====== Creutzfeldt-Jakob Disease Diagnosis ======

===== Diagnostic criteria =====

The complete “diagnostic triad” ([[dementia]], [[myoclonus]], and periodic EEG activity) may be absent in up to 25% of cases of [[Creutzfeldt-Jakob Disease]]. Diagnostic criteria have been published
((Brown P, Cathala F, Castaigne P, Gajdusek DC. [[Creutzfeldt-Jakob disease]]: clinical analysis of a consecutive series of 230 neuropathologically verified cases. Ann Neurol. 1986 Nov;20(5):597-602. doi: 10.1002/ana.410200507. PMID: 3539001.)) 
No patients in their series with a diagnosis other than CJD fulfilled the criteria for clinically definite CJD. The most common condition other than CJD fulfilling the criteria for clinically probable CJD was [[senile dementia of the Alzheimer type]] (especially difficult to distinguish in the early stages). 
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In patients with [[dementia]], a positive [[immunoassay]] for the [[14-3-3 protein]] in [[cerebrospinal fluid]] strongly supports a diagnosis of [[Creutzfeldt-Jakob disease]]. This finding, however, does not support the use of the test in patients without clinically evident dementia
((Hsich G, Kenney K, Gibbs CJ, Lee KH, Harrington MG. The 14-3-3 brain protein in cerebrospinal fluid as a marker for transmissible spongiform encephalopathies. N Engl J Med. 1996 Sep 26;335(13):924-30. doi: 10.1056/NEJM199609263351303. PMID: 8782499.))


===== Diagnostic tests =====

==== Imaging ====
No characteristic [[CT]] or [[MR]] finding. These studies are frequently normal but are essential to rule out other conditions, (e.g. [[herpes simplex encephalitis]], recent stroke…). Diffuse atrophy may be present, especially late. MRI may show increased intensity on [[T2 weighted image]] in areas typically involved (basal ganglion, striatum) in up to 79% of cases (retrospectively)
((Finkenstaedt M, Szudra A, Zerr I, et al. MR Imaging of Creutzfeldt-Jakob Disease. Radiology. 1996; 199: 793–798)).
This is nonspecific but may help differentiate CJD from [[senile dementia of the Alzheimer type]]
((Gertz H-J, Henkes H, Cervos-Navarro J. Creutzfeldt- Jakob Disease: Correlation of MRI and Neuropathologic Findings. Neurology. 1988; 38:1481–1482)).

==== Blood tests ====
Serum assays for [[S-100]] protein are so insensitive and nonspecific that it can only
be used as a diagnostic adjunct

==== CSF ====

[[Cerebrospinal fluid analysis for Creutzfeldt-Jakob Disease Diagnosis]].



==== EEG ====
Characteristic finding of bilateral, symmetrical, periodic bi- or triphasic synchronous sharpwave
complexes, AKA periodic spikes, AKA pseudoperiodic sharp-wave complexes (0.5–2 per second)
have ≈ 70% sensitivity and 86% specificity. They resemble PLEDs, but are responsive
to noxious stimulus (may be absent in familial CJD19 and in the recent UK variant 

==== SPECT scan ====
May be abnormal in vCJD even when EEG is normal36; however, the findings are not
specific for vCJD.

==== Tonsillar biopsy ====
Patients with variant CJD (vCJD) may have detectable levels of variant type 4 of
the abnormal prion protein (PrPSc) in their lymphoreticular system, which may be accessed by a
1cm wedge-biopsy of one palatine tonsil (using careful aseptic precautions)

==== Brain biopsy ====

[[Brain biopsy for Creutzfeldt-Jakob Disease Diagnosis]].