Clinical anatomy of MID BRAIN

1305Ajay sharma

MidbrainCerebral peduncles

PonsBasis pontis

Medulla

Ventral – Lateral View

The midbrain is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation

DIVISION OF THE MIDBRAIN

MIDBRAIN

CEREBRAL PEDUNCLE

CRUS CERBRI

TEGMENTUM

TECTUM

SUPERIOR COLLICUL

US

INFERIOR COLLICUL

US

AT THE LEVEL OF THE INFERIOR COLLICULUS

CAVITY

NUCLEI

MOTOR TRACTS

SENSORY TRACTS

INFERIOR COLLICULUS

SUBSTANTIA NIGRA

TROCHLEAR NUCLEUS

MESENCEPHALIC NUCLEI OF

CN V

INFERIOR COLLICULUS

NUCLEI

The substantia nigrais divisible into a dorsal part, the pars compacta; and a ventral part, the parsreticularis. The pars compacta contains dopaminergic and cholinergic neurons. Most of the neurons inSuperiorly, the pars reticularis becomes continuous with the globuspallidus. The substantia nigra is closely connected, functionally, with the corpus striatum (and in causationof Parkinsonism,

TRACTS

SENSORY

• TRIGEMINAL• SPINAL• MEDIAL• LATERAL• DECUSSATION OF SUPERIOR

CERBELLAR PEDUNCLE

MOTOR• CORTICOSPINAL• CORTICONUCLEAR• TEMPOROPONTINE• FRONTOPONTINE• MED. LONG. FASCICULUS

AT THE LEVEL OF THE SUPERIOR COLLICULUS

CAVITY

NUCLEI

MOTOR TRACTS

SENSORY TRACTS

SUPERIOR COLLICULUS

SUBSTANTIA NIGRA

OCULOMOTOR NUCLEUS

SUPERIOR COLLICULUS

MESENCEPHALIC NUCLEUS OF CN V

RED NUCLEUS

EDINGER WESTPHAL NUCLEUS

NUCLEI

TRACTS

MOTOR

CORTICOSPINAL

CORTICONUCLEAR

TEMPOROPONTINE

FRONTOPONTINE

MED. LONG. FASCICULUS

RUBROSPINAL TRACT

SENSORY

TRIGEMINAL

SPINAL

MEDIAL

Clinical aspects…..

Medial midbrain syndrome (paramedian branches of upper basilar and proximal posterior cerebral arteries)

ON SIDE OF LESION Eye "down and out"

secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers

ON OPPOSITE SIDE Paralysis of face, arm,

and leg: Corticobulbar and corticospinal tract descending in crus cerebri

Lateral midbrain syndrome (syndrome of small penetrating arteries arising from posterior cerebral artery) On side of lesion

Eye "down and out" secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers and/or third nerve nucleus

On side opposite lesion Hemiataxia,

hyperkinesias, tremor: Red nucleus, dentatorubrothalamic pathway

Weber’s syndrome injury to the cerebral peduncle causes ipsilateraloculomotor palsy with contralateral hemiparesis

WEBER’S SYNDROME

In Benedikt’s syndromeinjury to the red nucleus results in ipsilateral oculomotor palsyand contralateral tremor, chorea, and athetosis.

BENEDIKT’S SYNDROME

In Nothnagel’s syndrome , injuryto the superior cerebellar peduncle causes ipsilateral oculomotorpalsy and contralateral cerebellar ataxia.

superior cerebellar peduncle (brachium conjunctivum) is a paired structure of white matter that connects the cerebellum to the midbrain.

Claude's syndromeClaude’s syndrome

incorporates features of both of these syndromes, by injury to boththe red nucleus and the superior cerebellar peduncle.

 is a form of brainstem stroke syndrome characterized by the presence of an ipsilateral oculomotor nerve palsy, contralateral hemiparesis, contralateral ataxia, and contralateral hemiplegia of the lower face, tongue, and shoulder. Claude's syndrome affects occulomotor nerve,red nucleus and brachium conjunctivum

Parinaud's Syndrome also known as dorsal midbrain

syndrome, vertical gaze palsy, and Sunset Sign, is an inability to move the eyes up. It is caused by compression of the vertical gaze center at the rostral interstitial nucleus of medial longitudinal fasciculus

Conjugate down gaze in the primary position: "setting-sun sign". Neurosurgeons see this sign most commonly in patients with failed hydrocephalus shunts.

 it has been associated with three major groups:

Young patients with brain tumors in the pineal gland or midbrain: pinealoma (intracranial germinomas) are the most common lesion producing this syndrome.

Women in their 20s-30s with multiple sclerosis

Older patients following stroke of the upper brainstem

any other compression, ischemia or damage to this region can produce these phenomena: obstructive hydrocephalus, midbrain hemorrhage, cerebral arteriovenous malformation, trauma and brainstem toxoplasmosis infection. Neoplasms and giant aneurysms of the posterior fossa have also been associated with the midbrain syndrome.

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