Lacunar Infarction

Lacunar infarction is a small subcortical infarct, usually under 20 mm on diffusion weighted imaging, caused by occlusion of a single penetrating artery. It accounts for about 20 to 25% of ischaemic strokes.

The incidence rises with age. Risk factors are hypertension, diabetes, smoking and older age, and it is more common in people of African and East Asian ancestry.

Causes. Lipohyalinosis and fibrinoid necrosis of small arterioles (hypertensive arteriolopathy) account for most lesions; microatheroma at the origin of a perforator, parent artery disease and, less often, embolism are other causes.

Syndromes. Pure motor hemiparesis, pure sensory stroke, sensorimotor stroke, ataxic hemiparesis and dysarthria with clumsy hand. Cortical signs such as aphasia, neglect or visual field loss are absent.

Natural history. Early neurological worsening occurs in up to 20 to 30% of patients. Recurrent lacunes lead to vascular cognitive impairment, gait disorder and mood disturbance.

Pathophysiology.

Chronic hypertension and endothelial dysfunction thicken the wall of penetrating arterioles and narrow the lumen, reducing perfusion in end arterial territories (basal ganglia, thalamus, internal capsule, corona radiata and pons).

Lesion cavitation leaves a lacune, and diffuse small vessel disease causes white matter hyperintensities and microbleeds.

• Abrupt or stuttering unilateral weakness of face, arm and leg with no cortical signs, or a purely sensory deficit.
• Ataxic hemiparesis and dysarthria with clumsy hand localise to the pons or internal capsule.
• Early worsening within 48 to 72 hours is common, especially with capsular warning syndrome (repeated stereotyped TIAs).

Red flags.

• Capsular warning syndrome with repeated stereotyped episodes.
• Progressive worsening over days.
• Headache, impaired consciousness or cortical signs, which point to another cause.

• Brain MRI with diffusion weighted imaging: small acute infarct in a perforator territory; CT may be normal early.
• Vascular imaging of the head and neck to exclude large artery stenosis or carotid disease ipsilateral to the lesion.
• 12 lead ECG and ambulatory rhythm monitoring when the imaging is atypical or the patient is young.
• Blood tests: glucose, HbA1c, lipids, full blood count, creatinine, ESR or CRP.
• Neuropsychological screening for vascular cognitive impairment at follow up.

Differential diagnosis. Embolic or large artery stroke with a small infarct, hypertensive intracerebral haemorrhage, demyelination, CADASIL, vasculitis, tumour, abscess and migraine aura.

• Acute: intravenous thrombolysis when criteria are met, and early dual antiplatelet therapy for minor stroke.
• Aspirin 300 mg orally once as a loading dose (300 mg rectally if swallowing is impaired), then 75 mg orally once daily with food. Maximum 300 mg daily. Monitor for bleeding and dyspepsia, and check full blood count. Avoid in active peptic ulcer, bleeding disorders, aspirin sensitive asthma and in children under 16 years; use caution when eGFR is under 10; low dose use is acceptable in pregnancy when needed.
• Clopidogrel 300 mg orally once as a loading dose, then 75 mg orally once daily, combined with aspirin for 21 days only, then clopidogrel alone long term. Maximum 75 mg daily after loading. Monitor bleeding and full blood count. Avoid in active bleeding; use caution in severe hepatic impairment; reduced effect in CYP2C19 poor metabolisers; avoid omeprazole and esomeprazole; avoid in pregnancy unless clearly needed. Long term dual therapy increases bleeding and death without added benefit.
• Atorvastatin 80 mg orally once daily, long term. Maximum 80 mg daily. Monitor lipids at 4 to 12 weeks and ALT at baseline and if symptoms occur. No dose change in renal impairment; avoid in active liver disease; limit to 20 mg daily with clarithromycin and avoid with ciclosporin; contraindicated in pregnancy and breastfeeding. Aim for LDL cholesterol under 1.8 mmol/L.
• Blood pressure: lower to under 130/80 mmHg after the acute phase, with an ACE inhibitor, a thiazide like diuretic or a calcium channel blocker as tolerated.
• Amlodipine 5 mg orally once daily, increased to 10 mg after 2 to 4 weeks if needed, long term. Maximum 10 mg daily. Monitor blood pressure and ankle oedema. Start at 2.5 mg in older adults and in hepatic impairment; no renal adjustment; avoid in pregnancy unless benefit outweighs risk.
• Diabetes control, smoking cessation, exercise and weight reduction.
• Rehabilitation with physiotherapy, occupational therapy and speech therapy; screen for depression and cognitive decline.

Monitoring. Review at 1 week and 3 months, then yearly; track blood pressure, lipids, glucose and cognition.

Referral and escalation. Stroke unit admission in the first days; urgent re-imaging for early worsening; memory clinic for progressive cognitive impairment.

Special groups. Older adults: lower antihypertensive starting doses and watch for postural hypotension and falls.