5.2 - The pons

Pons location and boundaries

Brainstem between midbrain (pontomesencephalic junction) and medulla (pontomedullary junction)

Structures on the anterior surface of the pons

Basilar sulcus

Middle cerebellar penduncles

Trigeminal n. (5) ventrally

CN 6-8 at pontomedullary junction

Structures on the posterior surface of the pons

Upper floor of 4th ventricle

Facial colliculi

Vestibular area

Superior/middle/inferior cerebellar peduncles

Nuclei found in the pons (gray matter)

Motor nuclei - Trigeminal (5), abducens (6), facial (7)

Sensory nuclei - Trigeminal (5), vestibulocchlear (8)

Pontine respiratory nuclei

Pontine nuclei (relays to cerebellum)

Major tracts that pass through the pons (white matter)

Descending - corticospinal, corticobulbar

Ascending - medial lemniscus, spinal/trigmeninal lemnisci

Transverse pontine fibres

Medial longitudinal fasciculus (MLF)

Cranial nerve attachments to pons

CN 5 (mid-pons)

CN 6-8 (pontomedullary junction)

Systems regulated by the pons

Respiratory - pneumotaxic centre

Auditory - cochlear nuclei, trapezoid body

Balance - vestibular nuclei

Eye movement - MLF coordination

Facial sensation/movement - CN 5/7

Clinical signs of pontine (pons) damage

Millard-Gubler syndrome: CN 6/7 palsy + contra lateral hemiparesis (one-sided weakness of the body on the side opposite to brain injury)

Locked in syndrome: bilateral corticospinal tract damage

Hearing loss/vertigo: CN 8

Respiratory arrest: pontine respiratory centre damage

3 transverse structures

Trapezoid body (auditory)

Transverse pontine fibres (corticopontocerebellar)

Middle cerebellar penducle (largest cerebellar input)

Arteries that supply the pons

Basilar artery

AICA (anterior inferior cerebellar artery)

SCA (superior cerebellar artery)

Embryological structures that form the pons

Develops from the metencephalon (along with cerebellum)

Alar plate > sensory nuclei

Basal plate > motor nuclei