Saturday, 5 April 2014

Prions

High yield points on prions (harrison)
- infectious proteins
- no dna/rna
- death within 1yr of onset
- 50-75yrs age affected
- PrPc--->PrPsc
- chromosome 20 PRP gene PRNP protein
- dz can be infectious/genetic/sporadic
- biosafety level 2
- m/c=sporadic CJD(crutzfelt jacob dz) 85%
-others= familial CJD/fCJD, Fatal familial insomnia/FFI, Gerstmann straussler scheinker synd/GSSS
They are dominantly inherited
- KURU = seen in NEW GUINEA due to ritual CANNIBALISM
- Iatrogenic CJD = Dural/corneal graft, electrode, surgery, human GH, Gn
- Variant CJD = Teenage, europe, beef/cattle, bovine spongiform encephalopathy/mad cow dz
- FFI = substitution if asparagine for aspartic acid
- chronic wasting dz = highly communicable

Clinical features
- m/c myoclonus 90%
Persists during sleep
- dementia
- pyramidal symptoms like rigidity
- extrapyramidal symptoms like mask like face
- seizure
- GSS=ATAXIA(CEREBELLUM)
- FFI=INSOMNIA, dysautonomia
- variant CJD= dementia is a late feature

Investigations
-MRI= Cortical ribboning, basal ganglia hyperintensity
- EEG= 1-2Hz triphasic spikes
- Biopsy= spongiform degeneration
Radiology of prion disease :-
FLAIR MRI SEQUENCE USED COMMONLY

A, Normal FLAIR image at the level of the basal ganglia shows the thalamus is normally isointense or slightly hypointense relative to the putamen. This appearance is depicted with most sequences, particularly the FLAIR sequence.

B, Pulvinar sign of vCJD. FLAIR image shows marked, symmetrical hyperintensity of the pulvinar (posterior) thalamic nuclei. In this case, the pulvinar signal intensity was scored as grade 4 by both observers.

C, “Hockey-stick” sign of vCJD. FLAIR image shows symmetrical pulvinar and dorsomedial thalamic nuclear hyperintensity. This combination gives a characteristic “hockey-stick” appearance and was present in 93% of cases with FLAIR imaging.

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