Transcript Brain stem Anterior view

Brain stem Anterior view
Pons
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
Pons
• The pontocerebellar fibres pass to the contralateral 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
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
Pons
• The medial lemniscus also rotates through
90º so that it lies almost horizontally, marking
the boundary between ventral and tegmental
portions of pons
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
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
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
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
Section of Pons at the level of Facial
colliculus
Section of pons at the level of trigeminal
nuclei
Vestibular nuclei And Connections
Cochlear nuclei And Connections
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.
Lateral pontine syndrome
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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
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.
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?
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Left oculomotor nerve
Medial longitudinal fasciculus
Right abducens nerve
Right oculomotor nerve
Right trochlear nerve
Vestibulo Ocular Reflex
Internuclear ophthalmoplegia
Lesion involving left MLF
Defective left adduction and ataxic
nystagmus of right eye
Normal left gaze
Convergence intact if lesion discrete
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Demylination - usually bilateral
Vascular disease
Tumours of brainstem
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.
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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