J Clin Pathol 1993;46:193-197

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How to tackle a possible Creutzfeldt-Jakobdisease necropsy

J E Bell, JW Ironside

IntroductionThe clinical diagnosis of Creutzfeldt-Jakobdisease is based on a history of rapidly pro-gressive dementia, presence of myoclonicmovements, and a characteristic electroen-cephalogram.' However, clinical features arenot always clearcut, and diagnostic overlapwith other forms of dementia, includingAlzheimer's disease, remains a problem inmany cases.2 Some patients have atypicaldementing illnesses which defy clinical cate-gorisation; post mortem examination is nec-essary to achieve correct diagnosis in all casesof atypical dementia and suspectedCreutzfeldt-Jakob disease. Most patients withclassic Creutzfeldt-Jakob disease display atleast some spongiform change in braintissue.' This well recognised neuropathologi-cal feature is strongly supportive of a diagno-sis of Creutzfeldt-Jakob disease, but is notpathognomonic because it is also found occa-sionally in cases of diffuse Lewy body diseaseand even in Alzheimer's disease.4 However,other histological features, such as neurofib-rillary tangles, senile plaques, and Lewy bod-ies assist in clarifying the final diagnosis.Creutzfeldt-Jakob disease can be transmittedto animals or man following inoculation ortransplantation of infected tissue.5 Researchhas shown that Creutzfeldt-Jakob disease andthe related Gerstmann-Straussler syndromeare characterised by the presence of prionprotein (PrP) which constitutes a significantpart, if not the whole, of the infective agent.8Recent progress in molecular biology hasidentified abnormalities in the PrP gene insome cases of familial Creutzfeldt-Jakob dis-ease and in other cases of familial dementiawith no characteristic pathology.9 These find-ings represent a challenge to the currentclassification of dementia and require urgentinvestigation. This places a very high priorityon performing necropsy in cases suspected ofhaving Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease resembles spon-giform encephalopathy in animals and theepidemic of bovine spongiform encephalo-pathy (BSE) has led to anxiety that theincidence of Creutzfeldt-Jakob disease willrise.'0 Because of this concern, the Depart-ment of Health has funded the setting up of a

nationwide surveillance project to monitorthe incidence of Creutzfeldt-Jakob disease,and this study is based in Edinburgh." Theclinical surveillance is supervised by Dr RWill to whom all patients with a likely diagno-sis of Creutzfeldt-Jakob disease should benotified. A very important part of the study isto obtain the brain for histological examina-tion in as high a proportion of Creutzfeldt-Jakob disease cases as possible. Althoughguidelines for Creutzfeldt-Jakob diseasenecropsies have been published before,'2-14the safety protocols contained therein need tobe updated in the light of current knowledge.The Creutzfeldt-Jakob disease agent is a cate-gory 2 pathogen which presents special haz-ards in that it survives formalin fixation.Some Creutzfeldt-Jakob disease cases are

cared for in neurology units, and a neu-ropathologist with access to a specialised"high risk" mortuary may be asked to do thenecropsy. In these circumstances, providedwith dedicated instruments, autoclavablepower saw, and full protective clothing, anextended necropsy, including removal of thespinal cord, can be undertaken. However,some cases occur in hospitals with no readyaccess to such facilities, and in these cases amore limited necropsy has to be performed.This article has been prepared in response tonumerous requests for practical guidance bygeneral histopathologists who have beenasked to perform a necropsy in a case of pos-sible or probable Creutzfeldt-Jakob disease. Itis possible to remove the brain in a way whichavoids contamination of staff and environ-ment in all mortuaries with standard facilities.The method is outlined below and illustratedin figs 1-8.

MethodTHE NECROPSYAttendance at the necropsy is limited to thepathologist and a maximum of two mortuarystaff. All staff should wear disposable suits,masks, visors and two pairs of rubber gloves.Details of additional protective equipment aregiven in the Addendum.The body is placed supine on the table

with the neck supported on a block so that

NeuropathologyLaboratory,Department ofPathology, UniversityofEdinburghJ E Bell,JW IronsideCorrespondence to:Dr J E Bell NeuropathologyLaboratory Western GeneralHospital Crewe RoadEdinburgh EH4 2XUAccepted for publication3 June 1992

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Figs 1-7 Necropsysequence for safe and"contained" brain removalin a case of suspectedCreutzfeldt-Jakob disease.

Figure I An absorbent pad and colected instruments arearranged before necropsy begins.

Figure 2 The scalp is reflected in the usual way.

the head does not project beyond the end ofthe table. The table beneath the head is cov-ered with impermeable material such as asheet of polythene which is then covered byan absorbent pad (fig 1). The necessary toolswhich are to be used in the necropsy are gath-ered on the absorbent pad. These includescalpel, T-chisel, electric saw, mallet, durastripper, forceps and scissors (fig 1).The scalp is incised and reflected in the

usual way and the skull is prepared for theapplication of the saw (fig 2).A large, clear, polythene bag is placed over

the head of the cadaver and secured withstring around the neck so that quite a quanti-ty of air separates the inside of the bag fromthe surface of the skull (fig 3). The electricsaw is then introduced through a hole in thetop of the bag which is sealed around theneck of the saw as far back as possible, butnot enclosing the air vents further back on theshaft. This arrangement should allow enoughmovement of the saw blade within the bag sothat it can be applied easily at any pointaround the circumference of the skull.Keeping the bag clear of the blade when it isswitched on, the skull cap is drilled in theusual way. All the bone dust collects at thebase of the bag. When this stage has beencompleted, the necropsy saw is removedthrough the hole at the top of the bag and thishole is resealed. The necropsy saw is laiddown on the absorbent pad (as are all otherinstruments before and after use).

With the polythene bag still in place overthe head, the skull cap is removed using T-chisel, mallet, and dura stripper introducedthrough small incisions on the superior sur-face of the bag (figs 4 and 5). The skull capfalls to the bottom of the bag.The polythene bag may now be removed,

handling with care because it contains bonedust and blood (fig 5). The skull cap isretained on the absorbent pad (fig 6).The dura is incised and reflected from the

surface of the brain. At this stage, a specimenof cerebrospinal fluid may be aspirated from

Figure3 The skull vault is partially drilled by an electricnecropsy saw within a polythene bag.

Figures 4 and 5 The skull cap is loosened and removed within the polythene bag.

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How to tackle a possible Creutzfeldt-Jakob disease necropsy

Figures 6 and 7 After removal of the polythene bag, the brain is detached and placed in a pre-weighed container offornalin.

the third ventricle and tissue for freezingremoved from the frontal lobes and from thecerebellum. These should be placed directlyin universal containers labelled with warningof hazard and with patient identification. Thebrain is subsequently removed in the usualway (fig 6) and placed directly into a pre-weighed container of 10% formalin which issimilarly labelled (fig 7). The container ishandled by a clean assistant who brings it tothe necropsy table. The container is sealedand weighed again to determine brain weight.Finally, the pituitary gland is removed andfixed in formalin. Phenol should not be addedto the formalin as it has been shown to beineffective in decontamination.'5The body is reconstituted in the usual way

by packing the skull cap with cotton wool andreplacing it before the scalp is sutured.

If desired, the body cavities may be openedand the organs examined as usual, with tissuesampling for histology. Care should be taken,as before, to avoid contamination of the mor-tuary environment. The organs should beexamined on the necropsy table, or possiblyin situ in the body cavities. Large absorbentpads with impermeable backing should be inplace under the cadaver.

Great care should be taken to avoid cutsand needle stick injuries, particularly fromcontact with sharp bony edges, and duringsewing up.

POST-NECROPSY PROCEDUREAll instruments apart from the necropsy saware gathered from the absorbent pad into alarge stainless steel dish, wrapped, and steamautoclaved at 136°C for 1 hour, after whichthey may be cleaned by routine methods. Thenecropsy saw is cleaned by wiping repeatedlywith 2N sodium hydroxide solution. Theabsorbent pad and impermeable table cover,together with all disposable clothing, are dou-ble bagged for incineration. After removal ofthe body, the table and necropsy suite arecleaned in the usual way. No special precau-tions are needed because the surfaces have

not been contaminated. However, if contami-nation is suspected, a solution of 2N sodiumhydroxide should be used for cleaning sur-faces by repeated wetting over 1 hour. Therecommended dilution of chlorine solutionfor decontamination (20 000 ppm of freechlorine)'6 is highly unpleasant to use andcorrosive to steel.The fixed brain can be stored safely in 10%

formalin, in a box and an outer polythenebag, pending histological study. Samples forfreezing should be double bagged and storedat - 70°C. Notification of the necropsy to theEdinburgh Creutzfeldt-Jakob disease Surveil-lance Unit (see below) will be followed bycollection of the specimens and, in duecourse, return of a full pathology report.Any tissue blocks from non-central nervous

system tissues may be decontaminated forroutine microtomy by immersion for 1 hourin 96% formic acid, after formalin fixationand before processing.'7

DiscussionThis method of containment for removal ofinfective necropsy brain tissue within a poly-thene bag has been recommended in the pastfor AIDS cases'8 where specialist pathologysuites were not available. It is equally suitablefor cases of suspected Creutzfeldt-Jakob dis-ease and is quite straightforward to under-take. It is hoped that use of this methodwould help to alleviate anxiety among pathol-ogy staff when confronted with cases ofCreutzfeldt-Jakob disease and would allowthe necropsy examination to proceed.Although spread of this disease is not thoughtto occur through contact with blood or bone,and the main risk remains inoculation,'6 it isclearly wise to limit contamination of staffand mortuary, which is why we recommenduse of a polythene bag during skull removal.The relative risk of potential infectivity islower in non central nervous system tissuesapart perhaps from spleen and lymphoid tis-sue,"9 and examination of the whole body

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may be thought desirable at necropsy, toestablish the cause of death.

Creutzfeldt-Jakob disease is a rare disorder;previous epidemiological studies have sug-gested an incidence of around 05-1/millionpopulation worldwide. Although a few casesof Creutzfeldt-Jakob disease have beenreported in laboratory technical staff,20 andvery recently in a pathologist,2' epidemio-logical studies have repeatedly failed todemonstrate an excess incidence ofCreutzfeldt-Jakob disease in health careworkers and post mortem room staff. In theUnited Kingdom the theoretical risk of trans-mission of the BSE agent to humans via thefoodchain might result in an illness similar toCreutzfeldt-Jakob disease, hence the need fora longterm national prospective survey ofhuman spongiform encephalopathies. Theneed for necropsy examination of (at least)the brain in suspected cases is of paramountimportance for diagnostic verification andresearch, particularly in relation to cellpathology, molecular biology, and transmissi-bility. We hope that the work of the NationalCreutzfeldt-Jakob disease Surveillance Unitwill continue to be supported by histopathol-ogists, neuropathologists, and their mortuaryand laboratory technical staff throughout theUnited Kingdom, on whose cooperation thisproject depends. Without this sort of help thestudy will not be successful and any possiblehazards of BSE to human health will remainundetected.The need for histological studies in sus-

pected cases of Creutzfeldt-Jakob disease maypose further difficulties in relation to tissuehandling in routine laboratories. The agent isclassified as a category 2 pathogen, for whichappropriate containment facilities are re-quired. Furthermore, special precautions arerequired in relation to tissue sectioning, thedisposal of contaminated laboratory fluids,and decontamination of equipment and worksurfaces. These restrictions make it impracti-

Figure 8 Additional hand protection is afforded by theuse ofchain mail gloves worn between two pairs of rubbergloves. These protect against cuts and grazes but not-needlestick injuries.

cable for many laboratories to process andsection Creutzfeldt-Jakob disease tissue, inwhich case the National Creutzfeldt-Jakobdisease Surveillance Unit will arrange the col-lection, examination, and reporting of suchmaterial on request. Small non-central ner-vous system tissue blocks which do notrequire further trimming may be easilydecontaminated by immersion in formic acidand processed routinely.

For further details of the NationalCreutzfeldt-Jakob disease Surveillance Projectand for copies of necropsy protocols and tis-sue handling, please contact Miss JMackenzie (the Unit Coordinator) atCreutzfeldt-Jakob disease Surveillance Unit,Old Pharmacy Building, Western GeneralHospital. Tel: 031 3322117.

Addendum

NOTE ON PROTECTIVE CLOTHING ANDEQUIPMENTDisposable clothing is now readily availablein necropsy suites. As an extra precautionagainst cutting injury, a pair of chain mailgloves can be worn between double rubbergloves (fig 8). These are surprisingly flexibleand convenient to use but do not preventneedle stick injuries and they are expensive(Suppliers-Arco, PO Box 21, Waverley St.,Hull HUI 2SJ. Tel: 0482 27678).

Because the polythene bag restricts theamount of aerosol and reduces the risk ofsplash during necropsy, the need for eye andrespiratory tract protection is minimised.However, the use of a visor is recommendedduring any neuropathological necropsy. Iffurther safeguard is desired, a ventilated visorshould be considered. These are light andcomfortable to wear, although bulky, andprovide a filtered stream of air down over theface, (Suppliers-Pureflo Safety Ltd., MoatHouse, Wheathampstead, St. Albans, Herts.AL4 8QT. Tel: 0582 834242).A necropsy saw, with detachable auto-

clavable head, is now available which isentirely suitable for all necropsy needs and isparticularly suited for use in possibleCreutzfeldt-Jakob disease cases. (Suppliers-Mercian Surgical Supply Co. Ltd., 10Wolverhampton Road, Warley, BirminghamB68 OLH. Tel: 021 429 1133). A differentmodel, the Medezine Swordfish (Suppliers-Alfred Cox (Surgical) Ltd, Edward Road,Coulsdon, Surrey, CR5 2XA. Tel: 081 6682131) has an advantage in that it can beattached to an extra filtration unit, thusreducing the amount of aerosol. However, theSwordfish is not autoclavable and, being ofbulky construction, is less convenient whenremoving spinal cords.

We are grateful to colleagues from all over the UnitedKingdom who have gone to a great deal of trouble to notify usof cases, remove brains, or arrange for cases to be moved tothe nearest suitable necropsy facility. We thank Mr L Brettfor expert photography and Miss J Mackenzie for typing themanuscript.

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