Neuro - pathology Flashcards
What does myel- refer to?
Spinal cord
What doe polio- refer to?
Grey matter
What does leuko- refer to?
White matter
What does radiculo- refer to?
Spinal nerve roots
What does malacia mean?
Area of softening due to necrosis
What is the name of the myelinating cells of the CNS?
Oligodendrocytes
What are the gaps between the schwann cells?
Nodes of ranvier
What are the 3 main features to note about neurones?
High energy demand for O2 and glucose - lots of active transport
Limited energy reserve capacity
Lost neurones are not replaced
What are the two morphological changes of the neuronal cell body to injury?
Chromatolysis
Neuronal necrosis
What are the two morphological changes of axons to cell injury?
Axonal degeneration (wallerian degeneration)
Axonal regeneration
What is chromatolysis? What are its characteristics?
Degenerative change of the neuronal cell body, characterised by:
Swollen cell body
Dispersion/loss of Nissl substance
Nucleus displaced peripherally
What are the two consequences of chromatolysis?
May be reversible
May progress to cell death
What is neuronal necrosis? What are its characteristics?
Cell body change following irreversible injury
Deeply eosinophilic
Condensed nucleus (pyknosis)
Shrunken/swollen
Angular cytoplasm
What are the consequences of neuronal necrosis?
Death of cell body results in degeneration of the axon
Necrotic neurones are cleared by phagocytes
What is axonal/Wallerian degeneration?
Axon injury from traumatic cut or compression
Axon degenerates back to the next node of Ranvier proximal to injury site and distal to injury site
Cell body undergoes chromatolysis
What is the time course of axonal/Wallerian degeneration?
Hours - axonal swellings
Days - fragmentation of axon/myelin
Weeks/months (PNS) to months/years (CNS) - axonal and myelin debris removed by phagocytes within digestion chambers
What does axonal regeneration require?
Being in the PNS (doesnt happen in CNS)
Requires the cell body to be intact
Requires integrity of the endoneurial tube distal to the site of injury
What grow during axonal regeneration?
Schwann cells form columns in endoneurial tube
Axonal sprouts grow along endoneurial tube and is remyelinated
What are the 3 outcomes of axonal regeneration?
1 - Restored function
2 - Axon regeneration without restored function
3 - Unsuccessful regeneration and neuronal atrophy
What causes axonal regeneration without restored function?
Endoneurial tubes misaligned
What can cause unsuccessful axonal regeneration and neuronal atrophy?
Fibrosis blocking axonal stump
Loss of integrity of endoneurial tube
Why is there no/very limited axonal regeneration in the CNS?
Lack of scaffold - no endoneurium for sprouts to follow
Oligodendrocytes dont form columns like the schwann cells do
Axonal sprouting inhibited
What inflammatory infiltrate do bacterial and fungal infections cause?
Suppurative - neutrophils
What inflammatory infiltrate do viral infections cause?
Non-suppurative - lymphocytes, plasma cells, macrophages
What is granulomatous inflammatory infiltrate made up of?
macrophages
What inflammatory infiltrate do protozoal and helminth infections cause?
Eosinophilic
What is perivascular cuffing?
During inflammation around the CNS, inflammatory cells are concentrated around the blood vessels
What are the macrophage equivalent in the CNS?
Microglia - resident phagocytes
What are the large foamy blood derived macrophages in the CNS called?
Gitter cells
What cells are the main cells involved in repair of the CNS?
Astrocytes - can form a scar
(microglia also help heal)
Where are fibroblasts only present in the CNS?
In the meninges
What are the 3 causes of brain swelling?
Space occupying lesions
Congestive brain swelling
Brain oedema
What are the 3 main mechanisms of brain oedema?
Vasogenic oedema
Interstitial oedema
Cytotoxic oedema
What is vasogenic oedema? What can cause it?
Blood brain barrier disruption causes fluid to move from vasculature into neuroparenchyma
Secondary to inflammation, infarction, trauma
What is interstitial oedema? What can cause it?
Increased ventricular cerebrospinal fluid pressure forces CSF into the parenchyma
Associated with hydrocephalus
What is cytotoxic oedema? What can cause it?
Cellular swelling due to disturbed cellular fluid homeostasis
Toxic or metabolic disease
What is coning of the cerebellar vermis?
When the cerebellum herniates through the foramen magnus of the cranium
What does the occipital cortex herniate through?
Tentorium cerebelli
What are the main types of pathological processes that can affect the nervous system?
VITAMIN D
DAMNIT TV
What are the main types of pathological processes that can affect the nervous system?
VITAMIN D
DAMNIT TV
What are some anomalous causes of nervous system pathologies?
Cerebellar malformations
Hypdrocephalus
Syringomyelia
Chiari-like malformation
What can cause congenital malformations of the brain/nervous system?
Viral infections
Nutritional deficiencies
Genetics
Toxins/drugs
What can cause cerebellar malformations?
Primary - idiopathic
Secondary - viral infection
eg. Feline parvovirus, schmallenberg, BVD
What are the two mechanisms/causes of hydrocephalus?
Obstructive - blocked CSF flow
Compensatory - loss/absence of parenchyma so CSF fills space eg. necrosis of neural tissue in utero
What is a common site of obstruction in congenital obstructive hypdrocephalus?
Mesencephalic aqueduct
What diseases can cause congenital compensatory hypdrocephalus?
Schmallenberg virus
Bluetongue virus
Feline parvovirus (panleukopenia)
What can cause obstructive hydrocephalus?
Space occupying lesion
Inflammatory exudate from inflammation
What is syringomyelia?
Fluid filled cystic cavity in the spinal cord parenchyma
What is hydromyelia?
Dilation of the central canal in the spinal cord
What is occipital bone(Chiari-like) malformation?
When the brain skull caudal fossa is too small to hold cerebellum
Cerebellum herniates through foramen magnum
What is the main degenerative neuropathy that we need to know?
Age-related degenerative myelopathy - in dogs
(also known as chronic degenerative radiculomyelopathy)
What dogs are predisposed to Age-related degenerative myelopathy
Middle aged-older dogs
German shepherd dog predisposed
What is Age-related degenerative myelopathy? Where is most affected?
Axonal loss and myelin degeneration over time
Thoracic portion of spinal cord most affected - hind limb ataxia and weakness
What are the most common causes of metabolic/toxic nerve disorders?
Nutritional deficiencies - copper, thiamine
Endogenous toxins - hepatic encephalopathy
Exogenous toxins - tetanus, botulism
What is the pattern of lesions seen in the CNS from metabolic/toxic disorders?
Bilaterally symmetrical
What is copper deficiency called in sheep? What are the two kinds?
Swayback - congenital form
Enzootic ataxia - delayed form
Where are lesions seen in the CNS from solely swayback?
Cerebral lesions only - bilaterally symmetrical cerebral white matter cavitation/softening/degeneration
What lesions are seen in the CNS from swayback and enzootic ataxia?
Bilaterally symmetrical white matter degeneration in brain stem and spinal cord
What is the name of thiamine deficiency in ruminants?
Poliocephalomalacia
Cerebro-cortical necrosis (CCN)
What lesions are caused by thiamine deficiency?
Bilaterally symmetrical cerebrocortical necrosis
How does thiamine cause cerebrocortical necrosis?
Thiamine is used as a cofactor in carb metabolism - needed to make ATP
Reduced ATP causes neuronal necrosis and astrocyte dysfunction
How does thiamine deficiency arise?
From overgrowth of thiaminase-producing bacteria in the rumen
Ingestion of thiaminase-containing plants eg. bracken
How can you identify thiiamine deficiency/cerebrocortical necrosis?
Bilaterally symmetrical lesions
Flattening of gyri
Yellow discoloration of the grey matter
Shows autofluorescence under UV light
What counts as a primary tumour of nervous system?
Cells from neuroectodermal origin
What does multiple tumours in CNS suggest?
Metastatic spread from another site
What tumour is it likely to be if it is on the inner aspect of the brain?
Choroid plexus or ependymal cell origin
What tumour is it likely to be if it is on the outer aspect of the brain?
Meningioma
What tumour is it likely to be if it is in the parenchyma of the brain?
Glial cell/astrocyte tumours - tend to be diffuse
What tumour of the CNS has a gelatinous and greyish translucent appearance?
Oligodendroglioma
What is the most common tumour of the CNS?
Meningioma - slow growing lobulated white/tan coloured mass
What are 3 causes of random non-symmetrical vascular lesions in the CNS?
Infarctions
Thromboembolism
Vasculitis
What can cause global hypoxic-ischaemic injury in the brain?
Anaesthetic accidents
Asphyxiation
Severe anaemia
Cardiac arrest
Hypovolaemic shock
What regions of the brain are most sensitive to hypoxic-ischaemic injury?
Cerebral cortex
Hippocampus
Cerebellar purkinje cells
What are the routes of entry of infectious agents into the nervous system?
Haematogenous
Via CSF
Axonal transport
Direct extention from adjacent tissues
What causes purulent meningitis?
Haematogenous bacterial infection causing lesions in meninges, purulent exudate pooling in sulci
What animals in purulent meningitis most common in?
Neonates/juvenile large animals (lack of colostrum)
What is listerial encephalitis?
Encephalitis from spoiled silage, invades oral mucosa, infects trigeminal nerve and spreads to brainstem
In ruminants
What can be seen on histology from infectious brainstem lesions?
Microabcesses
Perivascular cuffing
What viruses can cause CNS infections?
Malignant catarrhal fever
Canine distemper virus
FIP
Rabies
Equine herpes virus
Louping ill
What are the main changes to the CNS from viral encephalitis?
Non-suppurative inflammation
Grey matter most affected
Congenital malformations
What is the most common cause of CNS inflammation in cats?
Feline infectious peritonitis
What parasite causes CNS signs in sheep?
Taenia multiceps
What protozoa cause inflammation in CNS in dogs, progressing to polyradiculoneuritis and hind limb paralysis?
Neospora caninum
Toxoplasma gondii
What are some immune mediated neurological diseases in dogs?
Necrotising/granulomatous/eosinophilic encephalitis/meningoencephalitis
What is an immune mediated neurological disease in horses?
Polyneuritis equi
What causes of CNS disease cause non suppurative inflammation?
Viral
Protozoal
Autoimmune/idiopathic
What are the 3 different types of CNS trauma?
Contusion - transient deformation, haemorrhage but tissue intact
Laceration - disruption of tissue
Compression - persistent deformation of tissue
What is the area of impact on the skull called?
The coup
What is the term for when the skull accelerates faster than the brain?
Inertia
What are the primary and secondary brain injuries from blunt trauma?
Primary - initial forces, nervous tissue and vascular injury
Secondary - Altered blood flow, ischaemia, oedena, herniation
What is the most common cause of spinal cord trauma?
Intervertebral disc herniation
What is hansen type 1 prolapse of the intervertebral disc?
Rupture of the dorsal annulus and massive extrusion of nucleus pulposus into the spinal canal
Causes sudden traumatic contusion and compressive injury to the spinal cord
What is hansen type 2 prolapse of the intervertebral disc?
partial rupture or bulging of the nucleus pulposus into the spinal canal
Slower onset
Compression of spinal cord
Which type of intervertebral disc prolapse is seen in what type of dogs?
Type 1 - young chondrodystrophic breeds
Type 2 - middle and older aged
non-chondrodystrophic dog breeds
What is neuropraxia when classifying peripheral nerve injury?
Compressive injury causes local demyelination - nerve remain intact but conduction interrupted
No wallerian degeneration - will gain function back but takes hours to months
What is axonotmesis when classifying peripheral nerve injury?
Axon disruption but preservation of the connective tissues
Wallerian degeneration distal to the injury
Regeneration takes months to years
What is neurotmesis when classifying peripheral nerve injury?
Axon disruption and partial or complete disruption of the connective tissues
Wallerian degeneration distal to injury
Regeneration may not be possible depending on severity
