Editing Fatal insomnia (section)

==Diagnosis==
{{Technical|section|date=June 2024}}
Diagnosis is based on symptoms and can be supported by a [[sleep study]], a [[PET scan]] and [[genetic testing]] if the patient's family has a history of the disease. As with other prion diseases, the diagnosis can be confirmed only by a brain [[autopsy]] post-mortem. 

The real-time quaking-induced conversion (RT-QuIC), a highly sensitive assay that detects minute amounts of PrP<sup>Sc</sup> in the cerebrospinal fluid (CSF), has been reported to have a sensitivity of 50% in FFI and sFI.<sup>[Cracco et al. Handb Clin Neurol 2018][Mock et al. Sci Rep. 2021]</sup> However, this low sensitivity may change since the examination was based on a low number of cases, and the RT-QuIC technology is continuously evolving. 

A test that measures the cerebral metabolic rate of glucose by positron emission tomography (PET), referred to as [18F]-FDG-PET, has demonstrated severe hypometabolism of the thalamus bilaterally in FFI and sFI, also in the earliest stages of the disease. This hypometabolism then spreads, eventually impacting most cortical regions.<sup>[Cortelli et al. Brain 2006]</sup> The complexity and cost of this test currently impedes its use in routine diagnosis.

===Differential diagnosis===
Other diseases involving the [[PRNP|mammalian prion protein]] are known.<ref name="PanegyresBurchell2016">{{cite journal | vauthors = Burchell JT, Panegyres PK | title = Prion diseases: immunotargets and therapy | journal = ImmunoTargets and Therapy | volume = 5 | pages = 57–68 | year = 2016 | pmid = 27529062 | pmc = 4970640 | doi = 10.2147/ITT.S64795 | doi-access = free }}</ref> Some are transmissible ([[transmissible spongiform encephalopathy|TSEs]], including FFI) such as [[kuru (disease)|kuru]], [[bovine spongiform encephalopathy]] (BSE, also known as mad cow disease) in cattle and [[chronic wasting disease]] in American [[deer]] and [[Elk|American elk]] in some areas of the United States and Canada, as well as [[Creutzfeldt–Jakob disease]] (CJD). Until recently prion diseases were thought to be transmissible only by direct contact with infected tissue, such as from eating infected tissue, transfusion or transplantation; research suggests that prions can be transmitted by aerosols but that the general public is not at risk of airborne infection.<ref>{{cite magazine |url=https://www.wired.com/wiredscience/2011/01/airborne-prions-disease/ |title=Airborne prions make for 100 percent lethal whiff | vauthors = Mosher D |magazine=[[Wired (magazine)|Wired]] |date=13 January 2011 |access-date=20 May 2011}}</ref>