Equine Neurology Flashcards
Neuro Exam
1. Mentation and behaviour
Observe the horse loose from a distance
* Stable or pasture
Altered consciousness
* QAR
* Dull/stupor
* (Comatose)
Aberrant behaviour
* Wandering
* Circling
* Head Pressing
* Excessive yawning
» Seizure activity
Neuro Exam
2. Cranial Nerves
LEARN TABLE
Neuro Exam
2. Cranial Nerves
Ocular examination
* Eyeball position controlled by CNs 3,4,6
* Strabismus: abnormal eyeball position
* Physiologic nystagmus (normal)
* Pupil size
* Pupillary light response(PLR)–CN2,3
* Menace response – Input CN 2, Output CN 7
* Palpebral response – Input CN 5, Output CN 7
Neuro Exam
2. Cranial Nerves
Facial examination/Head symmetry (CN5, CN7)
* Temporalis mm., masseter mm.
* Ears
* Eyes (eyelash angle)
* Nose
* Muzzle
* Facial nociception (Sensation)
Tongue/Swallowing: (CN9, 10, 12)
* Tongue symmetry (CN 12)
* Swallowing (CN 9, 10, 12)
Other
* CN 1, 8, 11
Neurologic Exam
3. Neck, Spinal Reflexes and muscle evaluation/palpation
Neck - ROM
Reflexes:
» Cervicofacial reflex – use a pen or forceps to test the region of C1–C3 = nose/muzzle twitch
» Cutaneous Trunci reflex – Continue testing over the shoulders and trunk region on both sides = skin twitches
» Thoracolaryngeal reflex (‘slap test’ - endoscopy is needed to do this properly)
» Tail tone
» Perineal Reflex
» Anal tone
» Hypoalgesia - Loss of skin sensation
» Hyperaesthesia - Increased sensitivity
» Abnormal sweating
» Muscle Atrophy
Neurologic Exam
4. Dynamic examination: Gait Analysis
Gait analysis done at walk, first without challenge, and then with challenges: » Straight line walk/trot
» Walk with head up
» Serpentine
» Tight circles **
» Proprioception (stop on tight circle)
» Poles
» Tail pull
» Up/down hill
» Up/down curbs
» Change of surface
» Neck flexion
» Neck stretch down
» Blindfold (care)
Neurologic Exam
4. Dynamic Examination: Proprioceptive deficits
Conscious proprioceptive deficits
» Abnormal stance at rest
» Cerebral cortex
» (Ability to correct after stopping on a circle)
Unconscious proprioceptive deficits
» Abnormal stance at movement
» Cerebellum
» (Backing up, circling, manipulation)
Neurologic Exam
4. Dynamic Examination: Abnormal Gait
Ataxia
» Incoordination of motor movements
» Loss of proprioception - reduced awareness of limb placement.
» Swaying of the trunk, prolonged pelvic limb stride, waving limbs, stepping on opposite limbs
Paresis
» Weakness/deficiency of voluntary movement » Knuckle, stumble, dragging limbs
Spasticity
» Stiffness, reduced flexion of joints, can be associated with UMN lesions
Dysmetria
» Abnormal range of movement
» Exaggerated limb movements/joint flexion = Hypermetria
Examinations of gait and posture - ataxia
Grade 0 = Normal strength and coordination
Grade 1 = Subtle neuro deficits only noted under special circumstances but mild (e.g. while walking in circles)
Grade 2 = Mild neuro deficits but apparent at all times/gaits
Grade 3 = Moderate deficits at all times/gaits that are obvious to all observers regardless of expertise
Grade 4 = Severe deficits with tendency to buckle, stumble spontaneously, and trip and fall.
Grade 5 = Recumbent, unable to stand
Ataxia:
» Vestibular ataxia
* Usually accompanied by nystagmus
* Blind fold exacerbates
» Cerebellar ataxia
* May also have intention tremor, blindness
* Cerebellar abiotrophy in young foals
» Spinal cord ataxia (Proprioceptive ataxia)
* Typically normal mentation and CN exam
* UMN&LMN
* Cervical vertebral stenotic myelopathy(CVSM)
* Cervical osteoarthropathy
Ataxia – UMN & LMN
» UMN
* Muscle tone
* Initiation of voluntary movement
» LMN
* Final link between CNS & muscles
* Direct stimulation to contract muscles
» Clinical signs depend on location and severity of lesion
Neuroanatomical localisation
C1-7 = rear limbs worse than front
C6-T2 = front limbs worse than rear
T-L = front normal, rear abnormal
Sacral = tail/bladder paralysis, perineal hypalgesia
Forebrain Disease - Aetiology:
» Head trauma
» Infectious encephalitis/meningitis
* Bacterial, viral
» Electrolyte disturbances
* Hyponatraemia, hypoglycaemia
» Hepatic encephalopathy &
hyperammonaemia
» Intra-carotid drug administration
» Poisoning/toxicity
* Plants, drugs etc
» Neoplasia
» Epilepsy (rare)
Forebrain Disease: Head Trauma
Head-On Trauma Consequences
» Lacerations
» Fractures of frontal/maxillary bone
» Sinus trauma – epistaxis
» Ocular injury
» Fracture of calvarium
» Cerebral contusion
» Increased intracranial pressure
Forebrain Disease: Head Trauma
Poll Trauma Consequences
» Fractures:
* Occiput
* Basilar skull
* Basisphenoid & Basioccipital bone
* Cranial C-spine
» Cerebral contusion
» Increased intracranial pressure
» Damage to brainstem
Forebrain Disease: Head Trauma
Fracture
»Basilar skull fracture:
* Damage to brainstem:
* Cranial nerve deficits
* Ataxia/incoordination
»Cervical spine fracture
CT**
Forebrain Disease: Head Trauma
Diagnostics:
» Often limited to neurological exam
* Assess cranial nerves
* Ocular reflexes
* Anisocoria, mydriasis and poor/absent PLR
= Increased ICP
» Plain radiography = skull and cranial C-spine
» Standing head CT
» GA often contraindicated in the acute case
Forebrain Disease: Head Trauma
Tx and Prognosis
» Treatment (conservative):
* NSAIDs: Phenylbutazone or flunixin
meglumine
* Vitamin E (antioxidant)
* Hyperosmolar fluids to try and reduce ICP
* Hypertonic saline v mannitol
» Seizure activity controlled with benzodiazepines
* (Diazepam)
» Nursing/supportive care
» If severe CNS signs, uncontrollable seizures, or no significant improvement after 24-48 hours then prognosis = very poor.
Forebrain Disease: Seizure activity and epilepsy
» Seizures ~ uncommon
» Idiopathic epilepsy = rare
» 2° to 1° cerebral lesion
* Inflammatory, traumatic, infectious,
ischaemic lesions
» Rare to actually witness seizure – assessment often based on owner reports
* Owners may only see post-ictal signs
» Clinical signs of generalised seizure include;
* Loss of consciousness
* Tonic/clonic muscular spasms
* Jaw clamping, paddling legs
* Loss of body functions
Forebrain Disease: Seizures - Diagnosis
» Accurate and detailed history
» Videos
» Establish if signs definitely neurological
* Cardiovascular –syncopal episode?
* Musculoskeletal weakness?
* GI – choke or paroxysmal colic signs?
* Sleep deprivation?
» Neurological exam
» Blood biochemistry
» CSF analysis
» Electroencephalography
» Advanced diagnostic imaging: CT, MRI
Forebrain Disease: Seizures Treatment
Emergency
» Most stop in a few mins
» Keep horse and people safe
» If venous access established, anticonvulsant tx can be helpful:
* Diazepam (0.1-0.5mg/kg IV)
* Phenobarbital (5-10mg/kg IV, up to 20mg/kg
IV per day)
» If anticonvulsants not available and veterinary intervention required:
* Sedation: Xylazine or detomidine +/
butorphanol
* Small vol pentobarbital (euthanasia solution)
in saline
Forebrain Disease: Seizures Treatment
Longer term
» Phenobarbital (5-10mg/kg PO BID)
* Potassium bromide (50-100mg/kg PO SID)
» Therapeutic drug monitoring
» Side effects: Sedation, ataxia, individual variation
» Safety concerns and cost often make long term treatment prohibitive
Facial Nerve Paralysis
» Central
* Damage to CN nucleus in brainstem or UMN
* W other signs of CN dysfunction
* Less common
» Peripheral
* Drooping of eye, ear, lip, deviation of nose,
reduced flaring of the nostril
Causes:
* Trauma during
anaesthesia/recumbency/restraint
* Guttural pouch disease
* Temporohyoid osteoarthropathy (THO)
» Always check the guttural pouch
* (Facial nerve courses along roof of GP)
