Thalamic Strokes & Sudden Sensory Losses
Overview
The thalamus is a deep subcortical relay that transmits most somatosensory information to the cortex and contributes to motor circuits, arousal, sleep, cognition and pain processing. Small thalamic infarcts commonly present with abrupt hemisensory loss and may be mistaken for peripheral neuropathy or radiculopathy.
Any sudden focal neurological deficit - including isolated sensory loss - requires urgent stroke pathway activation and rapid neuroimaging (NICE NG128; RCEM).
Anatomy, vascular supply and syndrome localisation
The clinical syndrome of a thalamic stroke depends on which thalamic nuclei and neighbouring structures are affected. Key vascular territories include:
- Paramedian (medial) thalamus - supplied by paramedian (thalamoperforator) branches from the P1 segment of the posterior cerebral artery (PCA); lesions may extend to the rostral midbrain.
- Inferolateral (thalamogeniculate) territory - supplied by thalamogeniculate arteries (PCA branches) and includes the ventral posterolateral (VPL) and ventral posteromedial (VPM) sensory nuclei.
- Anterior nucleus - supplied by tuberothalamic (polar) branches; involvement produces memory and behavioural disturbance.
- Posterior/pulvinar and posterior choroidal territories - involvement produces visual and sensory‑perceptual deficits.
Typical syndromes
- Inferolateral (thalamogeniculate) infarct: classical pure sensory stroke with contralateral hemisensory loss affecting face, arm and leg. Central post‑stroke pain (Dejerine-Roussy) is a well‑recognised late complication.