Path neurology Flashcards
Describe the neuronal body response to injury ?
Neuro response to injury
Neurons are the most vulnerable cell in the body to injury
- this is due to there size and inability to store glucose.
The response
Hallmark = Eosinophilic and shrunken
- ischaemic change (acute necrosis
- axons of degenerated ischaemic neurons may also release = glutamate
Glutamate causes injury to nearby neurons via calcium influx into the cell. (Neuroexcitatory).
Pigments and inclusions
Viral inclusions eg canine distemper
Lipofusin - increases with age (periodic Schiff (PAS) positive brown/golden pigment.
Hereditary lysosomal storage disease eg glycogen
Describe the response of the axon to injury in the CNS ?
Wallerian degeneration / axonal injury
Clinical signs
Digestive chambers - large empty spaces and macrophages
- swoolen axons = spheroids
- swollen, degeneration axon and myelin
- wont always be viewed as continuous
- fragment “ellipsoids”
Describe why there is a greater chance of recovery from axonal damage in the PNS than the CNS ?
PNS: Wallerian degeneration more likely to recover
Regeneration will occur given time and close apposition, peripheral nerves can regrow and restory function
- rapid phagocytosis of debris
- endoneuronal tube to guide axon regrowth
- Schawn cells can remyelinate axon
No repair of CNS eg spinal cord
- CNS myelin is chemically and antigenically different from PNS
- axon budding is inhibited by CNS myelin proteins
- oligodendrocyte arrangement prevents re myelination
- no endoneuronal tube to guide regrowth
Describe the function and injury of Astrocytes ?
Astrocytes
Function
- Naked nuclei no cytoplasm
- structural support and regulation
- repair (similar role to fibrocytes)
- foot processes: blood brain barrier
Response to injury
- proliferation, incrase in number
- attempt to wall off foreign body but incomplete
- hypertrophy
- acuteswelling
- Cytoplasm becomes visible (Gemistocytes)
Describe the response of Oligodendrocyte cells to injury ?
Oligodendrocytes
Function
- small dense cell
- produce myelin CNS
- each axon has only one cell
Acute swelling and degeneration
“satellitosis
- hypertrophy
- proliferation of precursor cells
Serious consequences
Selective myelin degeneration - primary demyelination
primary - viruses
seconday - axonal injury or death
Describe the response of Glia cells to injury ?
Glial cells
Immune surveilance / phagocytic
In response to injury
They are the first cells to respond to CNS injury
- proliferation
- Phagocytosis (neurons, myelin debris)
- Roles in inflammation ( antigen presentation, cytokine production).
Phagocytosis “Gitter cells”
Describe the layers of the meninges ?
Identify this lesion within the brain and describe its pathology and clinical signs ?
Hydrocephalus
(Fluid filled dilation of the brain)
Location depends upon the site of blockage
- obstruction within the ventricular system is most common
- affects ventricles &/or subarachnoid space
- causes pressure atrophy of ependymal cells and underlying brain
The cause is congenital
-can result from intrauterine infections (parainfluenza in dogs)
- injury of the ependymal cells of the aqueduct)
- genetic predisposition in brachycephalic
Clininical signs
doming of cranium
prominent frontanelles
Identify this lesion and describe its pathology ?
Hydromyelia
- Fluid filled dilation of the central canal in the spinal cord
- CSF accumulates in the cavity
- usually from damage to ependymal cells and altered CSF flow
Identify the lesion (black arrow), and describe its pathology ?
Porencephaly
Small fluid filled cyst in the ceerebral hemispheres
Path
Destruction of immature neuroblast during development
eg virus Akabane, Border disease or bluetoungue
Identify this lesion and describe its pathology ?
Hydranencephaly
Large fluid filled cavities in the brain
- this is a more severe form of porencephaly
- failure of cerebral hemispheres to develop
- ventricles expand into space
- fill with CSF
Identify this lesion and describe its potential pathology ?
Cerebellar hypoplasia
The most common causes
* Viruses
Destroy dividing germinal cells of external granular layer of the cerebellum during organogenesis.
- Parvoviruses
Cats = panleukopaenia
Dogs = parvovirus - Pestiviruses
Calves: BVDV
Piglets: Classical swine fever
Identify this lesion ?
Lissencephaly (Agyria)
= Lack of gyri
- smooth cortical surface
- genetic defect in neuronal migration
- DDX some species lack gyri.
Define Anencephaly ?
Anencephaly
A complete absence of the whole brain
- very rare
- often cerebral hemispheres missing cerebral aplasia
Identify this lesion and describe its pathology ?
Cranium bifida
Dorsal midline cranial defect
Meningeal +/- brain tissue can protrude
- meingococele and meningoencephalocoele
- genetic in pigs and cats
- Griseofulvin in 1st week of pregnancy in cats.
Identify this lesion and describe its pathology ?
Spina bifida
Dorsal vertebral arch defects
- often caudal spine affected
- meninges +/- spinal cord can protrude
- meningocoele and meingomyelocoele
Describe Spinabifida occulta ?
Spinabifida occulta
Absence of skin over the vertebral arches but no herniation
- horses, calves, sheep
Identify this lysosomal storage disease ?
Glycogenosis
Lysosomal storage disease
Pompe’s disease = deficiency alpha 1,4 glucosidase
Describe the pathology and clinical signs underlying Pompe’s disease ?
Glycogenosis
Pathology
Pompe’s disease of Brahmans and shorthorns
- deficiency of alpha 1,4-glucosidase
Lesions
large neurons of brainstem and spinal cord
- skeletal muscle vacuolation and degeneration
Clinical signs
Onset 2-12 months
- weakness and ataxia
- skeletal muscle affected first
Describe the pathology and clinical signs underlying Mannosidosis ?
Mannosidosis
(lysosomal storage disease)
Pathology
Deficiciency of B mannosidase
Storage of mannose rich oligosaccharides
- Murry grey and belted galloway cattle
- foamy change of neurons
Clinical signs
- ataxia
- tremors
- hypermetria (over-stepping).
Identify this lysosomal storage disease and describe its pathology ?
Globoid cell Leukoodystrophy
(Lipid storage disease)
Defective galactocerebrosidase
Accumulate psychosin which is toxic to Schwann and Oligodendrocyte cells.
Lesions
White matter degeneration
- phagocytosis of myelin produces large macrophages (globoid cells)
Identify this lysosomal storage disease ?
Ceroid Lipofuscinosis
Describe the pathology and clinical signs of Ceroid Lipofuscinosis ?
Ceroid lipofuscinosis
Abnormal metabolism of lipopigments
- Border collies blue cattle dogs
- onset 1-2 years
Clinical signs
- rapid progression
- blindness and behavioural changes
- dullness, restlessness
- loss of learned behaviour
Lesions
Atrophy of cerebrum and cerebellum
- reduced number of neurons
- remaining neurons contain pigment
What are the three main forces to cause CNS trauma ?
Forces which result in CNS trauma
- Compression (crushing)
- Tensile (stretching / pulling)
- Shearing (parallel to the surface)
Three main types of injury in the CNS
Concussion
Contusion
Laceration
Define a concussion
Concussion
Often a diffuse brain injury with no gross lesions
- causes temporary loss of consciousness with recovery
- can also undergo temporary spinal concussion
Identify this lesion and describe its pathology ?
Contusion
(more severe impact which results in haemorrhage).
Pathology
The causes of CNS haemorrhage
1. Trauma (most common)
2. Endothelial damage (septicaemia)
3. Coagulopathy ( anticoagulant rodenticide poisoning)
- Vasculitis
- Bovine malignant catarrhal fever
- FIV
- Equine Herpes virus 1
- Classical swine fever
Define a coup and countercuope injury ?
Coup
Direct injury at the point of impact
Countercoup
Stretching / tearing of nerves and vessels on the opposite side as the point of impact
Describe the consequences of intracranial haemorrhage / contusion ?
Identify this CNS trauma ?
CNS trauma Laceration
Distinct disruption of the tissue
- fracture of the cranium or vertebral column
- penetration of a shrp object (eg canine teeth
Identify this lesion and describe its pathology ?
Haematomyelia
(haemorrhage of the spinal cord).
Pathology
- can be associated with disc herniation
- can transect spinal cord
- can extend cranially and caudally from original site of trauma
Identify this lesion and describe its pathology ?
Inveretebral disc herniation ?
Pathology
* Nucleus pulposus degeneration
- loss of elasticity prevents even distribution of compressive loads
* Degeneration of the anular ligament
- sudden loading of vertebral column when felxed can cause so much pressure it ruptures.
Describe type one and two Intervertebral disc herniation ?
Invertebral disc herniation
Type 1 Disc herniation
Rupture of the annular ligament with fragments of nucleus pulposis present in the spinal canal
- acute onset
- Duchshund, beagle
Type two disc herniation
Protrusion of the spinal canal without rupture of the annular or dorsal longitudinal ligament
- often chronic progressive onset
- esp older larger breed dogs
- age related fibrous degeneration of nucleus pulposis
Identify this lesion and describe its pathology ?
Cervical Stenotic Myelopathy
(wobbler syndrome)
There is two forms in horses;
Static
Absolute narrowing of the lumen of the spinal canal
- - often 1-4 years
- C5 to C7
Dynamic
Narrowing only occurs during flexion of the neck.
- often younger - 2 years
- C3 - C5
Dogs
Most at C5 - C7 except basset hounds C3
Dobbermans, great danes
Describe the gross lesions and histopathology of Wobbler syndrome ?
Cervical stenotic myelopathy (wobbler syndrome)
Gross lesions
- may be very subtle esp dynamic type
- if slow development may see marked indentation of the cord
Histopathology - slow development
- may be mild lesions
- degenerated neurons and axons removed
Rapid onset
Acute ischaemic necrosis of white or grey matter
- Wallerian degeneration of axons cranially and caudally
- Gitter cells
Identify this lesion and describe its pathology ?
Discospondylitis
Inflammation of the spinal cord
Pathology
Brucella suis
Aspergillus spp
Arcanobacterium pyogenes
Provide a definition of Scoliosis and Kyphosis ?
