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Zhao et al. Developments in auxiliary examination of CJD

and cortex. [54,55] MRS imaging in brain tissue of basal ganglia or thalamic hypometabolism in CJD
CJD patients, especially striatum, display moderate patients, while the FFI patients only present a
reduction in NAA, suggesting neuronal loss or slight hypometabolism in the thalamus. Generally,
dysfunction. H-MRS can detect the absence of NAA, hypometabolism is more frequent and more severe in
1
creatine and choline peaks in late-stage CJD patients, cerebral lobe cortex than in basal ganglia structures,
indicating no neuronal activity. and rarely in cerebellum and brainstem. The
[57]
metabolic alterations on PET appear earlier than DWI
The metabolic changes of MRS can be detected hyperintensities, partly because some vacuoles in
in the initial clinical course of CJD, prior to the hypometabolism tissue are too small to be detected by
abnormal changes detected in DWI. For instance, DWI. Some abnormal lesions which cannot be seen
the reduction in NAA/Cr ratio can be found on DWI can be detected by PET especially in the early
in the brain tissue of CJD patients when DWI stage of CJD duration, suggesting a higher sensitivity
hyperintensity is still negative. [53] In one research of PET. Others proposed PET was more sensitive
[42]
on the differential diagnosis of patients with rapidly than DWI for cortex, and DWI was more sensitive than
progressive neurological signs similar to the clinical PET for basal ganglia. [57]
symptoms of sporadic prion disease, 1 H-MRS
presented great diagnostic value. The percentage of PET is highly sensitive and an effective means of
correctly diagnosed prion cases was 86% for DWI, identifying early-stage tumors which is important
86% for thalamic NAA/Cr ratio, 90% for thalamic for the differential diagnosis of CJD, particularly in
NAA/mI ratio and 86% for CSF 14-3-3 protein. The identified from cases of paraneoplastic neurologic
prion disease patients had reduced NAA/Cr ratios syndromes which shares similar performance
≤ 1.21. In this study, researchers proposed that including rapidly progressing dementia, prominent
the combination of thalamic MRS and DWI may psychiatric symptoms, seizures and dystaxia. [19]
increase the diagnostic accuracy of the MRI scan, [56] Hypometabolism can also be detected in other
whereas, other studies indicate that these changes rapidly progressive dementia diseases by PET,
in metabolism are sensitive but nonspecific. NAA is however, data on the specificity of PET among a
a neuronal marker that decreases in many conditions large populations are limited. In Alzheimer’s disease,
of neuronal injury, including degenerative disease. the parietal lobe and the temporal lobe are most
And myo-inositol is a glial marker, increased in glial likely involved in hypometabolism on PET, whereas
proliferation. The increased myo-inositol may also abnormal signals are less pronounced or occur later
be found in Alzheimer’s disease, herpes simplex in the frontal lobe. In dementia with Lewy bodies,
encephalitis, neuro-cysticercosis and progressive hypometabolism is most frequently detected in the
multifocal leukoencephalopathy. [53] Although MRS occipital and temporoparietal cortex together with
can quantitatively reveal the changes of chemical contrary hypermetabolism in putamen and pallidum.
components in brain tissue infected by CJD, the Hypometabolism in thalamic and upper brainstem
studies on the diagnostic value of MRS lack specificity can be observed in progressive supranuclear palsy. [57]
data. Larger sample controlled clinical trials are Further study should be carried out to explore the
certainly needed. value of PET for differential diagnosis between CJD
and other rapidly progressive dementia diseases.
18F-FDG PET/CT
18F-FDG PET/CT is a nuclear medicine examination In addition, some studies have reported that
method that can reveal the glucose metabolism of the abnormal hyperintensities on DWI and
tissue without influence on the internal environment hypometabolism areas on PET are correlated with
of human body. Clinical use of PET is now well the clinical symptoms. [19,42,58] For instance, abnormal
established in early diagnosis of tumor, Parkinson’s changes in basal ganglia predict extrapyramidal
disease, Alzheimer’s disease and in the accurate tract signs and the radiographic abnormality appears
positioning of epileptogenic focus. PET is also used to earlier than clinical symptoms. Additionally, there are
study neural receptors, neurotransmitters, and clinical consistencies among the regions of abnormalities on
pharmacology. Theoretically, there is hypometabolism DWI, PET and the regions of PSWCs. [59,60]
in the CJD patients’ brain tissue, which is probably
related to vacuolation and PrPsc accumulation. DEVELOPMENTS OF AUXILIARY
PET, as one of the most sensitive techniques to EXAMINATION CAUSING A REVOLUTION IN
detect glucose metabolism of tissue, may be of great DIAGNOSTIC CRITERIA
value for early diagnosis and appropriate differential
diagnosis of CJD. PET is expected to detect cortical, Pathology results from autopsy and brain biopsy
140 Neuroimmunology and Neuroinflammation ¦ Volume 4 ¦ July 21, 2017