Neurology Flashcards
Truncal ataxia
Postural instability, gait instability - disorderly, wide based gait with inconsistent foot positioning
Appendicular ataxia
Jerky uncoordinated movement of the limbs as though each muscle were working independently from the others
Dysmetria
Ability to control distance, power and speed of an action is impaired
Combo of hypo and hypermetria
Sensory ataxia
Abnormal postural reactions Limb paresis Loss of sense of limb/body position: - wide based stance - Increase stride length - Swaying/floating - Knuckling
Vestibular ataxia
Unilateral: Head tilt, leaning falling or rolling to one side
Bilateral: Wide excursions of the head +/- head tilt, crouched
Abnormal nystagmus
Positional strabismus
Normal (peripheral) or abnormal (central) postural reactions
Vestibular apparatus: vestibular nuclei (central), vestibular portion of VIII, vestibular receptors (peripheral)
Cerebellar ataxia
Wide based stance
Intention tremors (worse during voluntary movement)
Loss of balance and truncal sway
Delayed onset and dismetric hopping
Ipsilateral menace deficits with normal vision
No limb paresis or conscious proprioception deficits
Pendulum nystagmus
Ascending reticular activating system
Network of neurons within brainstem
Sends info to the forebrain
Parts of the neuro exam
1. Mentation
Level of consciousness (Alert, obtunded, stupor/semicoma, coma)
Quality of consciousness (Appropriate, Inappropriate - compulsion, dementia/delerium)
Parts of the neuro exam
2. Posture
Head:
- Tilt (roll) - vestibular
- Turn - forebrain
Limbs:
- Wide based stance (proprioceptive loss)
- Narrow based stance (weakness)
- Decrease weight gain (pain?)
Body:
- Decerebate - rear legs out, straight forelimbs, head up
- Decerebellate - rear end down
- Schiff-Schemington - back problems, front limb extension (in lateral recumbency), hindlimb paralysis
Parts of the neuro exam
3. Gait
Require integration of proprioceptive and motor systems
Normal/abnormal? What limbs?
Parts of the neuro exam
4. Postural reactions
Requires integration of proprioceptive and motor systems
Similar pathways to gait
Long pathways ‘sensitive/non-specific’
Interpret with gait spinal reflexes, muscle tone
Paw positioning, hopping, wheelbarrowing, hemiwalking, placing (tactile, visual), extensor postural thrust
UMN paresis
Muscle tone normal-increased in limbs caudal to lesion
Spinal reflexes normal-increased in limbs caudal to lesion
Stride - normal-increased caudal to the lesion, spasticity
+/- ataxia (sensory), swaying/floating, knuckling
LMN paresis
Muscle tone decrease in limbs with a reflex arc containing the lesion
Spinal reflexes decreased to absent
Stride: length normal-decreased, stiff, ‘bunny hopping,’ +/- collapse, +/- ataxia (sensory), knuckling
Excitation-contraction coupling
- Muscle action potential propragated
- Depolarisation of T-tubule causes opening of Ca2+ channel between myoplasm and sarcoplasmic reticulum (SR)
- Calcium release from SR - ‘calcium transient’
- Calcium binds to Troponin C
After muscle contraction
Ca+ ions pumped back in SR (Pump = Ca2+ ATPase, ATP required)
Absence of Ca2+ ions in the SR - no more muscle contraction
Source of dual innervation
Parasympathetic - craniosacral division, preganglionic cells bodies in 4 cranial nerves and sacral SC
Sympathetic - thoracolumbar, preganglionic cell bodies in thoracic and 2 lumbar segments of SC
Plexuses
Sympathetic post-ganglionic fibres form clusters within thorax, abdomen and pelvis
Fibres leave plexuses to be distributed to multiple organs
Adrenal gland
Modified form of post-ganglionic cell bodies that release epinephrine and norepinephrine directly into blood
Mimic symp NS
Hypothalamus
Regulates balance between sympathetic and parasympathetic
SMELL
Single receptor type
Dramatic convergence of info into glomeruli - interact and form spatial patterns of activity
Supporting cells secrete lipid-rich fluid and mucus to entrap chemicals
Vomeronasal organ
Links nasal and oral cavity
Blind ending caudal sacs (bilateral)
Flehman reaction to punp air in and out
Help detect heat (?)
TASTE (gustatory)
Receptor have single type
Afferent nerve fibres carry info from several different cell types - cross compared by brain
SIGHT
Lights splits rhodopsin in rods and cones - trigger signal through optic nerve (II)
HEARING
Sound funnelled to tympanic canal and membrane
Ossicles (maleus, incus and stapes) conducts sound through round window to the cochlea then to brain VII
Neurotransmission support cells
Astrocytes (nourish and support)
Oligodendrocytes (increase speed of impulses)
Microglia (phagocytes)
Epidymal cell (epithelium lining CNS)
Action potential
DEPOLARISATION
Stimulus causes membrane permeability to Na+ to increase causing reduction in membrane potential
Action potential
THRESHOLD
critical voltage reached and voltage sensitive Na+ and K+ undergo confomational change
Permeability to Na+ abruptly increases but K+ increase slowly
Action potential
REPOLARISATION
Na+ gates close at +35mV and K+ gates fully open removing K+ and transmembrane potential becomes negative
Neurotransmitters
Acetylcholine (released at NMJ, muscarinic or nicotinic)
Catecholamine (norepinephrine acts on adrenoceptors)
Glutamate (excitatory in the brain)
Glycine (inhibitory within spinal cord)
Gama aminobutynic acid (GABA) inhibitory with CNS
Acetylcholine receptors
Nicotinic NMJ and autonomic NS preganglionic neurons
Muscarinic postganglionic of parasympathetic NS
Adrenergic recepors
Alpha1 - smooth muscle contraction
Beta1 - myocardium - excitatory
Beta2 - smooth muscle relaxation
Diencephalon
Epithalamus, thalamus and hypothalamus
Telencephalon
Cerebral cortex, limbic system and olfactory bulb
Cerebral Lobes
Frontal lobe - planning, anxiety
Parietal lobe - motor, sensory, cutaneous and taste
Occipital lobe - vision
Temporal lobe - hearing and language
Cerebral arterial circle
Aka circle of Willis
Vessels within the brain and supply from the basilar artery
Drain to venous sinuses of the dura mater
Cerebral arterial circle
Species variations
Ruminant and cats - internal carotid regress to fibrous strands
Cattle - vertebral artery is a large part of blood supply
Dog, man, horse - internal carotid and basilar -> CAC -> most of brain; vertebral artery -> rest of brain
Sheep, cat - anastomosing rami of maxillary artery -> CAC and has rete mirabille; vertbral artery -> medulla oblongata ; basilar drains
Rete mirabille
Dense networks of vessels - heat exchange for thermoregulation
Very present in camels
Subarachnoid space
Contains CSF leaking from ventricular system
Largest parts are the cistern:
- cerebellomedullary cistern around foramen magnum
- lumbar cistern
Panniculus reflex
Sensory T3 - L1
Motor C8 -T1
Lesion 2 vertebral bodies - cranial to cut off
Perineal reflex
Sensory and motor from S1-S2
Mediated by pudendal nerve
Forelimb withdrawal
Sensory - median, ulna and radial nerves
Motor - median, ulna, musculocutaneous and axillary nerves
C6-T1
Hindlimb withdrawal
Sensory - perineal and tibial nerves
Motor - sciatic, peroneal and tibial nerves
L6-S1
Alpha motorneurons
Fibres innervate extrafusal (ordinary) muscle fibres
Gamma motorneurons
Fibres innervate intrafusal (muscle spindle) activation causes spindle to stretch so tightened during passive stretch
Controls slackness in muscle
Cranial nerve I
Olfactory
Sensory
Olfactory epithelium
Cranial nerve II
Optic
Sensory
Retina
Cranial nerve III
Oculomotor
Motor - Eye movements; dorsal, ventral and medial rectus and ventral oblique
Parasympathetic - pupil size; pupillary constrictor, cilary muscle of eyeball (via ciliary ganglion)
Cranial nerve IV
Trochlear
Motor - retractor bulbi and dorsal oblique
Cranial nerve V
Trigeminal
Opthalmic - sensory - face
Maxillary - sensory - face
Mandibular - sensory - both of face; motor - muscles of mastication
Cranial nerve VI
Abducens
Motor
Abducts eye - Lateral rectus
Cranial nerve VII
Facial
Motor - facial expression
Parasympathetic - glands - nasal, salivary, lacrimal
Sensory - inner ear, anterior 2/3 of tongue
Cranial nerve VIII
Vestibulocochlear
Sensory - sounds, rotation, gravity, balance and hearing
Cranial nerve IX
Glossopharyngeal
Sensory - carotid body and sinus, inner ear, pharynx, posterior 1/3 tongue
Motor - styropharyngeous
Parasympathetic - salivary glands
Cranial nerve X
Vagus
Sensory - pharynx, larynx, external ear, aortic arch and bodies, thoracic and abdominal viscera
Motor - soft palate, pharynx, larynx, upper oesophagus
Parasympathetic - CVS, respiratory and GIT systems
Cranial nerve XI
Accessory
Motor - sternomastoid and trapezius
Cranial nerve XII
Hypoglossal
Motor - intrinsic and extrinsic muscles of tongue
Equine guttural pouch pathology
Facial paralysis (n. VII)
Dysphagia, laryngeal paralysis (n. IX, X)
Lingual paralysis (n. XII)
Horner’s syndrome (sympathetic trunk)
Epistaxis, exsanguination (internal and external carotid)
Hearing
Outer ear
Directs sound waves to ear canal (boot shaped)
Ceruminous glands line surface of ear canal
Hearing
Middle ear
Malleus, incus, stapes - mechanical transmission of sound
Stapedius - n. VII
Tensor tympani - n. V through medial pterygoid nerve
Chorda typani nerve - carries gustatory fibre to anterior 2/3 tongue - passes through middle ear
Guttural pouch
Expansion of distal aspect of eustachian tube (connects middle ear and nasopharynx)
Hearing
Inner ear
Cochlea has membranous compartments n 3 levels
- Scala vestibule (upper)
- Scale tympani (lower)
- Cochlea duct/scale media (middle)
Hearing
Stereocilia (outer hair cell)
Bend and change length - changes local amplitude of travelling wave
Bends stereo cilia of inner hair cell -> release of glutamate at their basal poles -> produces excitatory potentials
Balance
Semicircular canals
When head is rotated in the plane of a particular semicircular canal, endolymph causes a deflection of the cupula
- > bowing of stereocilia
- > depolarisation/hyperpolarisation
Myasthenia gravis
Acquired: production of antibodies against nicotinic acetylcholine receptor (4m-4y or 9y-13y)
Congenital: Abnormal/lack of Ach receptors, 3-8w, often multiple in a litter (large purebred dogs, uncommon in cats)
Most common focal form -> oesophagus, muscle innervated by cranial nerves
Also seen: diffuse paralysis
Generalised form: after 10 min exercise, pelvis limbs first
Malformations hydrocephalus
Excessive CSF in brain/cranial cavity
Developmental obstructive hydrocephalus - congenital hydrocephalus:
- Interfere with flow/absorption of CSF
- Dogs borns with markedly expanded lateral ventricles, wider than normal 3rd ventricle
- Cerebral hemispheres
Cerebellar cortical abiotrophy
Common progressive clinical disorder in dogs 9/10w
- Mild intention head treor
- Slight stiffness in thoracic limb gait
- Progresses to obvious cerebellar ataxia
- After a few months, unable to stand/throw themselves around
Euthanase
Feline panleukopenia virus - cerebellar disease
Most common diffuse cerebellar disorder in cats
Congenital malformation
Parvovirus - predilection for rapidly dividing cells
Housebound and safe
BVD - cerebellar disease
In utero infection
Recumbency with opisthotonus and extensor rigidity of the limbs to mildly spastic hypermetric unsteady gait and slight head tremor
Usually alert and responsive with strong voluntary movements
Reduced cerebellum size
Facial nerve disorder
Lesions where the facial nerve emerges from the stylomastoid foramen -> complete facial paralysis
Signs: ear droops, lower lip droops, palpebral fissure decreases in size, nose and upper deviate to normal side
Incomplete facial paralysis -> lesions on individual branches
Otitis media: most common cause, facial nerve courses through the canal in the petrosal portion of the temporal bone - affected by middle inflammation
Canine distemper
Paramyxoviridae family: Mobillivirus
Hypermetria, hyperkeratic nose and pads, purulent nasal discharge, head pressing, head tilt,
Inflamed CSF
(Ferrets, foxes, lions)
Visual disturbances
Optic neuritis: inflammation of optic nerve (autoimmune?)
Disorders affecting optic chiasma: pituitary tumours, infarcts, inflammatory disorders
Lesions caudal to chiasma: neoplasia, trauma
Congenital diseases: hydrocephalus, metabolic storage diseases
Horner’s: disruption of sympathetic innervation to the eye (constricted pupil, protrusion of 3rd eyelid, prolapse of upper eyelid)
Hyperalgesia
Tissue damage release chemicals which increase sensitivity of nociceptors so even light touch can cause pain
Limbic system
Fringe around thalamus - group of deeply based structures
Functions: memory, behaviour, motivation, emotion
Components: hippocampus, fornix, cingulate gyrus, mammillary body
Fornix: bunch of fibres that come out of hippocampus
Mammillary bodies: centres in the hypothalamus, connected to hippocampus via fornix
Paleocortex: ventral surface, well developed in domestic species
Neocortex
Projection area: sensory and motor areas, projected down
Association areas: receive sensory input for sensory areas of cortex analysis received info, selects course of action
Structure: mostly short neurons with many dendrites linking one area to another
Sleep
Ascending reticulum systems generates arousal generate impulses -> higher centres (may be dampened by sleep centre in hypothalamus)
Slow wave/REM
Demyelinating disease
Human: multiple sclerosis
Dog: Canine distemper virus encephalitis (morbillovirus)
Got: caprine arthritis encephalitis syndome (lentivirus)
Sheep: Maida Vizna (lentivirus)
Mice: Theiler’s disease (picornavirus), mouse hepititis virus (coronavirus)
Stroke
Acute neurological deficit following focal disturbances to the vascular perfusion of the brain
Usually arterial blood vessels following thrombosis or emboli
e.g. Canine cerebellar stroke
Motor neuron disease
UMN: primary lateral sclerosis
LMN: progressive muscular atrophy
UMN and LMN: amyotrophic lateral sclerosis (ALS)
LMN (spinal cord): spinal muscle atrophy (most common)
Equine motor disease: sporadic, 8-10y, excessive sweating from minimal exercise, loss of muscle mass, odd stance, hate standing
Cerebellar hypoplasia
Calves - cerebellum should be 10% brainweight
In this incidence, is 10 times smaller than normal
BVD (pestivirus): infection before 180d gestation
Border disease (lambs): hairy shakers
(Bluetongue)
FPV
Feline parvovirus aka feline panleukopaenia virus
Virus attacks rapidly dividing cells
Vomiting, diarrhoea, panleukopaenia (adults)
Cause smalls cerebellum in kitten from infected queen
Equine herpesvirus 1 (EHV1)
Necrotic haemorrhagic lesions - affecting mostly ventral horns of grey matter
Ischaemic necrosis due to thrombus - ataxia, paralysis, paresis, recumbency
Virus targets epithelial cells - multiple -> thrombosis
CSF sample, isolate horse, lock down yard
FIP (CNS form)
Fairy uncommon
Mutated form of feline coronavirus
Wet/Dry/Mixed -> granulomatous, effusions
Vascular injury -> inflammatory effusion fills and dilates ventricles (hydrocephalus)
Meningitis
E.g. nystagmus (shifting from L to R involuntarily), paddling limbs, seizuring, death
Streptococcus suis - most common cause in piglets (Haemophilus parasuis - 2nd most common)
Rabies and rabies like infections
Excessive salivation, muzzle tremors, tenesmus, behavioural change, abnormal posture, seizures, opisthotonus (head, neck and back), paralysis, death
Rhabdovirus, Lyssavirus (UK bats)
Transmitted via saliva/bite wounds -> Retrograde axonal transport-> hippocampus -> replicates in brain -> travels via cranial nerves -> saliva -> prevents swallowing -> froth -> behavioural change
Negri bodies: intracytoplamic eosinophilic viral inclusion bodies
Diagnosis: histopathology, culture, PCR (brain tissue), immunohostochemistry
Parts of the neuro exam
5. Spinal reflexes
Tendon reflexes: Biceps, Musculocutaneous nerve - C6-8 Triceps, Radial nerve - C7-T2 Patellar, Femoral nerve - L4-6 Gastrocnemius, Sciatic nerve - L6-S2
Flexor (withdrawal):
Thoracic limb, multiple nerves - C6-T2
Pelvic limb, sciatic nerve - L6-S2
Decreased/absent: lesion in reflex arc, physical limitation to movement, excitement/fear, ‘spinal shock’
Increased: lesion to UMN pathways cranial to spinal cord segments tested, excitement/fear, pseudo-hyperreflexia (loss of antagonism)
Parts of the neuro exam
6. Cranial nerves
Vision, menace, PLR, Eye position, Eye movement, Palpebral, Corneal, Muscles of mastication, Muscles of facial expression, Schirmer tear test, Auditory/vestibular signs/physiologic nystagmus, Gag reflex, Tongue dysfunction
Parts of the neuro exam
7. Palpation
Light - swelling, atrophy
Deep - pain
Parts of the neuro exam
8. Nociception
Conscious perception of pain
Superficial: skin
Deep: bone (periosteum)
Neuro Hand Rule
- Onset
- Clinical course
- Pain
- Lateralising
- Neuro localisation
DAMNITV
Degenerative Anomaly Metabolic Neoplasia/Nutritional Inflammatory/Infectious/Idiopathic Trauma/Toxin Vascular
Focal seizures
Simple focal: no loss of consciousness
Complex focal: impairment of consciousness
Focal seizure with secondary generalisation
Status epilepticus
Prolonged seizure activity
>5min (clinical), >30min (brain damage), life threatening
Cluster seizures
More than 2 seizures in 24 hours
Serious
Events that can mimic seizures
Syncope: partial/complete loss of consciousness, lack of motor activity, no post-ictal signs, shorter
Narcolepsy: stimulated often by excitement, food, pharmacologically
Pain
Vestibular syndrome
Movement disorders:
- Scotty cramp
- CKCS: episode of tetany, hypertonicity, deer-stalking
- Norwich terriers
- Boxers: paryoxsmal dystonic choreoathetosis (Bichon Frise)
Idiopathic Epilepsy
Signalment
Dogs: 6m-6y
Generalised: Beagles, GSDs, Lab, Golden Retrievers, Burmese Mountain dogs, Belgian Tervuerencs, Keeshunds, Irish Wolfhounds
Mainly partial +/- 2nd generalisation: Vizlas, English Spaniels, Danish Labs, Langotto Romagnole, Standard Poodle, Finnish Spitz
Equine Seizures
Arab foals: congenital, grow out of it
Foals with perinatal asphyxia: neonatal maladjustment syndrome
Adults: structural or metabolic brain disease (trauma, parasite), intracarotid injection
Seizure treatment
When to start
1 seizure/every 6w or 2+ seizures with 6m
Lifetime commitment (2/3 dogs respond to anti-epilepsy drugs)
Chart seizure frequency
Side effects!
Seizure treatment
Barbiturate mechanism
Increase duration of chloride ion channel opening at the GABA receptor - increases efficacy of GABA
Seizure treatment
Benzodiazepines
Increased frequency of chloride channel opening at GASBA - increases the potency of GABA
Gamma-Amino Butyric acid (GABA)
Amino acid which acts as a neurotransmitter in the central nervous system
Inhibits nerve transmission in the brain, calming nervous activity
Phenobarbitol
First line treatment
Dose: about 2.5 mg/kg (loading 600mg/kg over 6d)
Time to steady state: 10-14 days
Therapeutic range: 15.0 - 30 ug/ml
Obtain plasma levels: 14d, 45d, 90d, 180d, 360d
Metabolised in liver
Side effects: sedation, PD, polyphagia, hepatotoxicity
Idiosyncratic reactions: behaviour alterations, immune-mediated neutropaenia, thrombocytopaenia, anaemia, superficial, necrolytic dermatitis, idiosynchratic hepatotoxic reactions
Potassium bromide
Add on/1st line
Dose: about 30-40 mg/kg (loading 12-24 mg/kg)
Time to steady state: 100-200d
Therapeutic range: 0.7-1.9mg/ml
Obtain plasma levels: 4w, 8-12w, q6m
Side effects: sedation, weakness, PU/PD, GI irritation/pancreatitis
Renal excretion
Diet: High chloride diet with lower serum concentration
Bromide toxicity (rare): severe ataxia, sedation, somnolence, skin reactions -> IV saline
Imepitoin
Comparable efficacy to Pentobarbitol
Dose: 10-30 mg/kg
Side effects: polyphagia, hyperactivity, PU/PD, somnolence, emesis, hypersalivation, ataxia, apathy, diarrhoea, prolapsed nictitating membrane , decreased sight and sensitivity to sound
Refractory epilepsy
Non-responder: reduce in seizure frequency of less than 50%
Add on: gabapentin, pregabalin, levetiracetam
Seizures
Secondary damage
Under 30 min: arterial hypertensions, increased cerebral blood flow, hypoxaemia, hypercabaemia, hyperglycemia, lactic acidosis
Over 30 min: continuous muscle contraction, hyperthermia, acidosis, myolysis (myoglobinuria, hyperkalaemia, renal failure), hypoglycaemia (energy depletion), cardiac arrhythmias
Clomipranine
Non-selective serotonin re-uptake inhibitor
Elevate mood, reduce anxiety, and block panic development
Takes up to 3 weeks to become clinically apparent
Benzodiazepinbes
Inhibits memory formation by affected NMDA (glutamate) receptors in the hippocampus - limited use when learning is required
Used for separation anxiety - licensed
Adverse effects: sedation, increased appetite, weight gain, hypotension, anti-allergy activity, delirium, seizure induction, decreased bronchial secretion, hyperthermia, tachycardia, blurred vision, insomnia, constipation, photophobia, dry mouth, narrow angle glaucoma
Selegiline
Increases the availability of dopamine for inclusion into secretory vesicles
Treatment of fears and phobias and cognitive decline where reduced dopamine levels are implicated
Pendular nystagmus
Siamese, Birman and Himalayan Congenital abnormality (larger number of fibres cross the chiasma) Cerebellar disorders and visual deficits
Horner’s syndrome
Loss of sympathetic innervation to the eye - Enophthalmus - 3rd eyelid protrusion - Ptosis - Miosis (Congested vessels)
Cerebellar syndrome
Spastic, dysmetric or hypermetric gait Intention tremor Ipsilateral menace deficit and normal vision Broadbased stance Postural reactions delayed with exaggerated responses \+/- contralateral anisocoria \+/- opisthotonus \+/- vestibular signs
Deafness
Test: BAER (brainstem auditory evoked responses)
Sensorineural: sensory dysfunction, neoplasia, infection, otitis interna, toxins, aminogycosides, chemo drugs, congenital (white coat and blue eyes e.g. Dalmation)
Conductive: failure of passage of sound, neoplasia, infection, otitis media, inflammation/inflammatory polyp
Megaoesophagus
Neurological causes:
- Nerve dysfunction -> reflex oesophageal dysfunction
- Myasthenia gravis
- Oesophagitis
- Generalised myositis
- Botulism
- Brainstem disease
Spinal cord anatomy
Sensory (proprioceptive) tracts: dorsal and lateral funiculi, ipsilateral, ataxia
- Tells LMN what to do
- Facilitates and inhibits flexor and extensor muscle groups
UMN tract: lateral and ventral funiculi, ipsilateral
LMN cell bodies: ventral horn grey matter, ipsilateral
Equine Rhabdomyolysis Syndrome
Muscle cramping/pain that occurs usually during or following exercise
aka Monday morning disease, set-fast, azoturia, myoglobinuria, tying up
Treat: analgesia, fluids, diuretics (minimise effects of myoglobin on kidneys)
Diagnosis: pre and post (6h) CK measurement
Overexertion:
- Eccentric contraction
- Metabolic exhaustion
- Oxidative injury
Prevent: oral dantrolene, high fat/low carb diet, regular exercise/turn out
Also happens in greyhounds and sled dogs
Polysaccharide storage myopathy (PSSM1)
Horses
Quarterhorses, warmbloods, draft horses, cobs etc.
Autosomal dominant disease
Cause ER (equine rhabdomyolysis), occasionally muscle atrophy/weakness in draft breeds
Abnormality of glucose metabolism
Diagnosis: DNA test (EDTA blood) or hair pluck
Treat: high fat/low carb diet, regular daily exercise - turning over glycogen in muscle to prevent crystals
The exhausted horse
Long rides in hot humid conditions in unfit animals
Signs: depression, dehydration, anorexia, decreased thirst, increased RR and HR, pyrexia, poor sweating performance, poor jugular distension, decreased gut sounds, laminitis, synchronous diaphragmatic flutter, muscle pain, stiffness
Treat: fluids +/- electrolytes, cooling, NSAIDs, evidence of rhabdomyolysis
Prevent: training, heat acclimitisation
Coccygeal muscle injury
Limber tail, cold tail, muddy tail
Labradors, pointers, working breeds
- Pain at tail base, mild elevation in CK
- Recovery over several days
Treat: rest, NSAIDs
Fibrotic myopathy
Horses
Common in QH: usually semitendinous (sometimes semi-membranous or gracilis)
Causes: muscle tear, IM injection, neuropathy
Treat: rest NSAIDs, surgical resection of fibrous tissue or tenotony
Atypical myopathy
Acute onset severe myopathy in horses at pasture (increase CK and AST)
Muscle biopsy pre or post mortem
Treat: Riboflavin (vitamin B2 supplementation), carnitine supplementation, support carb metabolism
Lumbosacral stenosis
Old larger breeds - GSDs
Bladder dysfunction - L4-S3 spinal cord segments
Stenosis of the vertebral canal and/or intervertebral foramina and/or the related vasculature
Hansen type II disc degeneration and protrusion at the lumbosacral junction
- Subluxation of the articular facets
- Thickening and folding of the interarcuate ligament
- Epidural fibrosis
- Thickened lamina and pedicle
- Can compress nerve roots
- Instability and misalignment between the last lumbar vertebrae and the sacrum
Treat: conservatively, dorsal laminectomy
Polyneuritis equi
Tail paralysis, dilated anus, faecal retention, perineal loss of sensation, muscle atrophy
Pathogenesis: immune-mediated damage to peripheral nerve of cauda equina
Diagnosis: tail head muscle biopsy, lymphocytic infiltrate seen in/around the intramuscular nerves
Treat: usually supportive
Assistance of bladder emptying
Block sympathetic alpha receptors: phenoxybenzamine, prozasin NB affects blood vessels
Blocked striated urethral muscle - diazepam
Autonomic neuropathy
Dilated pupils Constipation Decreased tear production Urinary retention Hyposalivation Reduced perianal reflex Bradycardia
Electromyogram
Normal EMG is silent
Fibrillation potentials:
- Denervation, inflammation, biphasic
- Spontaneous action potentials of single myofibres
Positive sharp waves:
- Denervation
- Positive deflection followed by shallow, negative deflection
- Spontaneous action potentials of single myofibres
Complex repetitive discharges:
- Polyphasic and serrated - each one has a uniform shape
- Many myofibrils in near synchrony
Pseudo myotonia:
- Myotonic potential
- Amplitude and frequency waxes and wanes due to independent, repetitive discharges of singled, injured myofibres
Equine botulism and flaccid paralysis
Toxin B important in the UK (C and D abroad, 8 in total)
Outbreaks due to contaminated feed
Toxin irreversibly blocks the release of acetylcholine at the neuromuscular junction
Treat:
- Antiserum to toxin B (and C and D - USA)
- Broad spectrum antibiotics for pneumonia, avoid procaine and aminoglycosides
- Fluid, nutrition, management of recumbent horse
- Available vaccines
Neuropathic syndrome:
Motor: LMN signs
Sensory: hypoalgesia, hypoaesthetic, CP deficits, self mutilating, reduced reflexes, not atrophy
Autonomic: pupillary changes, decreased tear production and salivation, bradycardia
Peripheral neuropathies in large animals
Post parturition:
- Calves: femoral nerve paresis
- Cows and horses: obturator nerve, compression against ventral ridge of wing of sacrum at delivery
Trauma:
- Brachial plexus injury
- Radial nerve paralysis
- ‘Sweeny’ suprascapular nerve damage with muscle atrophy of supra and infrascapular
Myopathic syndrome
Paresis Exercise intolerance Stiff, stilted gait Muscle atrophy or hyperatrophy Muscle pain on palpation
Exercise intolerance
Exercise induced collapse often in Labradors
Well muscles
Normal neuro exam between episodes
20-30min of exercise -> collapse (hyperthermia, para-tetraparesis, short rest than mobile)
Gene defect IDed
Treat: exercise restriction
