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Spinal trigeminal nucleus (pars caudalis)

The spinal trigeminal nucleus (pars caudalis) is the caudal subdivision of the spinal trigeminal nuclear complex and is functionally analogous to the dorsal horn of the spinal cord. It is primarily responsible for processing pain and temperature sensation from the face and oral cavity.

This nucleus extends caudally into the upper cervical spinal cord and forms a key relay station within the trigeminal sensory system, maintaining an organized somatotopic arrangement important for facial sensory perception.

Synonyms

  • Caudal spinal trigeminal nucleus

  • Spinal trigeminal nucleus caudalis

  • Trigeminal subnucleus caudalis

Location

  • Extends from the caudal medulla into the upper cervical spinal cord (C2–C3 levels)

  • Situated in the dorsolateral medulla

  • Located posterior to the spinal trigeminal tract

  • Lateral to the nucleus of the solitary tract

  • Inferior continuation of the spinal trigeminal nuclear complex

Anatomical organization

  • Forms part of the spinal trigeminal nuclear complex, which includes:

    • Pars oralis

    • Pars interpolaris

    • Pars caudalis

  • Pars caudalis is the largest and most caudal component

  • Layered cytoarchitecture resembling spinal dorsal horn laminae

  • Receives afferent fibers primarily from:

    • Trigeminal nerve (CN V)

    • Facial (CN VII), glossopharyngeal (CN IX), and vagus (CN X) sensory fibers (minor contributions)

Relations

Anteriorly:

  • Spinal trigeminal tract

Posteriorly:

  • Inferior cerebellar peduncle (restiform body)

Medially:

  • Nucleus of the solitary tract

  • Dorsal motor nucleus of the vagus (at medullary levels)

Laterally:

  • Surface of the dorsolateral medulla

Structures processed

  • Pain (nociception) from the face

  • Temperature sensation from facial structures

  • Crude tactile input from oral and perioral regions

Function

  • Facial pain processing: Primary relay for nociceptive facial stimuli

  • Thermal perception: Transmits temperature information from facial skin and mucosa

  • Reflex integration: Contributes to protective reflexes involving facial sensation

  • Somatotopic organization: Maintains ordered representation of facial regions

MRI appearance 

T1-weighted images:

  • Pars caudalis: Isointense to surrounding gray matter

  • Identification: Based on location rather than clear signal distinction

T2-weighted images:

  • Normal nucleus: Intermediate signal intensity

  • Appearance: Blends with adjacent gray-matter nuclei

FLAIR:

  • Normal: Typically inconspicuous

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal: No enhancement

CT appearance 

Non-contrast CT:

  • Nucleus: Not individually visualized

Post-contrast CT:

  • Normal: No focal enhancement related to the nucleus

MRI images

MRI Spinal trigeminal nucleus (pars caudalis) sag anatomy image -img-00000-00000