Difference between revisions of "CNS Idiopathic Conditions - Pathology"

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==Idiopathic Epilepsy==
 
 
 
* A seizure is a brain disorder which manifests as paroxysmal cerebral dysrhythmia.
 
** The episode has a sudden onset and ceases spontaneously.
 
** Seizures tend to recur.
 
* In epilepsy, individuals appear to have a low seizure threshold.
 
** This predisposes their neurons to depolarize of their own volition.
 
* "Idiopathic epilepsy" is said to occur when no other cause of seizuring is apparent.
 
 
 
===Pathogenesis===
 
 
 
* All seizures arise from a small group of neurons that periodically and spontaneously depolarize.
 
* In addition to being idiopathic (i.e. low seizure threshold), this sudden, uncontrolled neuronal discharge can occur due to:
 
** Structural causes
 
*** Neoplasms
 
*** Inflammation
 
*** Trauma
 
** Biochemical causes
 
*** Hypocalcaemia
 
*** hypoglycaemia
 
*** Hepatic encephalopathy.
 
 
 
==Pug Dog Encephalitis==
 
 
 
* A non-infectious [[CNS Inflammation - Pathology|central nervous inflammatory disease]]
 
* Affects pugs.
 
** Similar conditions are seen in yorkshire and maltese terriers.
 
* Officially known as necrotising meningoencephalitis of small dogs.
 
* Characterised by histological forebrain inflammation and necrosis.
 
* The disease is uniformly fatal.
 
** Corticosterid treatment has no effect.
 
 
 
==Granulomatous Meningoencephalitis==
 
 
 
* A non-infectious [[CNS Inflammation - Pathology|central nervous inflammatory disease]]
 
* May occur as:
 
** A disseminated disease
 
** A focal mass lesion
 
** A primary occular disease
 
* Brainstem signs are common, although the forebrain is primarily affected.
 
* May be incorrectly diagnosed as lymphoma.
 
* Changes are apparent in the CSF.
 
** There is usually a mononucloear pleocytosis.
 
** Sometimes only protein is elveated.
 
* Diffuse inflammatory changes or a mass lesion will be seen by advanced imaging.
 
** However, biopsy is required for a definative diagnosis.
 
* Life span is between 6 months and 1 year from diagnosis.
 
 
 
==Polyneuritis equi==
 
 
 
* A non-infectious [[CNS Inflammation - Pathology|central nervous inflammatory disease]]
 
* Polyneuritis equi (PNE) is an uncommon disease which affects mature horses
 
* Formerly known as 'cauda equina syndrome' or 'cauda equine neuritis'
 
* May occur as:
 
** A disease effecting the spinal nerve roots and ganglia of the cauda equina.
 
** A disease effecting the cranial nerves.
 
* Cauda equina disease is characterised by progressive loss of anal tone, tail paralysis, urinary and/or faecal incontinence, urine scalding of the hindlimbs, hyperaesthesia and muscle fasciculations over hindquarters.
 
* If the pelvic nerve roots are also involved, there may be changes in hindlimb gait.
 
* Cranial nerve signs may be apparent, including signs associated with facial nerve paralysis.
 
* Changes in the CSF are often non-specific.
 
** There is usually a moderate mononucloear pleocytosis.
 
** Protein is usually elveated.
 
* Histologically, the disease presents as a severe, chronic, destructive lymphocytic and histiocytic polyradiculoneuritis.
 
* Considered to be caused by a T-lymphocyte mediated response to myelin, followed by destruction of myelin and axons by macrophages
 
* Disease appears similar to:
 
** Guillain-Barré Syndrome (GBS), an autoimmune demyelinating diease in humans
 
** Experimental allergic neuritis (EAN) in laboratory animals
 
* Important differential diagnoses for progressive neurologic signs effecting the bladder, rectum, perineum, tail, penis and hindlimbs in horses include:
 
** Equine herpesvirus-1 myeloencephalopathy
 
** Sacral/coccygeal trauma
 
** Equine motor neuron disease
 
** Abberant parasite migration (e.g. ''Strongylus'')
 
** In endemic areas, ''Sarcocystis neurona'' myelitis (equine protozoal myelitis), rabies and ''rhodococcus equi'' myeloencepahlitis should also be considered.
 

Latest revision as of 13:37, 8 March 2011