Exam 3 Flashcards
Tympanic membrane
- concave or convex relative to lateral side?
- most depressed part called?
- concave
- umbo
Innervation of tympanic membrane + surrounding structures
Outer surface TM + external auditory canal:
CN V, VII, X (GSA)
Mucosa lining TM + auditory tube + mastoid air cells: CN IX (GVA)
Child has a middle ear infection. Otoscopic exam will show?
Dull or absent light reflex from the eardrum
Groove for cartilaginous part of auditory tube is found b/w what 2 bones?
b/w petrous part and temporal part of sphenoid bone (base of skull)
Tensor tympanic muscle
- location
- innervation
- action
- just above auditory tube
- CN V3
- attenuation reflex
Middle ear communicates w/ mastoid air cells by way of the?
Auditus -> mastoid antrum
The tympanic plexus is located where?
Formed from?
Gives rise to which nerve?
- promontory - basal turn of cochlea
- CN IX
- lesser petrosal nerve - preganglionic parasympathetic destined to the otic ganglion which supplies the parotid gland
Stapedius muscle housed in?
Innv by?
- pyramid (pyramidal eminence)
- nerve to stapedius (CN VII)
The facial nerve innervates all the glands of the head except the:
parotid (lesser petrosal nerve) and integumentary gland
Describe the path of the chorda tympani nerve
function?
comes off CN VII -> passes above tensor tympani muscle -> passes through petrotympanic fissure -> submandibular ganglion
taste from anterior 2/3 of tongue
secretomotor innervation to glands
Greater petrosal nerve
- branch of
- what type of fibers?
- CN VII
- GVE -> preganglionic parasympathetics
Rheumatoid fixation
Fibrous ankylosis (fixation) of synovial joint in rheumatoid arthritis
OTOSCLEROSIS
A bony ankylosis (knee) knits the bone of the middle ear to the stapes, preventing normal transmission of sound from the eardrum into the inner ear.
Hyperacusis
- define
- cause
Abnormal sensitivity to everyday sound levels or
noises, often sensitivity to higher pitched sounds, in the presence of essentially normal hearing.
Nerve to stapedius damage
Congenital absence of stria vascularis is due to failure of what? Consequence?
Neural crest cell migration
No endolymph production
Antibiotic induced ototoxicity mech?
destroy outer hair cells - loss of cochlear amplification
Structure responsible for calculating interaural INTENSITY differences
Trapezoid body in caudal pons
Structure responsible for calculating interaural SOUND differences
Superior olivary nucleus
Ear embryo
-otic vesicle filled with? form?
- vestibular and spiral ganglia formed from?
- mesenchyme develops into?
- endolymph/membranous components of inner ear
- statoacoustic ganglia
- cartilage, perilymphatic space and bone
Derivations from which arch?
- tensor tympani (malleus and incus)
- stapedius (Stapes)
- 1st arch (CN V)
- 2nd arch (CN VII)
Chromosomal and 1st arch syndromes commonly present w/ what clinical sign?
low set ears
duplication of what may form auricular pits?
first pharyngeal cleft
Movement of hair stereocilia:
- depolarized (opening of channel)
- repolarized (closing of channel)
- outwards
- inwards
2 theories for encoding sound frequency
- Placement theory – mapping of individual fibers
- Phase locking in an auditory nerve fiber
• Pattern of AP matches frequency of sound wave
o This doesn’t explain high frequency sound waves b/c can’t fire APs fast enough to keep up
2 theories for sound localization (horizontal)
- Intensity difference due to head being an obstacle is detected by lateral superior olive
o Only works for shorter wavelength sounds b/c head is not obstacle for longer wavelength sounds
o Best for high frequency - Comparing phase differences
o Peak of sound waves gets to opposite ear at a later time
o Best for low frequency
Audible frequency range
Human voice frequency range
- 20 to 20,000 Hz
- 250 to 7500 Hz
dB SPL vs. dB HL vs. dB SL
dB SPL - absolute
dB HL - human specific
dB SL - individual specific
Describe the auditory brainstem response test.
ECOLI
Way to assess neural component of middle ear
E - Eighth nerve (Waves I and II) C - cochlear nucleus (Wave III) O - olivary complex (Wave IV) L - lateral lemniscus (Wave V) I - inferior colliculus (Wave VI)
Good test to assess Meniere’s disease?
ECoG - check cochlear response
Describe otoacoustic emissions test (OAE)
- Measure sounds created converting mechanical to electrical energy for signal transport
- Absent if hearing loss exceeds 30 dB HL
- All infants get screening of this at birth
Profound hearing loss at what level?
> 90 dB HL -> non-auditory communication
Describe the aspects of conductive lesion
- Air/bone gap
- normal word recognition
- abnormal tympanogram
Describe aspects of a cochlear lesion
- loss of loudness
- word discrimination reduced proportional to degree of hearing loss
- presence of auditory recruitment
- normal tympanogram
- Absent OAE
- Normal ABR
- Acoustic reflex and decay okay
Describe aspects of a auditory nerve lesion
- Abnormal ABR
- word recognition to hearing loss disproportionate
- probs w/ acoustic reflex/decay
Describe Weber test
- Put tuning fork in midline of head
- Patient should hear it symmetrically
- If problem – tuning fork will lateralize
- Conductive loss – to side of loss
- If sensorineural – to opposite side of lesion
Describe Rinne test
- Compare air to bone conduction
- Air – in front of ear
- Mastoid process – bone
- If conductive problem – bone conduction > air conduction
Motor unit defintion
Alpha motor neuron and all the muscle fibers it innervates
Small vs large motor unit
Small
- less force
- fine control
- smother contractions
Large
-more powerful, coarse contractions
Purpose of stretch reflex?
Prevent muscle from being overstretched
Static vs dynamic stretch receptors
Static receptors
- slow and smooth response; non-adapting
- Stretch afferent fibers = II
- muscle tone and smooth movements
Dynamic receptors
- fast response and rapidly adapting
- Ia stretch afferent fibers
- clinical stretch reflex (DTR)
Reflexes - muscles, nerves and CNS level
- Biceps
- Triceps
- Brachioradialis
- Knee
- Ankle (gastroc)
- Jaw jerk
- Musculocutaneous nerve (C5,6)
- Radial nerve (C6-7)
- Radial nerve (C5,6)
- Femoral nerve (L2-4)
- Tibial nerve (S1)
- C.N. V (Pons)
Steps through which tone is generated
brainstem motor centers -> gamma motor neurons -> contraction of IFF fibrils -> inc tension on static stretch receptors -> inc firing of group II stretch afferents -> low level firing of alpha motor neurons
GAMMA LOOP
Brainstem LMN
Midbrain - III and IV
Pons - VI, V, VII
Medulla - IX, X, XII
List differences between early and late signs of LMN injury
LATE
Add
-atrophy (denervation type)
-fibrillations (spontaneous contractions of INDIVIDUAL muscle fibers)
Subtract
-fasciculations (except with ALS)
What’s pathognomonic for a LMN injury
Fibrillations
Brainstem reflexes
- Pupillary light reflex
- Corneal and Jaw jerk reflexes
- Gag
- VOR
- Midbrain
- Pons
- Medulla
- Medulla, pons and midbrain
Bilateral responses to stimulation on one side
What’s responsible for tonic stimulation of extensor gamma motor neurons for tone?
Vestibulospinal tract
Signs of isolated vestibular lesions
- abnormal nystagmus
- vertigo
- swaying or falling
- can be permanent
Signs of isolated reticular nuclei and/or red nucleus lesions
- difficulty w/ postural adjustments during whole body movements
- usually temporary
Difference b/w Broca’s and transcortical aphasia
lose ability of repeat a phrase with Broca’s
Describe alternating hemiplegia
Same side face (LMN) / opposite side limb (UMN) deficit from a single lesion
Describe a hemiplegic and diplegic gait
Hemiplegic
- arm flexed at elbow
- wrist/fingers flexed
- extension at knee
- plantar flexion
- hip rotated out
Diplegic
-scissoring of legs
Describe decorticate posturing
-level of lesion
-Elbow flexed and knee extended
ABOVE THE RED NUCLEUS
-rubrospinal and vestibulospinal systems intact
Describe decerebrate posturing
-level of lesion
- elbow extension/knee extension
- antigravitational muscles uninhibited
BELOW THE RED NUCLEUS and ABOVE THE VESTIBULAR NUCLEUS
-rubrospinal system lost
List the branchial motor nerves
V, VII, IX, X, XI
Define central pattern generators
- controller
- trigger
Preprogrammed circuit that causes rhythmic or oscillating movements
- controller -> cerebral cortex
- trigger -> brainstem
Max deficit time seen w/ Guillain-Barre?
2 weeks
3 most common causes of death with Guillain-Barre
- resp failure
- DVT
- Cardiac arrythmias
How to assess risk of resp failure
Check forced vital capacity
Length dependent peripheral neuropathy
- onset
- time course
- associated with (most common cause)
- serology to rule out
- Tx
o Onset w/ numb or tingling of toes and feet
o Develops over years
o Check diabetes (most common), B-12, SPEP, IFE
o Also check thyroid and serology for syphilis
o Tx the cause if you can find it – primary goal
o Tx the sxs if can’t find cause
•Amitriptyline – tricyclic antidepressant
-This is a more effective drug
•Duloxetine – SSRI
-Much more expensive
•Gabapentin -Anticonvulsant class of med
Differences b/w CIPD and Guillain-Barre
CIPD
- active beyond 8 weeks
- no resp failure
- responds to prednisone
- atypical pattern
Paraneoplastic pure sensory neuropathy
- presentation
- etiology and pathogenesis
PRESENTATION
- diffuse numbness
- painful paresthesias
- sensory ataxia
ETIOLOGY
-cancer -> commonly small cell lung
PATH
-Anti-Hu Abs attack DRG (sensory neuron selectivity)
Charcot Marie Tooth Disease
- etiology
- progression
- CMT-1 vs CMT-2
ETIOLOGY
-hereditary PN
PROGRESSION
- onset in teens
- no pain and slow development
CMT-1
- dysmyelinating
- PMP-22 duplication (myelin protein)
CMT-2 normal velocity (axonal)
List 4 mononeuropathies and which one does NOT have motor sxs
- Median @ wrist -> CTS (SENSORY ONLY)
- Ulnar @ elbow
- Fibular @ fibular head
- Radial in spiral groove
Risk factors for carpal tunnel
DM, thyroid disease, pregnancy
Dermatomes and myotomes for
- C5
- C7
- L5
- S1
a) C5
D -> just below clavicles and back of neck
M -> shoulder muscles and biceps
b) C7
D -> down back of arm and digits 2+3
M -> extensor muscles or arm and forearm
c) L5
D -> lateral thigh and front of leg down to the dorsal aspect of the feet
M -> glutes and leg muscles
d) S1
D -> posterolateral region of thigh and leg + outside area of butt
M -> glutes + posterior leg muscles + intrinsic foot muscles
Myasthenia gravis associated with?
Pathology
Thymus pathology (e.g. thymoma)
Abs against nicotinic Ach receptors
Signs and sxs of LEMS
Pathology
Common cause
Treatment
SIGNS AND SXS
• Lower leg weakness developing over months
• Dry mouth + absent reflexes
• EMG -> Greater response w/ exercise
PATHOLOGY
• Abs against VG Ca2+ channels
CAUSE
• Small cell lung cancer most common cause
Tx
• Diaminopyridine – blocks VG K+ channel
-More time to open Ca2+ channels
-Wider AP b/c membrane repolarizes slower
ALS
- signs (including lab tests)
- Treatment
SIGNS
- progressive weakness and wasting
- spastic (slow) dysarthria
- EMG -> fibrillations and fasciculations
Tx
-Riluzole -> glutamate antagonist
Lab value elevated with myopathies?
creatine kinase
Dystrophies vs myositis
- times course
- tx
DYSTROPHIES
- Slowly progressive and hereditary
- At present, disappointing Rx
Myositis
- weeks to months
- responsive to immunosuppression
Myopathies have (proximal/distal) muscle weakness?
Exception?
- Proximal
2. Exception -> Myotonic dystrophy
Which myositis has SLOW progression
Inclusion body (very slow) -unresponsive to steroids
Fxal divisions of cerebellar cortex
- Vestibulocerebellum
- flocculonodular lobe
- balance and coordinating head/eye movements - Spinocerebellum
- vermis + paravermal area
- anterior lobe included
- spinal cord input
- Control of posture, muscle tone and stereotyped movements (CPGs) - Cerebrocerebellum
- connections with cerebral CTX via pontine nuclei
- planning and initiation of movement coordination
Purkinje cells are (excitatory/inhibitory) on to deep cerebellar nuclei
Inhibitory
Climbing vs mossy fibers
Climbing
- from ION
- synapse on PC dendrites
Mossy
- not from ION
- synapse onto granule cells
Both are excitatory inputs
Dorsal vs ventral spinocerebellar tracts
Information about the position and status of muscles, tendons, joints and descending motor commands to the spinal cord.
Dorsal -> inferior cerebellar peduncle
Ventral -> superior
Which part of red nucleus do the following pathways go through?
- From interposed nuclei (spinocerebellum-paravermal cortex)
- From dentate nuclei (corticocerebellum)
- magnocellular -> forms rubrospinal tract
2. Parvocellular
Medulloblastoma can cause damage to which cerebellar structure/pathway?
What effects are seen?
- Damage to cerebellar vermis
- path to vestibular nucleus leading to malfunction of lateral vestibulospinal tract
- TRUNCAL ATAXIA - unable to stand upright w/out support
Cerebellar vermis
- Results in defective anticipatory function by the cerebellum
- Failure to counter the effect of gravity displacement produced by movement of a body part
Intention tremor results for damage to?
Disruption of what?
- Damage to lateral cerebellar lobe, dentate nucleus, or SCP
- Disruption of viscoelastic freeze arrangement
In unilateral cerebellar lesions, the fast phase of nystagmus is toward the side of the lesion or away?
Toward
Anterior lobe syndrome
- cause
- structures damaged
- manifestations
CAUSE
-malnutrition usually related to chronic alcoholism
STRUCTURES DAMAGED
- Purkinje cell death
- shrinking of cerebellar cortex
MANIFESTATIONS
-Loss of coordination chiefly in lower
limbs
-Depressed tendon reflexes
• Loss of tonic stimulation of gamma motor neurons via the reticulospinal tract
-Heel to shin test fail
Posterior lobe syndrome
- cause
- manifestations
CAUSE
-Commonly results from cerebral vascular accidents, tumor, trauma, or degenerative diseases
MANIFESTATIONS
- Loss of coordination of voluntary movements (ataxia) and hypotonia
- Rate, range, and force of movements are abnormal
- Intention tremor present
Flocconodular lobe syndrome
- Disturbance of balance manifested primarily as truncal ataxia
- Patients may not beable to sit or stand without falling
- Most often seen in children with medulloblastomas
Major breakdown product of DA which can be used to measure DA system activity
HVA - homovanillic acid
Describe 4 CNS dopaminergic pathways
- Nigrostriatal
- substantia nigra -> striatum (caudate+putamen)
- Parkinson destroys this
2/3. Mesolimbic + Mesocortical
- VTA -> nucleus accumbens + frontal cortex
- antipsychotics act here
- Hypothalamic
- arcuate nuc -> median eminence
- reg of PRL release for pituitary
- tuberoinfundibular
Highest brain [NE]?
[DA]?
NE -> LC
DA -> SN/ST
Effect of Desiparmine in DA vs NE neurons
NE -> inhibits reuptake
DA -> does not
Death from cocaine overdose is due to what?
Inc HR and Inc BP due to vasoconstriction
Peripheral effect
Why does L-dopa tx become less efficacious as time under tx goes on?
Continued destruction of DA neurons and NS path
Smaller window b/w off state of the drug and the dose at which patient experience dyskinesia during the on state
Output neurons of the striatum are?
What NT?
- medium spiny neurons
- GABAergic
Relate GPi/m output to movement
Increased output - less movement
Decreased output - increased movement
Define hemiballism and what causes it
- ballistic movements
- damage to subthalamic nucleus contralateral to affected side
- proximal musculature affected
Tx for essential tremor
- Drugs
- primidone
- propanolol (peripheral Beta-2 blockade)
- alcohol - Thalamotomy
- Vim thalamic stimulation (DBS)
Tx of huntington’s disease associated chorea
GABA agonists
- valproate
- clonazepam
Presynaptic DA depletes
- reserpine
- Alpha-methylparatyrosine
- Tetrabenazine
DA receptor blockers
Head of caudate nucleus is vascularized by
Recurrent artery of Heubner.
Branch off the anteromedial group of striate arteries
Superior part of internal capsule vascularized by
Lenticulostriate arteries
Anterolateral group - MCA + ACA
What does the anterior choroidal artery supply?
- Optic tract
- Medial temporal cortex - Parahippocampal gyrus
- Amygdala
- Posterior limb of internal capsule
- -Inferior
- -Sublenticular
- -Retrolenticular
Summarize blood supply to internal capsule
Superior part - lenticulostriate arteries
Inferior part
- posterior limb - anterior choroidal
- anterior limb + genu - medial striate arteries
2 important branches of ACA and structure(s) they supply
- Pericallosal – inferior to cingulate gyrus
- Callosomarginal – superior to cingulate gyrus
- They go to the paracentral lobule and supplementary motor cortex
The venous angle is landmark for?
formed from?
- interventricular foramen
- jx of thalamostriate vein and internal cerebral vein
