Brain stem Flashcards
What are the 3 general functions of the brainstem?
Conduit for ascending and descending tracts connecting spinal cord to forebrain
Contains important reflex centers associated with respiration, cardiovascular system, and consciousness
Contains nuclei of CN III to XII
Where are the olives (inferior olivary nuclei) located?
Posterolateral of the pyramids on the medulla
Where the hypoglossal N emerge from the brainstem?
From groove between the pyramid and olive
What structure connects the medulla to the cerebellum, located posterior to the olive?
Inferior cerebellar peduncles
Where is the posterior median sulcus?
Dorsal medulla, inferior lateral part outside of 4th ventricle
Where is the gracile tubercle (gracile nucleus)?
On either side of the posterior median sulcus on the medulla
What is the location of the cuneate tubercles (nucleus)?
Lateral to the gracile tubercles on the medulla
What is the superomedial zone?
Form the caudal part of the 4th ventricle in the medulla
What 3 elevations are seen in the superomedial zone?
Hypoglossal trigone
Vagal trigone
Vestibular area
Where is the basilar groove?
Ventral midline of bones
Houses basilar artery
Where does the trigeminal N emerge from the brainstem?
Anterolateral surface of the pons - two roots
What CNs emerge from the groove between the pons and the medulla medial to lateral?
Abducent N
Facial N (two roots)
Vestibulocochlear N
What forms the upper part of the fourth ventricle?
Posterior surface of the pons
Where is the medial eminence?
On either side of the median sulcus on the dorsal pons
Where is the locus ceruleus?
Rostral to median sulcus of dorsal pons
What is the interpeduncular fossa?
Deep depression in midline of ventral midbrain
Where is the crus cerebri?
Also called cerebral peduncle
On either side of the interpeduncular fossa of ventral midbrain
What is found in the floor of the interpeduncular fossa?
Pituitary stalk
Mammillary bodies
Posterior perforated substance
What separates the lateral surface of the midbrain from the parahippocampal gyrus?
Trochlear N
Where are the superior colliculi?
Centers for visual reflexes
On dorsal midbrain, connected to lateral geniculate body
Where are the inferior colliculi?
Centers for auditory pathways
On dorsal midbrain, connected to medial geniculate body
Where does the trochlear N emerge from the brainstem?
Dorsal midbrain, below the inferior colliculi
What are the general functions of the reticular formation?
Level of consciousness
Cardiovascular system
Respiratory system
Where do corticobulbar fibers terminate?
Midbrain, pons and medulla
What structures in the brainstem give rise to descending fibers to spinal cord?
Reticular formation
Red nucleus
Vestibular nuclei
What is the tectum?
Dorsal midbrain
What is the tegmentum?
Middle of midbrain
Dorsal for pons and medulla
Where are the nuclei for CN III located in the brainstem?
Oculomotor nucleus and Edinger-Westphal nucleus both in midbrain
Where are the nuclei for CN IV located in the brainstem?
Trochlear nucleus in midbrain
Where are the nuclei for CN V located in the brainstem?
Trigeminal sensory: mesencephalic in midbrain
Trigeminal sensory: primary in pons
Trigeminal sensory: spinal in medulla
Trigeminal nucleus in pons
Where are the nuclei for CN VI located in the brainstem?
Abducens nucleus in pons
Where are the nuclei for CN VII located in the brainstem?
Trigeminal sensory: mesencephalic in midbrain
Trigeminal sensory: primary in pons
Trigeminal sensory: spinal in medulla
Facial nucleus in pons
Superior salivatory nucleus in pons
Nucleus of solitary tract in pons and medulla
Where are the nuclei for CN VIII located in the brainstem?
Vestibular nuclei and cochlear nuclei of pons and medulla
Where are the nuclei for CN IX located in the brainstem?
Inferior salivatory nucleus in pons
Trigeminal sensory: primary in pons
Trigeminal sensory: spinal in medulla
Nucleus ambiguus in medulla
Nucleus of solitary tract in pons and medulla
Where are the nuclei for CN X located in the brainstem?
Trigeminal sensory: primary in pons
Trigeminal sensory: spinal in medulla
Nucleus ambiguus in medulla
Nucleus of solitary tract in pons and medulla
Dorsal nucleus of vagus N in medulla
Where the nuclei for CN XI located in the brainstem?
Spinal accessory nucleus in medulla
Also some from cervical spinal cord
Where are the nuclei for CN XII located?
Hypoglossal nucleus in medulla
What is the arterial supply to the medulla?
Anterior spinal A and PICA branches of vertebral A
What is the arterial supply to the pons?
Short and long circumferential branches of basilar A
What is the arterial supply of the midbrain?
Superior cerebellar A and quadrigeminal A branches of basilar A
Also supplied by anterior and posterior choroidal arteries
What causes medial medullary syndrome?
Occlusion of branches of the anterior spinal A
What are symptoms of medial medullary syndrome?
Contralateral hemiplegia of body
Contralateral loss of proprioception, vibration, and discriminatory touch of body
Deviation of tongue to side of lesion
What causes lateral medullary syndrome?
Occlusion of PICA
What are symptoms of lateral medullary syndrome?
Contralateral loss of pain and temp of body
Ipsilateral loss of pain and temp on face
Dysphagia, hoarseness, soft palate paralysis, and diminished gag reflex
Ipsilateral Horner’s syndrome
Nausea, vertigo, and nystagmus
Ipsilateral ataxia
What causes lateral pontine syndrome?
Occlusion of AICA and SCA
What are symptoms of lateral pontine syndrome?
Contralateral loss of pain and temp of body
Ipsilateral loss of pain and temp of face
ipsilateral facial paralysis
Ipsilateral paralysis of mastication
Ipsilateral Horner’s syndrome
Nausea, vertigo, nystagmus, hearing loss, tinnitus
Ipsilateral ataxia
What causes medial pontine syndrome?
Occlusion of paramedian branches of basilar A
What are symptoms of medial pontine syndrome?
Contralateral hemiplegia of body
Contralateral loss of proprioception, vibration, and discriminatory touch of body
Ipsilateral paralysis of lateral rectus - internal strabismus
Paralysis of conjugate gaze toward side of lesion
What causes medial midbrain syndrome (Weber)?
Occlusion of paramedian branches of P1 segment of PCA?
What are symptoms of medial midbrain/Weber syndrome?
Contralateral hemiplegia of body
Contralateral lower face muscle weakness
Ipsilateral external strabismus, dilated fixed pupil and severe ptosis
What causes Benedikt syndrome?
Larger lesion of midbrain including both areas of Weber and Claude
What are symptoms of Benedikt syndrome?
Contralateral hemiplegia of body
Ipsilateral paralysis of eye movement with dilated pupil
Cerebellar and rubral tremor and ataxia
What causes Parinaud syndrome?
Usually a tumor in pineal region that impinges on the superior colliculi of midbrain
Why may hydrocephalus occur in Parinaud syndrome?
Pineal tumor may occlude the cerebral aqueduct
What are symptoms of Parinaud syndrome?
Paralysis of upward gaze
Eventual failure of eye movement
Nystagmus
Hydrocephalus
