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Referrals:  a simple count of all the cases which have been referred to the National CJD Surveillance Unit for further investigation in the year in question.  CJD may be no more than suspected; about half the cases referred in the past have turned out not to be CJD.  Cases are notified to the Unit  from a variety of sources including neurologists, neuropathologists, neurophysiologists, general physicians, psychiatrists, electroencephalogram (EEG) departments etc.  As a safety net, death certificates coded under the specific rubrics 046.1 and 331.9 in the 9th ICD Revisions are obtained from the Office for National Statistics in England and Wales, the General Register Office for Scotland and the General Register Office for Northern Ireland.

Deaths: All columns show the number of deaths that have occurred in definite and probable cases of all types of CJD and GSS in the year shown. The figures include both cases referred to the Unit for investigation while the patient was still alive and those where CJD was only discovered post mortem (including a few cases picked up by the Unit from death certificates). There is  therefore no read across from these columns to the referrals column. The figures will be subject to retrospective adjustment as diagnoses are confirmed.

Definite cases: this refers to the diagnostic status of cases. In definite cases the diagnosis will have been pathologically confirmed, in most cases by post mortem examination of brain tissue (rarely it may be possible  to establish a definite diagnosis by brain biopsy while the patient is still alive).

Probable vCJD cases: are those who fulfil the 'probable' criteria set out in the Annex and are either still alive, or have died and await post mortem pathological confirmation. Those still alive will always be shown  within the current year's figures.

Sporadic: Classic CJD cases with typical EEG and brain pathology. Sporadic cases appear to occur spontaneously with no identifiable cause and account for 85% of all cases.

Probable sporadic: Cases with a history of rapidly progressive dementia, typical EEG and at least two of the following clinical features; myoclonus, visual or cerebellar signs, pyramidal/extrapyramidalsigns or akinetic mutism.

Iatrogenic:  where infection with classic CJD has occurred accidentally as the result of a medical procedure.  All UK cases have resulted from treatment with human derived pituitary growth  hormones or from grafts using dura mater (a membrane lining the skull).

Familial: cases occurring in families associated with mutations in the PrP gene (10 - 15%  of cases).

GSS: Gerstmann-Straussler-Scheinker syndrome - an exceedingly rare inherited autosomal dominant disease, typified by chronic progressive ataxia and terminal dementia. The clinical duration is from 2 to 10 years, much longer than for CJD.

vCJD: Variant CJD, the hitherto unrecognised variant of CJD discovered by the National CJD Surveillance Unit and reported in The Lancet on 6 April 1996. This is characterised clinically by a progressive  neuropsychiatric disorder leading to ataxia, dementia and myoclonus (or chorea) without the typical EEG  appearance of CJD. Neuropathology shows marked spongiform change and extensive florid plaques throughout the brain.

Definite vCJD cases still alive: These will be cases where the diagnosis has been pathologically confirmed (by brain biopsy).

Annex: Diagnostic criteria for variant CJD

I

II    

III   

IV   

Definite: IA (Progressive neuropsychiatric disorder) and neuropathological confirmation of vCJD (spongiform change and extensive PrP deposition with florid plaques, throughout the cerebrum and cerebellum)

Probable: I and 4/5 of II and III A and III B; or I and IV A