DEVIC'S disease,also known as neuromyelitis optica.
Introduction:
As the name suggests,it affects the nervous system esp the spinal cord and the optic nerve.
this is considered to be a variant of multiple sclerosis,a post viral encephalomyelitis,perhaps varicella as the causal element;although another school of thought says,its a separate entity,may be with an autoimmune etiology.
epidemiology:
this is more common in asians,than caucasians.
no sex prediliction.(remember multiple sclerosis liked female population more!)
young adults more commonly affected.
the optic involvment:
devic's is characterised by attacks of acute optic neuritis,usually bilateral.
this optic neuritis is often retrobulbar.
the myelitis:
at the same time as optic neuritis appears,or within few days of its appearance this optic neuritis is followed by severe transverse myelitis.
this can sometimes take weeks or even months to appear.
in a few 20% cases,this transverse myelitis can appear before optic neuritis becomes evident.
this acute transverse myelitis is usually with thoracic localization.
its ascending type.n when this reaches the cervical cord,respiratory failure is the most important complication.
THE RESULT:
due to the above mentioned lesions,the patient presents with marked loss of vision in both eyes,usually(optic neuritis).this is followed by numbness,muscle weakness,spasticity,incoordination,ataxia,urinary, bowel,sexual and autonomic dysfunction in parts of the trunk and limbs served by nerves exiting the spine below the spinal lesion(myelitis).
THE REMISSIONS n RELAPSES:
recovery from attacks of devic's is typically poorer than remissions from the relapsing multiple sclerosis,but the relapses are usually less frequent.
THE MRI:
the charactersitic lesion in MRI,is a TRANSIENTLY enhancing focal region of swelling and cavitation,that extends over three or more spinal cord segments.
the histopathology of these areas reveal areas of necrosis and thickening of blood vessel walls.
WATS THE DIFFERENCE:
the most obvious difference between multiple sclerosis n devic's is dat,the devic's typically attacks the optic tract,and spinal cord--and usually bilaterally.
wheras,MS lesions can appear anywhere in the CNS white matter,with of course a prefrence for the optic nerve,brainstem,corpus callosum and periventricular regions.
another characteristic difference is,
the OLIGOCLONAL BANDS in CSF.
this is seen characteristicaly in MS(90% cases),n is due to an increased production of IgG,in the CSF.
this oligoclonal band is absent in devic's.
the CSF in devic's,show pleocytosis,with PMN cells and a protein content that is higher than for MS.
The swelling n signal change on MRI and also the tissue destruction and cavitation,(already mentioned above),is seen more often n characteristically in devic's.
PROGNOSIS:
its a self limiting disease but with a poorer outcome than multiple sclerosis.
The role of disease modifying therapies is still under R&D.
the 5 yr survival rate is usually 70%.
Happy Devic's studying!
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