Thalamic infarct

Thalamic infarcts refer to ischemic strokes that affect the subcortical grey matter complex of nuclei known as the thalamus.

Epidemiology

Pure thalamic infarcts are reported to make up 3-4% of ischemic strokes ¹. 

Risk factors

Most of the risk factors are common to all types of ischemic strokes ² such as:

• age

• male sex

• hypertension

• diabetes mellitus

• hypercholesterolemia

• cigarette smoking

• atrial fibrillation

Clinical presentation

Presentation is dependent on the region infarcted ^2,5:

• anterior territory and (postero)medial territory

  • decreased level of consciousness, impaired memory, personality change

  • left hemisphere lesions: aphasia

  • right hemisphere lesions: hemineglect (hemi-extinction)

• ventrolateral territory

  • sensorimotor deficits

  • Dé​jerine-Roussy syndrome (thalamic pain syndrome)

• posterolateral territory

  • visual field defects

  • variable sensorimotor deficits

Pathology

Thalamic infarction can be caused by small vessel disease (most common), large artery atherosclerosis, cardioembolism, or unknown factors (cryptogenic) ³. 

Classic thalamic territories include the following groups based on vascular supply and corresponding thalamic nuclei ^3,5:

• anterior territory

  • supplied by tuberothalamic/polar artery from the posterior communicating artery, although this is absent in a third of patients so the territory is irrigated by the paramedian artery

  • includes reticular nucleus, intralaminar nucleus, ventral pole of medial dorsal nucleus, anterior nuclei, ventral anterior nucleus, and rostral ventral lateral nucleus

• posteromedial territory

  • supplied by paramedian/thalamoperforating artery from the P1 segment of the posterior cerebral artery

  • includes medial dorsal nucleus and intralaminar nuclei

• ventrolateral territory

  • supplied by thalamogeniculate/inferolateral arteries from the P2 segment of the posterior cerebral artery

  • includes ventral lateral nucleus and ventral posterior nucleus (including ventral posterolateral and ventral posteromedial subnuclei)

• posterolateral territory

  • supplied by posterior choroidal artery from the P2 segment of the posterior cerebral artery

  • includes lateral and medial geniculate nuclei

Different territory involvement has an association with some stroke etiologies ³. Large artery disease-related thalamic infarcts most often involve the posteromedial territory, while small vessel disease-related thalamic infarcts usually involve the ventrolateral territory.

The topography of thalamic strokes is associated with broader stroke syndrome ³. Both isolated thalamic (lacunar) strokes and posterior cerebral artery territorial strokes most commonly present involving the ventrolateral territory. In contrast, basilar and vertebrobasilar (extended posterior circulation) strokes most commonly involve the posteromedial territory of the thalamus.

Radiographic features

CT

Non-contrast CT may show ill-defined hypodensities of the thalamus or obscuration of the grey-white matter border between the adjacent internal capsule ⁴.

MRI

In the acute phase (within 72 hours) ⁴:

• T2/FLAIR: normal to slightly hyperintense grey-matter (as infarct progresses)

• DWI: hyperintense

• ADC: hypointense

Treatment and prognosis

Thalamic strokes are managed as other ischemic strokes are, with thrombectomy, thrombolysis, and/or antithrombotic therapy depending on the acuity, severity of deficits, suspected caliber of occluded vessel, and etiology.

Thalamic ischemic strokes have a wide variety of prognoses depending on the location, size, and nature of the infarct. Cases have reported good outcomes regarding return to normal neurological function. The exception is with bilateral paramedian territory infarctions where cognitive deficits tend to persist in follow-up ¹.

See also

• artery of Percheron infarct