week 11 Flashcards
vestibular system maintains
head and body posture maintained in relation to head
vestibular disease is an ____ disease
assymetric
what can cause vestibular disease
inner ear on one side
CN VIII on one side
medulla lesion that gets one vestibular trigone, but not the other
what is the classic sign of vestibular disease
head tilt
head tilt is on what side
the side of the least vestibular tone (usually the side of the lesion)
what are the receptros for the vestibular system
crista ampullaris
macula
crista ampullaris
dendritic zone of CN VIII (vestibular part), tonically active, on/off
adjusts body posture in relation to head movement to maintain balance
macula
dendritic zone of CN VIII; primarily affected by gravity
detects static head position and linear acceleration/deceleration
cranial nerve VIII
receptors, axonz, vestibular ganglion, axons, into medulla, vestibular nuclei
important projections from the vestibular nuclei
vestibulospinal tract
medial longitudinal fasciculus
projection to cerebellum
what are the signs of vestibular disease
head tilt rolling, falling, circling vestibular ataxia abnormal nystagmus ventrolateral strabismus (transient)
normal nystagmus
same sized pupils
eyes centrally located in orbit
eye should not be moving
spontaneous nystagmus
loss of tonic stimulation of CN II, IV, VI
Vertrical
central!
pendulous
no fast or slow phase
oscillatory movements back and forth
typically not vestibular (genetic in siamese)
positional nystagmus
elevate head, turn head to side, or twist head
if nystagmus ensues-> positional
vertical -> central
changes position -> central
peripheral disease
lesion in PNS CN VIII or Inner ear head tilt towards side of lesion asymmetric ataxia horizontal or rotary nystagmus (fast phase away from side of lesion); more commonly acutely eye drop on side of lesion
3 keys to peripheral
classic vestibular signs
no loss of strength
postural responses
bilateral peripheral disease
no head tllt; no vestibular nystagmus
central disease
lesion in CNS (medulla)
classic vestibular signs
spastic hemiparesis/paresis (UMN)
proprioceptive ataxia (GP below trigone)
postural response deficits (UMN and GP)
Vertical nystagmus
nystagmus with fast phase towards head tilt
nystagmus that changes directions when you move head
change in mentation
also could see LMN signs of CNN V, VI, VII, IX, X, XII
Horner’s syndrome
sympathetic neuron cell bodies to eye (T1, T2, T3); cranial cervical ganlgion to middle ear; CN VII, VIII
Moving head to right turns off
left
if still and looking to right
left turned on
central lesion in cerebellum that affects the vestibular nerve occurs where
flocculonodular lobe or more commonly, the caudal peduncle
caudal peduncle carries
inhibitory purkinje fibers from flocculonodular lobe to vestibular nuclei
in paradoxical vestibular disease, you have increased vestibular tone on what side
on side of lesion (due to loss of inhibition); appears as though unaffected side has decreased vestibular tone
therefore, head tilt, rolling, falling, circling on what side
unaffected side
can see hemiparesis on
opposite side
out of the 18 UMN, how many descend into the spinal cord
8
most UMN synapse on
interneurons
UMN fibers are ______ size
medium
larger diamter neurons are more prone to
compression
what size motor neurons have faster transmission
larger
pyramidal system includes
UMN that travel through pyramids
lateral corticospinal tract
important in primates for voluntary movement; 100% crossover; not important in domestic animals for movement
forebrain disease in domestic species
have fairly normal gait but postural responses will NOT be normal due to pyramidal system
forebrain signs include
behavior changes seizures visual loss wit intact PLR normal gait but, postural response deficits
damage and clinical deficits with a brain lesion
opposite side affected
damge to cord lesion
same side affected
postural responses
the entire nervous system must be working properly for them to work
extrapyramidal system cell bodies located in
brainstem (3 midbrain, 1 pons, 3 medulla)
extrapyramidal system under control of
frontal cortex and basal nuclei
extrapyramidal system important in domestic animals
initiates voluntary movement
initiate and maintain normal posture
rubrospinal tract located in
mesencephalon
rubrospinal tract starts in
red nucleus (very vascular; red)
rubrospinal tract important in domestic animals because
excitatory to LMNs of flexors
if damaged, rubrospinal tract
difficult initiating voluntary movement
profound gait deficits
UMN signs likely
postural response deficits
tectospinal tract located in
mesencephalon
tectospinal tract begins at
tectum
function of tectospinal tract
excitatory to LMNS of flexors primarily in neck (rostral and caudal colliculi for sight and sounds avoidance)
tectotegmentospinal tract located in
mesencephalon
tectotegmentospinal tract originates from
tectum and tegmentum (2 locations for cell bodies)
sympathetic control of the eye
umn center for GVE nerve fibers destined to go to the head; pupillary dilation (LMNs T1-T3)
pupillary dilation
turn off parasympathetic
turn on sympathetic
preganglionic parasympathetic in midbrain, post ganlgionic in ciliary ganglion
where can damage occur to cause damage to sympahtetic innervation
spinal cord cranial to cell bodies (UMN)
C6-T2)
VAGOSYPATHETIC TRUNK
MIDDLE EAR INFECTION
what are the clinical signs of horner’s syndrome
miosis (constricted pupil) enophthalmis 3rd eyelid protrusion ptosis sweating in horses due to increased blood flow *signs can have degree of severity*
pontine reticulospinal tract begins in the
pons
pontine reticulospinal tract function
excitatory to extensors
medullary reticulospinal tract begins in
medulla
medullary reticulospinal tract inhibitory to
LMNs of extensors
together, medullary reticoluospinal and pontine reticulospinal control
rest of GVE LMNs in cord; primarly urination/defecation
medial longitudinal fasciculus is in the
myelencephalon
medial longitudinal fasciculus is UMN tract for
CN 3, 4, 6
Medial longitudinal fasciculus also runs caudally in
ventral funiculus of cord
