Thalamic infarct

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

Epidemiology

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

Risk factors

Most of the risk factors are common to all types of ischemic infarcts ² and include:

• age
• male sex
• hypertension
• diabetes mellitus
• hypercholesterolemia
• cigarette smoking
• atrial fibrillation

Clinical presentation

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

• tuberothalamic (anterior) artery territory
  • cognitive and behavioral disturbances
  • left hemisphere lesions: memory, language deficit and acalculia
  • right hemisphere lesions: hemineglect
  • chronotaraxis (loss of time sense)
• paramedian artery territory
  • decreased levels of consciousness
  • left hemisphere lesions: aphasia
  • right hemisphere lesions: hemineglect
  • vertical gaze abnormalities and other complex ophthalmoplegias
• inferolateral artery territory
  • sensorimotor deficits
  • Dé​jerine-Roussy syndrome (thalamic pain syndrome)
• posterior choroidal artery territory
  • sensorimotor deficits
  • visual field defects

Pathology

The main cause of infarction is thrombotic occlusion secondary to atherosclerosis, the most common sites being the carotid bifurcation, the origin of the middle cerebral artery and the basilar tip ³. 

Classic thalamic territories include ⁵:

• anterior territory (polar/tuberothalamic arteries)
  • arteries arise from the posterior communicating artery
• paramedian (paramedian arteries)
  • arteries arise from the P1 segment of the posterior cerebral artery
• Inferolateral (thalamogenicular arteries)
  • arteries arise from the P2 segment of the posterior cerebral artery
• posterior (posterior choroidal arteries)
  • arteries arise from the P2 segment of the posterior cerebral artery

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 typically medically managed and 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.