The Wobbly Horse Flashcards
1
Q
What diagnostic approach for ataxia
A
2
Q
What should your STATIC neuro exam include
A
- Observation - bhvr, mentation
- Cranial nerve function
- Posture -> proprioception palpation to assess body mass pm detect muscle symmetry, tone and pain, Flexion tests
- Segmental reflexes -> cervicofacial, cutaneous trunci, thoracolaryngeal, perianal
3
Q
Dynamic Exam ?
A
- Straight line walk and trot
- Straight line head raised
- Serpentine
- Poles
- Tail pull
- Hill
- Tight circles
- Neck flexion
- Blindfold?
4
Q
What neuroanatomic localisation
A
- UMN vs LMN
- Cerebral cortex
- Brainstem
- Vestibular system
- Spinal cord -> cervical, thoracic, lumbar, coccygeal
- Multifocal?
- Peripheral nerve
5
Q
UMN & LMN
A
- CNS influences skeletal mm activity through UMN & LMN
- UMN: initiation of gait generation
- LMN: Final link b/wCNS & muscles
6
Q
Compare signs of UMN vs LMN weakness?
A
7
Q
What is Ataxia?
A
Inconsistent gait due to a deficit in proprioception caused by lesions in the proprioceptive sensory tracts to the brain. (Hahn 2006)
* Incoordination of motor movements
* Loss of proprioception (reduced awareness of limb placement)
8
Q
How might ataxia manifest as?
A
- Hypermetria, hypometria, or dysmetria
- Swaying of pelvis/trunk/neck/whole body
- Weaving of affected limb during swing phase
- Abnormal foot placement in abducted or adducted positions
- Stepping on opposite foot
- Pacing (ie moving both feet of same side at same time)
- Circumduction when turning/circling
- Pivoting around one limb
9
Q
What is Paresis ?
A
Poor ability to initiate a gait, to maintain a posture, to support weight of the body or its parts and to resist gravity
10
Q
How does Paresis manifest ?
A
- Weakness, deficiency of voluntary movements
- Knuckle, stumble, dragging limbs
- Often get ataxia and paresis together (~always if spinal cord ataxia).
- Can be difficult to distinguish the two in reality
11
Q
How do we grade ataxia?
A
Grade 0 Normal
Grade 1 Visible only on repeated testing and a trained observer
Grade 2 Visible on testing by most people
Grade 3 Clearly visible without testing
Grade 4 Upon testing you could make the horse fall
Grade 5 Recumbent
12
Q
What diagnostics for Ataxia?
A
- Neurological examination
- Orthopaedic examination
- Ophthalmic examination
- Guttural pouch endoscopy
- Pharyngeal endoscopy
- CT/CT myelography
- MRI?
- Radiography/myelography
- Haematology/biochemistry
- Blood testing for specific diseases (EHV, WNV, EPM, etc)
- CSF analysis
- Muscle biopsy
- EMG/EEG
13
Q
Should we ride them?
A
- What grade?
- What diagnosis?
- Who is riding and what is their age? (Consenting adult?)
- Intended use?
- Insurance?
- Referral/second opinion?
- No easy answer!
=> ALWAYS NO FOR minors
14
Q
What are the three classifications of Ataxia?
A
- cerebellar ataxia
- Vestibular ataxia
- Spinal cord ataxia
15
Q
describe cerebellar ataxia
A
16
Q
describe vestibular ataxia
A
17
Q
Describe spinal cord ataxia?
A
18
Q
What is NOT affected in cerebellar ataxia?
A
- Lesions fo not result in wekaness
- Menation, strength not affected
- CP is not affected so no abnormal placement while horse standing still
- Intention tremors
- reduced menace response with intact vision
19
Q
What is cerebellar abiotrophy?
A
20
Q
Function of VS?
A
to maintain appropriate orientation of body, head & eyes
21
Q
What happens with vestibular ataxia?
A
- Loss on one side = tilt of head/ body
- ‘Room spinning’ - wide based stance, short strides, reluctance to move
- Compensate with vision - head and body tilt can be exaggerated by applying a blindfold
- Nystagmus if acute (fast phase away from L)
22
Q
T/F central vestibular disease is uncommon in horses?
A
True
23
Q
Whats the difference between peripheral and central vestibular ataxia?
A
24
Q
What is a common cause of peripheral vestibular dx?
A
Temporohyoid osteoarthropathy (THO)
- Older horses
- Arthritic prolif of temporohyoid joint and proximal stylohyoid bone => fusio of joint, predisp to stylohyoid fract, compression /trauma of peripheral CN
25
What main feature of THO?
Acute onset facial n +/- vestibular n. dysfucntion
26
Diagnosis of THO?
Clinical signs, imaging, head radiograph and GP endoscopy
27
Tx & Pg for THO?
* Treatment: anti-inflammatories, antibiotics, supportive vs. surgical (ceratohyoidectomy)
* Prognosis: Variable, but can be successful
28
Describe Spinal cord ataxia?
* Conscious proprioception is affected
(horse leaves limbs in inappropriate
positions, especially at rest).
* If all limbs are affected, then at least
part of the lesion = cranial to C7.
* If severe pelvic limb signs and no
thoracic limb signs, lesion = caudal to
T2.
29
Describe Cervical Vertebral stenotic myelopathy
- Static vs dynamic (neutral vs flex/extension)
- Stenosis of spinal cord at a single or multiple sites
30
Type 1 (developmental CVSM) ?
* ~1-5 yo, large growing horses
* Developmental abnormality of the cervical spine and/or displacement
* Often C2-C5
31
Type 2/ OA of cervical spine?
* Similar clinical disease in older horses due to OA changes
* Often C6-T1
* Variable signs/pathology depending on how the spinal cord is affected
32
T/F there is a genetic preidsp to CVSM
yes
33
What neuro signs of CVSM?
* Reduced proprioception
* Hind limbs > fore limbs
* Progressing to paresis and/or spasticity as the compression worsens
* Bilateral, but degree of change in each limb can vary depending on area of compression
34
DIAGNOSIS OF CVSM?
* History, CE, neuro exam, imaging
* Radiography +/-myelogram (if suitable)
* Intra-vertebral sagittal ratio, inter-vertebral sagittal ratio
* CT myelogram
* Better but more research required to quantify compression
35
Tx for CVSM?
* Restrict Growth (dietary modification)
* Surgical correction of displacements: 1 grade improvement
* Kerf cut cylinder (‘basket’ surgery)
* Polyaxial screws and rods
* Custom titanium plate and spacer
* NSAIDs (little response)
36
PG for CVSM?
guarded for normality
37
Describe Cervical Osteoarthritis?
* Arthritis of vertebral facet joints
* More common to cause neck pain & lameness/poor performance, but can cause ataxia
* Compressive neuropathy secondary to DJD of facet joints (radiculopathy)
* Especially older horses
38
Diagnostics for cervical OA?
* Radiography?
* Scintigraphy?
* *CT*
39
TX? cervical OA
* Intra-articular steroids may help (ultrasound guided)
* NSAIDs
* Retire/reduce work
* Endoscopic foraminotomy?
40
describe signs of EHV1 Myeloencephalopathy
* Background respiratory dz
* Pyrexia, dull, inappetent – viraemic phase
* Sudden onset neurological signs
* Ataxia – particularly hind limbs
* Caudal spinal cord segments:
- Bladder distension & urinary incontinence
- Penile protrusion in males
- Flaccid tail & anus
41
Diagnosis of EHV?
* Nasopharyngeal swab PCR
* Serology (paired sera)
* Virus isolation
* CSF xanthochromic/yellow
* Immunohistochemistry (PM diagnosis)
42
CSF collection - describe
* Atlanto-occipital vs lumbosacral
* AO usually requires GA
* Lumbosacral
- Standing sedation
- Need excellent sedation/restraint
- Stocks
* Ultrasound guided C1-C2 centesis
- Standing sedation
43
How to analyse CSF analysis
44
When is CSF useful ?
* Useful in diagnosis of CNS disorders
* Viral/bacterial encephalitis, meningitis, abscess, haemhorrhage, neoplastic disease
* Cytological analysis may help in treatment plan
45
What biosecurity for EHM?
* Isolate the case!
* To prevent the spread of infection to other horses
* Limit horse to horse contact
* Limit personnel and equipment
* Test and release until the disease is under control
46
Tx for EHM
* Supportive & nursing Care
* Palatable feed
* IVFT
* NSAIDs to reduce fever and inflammation
* Heparin to prevent thrombus formation
* Valacyclovir to reduce viraemia
47
Pg?
variable
48
Vaccination in outbrreak (EHM)
Divided opinion but may increase risk?, no proven efficacy, can hamper testing
49
Head Trauma?
- Neurolocolisation essential
- Dx: neuro exam +/- neck radiograhy, head CT
- Tx:
- Symptomatic/ supportve care - NSAIds, seiure control, nutritional support
- Steroids - NO - >hyperglycaemia
- Inc ICP hypertonic > mannitol
50
Neoplasia ?
- Rare in horses
- Melanoma -> space occupying, central
- Chondrosarcoma
- Various central tumours
- Dx & tx dependent on CS
51
Helicephalobus gingivalis
* A Nematode
* Other parasites too
* Uncommon (several case studies)
* Eosinophilic/granulomatous meningoencephalitis
* Behavioural abnormalities progressing to severe ataxia, reduced mentation status &
cranial nerve signs
* Usually diagnosed on PM
52
Meningitis/ Meningoencephalomyelitis
* Uncommon
* Causes: most: local trauma,
ascending infection, or
haematogenous spread of infection
* Neurological deficits, neutropenia,
lymphopenia, hyperfibrinogenaemia
& CSF with neutrophilic pleocytosis
common findings Toth et al 2012
* Treatment: supportive, antimicrobials
etc
* Typically poor prognosis
53
hyperammonaemia can be ..
- Hepatic encephalopathy
- Intestinal hyperammonaemia
54
Detail hepatic encephalopathy
* Relatively common
* Dull/depressed or hyperactive/manic walking, head pressing
* Central blindness
55
Dx & Tx for Hepatic e.
Diagnosis:
* Biochemistry (GGT, GLDH, BA, ammonia)
* Ammonia: labile
Treatment:
* Lactulose, steroids, antibiotics, (hypertonic saline?)
* Tracheostomy if respiratory compromise (Bilateral laryngeal paralysis)
* May cause gastric impactions/rupture
56
Detail Intestinal hyperammonaemia
* Infrequent
* Usually secondary to d+
Diagnosis: * Ammonia
Treatment: * Hypertonic, lactulose, metronidazole (
57
What diseases can mimic ataxia?
- Equine motor neuron dx, vit E deficiency
- Pyrexia/ dehydration
58
Describe CLS of EMND
* Weakness, narrow-base stance
* Muscle atrophy
* Trembling and muscle fasciculations
* Weight shifting
59
Diagnosis of EMND
* Sacrocaudalis dorsalis Muscle biopsy
* Serum α-tocopherol (May be normal)
60
Tx for EMND?
* Oral α-tocopherol supplementation
* Not powders, needs to be v bioavailable
* Is diet deficient, or can horse not absorb it? Re-test
61
Signalment for head shaking?
* Any age, median 8, 9 and 10
* Geldings overrepresented
* All breeds/disciplines
62
Clinical signs for headshaking?
* Mild intermittent to violent, persistent
* Vertical or side to side
* 59% are Seasonal
* Of these, 91% spring & early summer, cease in late summer/autumn
* ‘Photic headshakers’…
* Wind, sound, exercise…
63
Aetiology for headshaking
* Multiple triggers that can activate a trigeminal response - low threshold of nerve activity?
* Similarities to trigeminal neuralgia – most headshakers are ‘trigeminal mediated’.
* Pathogenesis shown to differ from human trigeminal neuralgia (but aetiology unknown).
* Specific causes of headshaking identified in small number of cases
* Trigeminal-mediated headshaking is a diagnosis of exclusion.
64
What diagnostics in headshaking case?
- Ce: particular attention to oral cavity, nasal passages, ears, eyes, sinuses and GP
- Examine with bridle/ under saddle if happens only when ridden
- Rule out other causes
