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Brainstem Neuroanatomy and Functional Pathways

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Brainstem Alar Plate Sensitivity

General Visceral Sensory (GVS): Cardiorespiratory Nucleus
Medial solitary tract: Receives information from the Vagus (CN X) and Glossopharyngeal (CN IX) nerves. The primary neuron is located in the inferior ganglion of the Vagus nerve.

Special Visceral Sensory (SVS): Taste Nucleus
Lateral to the solitary tract: Receives information from the inferior CN IX and CN X. It is located in the ganglion (No GVS).

General Somatic Sensory (GSS): Trigeminal Nucleus
Three parts: Mesencephalic, Sensory, and Spinal.
Information received:

  • Principal part: Proprioceptive information.
  • Superior spinal part: Non-discriminative tactile information.
  • Caudal spinal part: Thermoanalgesic information.

Special Somatic (SS): Acoustic and Labial Nuclei

Ascending Pathways of the Brainstem

Originating from the spinal cord: Posterior Column (PC); Anterolateral System (ALS) (including neospinothalamic, spinoreticular, spino-olivary, spinomesencephalic, and spinotectal pathways); PET; CCA, and ECA.

Pathways Originating in the Brainstem

Trigeminal System (GSS):

  • Dorsal Trigeminothalamic Tract: Internal mouth information; Gasserian Ganglion to the Principal Sensory Trigeminal Nucleus (ipsilateral).
  • Anterior Trigeminothalamic Tract: Information from most of the face; Gasserian Ganglion to the Principal Sensory Trigeminal Nucleus; reaches the thalamus medially attached to the Posterior Column.
  • Trigeminothalamic Pathway (ALS equivalent): Protopathic information; Gasserian Ganglion to the Trigeminal Nucleus (interpolated in the caudal portion); reaches the thalamus with the ALS (contralaterally).

Solitary Nuclei System:

  • Lateral Solitary Tract (SVS): Taste information; 1st neuron (CN VII, IX, or X); 2nd neuron in the lateral solitary nucleus to the ipsilateral thalamus.
  • Medial Solitary Tract (GVS): Ganglia of CN IX and X to the medial solitary nucleus (ipsilateral rise via the dorsal aspect).

Descending Pathways in the Brainstem

Pathways to the Spinal Cord

VEL, VEM, REM, REL, TE, RUE, SAR, RUE, HIP-ES, COR-EN

Pathways Remaining in the Brainstem

Corticopontine Cerebellar Pathways: Cortex to the Pons (bump) to the contralateral Cerebellum.

Corticonuclear (Corticobulbar) Pathways:

  • Sensory nuclei of the brainstem.
  • Somatic and visceral motor nuclei of the brainstem.
  • Corticorubral and Corticoreticular pathways.

Bilateral: CN V. Ipsilateral: Sternocleidomastoid (CN XI), IV, VII, VI. Contralateral: IX, X, XI (Trapezius).
* Nucleus of XII: Bilateral (medial cord); Contralateral (lateral cord).

Vestibular Nuclei: Afferent and Efferent Connections

The vestibular nuclei consist of the superior, lateral, inferior, and medial nuclei.

Afferent Connections

  1. Vestibular Ganglion: Ipsilateral; also ends in the cerebellum (nodule and uvula).
  2. Contralateral Vestibular Nuclei: For precise bilateral coordination.
  3. Cerebellum: From the fastigial nucleus.
  4. Medulla: Proprioceptive information.
  5. Reticular Formation (RF): For the purpose of equilibrium.
  6. Accessory Optic Nuclei: Located in the midbrain.

Efferent Connections

  1. Spinal Cord:
    • 1.1. Lateral Vestibulospinal Tract (bilateral).
    • 1.2. Medial Vestibulospinal Tract (ipsilateral).
  2. Cerebellum and Reticular Formation: To control visceral physiological changes.
  3. Oculomotor and Preoculomotor Nuclei: Via the medial longitudinal fasciculus (Sensory: ipsilateral; Motor: contralateral).
  4. Thalamus: Specifically the VPL and VPI nuclei.
  5. Vestibular Receptors: To regulate the sensitivity of the receiving cells.

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