Thalamus

Aka: Thalamus, Ventral Posterolateral Nucleus, Ventral Posteromedial Nucleus, Anterior Thalamic Nucleus, Ventral Lateral Nucleus, Ventral Thalamic Nucleus, Artery of Pancheron Stroke, Thalamic Infarction, Thalamus CVA

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II. Definitions

  1. Thalamus
    1. Functions as a central hub for incoming sensory signals relayed to the cerebral cortex
      1. Includes Hearing, Vision, touch and taste (but not olfactory)
    2. Motor interconnections between the Cerebellum, cerebral cortex and target peripheral Neurons
    3. Also integral to attention, consciousness and sleep
    4. Thalamus functionality is divided among its 9 thalamic nucleii

III. Anatomy

  1. General
    1. Paired sensory relays
    2. Located in the posterior Diencephalon of the brain
    3. Thalamus located on each side of Third Ventricle
  2. Nucleii
    1. Ventral Posterolateral Nucleus (VPL)
      1. Spinal sensory Neurons from the periphery Synapse
    2. Ventral Posteromedial Nucleus (VPM)
      1. Trigeminal LemniscusSynapse
    3. Anterior Thalamic Nucleus
      1. Portion of the Papez Circuit
    4. Ventral Lateral Nucleus (VL)
      1. Cerebellum input
  3. Vascular supply is from vertebrobasilar circulation
    1. Posterior Cerebral Artery (PCA)
      1. Paramedian artery
        1. Arises from P1 segment and supplies medial Thalamus
        2. In some patients, paramedian artery supplies bilateral medial Thalamus (see Artery of Pancheron Stroke below)
      2. Posterior Choroidal artery
        1. Arises from P2 segment and supplies posterior Thalamus
      3. Thalamogeniculate artery
        1. Arises from the P2 segment and supplies lateral Thalamus
    2. Posterior Communicating Artery (PCoA, arises from the PCA)
      1. Tuberothalamic artery
        1. Supplies the anterior Thalamus
  4. Images
    1. neuroThalamus.png
    2. neuroBrainXsGrayBB717.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
    3. neuroBrainXsGrayBB716.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

IV. Physiology

  1. Thalamus acts as a relay and integrative center for sensory input
  2. Receives peripheral sensory signals through the Brainstem
  3. Communicates with the Cerebellum, Basal Ganglia and Hypothalamus
  4. Transmits sensory signals to the cerebral cortex
    1. Motor signsal from the cerebral cortex bypass the Thalamus via the Internal Capsule

V. Signs: Thalamic Lesion Syndromes

  1. See Posterior Cerebral Artery CVA
  2. Contralateral sensory loss
    1. Pure sensory loss of all modalities may occur
    2. May cause intense pain refractory to Analgesics
  3. Visual Findings
    1. Vertical Gaze Paresis
    2. Quadrantanopsia
    3. Visual Hallucinations
    4. Impaired pursuit (on finger following)
  4. Motor findings are uncommon in thalamic CVA
    1. Hyperreflexia
    2. Positive Babinski Reflex
    3. Extremity movement may be affected
  5. Cognitive, Language and Behavior findings
    1. Decreased Level of Consciousness
    2. Confabulation
    3. Perseveration
    4. Amnesia
    5. Wandering thoughts
    6. Aphasia
  6. Artery of Pancheron Stroke (0.7% of all Ischemic Strokes, 18% of thalamic strokes)
    1. Single paramedian artery may supply bilateral medial Thalamus (vascular anomaly)
    2. May result in bilateral thalamic stroke
      1. Altered Mental Status
      2. Vertical Gaze Palsy
      3. Impaired memory

VI. References

  1. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 105
  2. Swaminathan and Marcolini (2026) Thalamic Stroke, EM:Rap, 4/20/2026
  3. Newton (1994) Am Fam Physician 49(4): 787-97 [PubMed]

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