Neuro - pathology Flashcards by Mary Tilling

What does myel- refer to?

Spinal cord

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What doe polio- refer to?

Grey matter

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What does leuko- refer to?

White matter

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What does radiculo- refer to?

Spinal nerve roots

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What does malacia mean?

Area of softening due to necrosis

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What is the name of the myelinating cells of the CNS?

Oligodendrocytes

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What are the gaps between the schwann cells?

Nodes of ranvier

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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

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What are the two morphological changes of the neuronal cell body to injury?

Chromatolysis
Neuronal necrosis

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What are the two morphological changes of axons to cell injury?

Axonal degeneration (wallerian degeneration)
Axonal regeneration

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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

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What are the two consequences of chromatolysis?

May be reversible
May progress to cell death

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What is neuronal necrosis? What are its characteristics?

Cell body change following irreversible injury
Deeply eosinophilic
Condensed nucleus (pyknosis)
Shrunken/swollen
Angular cytoplasm

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What are the consequences of neuronal necrosis?

Death of cell body results in degeneration of the axon
Necrotic neurones are cleared by phagocytes

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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

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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

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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

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What grow during axonal regeneration?

Schwann cells form columns in endoneurial tube
Axonal sprouts grow along endoneurial tube and is remyelinated

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What are the 3 outcomes of axonal regeneration?

1 - Restored function
2 - Axon regeneration without restored function
3 - Unsuccessful regeneration and neuronal atrophy

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What causes axonal regeneration without restored function?

Endoneurial tubes misaligned

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What can cause unsuccessful axonal regeneration and neuronal atrophy?

Fibrosis blocking axonal stump
Loss of integrity of endoneurial tube

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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

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What inflammatory infiltrate do bacterial and fungal infections cause?

Suppurative - neutrophils

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What inflammatory infiltrate do viral infections cause?

Non-suppurative - lymphocytes, plasma cells, macrophages

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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