Case 1Right-click crosses out. Double-click marks.
Subcortical structures
Thalamus Relay Room
Every big sensory signal, except smell, hits the thalamic switchboard before cortex. Learn the board move: modality plus body map plus missing cortical signs.
VPL/VPMbody and face sensory relays
LGN/MGNvision and hearing relays
VLmotor circuit handoff
First lock
A lacunar stroke causes contralateral face, arm, and leg sensory loss with no weakness or aphasia. Where is the lesion?
One pattern
The thalamus is not a blob. It is a routing table.
Do not memorize nuclei as floating names. Ask what signal is entering, what cortical area needs it, and whether the deficit is pure sensory, sensory plus cortical, or motor relay.
VPL
Body pain, temperature, vibration, proprioception, and touch from spinothalamic plus dorsal column-medial lemniscus.
VPM
Face sensation and taste. If trigeminal or gustatory information is the stem, think VPM.
LGN
Vision relay from optic tract to calcarine cortex.
MGN
Auditory relay from brainstem auditory pathways to temporal cortex.
VL
Motor relay receiving basal ganglia and cerebellar output before motor cortex.
Smell
The exception. Olfaction reaches cortex without first stopping at thalamus.
Switchboard drill
Pick the relay from the signal.
The board trick is to name the input before naming the nucleus. Body sensory gets VPL. Face and taste get VPM. Light gets LGN. Music gets MGN. Motor plan gets VL.
Pure sensory lacune
Contralateral face, arm, trunk, and leg sensory loss across modalities, with no aphasia, neglect, or weakness, is thalamus until proven otherwise.
Thalamic pain syndrome
After the original numbness improves, the damaged relay can generate burning central pain that is triggered by light touch.
LGN versus MGN
Lateral geniculate is vision. Medial geniculate is hearing. The sensory word in the stem gives the nucleus.
VL
VL is the thalamic handoff for basal ganglia and cerebellar output to motor cortex, so tremor and movement circuits can point there.
Fast decision
A deep lesion gives one clean pattern. Which detail rescues you from overcalling cortex?
Visual anchors
Three pictures, three anchors.
Use the real anatomy only as a locator. The functional map comes from the signal: body, face, vision, hearing, or motor plan.
Commit before reveal
Six thalamus cases
Commit to the relay before reading the explanation. The clues glow only after you answer.
Memory lock
The thalamus lock
When the question feels vague, force it through these four gates.
All modalities
If pain, temperature, vibration, proprioception, and light touch fall together, the signal has converged.
Face plus body
Face and body on the same side of the deficit means a relay above the brainstem.
No cortical signs
No aphasia, neglect, seizure, or higher-order sensory loss makes deep thalamus more likely.
Delayed burning pain
Old thalamic sensory injury can become central pain even after the exam improves.