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Spinal trigeminal nucleus (pars oralis)

The spinal trigeminal nucleus (pars oralis) is the rostral subdivision of the spinal trigeminal nucleus complex, located in the brainstem. It is involved primarily in processing crude touch and pressure sensations from the face, forming part of the trigeminal sensory system.

Together with the pars interpolaris and pars caudalis, it contributes to the central processing of somatosensory input from the trigeminal nerve and serves as an important anatomical landmark within the pontine and upper medullary tegmentum.

Synonyms

  • Pars oralis of the spinal trigeminal nucleus

  • Oral part of spinal trigeminal nucleus

Location

  • Located in the rostral brainstem, mainly within the caudal pons

  • Extends superiorly toward the mid-pons

  • Positioned lateral to the pontine tegmentum

  • Medial to the spinal trigeminal tract

  • Superior to the pars interpolaris and rostral to the pars caudalis

Anatomical course

  • Receives primary afferent fibers from the trigeminal nerve (CN V)

  • Fibers descend slightly in the spinal trigeminal tract before synapsing

  • Second-order neurons project contralaterally via trigeminothalamic pathways

  • Connections ascend toward the ventral posteromedial (VPM) nucleus of the thalamus

Relations

Anteriorly:

  • Pontine tegmentum

Posteriorly:

  • Reticular formation

Medially:

  • Medial lemniscus

Laterally:

  • Spinal trigeminal tract

Superiorly:

  • Principal (chief) sensory nucleus of the trigeminal nerve

Inferiorly:

  • Pars interpolaris of the spinal trigeminal nucleus

Structures conveyed

  • Crude touch from the face

  • Pressure sensation from facial structures

Function

  • Facial somatosensation: Processes non-discriminative touch and pressure from trigeminal territories

  • Sensory relay: Transfers facial sensory information to higher brainstem and thalamic centers

  • Integration: Works in coordination with other trigeminal sensory nuclei for complete facial sensation

MRI appearance 

T1-weighted images:

  • Pars oralis: Isointense to surrounding brainstem gray matter

  • Margins: Not sharply demarcated, identified by anatomical location

T2-weighted images:

  • Normal nucleus: Intermediate signal similar to adjacent gray matter

  • Symmetry: Bilateral and symmetric appearance

FLAIR:

  • Normal: Subtle gray-matter signal without focal abnormality

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal: No enhancement

CT appearance 

Non-contrast CT:

  • Pars oralis: Not individually visualized

Post-contrast CT:

  • Normal: No focal enhancement

MRI images

MRI Spinal trigeminal nucleus (pars oralis) axial anatomy image -img-00000-00000

MRI images

MRI Spinal trigeminal nucleus (pars oralis) axial anatomy image -img-00000-00000_00001