1. Brain stem Anterior view

2. Pons

3. Pons
The pons may be divided into ventral or basal portion and a dorsal portion, also known as tegmentum
The ventral portion is marked by numerous transversely oriented fascicles of pontocerebellar fibres that originate from scattered cell groups called pontine nuclei

6. Pons
The pontocerebellar fibres pass to the contra- lateral side of the cerebellum through the massive middle cerebellar peduncle
Corticospinal fibres appear as small and separate bundles running longitudinally between the fascicles of transverse pontine fibres

7. Pons
The ascending fibres of the medial lemniscus become separated from the pyramid and displaced dorsally together with the spinal lemniscus and trigeminothalamic tract, by intervening transverse pontocerebellar fibres

10. Pons
The medial lemniscus also rotates through 90º so that it lies almost horizontally, marking the boundary between ventral and tegmental portions of pons

11. Pons
In the caudal pons, an additional group of transversely running fibres is located ventral to the ascending lemniscal fibres but dorsal to the pontocerebellar fibres
This is the trapezoid body which consists of acoustic fibres crossing the brain stem from the cochlear nuclei

13. Pons
They ascend into the midbrain as the lateral lemniscus and terminate in the inferior colliculus
Beneath the floor of the fourth ventricle, in the pontine tegmentum lie a number of cranial nerve nuclei

14. Pons These nuclei include: Abducens nucleus for lateral rectus muscle
Facial motor nucleus for muscles of facial expression
Trigeminal motor nucleus for muscles of mastication

17. Pons Each nucleus supply to their respective cranial nerves
Trigeminal sensory nucleus encountered in the medulla
It reaches its maximum extent in the pons, adjacent to the origin of the trigeminal nerve

19. Section of Pons at the level of Facial colliculus

20. Section of pons at the level of trigeminal nuclei

21. Vestibular nuclei And Connections

22. Cochlear nuclei And Connections

23. Pontine syndromes Medial pontine Syndrome
Structures Associated
CST
Medial lemniscus
6th nerve fibers
7th nerve fibres
Sign
Contralateral spastic hemiparesis of the body
Contralateral loss of position and vibration of the body
Medial strabismus
Raymond's Syndrome
Alternating abducent hemiplegia
Miller-gubler syndrome
Alternating Facial hemiplegia.

24. Lateral pontine syndrome
Structure
ICP
Spinal 5
Spinothalamic
Fibers of 7
Fibers of 8
Sign
Ipsilateral limb ataxia
Ipsilateral pain and temp loss - Face
Contralateral pain and temp-Body
Horner’s syndrome (Ipsilateral)
Hearing loss
Ipsilateral facial paralysis

25. Clinical Case
A 50-year-old man with hypertension, congestive heart failure, and polysubstance abuse (cocaine, cigarettes, alcohol, and marijuana) experienced three days of acute onset of horizontal diplopia, left mouth drooling, and left-sided weakness. On examination he had right abducens nerve palsy, left-sided central paresis of the lower part of the face and limbs, and left hyperreflexia. Pupils were equal, round, and reactive to light and accommodation. He did not exhibit ptosis. There was no muscle tenderness. Sensation was normal and intact. Cerebellar coordination exam was normal on the right but limited on the left due to weakness.

26. Case .
A 41-year-old woman presents to her physician with "double vision" and is unable to adduct her right eye on attempted left lateral gaze. Convergence is intact. Both direct and consensual light reflexes are normal. Which of the following structures is most likely to be affected?
Left oculomotor nerve
Medial longitudinal fasciculus
Right abducens nerve
Right oculomotor nerve
Right trochlear nerve

27. Vestibulo Ocular Reflex

28. Internuclear ophthalmoplegia
Lesion involving left MLF
Normal left gaze
Defective left adduction and ataxic
nystagmus of right eye
Convergence intact if lesion discrete
Demylination - usually bilateral
Vascular disease
Tumours of brainstem

29. Case 2.
A patient with a bullet wound to the head is referred to you for neurological examination. Upon entering the hospital room you find the patient on a respiratory and cardiac monitor. You have difficulty arousing the patient and once awake you note the following: Right pupil is constricted; there is medial strabismus of the right eye and upon attempted right lateral gaze the left eye fails to adduct; loss of pain and temperature sensitivity on the right side of the face and left side of the body; deafness of the right ear; a pronounced intention tremor in the right arm and leg. The deep tendon reflexes on the right side are not as brisk as those on the left and there appears to be a complete facial paralysis on the right side.
The likely site for this lesion is:
The left internal capsule
The right caudal pons
The left cerebellar hemisphere
The left side of the midbrain at the level of the superior colliculus
The right side of the medulla at the level of the dorsal column nuclei