Brainstem & Cranial Nerves Flashcards
name the 12 cranial nerves
- olfactory
- optic
- occulomotor
- trochealar
- trigeminal (ophthalmic, maxillary and mandibular)
- abducens
- facial
- vestibulocochlear/ auditory
- glossopharyngeal
- vagus
- accessory (spinal)
- hypoglossal
name the exit points of the cranial nerves
- olfactory - cribriform plate of ethmoid bone
- optic - optic canal
- occulomotor - SOF
- trochealar - SOF
- trigeminal (ophthalmic - SOF, maxillary - foramen rotandum and mandibular - foramen ovale)
- abducens - SOF
- facial - IAM
- vestibulocochlear/ auditory - IAM
- glossopharyngeal - Jugular foramen
- vagus - JF
- accessory (spinal) - JF
- hypoglossal - hypoglossal canal
what is the function of CN 1-6
- olfactory - smell
- optic - vision
- occulomotor - eye movement, pupillary constriction and accommodation
- trochealar - eye movement
- trigeminal - motor:mastication, sensory: facial sensation (nerves from the head)
- abducens - eye movement
what are the three main components of the brainstem?and what can they be further divided into?
- midbrain
- pons
- medulla oblongata
they can be further divided into dorsal tectum and ventral tegmentum which lie dorsal and ventral to the aqueduct of the midbrain and fourth ventricle respectively
define a pyramid/pyramidal (corticospinal) tract
an elongated eminence marking the position of underlying fibres passing from the cerebral hemispheres to the cord referred to as corticospinal or pyramidal tract
what is the decussation of pyramids?
diagonally orientated bundles of fibres cross the fissure via which 80% of corticospinal tracts cross the midline to enter the opposite lateral white column of SC
what is the tectum and tegmentum made of?
tectum (dorsal to aqueduct) made of collucli
tegmentum (ventral to aqueduct) made of nerve fibres
what is the function of superior collucli and inferior collucli?
superior collucli - part of visual system, concerned with eye reflexes
inferior collucli - part of auditory system, concerned with reflex of looking towards a loud noise
what is the superior cerebellar peduncle?
a fibre bundle passing from the cerebellar to the midbrain
what is pineal gland and its function?
an endocrine gland that synthesises melatonin
which are the 2 important nerve pathways? (MALE)
- inferior branchium - conveys Auditory information from the Medial geniculate body to the inferior collucli
- superior branchium - conveys visual (Eyes) information from the Lateral geniculate body to the superior collucli
which of the cranial nerve nuclei is present in the tegmentum consists of in pons and medulla?
tegmentum of pons - nuclei of CN 5,6,7
tegmentum of medulla - nuclei of CN 9,10,11 and 12
where is gracile and cuneate tubercle?
gracile - a round swelling of on either side of the midline (of medulla)
cuneate - a swelling lateral to the gracile
what is the dorsal column nuclei and its function?
the nuclei underlying the gracile and cuneate nucleus are called dorsal column nuclei and are a major relay site for dorsal column sensory pathway
what is Bell’s palsy? its symptoms and signs?
- it is the acute unilateral inflammation of facial nerve (LMN)
- symptoms (unilateral): pain behind the ear, paralysis of facial muscles and failure to close eyes
- signs: loss of taste on the anterior 2/3 of tongue, absent corneal reflex, hyperacusis (certain sounds heard unpleasantly loudly)
- if caused by herpes zoster (virus that causes shingles), a vesicular rash is present in external auditory canal and on the oropharynx
what is bulbar palsy? its symptoms, signs and causes?
- impairment of functions of CN9-12
- symptoms: dysphagia (difficulty swallowing), slurring of speech, dysphonia (difficulty forming sounds/speaking) and excess saliva - dribbling
- signs: wasting and fasciculation tongue, absent gag reflex
- causes: motor neuron disease, Guillain-barre syndrome
what is central pontine myelinolysis?
what are its symptoms?
when does it occur?
- it is the destruction of myelin in the pons
- it causes: confusion, imbalance, dysphagia, hallucinations, reduced consciousness, slurred speech, tremor and weakness in face or limbs
- occurs when Na+ levels are corrected too quickly, therefore, care must be taken to increase sodium levels slowly when the patient is hyponatraemic
what is the function of CN 7-12
- facial - motor: facial movement, sensory: taste (anterior 2/3 of tongue), para: salivation and lacrimation
- vestibulocochlear/auditory - hearing and balance
- glossopharyngeal - motor: swallowing; sensory: taste (posterior 1/3 tongue), chemo/baroception, general sensation, para: salivation
- vagus - motor: speech, swallowing, sensory: general sensation, chemo/baroreception, para: HR,BR etc
- accessory (spinal) - head and shoulder movement
- hypoglossal - tongue movement
structures innervated by the CN1-6
- olfactory - olfactory epithelium
- optic - retina
- occulomotor - superior, inferior, medial rectus and inferior oblique muscle
- trochlear - superior oblique
- trigeminal - motor: mastication muscle - tensory tympani
- abducens - lateral rectus
structures innervated by the CN7-12
- facial - motor - facial expression muscle - stapedius muscle, sensory: anterior 2/3 of tongue, para: salivary and lacrimal (tears) glands
- vestibulocochlear/ auditory - vestibular apparatus, cochlea
- glossopharyngeal - motor: swallowing muscle - stylopharyngeus muscle, sensory: posterior 1/3 tongue, pharynx, Eustachian tube, middle ear; carotid body, carotid sinus, para: parotid salivary gland
- vagus - motor: pharynx, larynx, upper oesophagus and soft palate; sensory: pharynx, larynx, trachea, oesophagus, external ear, para: cardiac muscle, smooth muscle, glands of cardiovascular system, respiratory and gastrointestinal system
- accessory (spinal) - sternomastoid and trapezius
- hypoglossal - intrinsic and extrinsic muscle of tongue
a lesion in the following places results in what type of blindness
- optic nerve
- optic chiasm
- optic tracts
- outer optic radiation (Meyers loop)
- inner optic radiation
- optic nerve - monocular blindness
- optic chiasm - biotemporal hemianopia (same side as lesion)
- optic tracts - homonymous hemianopia (opposite side of lesion)
- outer optic radiation (Meyers loop) - upper quadrantinopia (opposite side of lesion, lower retina)
- inner optic radiation - lower quadrantinopia (opposite side of lesion, upper retina)
name the main extra ocular eye muscles and their function
- lateral rectus - abducts - out
- medial rectus - adducts - in
- superior rectus - elevation + adduction = up and in
- inferior rectus - depression + adduction = down and in
- superior oblique - depression + abduction = down and out
- inferior oblique - elevation + abduction = up and out
which muscles carry out intorsion and extortion
intorsion - medial rotation - superior rectus, superior oblique muscles
extorsion - lateral rotation - inferior rectus, inferior oblique muscles
what are the symptoms of psudobulbar palsy and what is it caused by?
- similar symptoms as bulbar plays but the lesion is in upper motor neurone
- caused by stroke or MS
what is a pituitary tumour? its causes and its consequences?
- most a adenoma (a benign glandular tumour)
- caused due to under or overproduction of hormones (TSH,ACTH,GH,FSH,LH, prolactin, oxytocin, vasopressin)
- may lead to bitemporal hemianopia due to pressing on optic chiasm
how do the neurons travel in the brain for outer and inner optic radiation?
outer optic radiation - from inferior retina - thus, temporal to occipital - upper homonymous quadrantinopia
inner optic radiation - from superior retina - thus, parietal to occipital - lower homonymous quadrantinopia
what is jugular foramen syndrome? its symptoms?
- compression of multiple cranial nerves (9,10,11)
- symptoms: dysphonia, absent gag reflex, unilateral wasting of sternocleidomastoid and trapezius muscles
what is foramen magnum syndrome? its signs and symptoms?
- compression of SC, lower brain stem and part of cerebellum
- symptoms: pain in head, neck, limbs, trunk made worse by straining
- cerebellar symptoms: vertigo, gait disturbance
- signs: decerebrate posture, pyramidal signs, cardiorespiratory failure, death
what is Arnold chiari malformation?
- congenital malformation
- displacement of cerebellar tonsils down through he foramen magnum
- sometimes blocks the CSF causing hydrocephalus
- symptoms: headache, fatigue, muscle weakness in head and face, difficulty swallowing, dizziness, nausea, impaired coordination
- patients may also develop syringomyelia (disorder of cavity in SC)
what is acoustic neuroma?
- benign tumour of myelin sheath of CN 8 - vestibulocochlear
- symptoms: (unilateral) deafness, dizziness, fullness in ear and tinnitus
- if undetected, it progresses to include ataxia and paralysis of CN 7 (facial) and CN 5 (trigeminal), this is termed cerebellopontine angle syndrome
- around 5-10% caused by rare genetic condition - neurofibromatosis type 2
