Lacunar syndromes and small-vessel disease

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Penetrating arteries arise from larger intracranial vessels and travel directly into deep brain tissue with limited collateral supply. Lipohyalinosis, arteriolosclerosis and occlusion at the origin of a perforator can produce a small deep infarct. A lacune is the small fluid-filled cavity that may remain after such an infarction; the terms lacunar infarct and lacune are therefore related but not interchangeable at every time point. A small subcortical infarct can also arise from embolism or parent-artery atheroma, so the radiological size does not by itself prove the mechanism.

Clinical localisation remains valuable. Pure motor weakness commonly reflects corticospinal tract involvement in the posterior limb of the internal capsule, corona radiata or basis pontis. Pure hemisensory loss often localises to the thalamus, while ataxic hemiparesis and dysarthria–clumsy hand syndromes point towards compact corticopontocerebellar or corticobulbar pathways. Dense weakness can result from a tiny lesion because motor fibres are tightly packed. Conversely, aphasia or neglect indicates cortical network dysfunction and should challenge a lacunar label.

Cerebral small-vessel disease is a chronic whole-brain process rather than a collection of incidental white spots. MRI is more sensitive than CT for recent small subcortical infarction and for chronic markers, but imaging must be interpreted with age, vascular exposures and symptoms. Individual treatment is governed by local stroke protocols, specialist neuroradiology interpretation and the latest national eligibility rules.

Key points

Lacunar infarcts are small subcortical infarctions, usually caused by disease of a penetrating arteriole supplying structures such as the internal capsule, thalamus, basal ganglia, corona radiata or pons.
The five useful bedside patterns are pure motor stroke, pure sensory stroke, sensorimotor stroke, ataxic hemiparesis and dysarthria–clumsy hand syndrome; real presentations can be incomplete or overlap.
A convincing lacunar syndrome lacks cortical signs: aphasia, neglect, gaze deviation, visual field loss and a clear cortical sensory deficit should prompt consideration of a cortical or larger-vessel lesion.
Small-vessel disease is broader than an acute lacune and includes white-matter hyperintensities, old lacunes, cerebral microbleeds, enlarged perivascular spaces and small-vessel-related brain atrophy on MRI.
Do not assume that a mild deficit or a deep clinical pattern excludes a treatable proximal occlusion; thrombolysis and thrombectomy decisions depend on current imaging, time and eligibility criteria.
Hypertension, ageing, diabetes, smoking, dyslipidaemia and chronic kidney disease increase small-vessel injury, but unusual age or imaging distribution should widen the differential to inherited, inflammatory or toxic arteriopathies.
An acute non-cardioembolic lacunar infarct generally enters the same antiplatelet and vascular-risk pathway as other ischaemic strokes after intracranial haemorrhage has been excluded.
The burden of apparently silent small-vessel disease matters: it predicts future stroke, gait impairment, cognitive decline, mood disorder and reduced resilience to other cerebral insults.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Hypertensive arteriopathy

Ageing and sustained hypertension promote lipohyalinosis and wall thickening in penetrating arterioles supplying deep brain structures.

Metabolic vascular risk

Diabetes, smoking, dyslipidaemia and chronic kidney disease compound endothelial injury and reduce resilience of small cerebral vessels.

Inherited or inflammatory arteriopathy

Unusual age, family history or imaging distribution raises genetic, inflammatory and toxic small-vessel disorders beyond common sporadic disease.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Penetrating-artery injury
Chronic endothelial dysfunction, wall thickening and microatheroma narrow small deep vessels and impair cerebral autoregulation over time.
2
Acute deep occlusion
Thrombosis or branch blockage infarcts a compact internal-capsule, thalamic, pontine or deep white-matter territory, producing a lacunar syndrome.
3
Chronic tissue damage
Repeated leakage and hypoperfusion cause white-matter injury, lacunes, microbleeds and atrophy beyond recognised clinical strokes over time.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Pure motor syndromeRed flag

Unilateral face, arm and leg weakness without aphasia, neglect, hemianopia or a primary sensory deficit suggests a compact corticospinal or corticobulbar lesion, classically in the internal capsule or pons.

Pure sensory syndromeRed flag

Abrupt numbness or altered sensation affecting the contralateral face and body, without weakness or cortical sensory dysfunction, is compatible with a thalamic lacunar infarct after mimics are considered.

Ataxic hemiparesisRed flag

Ipsilateral limb weakness with disproportionate incoordination can follow a lesion in the pons, internal capsule or corona radiata; cerebellar and posterior-circulation alternatives still require urgent imaging.

Dysarthria–clumsy handRed flag

Prominent dysarthria, facial weakness and impaired fine hand movement with little limb weakness is a recognised perforator syndrome, but dysphagia and airway safety must be assessed rather than dismissed as minor.

Chronic small-vessel phenotype

Slowed processing, executive dysfunction, short-stepped gait, falls, urinary symptoms and pseudobulbar features may accompany extensive white-matter injury, although each symptom needs evaluation for competing causes.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Immediate non-contrast CT brainFirst step
Why
Exclude intracranial haemorrhage and major structural mimics before acute antithrombotic or reperfusion decisions.
Interpretation and limitations
Early small deep infarcts are often invisible on CT. A normal scan does not refute an acute lacunar syndrome; it mainly answers urgent questions about blood, established large infarction and alternative pathology.
02
CT angiography with reperfusion imaging when indicated
Why
Identify a proximal arterial occlusion, stenosis or other vascular lesion that would alter time-critical treatment.
Interpretation and limitations
Absence of a large-vessel occlusion supports but does not prove perforator disease. A deep clinical syndrome can coexist with parent-artery disease, and current local thrombectomy pathways determine additional imaging.
03
MRI brain with diffusion and blood-sensitive sequences
Why
Confirm a recent small subcortical infarct and characterise the background burden of small-vessel disease.
Interpretation and limitations
Restricted diffusion supports acute infarction; FLAIR hyperintensity, old lacunes and susceptibility-detected microbleeds describe chronic burden. MRI-negative stroke remains possible, especially early or in the brainstem.
04
ECG and cardiac rhythm assessment
Why
Detect atrial fibrillation or another cardiac source rather than attributing every small infarct to intrinsic arteriolar disease.
Interpretation and limitations
Atrial fibrillation changes secondary prevention towards anticoagulation after specialist timing assessment. Sinus rhythm on one ECG does not exclude intermittent arrhythmia where suspicion persists.
05
Vascular risk and cause screen
Why
Measure blood pressure, HbA1c or glucose, lipids, renal function and relevant lifestyle exposures while identifying atypical features.
Interpretation and limitations
Results guide prevention but rarely establish the acute mechanism alone. Young age, family history, systemic inflammation or disproportionate imaging disease should prompt specialist investigation for non-sporadic arteriopathy.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Cortical ischaemic stroke

Aphasia, neglect, gaze deviation or visual-field loss indicates cortical involvement and should prompt assessment for larger-vessel occlusion.

Small intracerebral haemorrhage

Deep haemorrhage produces the same compact deficit and can only be distinguished reliably by urgent brain imaging.

Demyelination or tumour

Subacute evolution, enhancement or lesions outside a vascular territory favour inflammatory or neoplastic disease rather than an acute lacune.

Metabolic or functional mimic

Hypoglycaemia and positive functional inconsistency can imitate pure motor or sensory syndromes, but neither should delay emergency stroke imaging.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01HyperacuteTreat the syndrome as strokeFirst stepAny new, persistent focal deficit compatible with a lacunar syndrome.

11. Record onset or last-known-well time, perform ABCDE, check capillary glucose and quantify the deficit with the local stroke assessment.
22. Activate urgent stroke imaging, including arterial imaging when the pathway requires it, without waiting for a presumed small-vessel diagnosis.
33. Assess thrombolysis or thrombectomy eligibility with the stroke team; symptom severity and disability are judged clinically rather than from the word lacunar.
44. After haemorrhage is excluded, start acute antithrombotic and supportive measures at the timing specified by the national and local stroke protocol.

02LocaliseTest the lacunar hypothesisInitial examination suggests a small deep lesion.

11. Map face, arm and leg power, sensory modalities, coordination, eye movements, language, visual fields, attention and cortical sensory function.
22. Search specifically for aphasia, neglect, gaze preference, hemianopia, seizures or reduced consciousness, which weaken a simple lacunar explanation.
33. Reconcile the phenotype with CT angiography and subsequent MRI, accepting that clinical and radiological classification may evolve.
44. Complete a proportionate aetiological assessment rather than omitting rhythm, vascular and metabolic evaluation because the lesion is small.

03PreventionReduce cumulative small-vessel injuryOnce acute safety and stroke mechanism have been addressed.

11. Establish the appropriate long-term antithrombotic strategy, separating non-cardioembolic disease from atrial-fibrillation-related stroke.
22. Optimise blood pressure, lipids, glycaemia, smoking cessation, activity and weight through shared decisions and tolerability review.
33. Assess cognition, mood, mobility, swallowing and daily function, referring for needs-based multidisciplinary rehabilitation rather than using lesion size as a proxy for impact.
44. Explain recurrent stroke symptoms, adherence and follow-up, and arrange specialist review for early-onset, familial or radiologically atypical disease.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Provides early antiplatelet therapy for acute ischaemic stroke while the definitive secondary-prevention regimen is established.

Aspirin in acute ischaemic stroke

After intracranial haemorrhage is excluded, NICE recommends 300 mg orally or rectally as soon as possible and within 24 hours, continued according to the acute stroke plan; timing differs after thrombolysis.

Do not give before imaging has excluded haemorrhage. Check allergy and active bleeding, and follow the stroke team’s timing after thrombolysis or if anticoagulation is indicated.

Reduces recurrent atherothrombotic events after non-cardioembolic ischaemic stroke, including most lacunar infarctions.

Clopidogrel for long-term non-cardioembolic prevention

A common adult maintenance regimen is 75 mg once daily after the acute aspirin phase, selected in accordance with the current stroke secondary-prevention pathway.

Review bleeding, interactions and adherence. It is not a substitute for anticoagulation when atrial fibrillation is the likely mechanism, and combinations require a defined indication and duration.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Recurrent stroke

Ongoing arteriolar disease causes further lacunar infarcts or deep haemorrhage, accumulating disability even when each event seems mild.

Cognitive and gait decline

Diffuse white-matter damage disrupts frontal-subcortical networks, producing slowed processing, executive dysfunction, urinary symptoms and impaired balance.

Mood and swallowing problems

Strategic deep lesions can cause depression, emotional lability, dysarthria and dysphagia with aspiration risk after strategic infarction.

Reduced cerebral resilience

High small-vessel burden increases vulnerability to delirium, falls and functional decline after otherwise modest systemic or neurological insults.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Repeat neurological observations during the acute phase because deterioration may reflect infarct extension, haemorrhagic transformation, oedema, aspiration, seizure or a different diagnosis.
Track blood pressure over time and titrate prevention gradually once the hyperacute plan permits; avoid extrapolating from a single stress-related reading.
Review gait, upper-limb dexterity, swallowing, communication, mood, cognition and continence, since a small lesion can produce major functional consequences.
Monitor antithrombotic tolerance, bleeding, lipid response, glycaemic control and renal function at intervals matched to the selected prevention medicines.
Reassess unexplained progression or recurrent stereotyped deficits; repeated events may expose intracranial stenosis, embolism, capsular warning syndrome or an inflammatory or inherited arteriopathy.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Small lesion, dense deficit

The internal capsule contains tightly crowded descending fibres, so a millimetre-scale infarct can cause striking face–arm–leg weakness despite a modest imaging volume.

A lacune is a later cavity

A recent small subcortical infarct may become a CSF-like cavity, but not every small cavity is symptomatic and not every acute perforator infarct ultimately cavitates.

Microbleeds are context markers

Susceptibility lesions suggest haemorrhage-prone small-vessel pathology and inform specialist risk discussion, but their number and distribution must be considered alongside the strong indication for preventing ischaemic events.

White-matter change is cumulative

Confluent disease can disrupt distributed frontal–subcortical networks, explaining executive slowing and gait disturbance even without one dramatic territorial stroke.

Mechanism can remain mixed

Perforator occlusion may reflect intrinsic arteriolar disease, a plaque at the parent-artery branch or embolism; confident secondary prevention follows the whole work-up, not morphology alone.

11Common pitfallsFrequent interpretation and management errors.

01
Withholding urgent stroke imaging because the presentation sounds lacunar can miss haemorrhage, basilar disease or a proximal occlusion with a treatment opportunity.
02
Calling any white-matter hypodensity a previous stroke ignores migraine, demyelination, inflammatory disease and non-specific age-related change in the differential.
03
Equating absence of cortical signs with diagnostic certainty overlooks brainstem mimics, small haemorrhage, postictal weakness and functional neurological symptoms.
04
Treating chronic small-vessel burden only with medication misses rehabilitation, falls prevention, cognition, mood and the practical work of sustained risk-factor control.
05
Assuming all small deep infarcts are non-cardioembolic may deny anticoagulation to a patient in whom atrial fibrillation is subsequently demonstrated.