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LACUNAR STROKE SYNDROMES
Definition


A “lacune” is a small cavity (<1.5 cm) remaining in the brain tissue that develops after the necrotic tissue of a deep infarct has been removed (lacune in Latin means small lake). Lacunes typically follow as a result of lacunar stroke. Lacunar stroke is a result of blockage of blood flow to a single small deep penetrating vessel (lacunar strokes as also known as small vessel disease) supplying the subcortical white matter region, basal ganglia, internal capsule, corona radiata, thalamus, or paramedian pons. The blood vessels responsible for these areas include the lenticulostriates of the MCA, the thalamogeniculate arteries of the PCA and the paramedian perforators of the basilar artery. The pathogenesis is thought to involve lipohyalinosis or formation of microatheroma within the penetrating vessel.

Above: the diagram shows some of the common areas where lacunar infarction occurs (note - some of these are the same locations and vessels responsible for hypertensive intracranial hemorrhage). (A) lenticulostriate branches of the MCA, (B) Thalamogeniculate arteries of PCA, (C) paramedian perforators from basilar artery. Adapted from Qureshi et al. Spontaneous Intracerebral Hemorrhage, NEJM. 344 (19): 1450, Figure 2. May 10, 2001
 

Above: pathologic specimen showed two areas of lacunar infarction (black arrows).
 
The finding of a lacune does not necessarily imply a lacunar stroke has occurred, as most lacunes are asymptomatic. A stroke can be classified as a lacunar infarction if a patient presents with a classic lacunar syndrome and imaging reveals evidence of focal acute ischemia in a penetrating artery distribution. CT scan is not very sensitive at detecting lacunar infarctions. MRI with diffusion-weighted imaging is the imaging modality of choice to detect a lacunar infarction.
 

The above MRI shows a typical pontine small vessel penetrating artery infarction. This patient had pure motor hemiparesis of the face, arm and leg.
Common Lacunar Syndromes

• Pure motor hemiparesis

The most common lacunar syndrome (33-50%). Usually involves the posterior limb of the internal capsule, corona radiata, or basis pontis; presents clinically with contralateral hemiparesis of face, arm, and leg to an approximately equal degree. There is no sensory deficit on exam. There are no cortical findings including aphasia or visual field abnormalities. Dysarthria may be present.

• Ataxic hemiparesis

Typically involves the internal capsule, pons or corona radiata; presents with contralateral hemiparesis of the face and leg, and ataxia of the contralateral arm and leg.

• Pure Sensory stroke

Usually involves the thalamus or corona radiata; presents clinically with persistent/transient contralateral hemisensory loss involving the face, arm and leg to an approximately equal degree. No cortical findings are present.

• Dysarthria-Clumsy Hand

Usually involves the pons or internal capsule; presents clinically with dysarthria, dysphagia, contralateral facial paresis and tongue weakness, contralateral paresis/clumsiness of the arm and hand.

• Sensory-motor stroke

Typically involves the thalamus, internal capsule or putamen-capsule-caudate; presents clinically with a combination of ipsilateral sensory and motor loss (face, arm, leg). There is no aphasia, visual field abnormality or other cortical findings.

Prevention for recurrence of lacunar stroke involves aggressive risk factor modification and antiplatelet therapy with aspirin or plavix.