Brainstem and Cranial Nerves Flashcards
Edinger-Westphal n.
Parasymp of CN III
Superior colliculus, only a little bit higher than oculomotor nucleus (Edinger-Westphal is with red nucleus)
Trochlear n.
Decussate at Inferior colliculus
Contralateral
Emerges immediately below inferior colliculus
Motor to superior oblique m.
mesencephalic n. of CN V
Extends from midbrain down to midpons
Propioception of face
Chief n. of face
Fine touch of face
Nucleus spinal tract of CN V
Extends from midpons to upper cervical cord
Pain of face
Motor n. of CN V
Muscles of mastication
At the same level as sensory n. Of CN V
Between mesencephalic nuclei &tract and spinal nuclei &tract of CN V
Caudal pons CN nuclei
Abducens n. = lateral rectus m.
Parabucen n. (PPRF)
Facial n.
Superior salivatory n.
Parabucen n. (PPRF) fxn
horizontal conjugate eye movement
Superior salivatory n. fxns
Secretion from lacrimal gland, submandibular, sublingual salivary glands
Pontomedullary jxn nuclei
Inferior salivatory n. –> CN IX, parotid gland secretion
Medulla nuclei
Nucleus ambiguus (CN IX, X, XI)
Dorsal motor n of CN X
hypoglossal n.
Solitary n.
Nucleus ambiguus
Motor to muscles of pharynx & larynx
Dorsal motor nuc. of CN X
parasymp. of CN X
Hypoglossal n.
motor to tongue m.
Solitary n.
taste & visceral sensation
Accessory n.
Spinal part of CN XI
Motor to trapezius and SCM m.
CN III palsy
Diplopia, lateral squint, ptosis, dilated pupil, decreased light reflex
CN IV palsy
Difficulty in looking down e.g. down the stairs
CN V palsy
Decreased sensation of face, corneal reflex
CN VI palsy
Medial squint, diplopia
CN VII palsy
Weakness of ipsilateral facial muscles
CN VIII palsy
Neurosensory hearing loss
CN IX, X palsy
decreased gag reflex, uvula deviation (away from lesion), hoarseness
CN XII palsy
Ispilateral tongue atrophy, deviation towards the same side
Medial brainstem lesions
- Motor (pyramidal) tract
- Medial lemniscus
- Motor nuclei & CN 3, 6, 12
Lateral brainstem lesions
To the Side
Spinocerebellar
Spinothalamic / spinal lemniscus
Sensory nucleus of CN V, VIII
Sympathetic pathway
Midbrain is supplied by … branches
PCA
Rostral pons is supplied by … branches
paramedian b. of basilar, superior cerebellar a.
Midpons is supplied by … branches
Paramedian b of basilar, short circumferential of basilar
Caudal pons is supplied by … branches
Paramedian b of basilar, AICA
Medulla is supplied by … branches
Anterior spinal a, PICA
Extrinsic vs intrinsic brainstem lesions
Extrinsic:
- Multiple CN palsies
- Unilateral hearing loss
- No or late long-tract signs (hemiparesis, hemianesthesia)
Intrinsic: early long tract signs, deterioration of consciousness
Parinaud syndrome
Often due to pinealoma or geminoma of the pineal gland.
Compression of tectum (posterior midbrain) causes:
- Impaired light reflex, upward gaze, convergence, accomodation
Can cause noncommunicating hydrocephalus
Benedikt syndrome
Paramedian midbrain syndrome
- CN III palsy
- Ipsilateral fixed and dilated pupil (ophthalmoplegia)
- contralateral loss of conscious proprioception, fine touch, and vibration from trunk and extremities
- Red nucleus: contra cerebellar dystaxia with intention tremor
Uncal herniation classical triads
- Ipsilateral fixed dilated pupil (CN III palsy)
- Contralateral hemiparesis due to compression of pyramidal tract
- Coma due to compression of reticular formation
In some cases, Kernohan phenomenon causes the contralateral cerebral peduncle to the compressed against the tentorial notch
Pontine lesions anatomical analysis using CN V
- Contralateral hemianesthesia is caused by a lesion ABOVE MIDPONS
- Alternating hemianesthesia is caused by a lesion BELOW MIDPONS
Entire face hemiparesis is caused by
Ipsilateral LMN lesion of facial nerve (below caudal pons)
Corticobulbar tract lesion causes
Contralateral lower portion of face hemiparesis
(UMN lesion of facial nerve)
Stapedius muscle is innervated by
CN VII
Tensor tympani is innervated by
AICA syndrome
Lateral inferior pontine syndrome
- CN VII
CN VIII
CN V
Cerebellum
Spinothalamic (contralateral)
Descending symp. tract
Lateral midpontine syndrome
Circumferential branch of basilar occlusion
- CN V nerve root
- Brachium pontis: ipsilateral limb and gait dystaxia
Locked-in syndrome or pseudocoma patients
Results from infarction of the base of superior pons, infarctions include corticobulbar and corticospinal tracts resulting in quadriplegia and paralysis of lower CN.
They can only use CN III, CV IV (blink and move eyes vertically)
Hypoglossal palsy location
Medulla, dorsal near 4th ventricle
Wallenburg syndrome
PICA syndrome
What causes coma?
- Dysfunction of upper brainstem
- Bilateral dyencephalic dysfunction
- Diffuse lesions in both cerebral hemispheres (white matter)
Brain death criteria
- Irreversible cessation of all functions of the brain, including the brainstem (absence of brainstem reflexes)
- Apnea even after PaCO2 increases
- Coma (no cortical mediated responses to pain)
Storage phase of micturition is mediated by
- Increased sympathetic decreased parasymp via HYPOGASTRIC NERVE causes relaxation of detrusor m. and contraction of internal urethral sphincter
- LMN from Onuf n. promotes contraction of external urethral sphincter via PUDENDAL NERVE
Signals of bladder wall stretch is sent to
the PAG periaqueductal gray in the midbrain
which sends it to the insula
Higher control of micturition
Frontal lobe: prefrontal cortex, SMA, ant. cingulate gyrus
Insular lobe
Controls the switch from storage to voiding via the PAG
Pathway of voiding phase of micturition
- Higher cortical areas tell PAG to start voiding
- PAG activates PMC
- PMC inhibits hypogastric, pudendal
- PMC activates sacral parasymp. nucleus to stimulate contraction of detrusor
Suprapontine/supraspinal lesions affect micturition…
- Decreased inhibitor signals to PAG, PMC = detrusor hyperactivity (once bladder reaches threshold –> uncontrolled voiding reflex)
- Urinary frequency, urgency, nocturia, and occasionally urge incontinence
Suprasacral cord lesions affect micturition …
- Detrusor overactivity and loss of voluntary control of striated sphincter
- Dyssynergic straited sphincter causes functional obstruction with poor bladder emptying
Sulcus limitans
Separates hypoglossal trigone (above) and vagal trigone (below) in the floor of 4th ventricle, posterior to pons and medulla
What are the sensory pathways in the brainstem?
- Pain & temperature: lateral spinothalamic, trigeminothalamic
- propioceptive
Midbrain contents
- Tectum
- Tegmentum
- Cerebral peduncle
What nuclei are found in the rostral pons?
Mesencephalic root of CN V and nuclei
Parabrachial nucleus
Which nuclei are found in midpons?
Motor nucleus of CN V
Chief sensory nucleus of CN V
Mesencephalic root of CN V and nuclei
Which nuclei are found in caudal pons?
Abducens nucleus (CN VI)
Facial nucleus (CN VII)
Lacrimal and superior salivatory nuclei (CN VII) Lateral and superior vestibular nuclei (CN VIII) Dorsal and ventral cochlear nuclei (CN VIII)
What consciousness system is found in pons?
Pontine reticular formation – Raphe’ nuclei
Locus coeruleus
Oculomotor light reflex center
Pretectal nuclei, midbrain
Posterior commisure
Upward gaze center
Tectum of superior colliculi
Convergence center
Nucleus of Perlia, midbrain
Tectum of inferior colliculus
Auditory system
Parabducens nucleus (Paramedian pontine reticular formation; PPRF) is…
Lateral gaze center in pons
Medial longitudinal fasciculus MLF
Conjugate eye movement, pons
Auditory system tract: cochlear
- Stereocilia on basilar membrane are stimulated
- Glutamate stimulates bipolar neurons in spiral ganglion
- Cochlear nerve
- Cochlear nuclei (bilateral projections = trapezoid body, in medulla)
- Superior olivary nucleus (medulla)
- Lateral lemnisci
- Inferior colliculus in midbrain
- Medial geniculate nuclei
- acoustic area of temporal lobe cortex
Transverse temporal gyrus, more medial - primary
Superior transverse gyrus, more lateral - auditory association area
Trapezoid body
Bilateral projections of auditory system (cochlear) in medulla from cochlear nuclei to superior olivary nucleus
Lateral lemnisci
Fibers from superior olivary nuclei to inferior colliculus to MGN
What neurotransmitter is used to stimulate the spiral ganglion in hearing?
Glutamate
Transverse temporal gyrus
Can only be seen by cutting away some portions of parietal / frontal lobe.
Primary auditory area
Superior transverse gyrus
more lateral than transverse temporal gyrus - auditory association area
Solitary nucleus
Nucleus location
Medulla oblongata of the brainstem
Ascending fibers to the nucleus
Lateral and caudal parts - taste sensation via vagus nerve (CN X)
Rostrocaudal part - visceral sensation from tonsils, tongue, palate, pharynx and posterior one-third of the tongue via glossopharyngeal nerve (CN IX)
Rostral part - visceral sensation from the roof of the oral cavity and anterior two-thirds of the tongue via facial nerve (CN VII)
A tract formed by the fibers of the glossopharyngeal nerve (CN IX), fibers of the inferior ganglion of the vagus nerve (CN X) and geniculate ganglion of the facial nerve (CN VII).
- Mnemonic: Non Stop Training (Ninth, Seventh, Tenth)
Function
Relays signals of satiety
Generates and synchronizes the peristaltic activity of the upper gastrointestinal tract during swallowing
Generates and coordinates respiratory patterns
