Rostral Midbrain
Tracts (3) of Rostral midbrain
1. medial lemniscus 2. trigeminothalamic tract 3. spinothalamic tract They are more laterally than in the caudal midbrain The medial lemniscus now looks like "Santa's hat" on a centrally located red nucleus. The MLF and cerebral peduncles have kept their positions.
Nuclei of Rostral Midbrain
1. oculomotor nuclei 2. red nucleus 3. substantia nigra 4. ventral tegmental area 5. periaqueductal gray
Oculomotor nerve (III)
Locate at the level of the superior colliculus. Skeletal muscle component from the oculomotor nucleus. Exits between superior cerebellar and posterior cerebral peduncles. Innervates extraocular muscles except lateral rectus and superior oblique. Parasympathetic activity, from nucleus of Edinger-W next to oculomotor nucleus: pupillary constriction, accommodation
Lesion to cochlear nerve, what happens?
causes diplopia on the ipsilateral eye, since the nerve decussates quickly after leaving the posterior brain stem. The patient will present with the head tilted away from the side of the nerve lesion.
Red nucleus
centrally placed, is involved in relaying cerebellar information to the brain stem and spinal cord.
Periaqueductal gray:
diffuse collection of neuronal cell bodies involved in pain recognition and defensive behavior
Parkinson's Disease
dopamine loss in substantia nigra
Oculomotor nuclei
found in the posteromedial aspect of the tegmentum, just posterior to the MLF.
Superior Collliculi
in the tectum, relay nuclei for visual input.
Trochlear nerve (IV)
only cranial nerve that exits posteriorly. Motor nerve that innervates the superior oblique muscle, the cells bodies are in the trochlear nucleus in the caudal midbrain, the axons take a unique course through the tectum (subarachnoid space) to exits in the posterior contralateral surface of the brain stem.
Weber's Syndrome
superior alternating hemiplegia. Caused by stroke in branch of posterior cerebral artery or basilar artery. Ipsilateral loss of III, contralateral loss of motor control of skeletal muscles (loss of blood supply to cerebral peduncle).
