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Lacunar Stroke – Small Vessel Disease
Cause of Lacunar Stroke – Lipohyalinosis – Risk Factors of Small Vessel Disease – Lacunar stroke Treatment and Prevention – Typical Lacunar Stroke Syndromes
Lacunar stroke is caused by obstruction of flow in a tiny blood vessel. The mechanism of blood flow compromise is often different from other stroke types. Lacunar stroke causes and treatment options have been debated for years. Some of lacunar stroke causes are proven and some remain speculative.
Many drugs used for secondary lacunar stroke prevention are the same as for other stroke types. There is a strong association of lacunar stroke with hypertension and diabetes. Lacunar strokes account for 20% to 30% of all ischemic strokes.
Why differentiation of lacunar strokes is such a big deal? They have unique mechanisms, carry different prognosis, and probably have to be managed differently. Lacunar strokes are caused by a small vessel disease.
The same changes in the small blood vessels are also responsible for some of hemorrhagic strokes (bleeding into the brain tissue).
Lacunar Stroke Symptoms
Lacunar stroke produces a specific combination of symptoms in each particular patient. The most common lacunar syndromes in order of decreasing frequency are:
– Weakness in the half of the body (face, arm and leg)
– Numbness in the half of the body
– Loss of coordination on one side with minimal weakness
– Numbness and weakness on one side of the body
– Weakness in the face, difficulty swallowing, slurred speech in combination with clumsiness of one hand
There is more than a dozen of other lacunar stroke symptoms.
It sounds confusing even for many doctors. The same symptoms are caused by large strokes. The difference is lack of any other symptoms associated with large brain strokes.
Lacunar strokes never cause difficulty finding words, understanding speech, or calculation problems; no issues with spatial reasoning, vision, or visual fields. Lacunar strokes cause no confusion, coma, change in level of alertness, or seizures. There is no change in personality. These patients notice nothing but lack of a particular function or specific set of symptoms.
Lacunar stroke typically destroys a limited area of the white matter. White matter is composed of nerve fibers connecting different brain areas. It is similar to partial damage to a thick telephone cable.
Since wiring and blood supply within the brain are organized in predictable pattern, potential sets of symptoms are limited. Some are more common than others.
There is one more remarkable feature of lacunar strokes. Unlike other types of stroke, loss of function may be insidious, lingering back and forth, or progressing over hours to even days. TIAs are very common prior to lacunar strokes.
Please note, only the intensity of symptoms is changing, but not the type of symptoms. Here is an example. Someday there is weakness on the right side lasting for a few minutes. Then, the following day, the same weakness comes back and stays this time.
Another possible scenario is a step-like worsening of symptoms over hours.
This pattern is sometimes confusing, making it suspicious for other causes.
Lacunar Stroke Causes
Lacunar stokes occur almost exclusively in specific brain regions. These areas are called basal ganglia, thalamus, internal capsule, brainstem (pons), and corona radiata, or deep white matter. The important factor is the type of blood supply these areas receive.
They are supplied by penetrating arteries. These are small arteries deriving perpendicularly directly from relatively large arteries with high blood pressure. As a result, penetrating arteries are undergoing a significant stress at the times when the blood pressure is high.
Long lasting stress years after years leads to damage of the blood vessel wall. Tiny muscles in the penetrating arteries branches walls degenerate and the walls get stretched. Normal tissues in the walls are substituted by scar-like material. These changes are called lipohyalinosis. Distended artery walls form small aneurysms.
Blood flow slows down and clots are formed along the walls. The blood clots may eventually block the vessel completely, which leads to lacunar stroke. Lacunar strokes are usually not larger than 15 mm. Tiny aneurysms may rupture and cause bleeding.
Another mechanism of rather larger strokes in the same areas may be caused by atherosclerosis. Similar to larger arteries, a tiny atherosclerotic plaque may form in the wall of penetrating artery and block the vessel.
Embolism is a possibility as well. A fragment of some blood clot formed somewhere else (embolus) traveling with a blood flow, plugs one of these tiny blood vessels. This mechanism remains rather speculative in lacunar stroke. Any proof of embolism in this type of stroke is lacking.
A term “small vessel disease” is commonly used. This term reflects presence of changes described above in the brain small vessels.
Risk factors for small vessel disease are poorly controlled diabetes and hypertension, smoking, lack of physical activity, and aging.
Lacunar strokes often produce no symptoms. It is not unusual to see lacunar strokes on Brain MRIs with lack of any history suggestive for strokes. Extensive small vessel disease is often associated with multiple lacunar strokes. Multiple lacunar strokes may destroy a substantial portion of the brain tissue, which in turn may lead to cognitive decline, or dementia.
There are some genetic disorders, CADASIL for example, which cause severe small vessel disease with multiple lacunar strokes. They cause severe dementia and eventually death.
Lacunar Stroke Diagnosis
Diagnosis of lacunar stroke is based on typical symptoms described above and findings on the Brain MRI suggestive for a recent lacunar stroke.
MRI allows to determine if the stroke occurred over the past a few hours or days. Accurate dating further back is not possible.
Modern technology does not allow detection of small penetrating arteries branches occlusion. Strokes are called lacunar based on the location, size and shape.
Lacunar Stroke Treatment
Acute lacunar stroke treatment
Modern approach to acute stroke treatment is called Thrombolytic Therapy. A special enzyme (tPA, Alteplase) is injected intravenously. This enzyme dissolves blood clots. Details of this treatment approach are described on a separate page.
It is believed that thrombolytic therapy is effective for lacunar stroke. There is a special protocol prior to this therapy, which does not include studies of the blood vessels. So, the type of stroke in many cases is not known prior to treatment.
Considering relatively benign prognosis in lacunar strokes and potential serious complications of thrombolytic therapy, tPA use in lacunar stokes remains controversial.
Another option is taking aspirin as soon as hemorrhagic stroke is ruled out by CAT scan.
Lacunar stroke prevention
The most reasonable approach to lacunar stroke prevention is a tight control of risk factors (if present), such as diabetes, hypertension, and smoking. Depending on general health condition and level of fitness, appropriate level of physical activity also helps.
Drug prevention with antiplatelet agents (Aspirin, Plavix, Aggrenox) is routinely employed, but study proved evidence of their effectiveness in lacunar stroke is not sufficient.
Besides, small vessel disease might be caused by brain amyloidosis. This condition is known to cause brain hemorrhages, so these drugs may increase the chance of bleeding.
Statins (Lipitor, Zocor, etc.) are also commonly utilized for lacunar stroke prevention. Their effectiveness is not proven either.
Lacunar Stroke Prognosis
People who sustained lacunar strokes have better prognoses than those who suffered strokes due to other mechanisms, at least short term.
Death due to lacunar strokes is almost nonexistent.
The extent of function recovery is also much greater.
Stroke recurrence rate is lower in lacunar strokes in the first year.
Prognostic advantages of lacunar strokes gradually fade over years. Poor control of risk factors leads to progression of small vessel disease, recurrent strokes and cognitive decline or other forms of disability in some patients.