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316 Chapter 7: Nervous system

Lewy bodies – eosinophilic cytoplasmic neuronal in- does not contain any nucleic acid. It is resistant to

clusions, in some cases. These are also seen in Lewy many of the normal methods of sterilisation including
body dementia. heat.
Neuronal loss is seen from the cortex particularly in Sporadic CJD remains the most common type.

patients under the age of 80 years. Iatrogenic CJD (iCJD) results from transplantation
of tissue from an infected individual, such as corneal
grafts, cadaveric pituitary hormones and contami-
Investigations
nated neurosurgical instruments. No cases have been
The diagnosis is clinical although investigations to ex-
shown from blood transfusion products.
clude other causes of dementia are necessary. AD cannot
Variant CJD (vCJD) –1996 saw the identification of a
be definitively diagnosed until brain tissue is obtained,
‘new’ form of CJD primarily affecting younger peo-
e.g.atpost-mortem,butinmostcasesaclinicaldiagnosis
ple. There is reasonable evidence that this may be due
is accurate.
to the ingestion of Bovine Spongiform Encephalopa-
thy (BSE) infected beef. There have been reported
Management
cases of person-to-person transmission by blood
The management of AD includes those used for all types
transfusion.
of dementia.
In addition, for early AD, acetylcholinesterase in-
Pathophysiology
hibitors such as donepezil, have been shown to improve
Prion diseases appear to have a long incubation period,
cognitive function and delay decline by the equivalent of
but once clinically apparent, show rapid progression.
2months per year.
Neither the transmission nor the mechanism of action of
The gene of one of the enzymes which cleaves APP
the prion in CJD is clearly understood. There are other
(β secretase) has been cloned, leading to hopes of other
prion diseases such as
targeted therapies.
Kuru–which used to be prevalent in Papua New

Guinea and is believed to have been spread by ritual
Prognosis cannibalism.
Mostpatientsdiewithin5–10yearsofdiagnosis.Younger Scrapie in sheep and BSE in cattle.
patients appear to progress more slowly. Hereditarypriondiseasesduetomutationsinthegene
(PRNP) on chromosome 20 can cause several clini-
cal entities within the same kindred including CJD,
Creutzfeld–Jakob disease
Gerstmann–Straussler–Sheinker syndrome and fatal
Definition familial insomnia.
Rapidly progressive dementia caused by a prion (pro- It is currently thought that a normal glycoprotein
teinaceous infectious agent), described in 1982 by neu- in the brain (the function of which is unknown)
rologist Stanley Prusiner undergoes conformational change to become prion pro-
tein (PrP). This abnormally conformed protein is resis-
tant to digestion by proteases and tends to form poly-
Incidence
mers. The disease appears to be propagated further
One case per million worldwide.
by the abnormally conformed protein inducing nor-
mal protein to conformationally change, leading to fur-
Geography
ther polymer formation. In familial cases, it appears
More common in certain parts of the world due to fa-
that the abnormal protein arises spontaneously due to a
milial cases, e.g. Israel and North Africa.
mutation of the gene encoding PrP, whereas in other
cases there appears to be inoculation or ingestion of
Aetiology the prion, which is transported to the nervous sys-
Caused by a transmissable proteinaceous particle which tem and can then cause prion disease in susceptible
is a modified version of a normal human protein. It individuals.