Difference between revisions of "Peripheral Nervous System Pathology Overview"

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==Nerve Injury==
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===Classification of Peripheral Nerve Disease===
|linkpage = Nervous System - Pathology
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{| cellpadding="4" cellspacing="0" border="2"
|linktext =Nervous System
+
|-
|maplink = Nervous System (Content Map) - Pathology
+
|style="background:#B0E0E6; color:black" width="200"|'''By Nerve Type
|pagetype =Pathology
+
|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>
 
<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"|'''Axonotmesis:'''||
 +
*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"|'''Neurotmesis:'''||
 +
*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
 +
|
 +
*Anisocoria (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>'''[[Polyneuritis Equi|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>'''[[Key-Gaskell Syndrome|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>'''[[Laryngeal Hemiplegia|Idiopathic Laryngeal Hemiplagia (ILH)]]'''</big></center>
 +
|
 +
*Progressive loss of fibres (esp. large diameter) within left recurrent laryngeal nerve compared to right
 +
*[[Peripheral Nervous System - Response 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>'''[[Polyneuritis Equi|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
 +
*[[Peripheral Nervous System - Response to Injury#Chromatolysis|Chromatolysis]]
 +
*Neurofilament accumulation
 +
*Gliosis
 +
*[[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>
 +
|
 +
*'''"Sweeney"'''
 +
*Commonly damaged by horse colliding into objects
 +
*Fibrous entrapment as nerve reflected around wing of scapula
 +
*Atrophy of supra- and 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
 +
 +
 +
[[Category:Peripheral Nervous System - Pathology|A]]

Latest revision as of 13:04, 10 March 2011

Nerve Injury

Classification of Peripheral Nerve Disease

By Nerve Type By Anatomy By Pathology
  • Mixed
  • NMJ
Neuronopathy : The Whole nerve cell
  • Motor
  • Distal / Proximal
Axonopathy : The axon
  • Sensory
  • Root / Spinal Cord
Demyelination: Schwann cell


Types of Injury

Neuropraxia:
  • Temporary interruption of conduction - no histological change.
Axonotmesis:
  • Axon interupted but basal lamina intact (e.g. crush injury)
  • Regeneration occurs along original path - prospect for functional recovery good.
Neurotmesis:
  • Axon and basal lamina interupted (e.g. transection injury)
  • Success of regeneration depends on finding the correct distal stump


Clinical Signs with Peripheral Nerve Disease

Motor Neuropathy Signs (LMN signs)
Sensory Neuropathy
Autonomic Neuropathy
  • Flaccid paresis/paralysis of innervated structures
  • Decreased or abherrant 'pain' response or sensation
  • Anisocoria (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


Peripheral Nerve Disease in Small Animals

Disease
Pathology
Clinical Signs
Diagnosis
Prognosis + Treatment
Distal Denervating Disease
  • 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
Idiopathic Polyradiculoneuritis
  • 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)
Cauda Equina Traction
  • 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
Peripheral Nerve Tumours
  • 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?
Feline Dysautonomia
  • 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

Disease
Pathology
Clinical Signs
Diagnosis
Prognosis + Treatment
Idiopathic Laryngeal Hemiplagia (ILH)
  • Progressive loss of fibres (esp. large diameter) within left recurrent laryngeal nerve compared to right
  • 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
Cauda Equina Neuritis
  • Equine version of 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.
Stringhalt
  • 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
Equine Motor Neuron Disease
  • 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
Suprascapular Nerve Injury
  • "Sweeney"
  • Commonly damaged by horse colliding into objects
  • Fibrous entrapment as nerve reflected around wing of scapula
  • Atrophy of supra- and 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