no edit summary
Line 7: Line 7:  
}}
 
}}
 
<br>
 
<br>
 +
==Nerve Injury==
 +
===Classification of Peripheral Nerve Disease===
 +
{| cellpadding="4" cellspacing="0" border="2"
 +
|-
 +
|style="background:#B0E0E6; color:black" width="200"|'''By Nerve Type
 +
|style="background:#B0E0E6; color:black" width="200"|'''By Anatomy'''
 +
|style="background:#B0E0E6; color:black" width="250"|'''By Pathology'''
 +
|-
 +
|
 +
*Mixed
 +
|
 +
*NMJ
 +
|'''Neuronopathy :'''    ''The Whole nerve cell''
 +
|-
 +
|
 +
*Motor
 +
|
 +
*Distal / Proximal
 +
|'''Axonopathy      :'''    ''The axon''
 +
|-
 +
|
 +
*Sensory
 +
|
 +
*Root / Spinal Cord
 +
|'''Demyelination:'''    ''Schwann cell''
 +
|-
 +
|}
 +
<br>
 +
 +
===Types of Injury===
 +
{| cellpadding="4" cellspacing="0" border="2"
 +
|-
 +
|style="background:#B0E0E6; color:black"|'''Neuropraxia:'''||
 +
*Temporary interruption of conduction - no histological change.
 +
|-
 +
|style="background:#B0E0E6; color:black"|'''Axonotemesis:'''||
 +
*Axon interupted but basal lamina intact (e.g. crush injury)
 +
*Regeneration occurs along original path - prospect for functional recovery good.
 +
|-
 +
|style="background:#B0E0E6; color:black"|'''Neurotemesis:'''||
 +
*Axon '''and''' basal lamina interupted (e.g. transection injury)
 +
*Success of regeneration depends on finding the correct distal stump
 +
|}
 +
<br>
 +
 +
===Clinical Signs with Peripheral Nerve Disease===
 +
{| align="center" cellpadding="4" cellspacing="0" border="0"
 +
|width="350"|
 +
:<u>'''Motor Neuropathy Signs (LMN signs)'''</u>
 +
|width="350"|
 +
:<u>'''Sensory Neuropathy'''</u>
 +
|width="350"|
 +
:<u>'''Autonomic Neuropathy'''</u>
 +
|-
 +
|
 +
*Flaccid paresis/paralysis of innervated structures
 +
|
 +
*Decreased or abherrant 'pain' response or sensation
 +
|
 +
*Aniscoria (dilated / constricted pupils)
 +
|-
 +
|
 +
*Neurogenic muscle atrophy (very rapid)
 +
|
 +
*Proprioceptive defects
 +
|
 +
*Decreased tear production
 +
|-
 +
|
 +
*Reduced / absent reflexes and muscle tone
 +
|
 +
*Abnormal sensation (paraesthesia)/sensitivity (dysthesia)
 +
|
 +
*Decreased salivation
 +
|-
 +
|
 +
|
 +
*Reduced / absent reflexes without muscle atrophy
 +
|
 +
*Bradycardia
 +
|}
 +
<br>
 +
 +
==Peripheral Nerve Disease in Small Animals==
 +
{| cellpadding="4" cellspacing="0" border="2"
 +
|- style="background:#B0E0E6; color:black"
 +
|width="150"|<center><big>'''Disease'''</big></center>
 +
|width="200"|<center><big>'''Pathology'''</big></center>
 +
|width="250"|<center><big>'''Clinical Signs'''</big></center>
 +
|width="250"|<center><big>'''Diagnosis'''</big></center>
 +
|width="250"|<center><big>'''Prognosis + Treatment'''</big></center>
 +
|-
 +
|<center><big>'''Distal Denervating Disease'''</big></center>
 +
|
 +
*Distal axonopathy, possibly of toxic origin
 +
|
 +
*Tetraparesis
 +
*Dysphonia / Aphonia
 +
*Neck Weakness
 +
*Tetraparesis developing to tetraplegia in severe cases ''floppy dog''
 +
*Sensory function preserved: Pain but '''no''' withdrawal
 +
|
 +
*Biopsy / EMG unhelpful
 +
|
 +
*Very good prognosis
 +
*Recovery in 3-6 weeks by '''axon regeneration'''
 +
*Good nursing to prevent pressure sores in the recumbant animal
 +
|- style="background:#F0F8FF; color:black"
 +
|<center><big><span id="IPRN">'''Idiopathic Polyradiculoneuritis'''</span></big></center>
 +
|
 +
*Immune mediated demyelination often involving roots, directed against unknown epitopes in peripheral myelin.
 +
*May be post infection
 +
*May get axonal injury if severe
 +
|
 +
*As for distal denervating (although more rapid onset)
 +
*May have sensory involvement.
 +
|
 +
*By clinical signs
 +
*CSF changes if roots involved
 +
*Slower nerve conduction
 +
*H reflexes and F-waves may be lost
 +
|
 +
*Very good prognosis
 +
*Recovery in 3-6 weeks by '''remyelination'''
 +
*Immunosuppresive levels of corticosteroids (although may delay remyelination)
 +
|-
 +
|<center><big>'''Cauda Equina Traction'''</big></center>
 +
|
 +
*Tail pull injury
 +
*Esp. cats after RTA
 +
*Lesion via longitudinal traction
 +
*Sacrocaudal dislocation/fracture
 +
|
 +
*Limp tail
 +
*Incontinence
 +
*Hindlimb Paresis
 +
|
 +
*Diagnosis on Clinical signs and history
 +
*+/- Radiographs to show dislocation/fracture
 +
|
 +
*Prognosis difficult to predict
 +
*Poor prognosis if tail limp & no anal tone
 +
*Supportive treatment
 +
*'''Persist for >3 months if possible'''
 +
|- style="background:#F0F8FF; color:black"
 +
|<center><big>'''Peripheral Nerve Tumours'''</big></center>
 +
|
 +
*Nerve sheath tumours
 +
*Generally tumours of Schwann cells
 +
*Common in dog Brachial plexus
 +
|
 +
*Chronic single forelimb lameness
 +
*Weakness
 +
*Muscle Atrophy
 +
*Pain in Axilla
 +
*LMN signs (may get UMN if grows into spinal cord
 +
|
 +
*Clinical signs
 +
*Imaging
 +
|
 +
*Prognosis dependant on location
 +
*Poor prognosis if in spinal cord
 +
*Amputation of limb?
 +
|-
 +
|<center><big>'''Feline Dysautonomia'''</big></center>
 +
|
 +
*Common in 1980's - Sporadic now
 +
*Degeneration (toxic?) of autonomic ganglia
 +
|
 +
*Mainly Parasympathetic
 +
*Vomiting
 +
*3rd Eyelid protrusion
 +
*Dilated pupils + poor PLR
 +
*Reduced Lacrimation
 +
*Megaoesophagus
 +
*Bradycardia
 +
|
 +
*Clinical signs
 +
|
 +
*Poor Prognosis
 +
*Supportive therapy only
 +
*Similar sporadic disease seen in dogs
 +
|-
 +
|}
 +
 +
==Peripheral Nerve Disease in Large Animals==
 +
{| cellpadding="4" cellspacing="0" border="2"
 +
|-- style="background:#B0E0E6; color:black"
 +
|width="150"|<center><big>'''Disease'''</big></center>
 +
|width="200"|<center><big>'''Pathology'''</big></center>
 +
|width="250"|<center><big>'''Clinical Signs'''</big></center>
 +
|width="250"|<center><big>'''Diagnosis'''</big></center>
 +
|width="250"|<center><big>'''Prognosis + Treatment'''</big></center>
 +
|-
 +
|<center><big>'''Idiopathic Laryngeal Hemiplagia (ILH)'''</big></center>
 +
|
 +
*Progressive loss of fibres (esp. large diameter) within left recurrent laryngeal nerve compared to right
 +
*[[PNS Repsonses to Injury#The 'Dying Back' Phenomenon|Dying back]] axonopathy with myelin sheath involvement:
 +
**Degenerating fibres
 +
**Regenerating clusters
 +
**De/Re-myelination
 +
*Flattening of nerve between aorta & trachea
 +
|
 +
*Inspiratory 'roaring' noise - flapping of vocal fold
 +
|
 +
*'Slap test' - adduction of contralateral arytenoid during expiration
 +
*Endoscopic examination - assymetric arytenoids, poor abduction of left vocal fold.
 +
*Palpable atrophy of laryngeal musculature
 +
|
 +
*Laryngeal Ventriculectomy (Hobday procedure)
 +
*'Tie Back'
 +
*Laryngeal muscle prosthesis
 +
*Prognosis usually good
 +
|-style="background:#F0F8FF; color:black"
 +
|<center><big>'''Cauda Equina Neuritis'''</big></center>
 +
|
 +
*Equine version of [[#IPRN|Idiopathic polyradiculoneuritis]]
 +
*Extradural nerve roots of cauda equina thickened and discoloured
 +
*Inflammatory infiltrate (lymphocytes, plasma cells, macrophages)
 +
*Extensive axonal damage and demyelination
 +
*Cranial nerve involvement often occurs
 +
*Aetiology unknown:
 +
**Antecedent infection?
 +
**Antibodies to PNS myelin?
 +
|
 +
*Paralysis & anaesthesia of tail
 +
*Urinary incontinence
 +
*Loss of anal reflex
 +
*Failure to defaecate
 +
*Pain/hypersensitivity in gluteal/tail-head area
 +
|
 +
*Clinical signs
 +
|
 +
*Recovery unlikely - most animals are destroyed.
 +
|-
 +
|<center><big>'''Stringhalt'''</big></center>
 +
|
 +
*Causes poorly understood - similar signs caused by sweat pea plant ingestion (lathyrism)
 +
*Distal axonopathy (esp. large diameter fibres)
 +
|
 +
*Abrupt onset continuous / intermittent hyperflexion of one or both hind limbs
 +
*May also have ataxia, urinary incontinence, perineal flaccidity
 +
|
 +
*Differential diagnosis : Upward fixation of patella
 +
|
 +
*May get spontaneous recovery
 +
*Move pasture
 +
*Tenectomy of lateral digital extensor may help
 +
|-
 +
|-style="background:#F0F8FF; color:black"
 +
|<center><big>'''Equine Motor Neuron Disease'''</big></center>
 +
|
 +
*Generalised LMN disorder
 +
*Degeneration of Ventral horn motor neuron
 +
*[[PNS Repsonses to Injury#Chromatolysis|Chromatolysis]]
 +
*Neurofilament accumulation
 +
*Gliosis
 +
*[[PNS Repsonses to Injury#Wallerian Degeneration|Wallerian degeneration]]
 +
*Denervation changes in muscle
 +
|
 +
*Weight Loss
 +
*Muscle atrophy
 +
*Generalised Weakness
 +
*Short strided gait + narrow based stance
 +
*Trembling
 +
*Sweating and fasiculations
 +
*Increased recumbency
 +
|
 +
*Elevated CK
 +
*CSF protein
 +
*Denervation of EMG
 +
|
 +
*May progress to constant recumbency (destroy), stabilise or improve
 +
|-
 +
|<center><big>'''Suprascapular Nerve Injury'''</big></center>
 +
|
 +
*'''"Sweeny"'''
 +
*Commonly damaged by horse coliding into objects
 +
*Fibrous entrapment as nerve reflected around wing of scapula
 +
*Atrophy of supra- & infra- spinatous muscles
 +
|
 +
*Lateral luxation of shoulder when weight bearing
 +
*Muscle wasting around shoulder
 +
|
 +
*Clinical signs
 +
*History
 +
|
 +
*No more than 30cm regrowth in 12 months expected due to irreversible muscle fibrosis.
 +
 +
|-
 +
|}
 +
 +
==Other Polyneuropathies==
 +
*Tick Paralysis
 +
*Vincristine Toxicity
 +
*Endocrine polyneuropathy
 +
**Dogs - hypothyroidism, insulinoma, diabetes mellitus
 +
**Cats - diabetes mellitus
 +
*Genetic polyneuropathies
 +
*Protozoan polyradiculoneuritis
 +
*Idiopathic facial paralysis (e.g. Bell's Palsy)
 +
*Botulism
 +
 +
==Learning Tools==