Flashcards in LA Neuro Exam Deck (38):
What does a dropped elbow indicate in horses?
- radial n. damage and paralysis
- d/t scapula avulsion on brachial plexus with trauma
Where does white and grey matter lie within the brain and spinal cord?
> Spinal cord
- white matter outside, grey inside
- grey matter outside, white inside
What is grey and white matter/
- white = myelinated axons
- grey = cell bodies
What clues int he history may help with your dx?
- horse looking or acting clumsy before being found down?
- respiratoy disease?
- other horses involved?
- behavioural abnormlaities/video
What clues in the PE may help with your dx?
- non-neuro reason?
- icteric hore with depression indicating 1* liver/systemic problem
- lameness eg. foot abscess?
What is a radiculopathy?
- trapped nerve base of neck leads to problems only when neck is in flexion (eg. with long reins)
How can forebrain function be assessed?
> mentation - bright or depressed, responsive ?
> behaviour - bizarre circling, hyperaesthesia, head TURN, odd postures, reversing
Where do seizures occour?
Is cerebellar dz common in horses ?
No v rare cf. smallies
- BUT high level well bred dressage horses with high floating gate show some abnormalities of the spinal canal that may indicate spinal compression causing the hypermetria - interesting. nb. this is not cerebellar dz/
What cranial nerve response is affected by cerebellar disease?
Menace absent or dimished
Is weakness seen with cerebellar disease?
What inherited condition is present in arabs?
- v rare still
What structures are present int he brainstem? What clinical relevance is this?
- pons and medulla
- reticular formation (controls levels of consciousness)
- ascending propriceptive and descending upper motor neuron pathways
- cranial nerve nuclei
> dysfunction of a combination of these modalities - suspect brainstem, including
- altered levels of conciousness
- weakness (shuffly gait) and ataxia
- CN deficits
How are acute brainstem lesions gained in horses?
- fx basioccipital and basiethmoid?? bone underlying brainstem when they rear and fall backwards
-> heamatoma and haemorrhage into the GPs
What is the afferent and efferent limbs of the PLR?
- afferent optic 2
- efferent parasympathetic fibres of occulomotor 3
Pathway of menace?
- optic nerve
- optic chiasm
- OPPOSITE occipital cortex
- facial n. and nucleus
> FOREBRAIN INVOLVED
Which species have the highest proportion of decussation at the optic chiasm?
- prey species d/t no need for binocular vision (85% cf. predators 50%)
How is vision best assessed?
- walk around obstacles
- fundic exam
- menace (afferent limb)
Which nerves control occular position?
III, IV, VI
afferent and efferent limbs of the retractor oculi reflex?
press on cornea through eyelid + feel for retraction
- afferent trigem V
- efferent aducens VI
What does trigem 5 provide?
- sensory to majority of face
- motor mm. of astication (masseter and temporalis mm.)
Which cranial nerves are often affected together?
facial VII and vestibular VIII d/t anatomical location
Which way do head tilts go wrt the lesion?
TOWARDS the lesion d/t loss of innervation of extensor muscles ?? LOOK UP
How can central and peropheral vestibular dz be differentiated?
- type of nystagmus (central anything and can change, peripheral always HORIZONTAL)
- other CNs involved
How can lesion be identified from nystagmus?
- fast phase always AWAY from lesion (run away!)
How can pharyngeal/laryngeal function be tested?
- slap test for intrinsic laryngeal mm.?? (old, not really used anymore)
> tests IX and X glossopharyngeal and vagus
What are extra-pyramidal effects and what are they seen with commonly? Tx?
-behavioural changes at level of midbrain (look Up)
- can be seen with FLUPHENAZINE toxicity (used illegallly as sedative)
- Tx: Diphenhydramine
How is Horner's system seen in horses?
(interuption of sympathetic nerve pathyway between hypothalamus and eye)
- ptsosis (eyelashes)
- enopthalmus and prominent TE
- conjunctival and nasal hyperaemia
- patchy SWEATING in the region where nerve supply interrupted (different to other species as PS controlled so vasodialtion -> ^ sweating)
Where does sympathetic supplies to the skin and eyes originate? What branches are there?
- hypothalamus, travels down neck to exit C____-C____
- vagosympathetic trunk from cervical spine to head, 3rd order neurons to eye and skin
- vertebral n. branch supplies the neck (so if neck not sweating can localise lesion to head)
- shorter branches supply the dorsal trunk
What are the main signs associated with ataxia in the horse?
- dysmetria (combo)
- TRUNCAL SWAY
How can neuromuscular and neurological gait defects be distinguished (crudely!)
- irregularly irregular = neuro
- regularly irregular = (neuro??)muscular/musculoskeletal
Give an example of lamnesses that can present as ataxia like gait
- bilateral pelvic limb suspensory desmitis
- sacroiliac pain
> deficit still usually regular
Potential causes of weakness?
Neuro or systemic
- eg. granulomatous enteritis v. equine motor neuron disease
What does the tail pull test show?
- LMN deficit
- UMN deficit
Give some lamenesses caused by muscle disease
- post excercise lamenss
- exertional rhabdomyolysis
- polysaccharide storage myopathy
- ischaemic myopathy d/t parasites (aorto-iliac thrombosis)
- measure CK and AST
Are spinal reflexes tested in horses?
> not really
- if horse is standing,a ssume spinal reflexes intact
> withdrawal reflexes useful if recumbent
> limb weakness can indicate local spinal cord damge
What sacral and perineal signs may be seen in horses and what do these indicate damage to?
- perineal reflex
- tail flaccidity
- rectal exam
- urinary incontinence
> cauda equina damage commonly d/t sacral fx
> can cause hyperaesthesia, will rub hair off