LA Neuro Exam Flashcards
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
Brain
- 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?
FOREBRAIN
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?
NO
What inherited condition is present in arabs?
cerebellar abiotrophy
- 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
- thalamus
- OPPOSITE occipital cortex
- facial n. and nucleus
- cerebellum
> 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)
- weakness
- 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?
- swallowing
- vocalisation
- slap test for intrinsic laryngeal mm.?? (old, not really used anymore)
- endoscopy
> 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)
- miosis
- 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?
- hypermetria
- hypometria
- dysmetria (combo)
- TRUNCAL SWAY
- PACING
- CIRCUMDUCTION
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?
> standing
- LMN deficit
walking
- 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
- sensation
- tail flaccidity
- rectal exam
- urinary incontinence
> cauda equina damage commonly d/t sacral fx
> can cause hyperaesthesia, will rub hair off
Potential systemiatic methods of neuro exam in the horse?
- systematic modality approach (proprioception, reflexes etc.)
- anatomic head to tail approach
- combo?
