis pontis, and corona radiata.
Symptoms include weakness and clumsiness on the opposite side of the body to which the stroke occurred. It often affects the leg more than the arm, and the onset of symptoms may be over hours or over days.
Occurs with a stroke in the pons. The main symptoms are difficulty speaking (dysarthria) and clumsiness and weakness of the hand. There may also be some numbness.
Mixed sensorimotor stroke
Occurs when the stroke is in the thalamus and adjacent posterior internal capsule, or lateral pons. Symptoms include weakness (hemiparesis) and/or paralysis (hemiplegia) on one side of the body, along with sensory impairment.
In a person with untreated high blood pressure, multiple lacunar strokes can occur. Multiple strokes can cause additional symptoms, such as emotional behaviour, depression, mood changes and lead to dementia. Multiple strokes also significantly increase the risk of the person suffering a major stroke.
Treatment of lacunar stroke
Treatment depends on the severity of the stroke. As with all strokes, if a person is exhibiting signs and symptoms it is a medical emergency. The sooner the person gets to hospital and treatment started, the better the outcome. Immediate treatment involves clot busting medication to dissolve the blockage, and restore oxygen to the affected area of the brain. In up to 50% of cases, there is complete recovery, with no long term deficits.
A person who has had a lacunar stroke will be hospitalised for observation, in case symptoms worsen.
If the stroke is severe, the person may need help with self care, feeding and mobility. Where there is paralysis and weakness, rehabilitation, physio therapy and occupational therapy are required. Social workers and psychologists can offer emotional and family support during the rehabilitation process.
In minor strokes, treatment is focused on prevention, as having had a lacunar stroke significantly increases a patient’s risk of having a future major stroke. Aspirin is prescribed to be taken daily, and other risk factors, such as high blood pressure, diabetes and smoking need to be addressed, with lifestyle changes (diet and exercise) and/or medication.
Lacunar strokes have a higher recovery rate than strokes that affect the larger blood vessels of the brain. People often begin to recover within hours of a lacunar stroke, and up to 90% will have substantially recovered within the first three months following the stroke.