ANATOMY OF PONS AND CEREBELLUM

DR PRATIK MISTRY

PONS

INTRODUCTION• Pons means

“bridge” connect midbrain and hind brain

• Extent• Relations: ventrally

and dorsally• Laterally connected

with middle cerebellar peduncle

EXTERNAL FEATURES

• VENTRAL SURFACE: Sulcus basilaris Laterally continue with

MCP Show transverse ridges

and grooves because of ponto-cerebellar fibres

Ponto-medullary junction attachment to 6th, 7th, 8th CN

Cerebello-pontine angles

EXTERNAL FEATURES

• DORSAL SURFACE: Form upper part of floor

of 4th ventricle above medullary stria

Facial colliculus formed by

Vestibular area Locus ceruleus

(substantia ferruginea)

INTERNAL FEATURES

• Ventral, basilar part (pons proper)• Dorsal, tegmental part

BASILAR PART• Traversed by

longitudinal & transverse fibres and scattered pontine nuclei

• Longitudinal fibres

• Transverse fibres

• Nuclei pontis and their role

TEGMENTAL PART• Traversed by number of ascending and

descending tracts• Contain decussation of trapezoid body, nuclei of

6th, 7th, 8th and 5th cranial nerves• Also has pontine reticular formation• Described in two parts:1. At the level of facial colliculus2. Above the level of facial colliculus

AT THE LEVEL OF FACIAL COLLICULUS

• Necklace of ascending tracts

• Medial lemniscus• Trigeminal

lemniscus• Spinal lemniscus• Trapezoid body• Nucleus of

trapezoid body and superior olivary nuclear complex

AT THE LEVEL OF FACIAL COLLICULUS• Dorsally, motor

nucleus facial nerve

• Abducent nucleus• neurobiotaxis• Superior

salivatory nucleus

• Nucleus of spinal tract of 5th CN

• Central tegmental tract

AT THE LEVEL OF FACIAL COLLICULUS• In the middle,

• MLF• Tecto-spinal tract• Rubro-spinal

tract

AT THE LEVEL OF FACIAL COLLICULUS• Dorso-laterally

• Middle cerebellar peduncle

• Ventral & dorsal cochlear nuclei

• Ant. Spino-cerebellar tract

• Part of inferior cerebellar peduncle

• Vestibular nuclei

SECTION OF PONS ABOVE THE FACIAL

COLLICULUS

ABOVE THE LEVEL OF FACIAL COLLICULUS• Smaller cavity of

4th ventricle bounded by

• Ant. Spino-cerebellar tract

• Middle cerebellar peduncle with motor and sensory roots of 5th nerve

ABOVE THE LEVEL OF FACIAL COLLICULUS• Motor nucleus of

5th nerve• Principal sensory

nucleus of 5th nerve – touch & pressure

• Mesencephlic nucleus of trigeminal nerve – proproiceptive fibres from muscles of mastication & TM Joint

APPLIED ANATOMY• Cerebello-pontine

syndrome (acoustic neuroma)

• Raymond’s syndrome (alternate abducent hemiplegia)

• Millard- Gubler syndrome (alternate facial hemiplegia)

• Foville syndrome• Alternating trigeminal

hemiplegia• Pontine haemorrhage