Transcranial brain parenchyma sonography and DaTscan Spect in the diagnosis of Parkinson’s Disease: comparison between these two methods in real clinical practice

Parkinson's disease (PD) is the second most widespread neurodegenerative disorder, following Alzheimer's disease, and its prevalence grows with age, ranging from about 1% in those over 60 to roughly 4% in individuals over 85. It has been connected to a greater likelihood of developing dementia and a decreased life expectancy. The diagnosis of PD is typically made based on distinct clinical symptoms. These are tremor at rest, rigidity and bradykinesia, associated with an asymmetric disease onset and a positive response to levodopa. Along with motor symptoms, PD is also marked by at the presence of non-motor symptoms, which can include cognitive decline, autonomic dysfunction, sleep disturbances, and neuropsychiatric issues. The clinical picture, however, especially at the onset, can be vague or incomplete, making the diagnosis challenging. It is important to note that by the time typical motor symptoms manifest, over 60% of the nigrostriatal neurons have already been lost. SPECT is a widely recognized technique that can assist in the diagnosis. DaTscan (123I-FP-CIT) is a radioactive tracer with a strong binding affinity for the presynaptic dopamine transporter (DAT), offering a quantitative assessment of the number of functioning dopaminergic neurons in the striatum. However its specificity is low in early-phase disease, and it does not differentiate among PD and atypical parkinsonisms. Furthermore it is invasive and expensive. Transcranial brain parenchyma sonography (TCS) is an other diagnostic technique that allows non-invasive evaluation of the brain parenchyma and ventricular system. It can visualize the substantia nigra (SN) in the midbrain, which appears hyperechogenic in PD, as well as other structures in the diencephalon, such as the median raphe (RM) and lenticular nucleus (NL), which may be altered in certain atypical forms of parkinsonism, thus aiding in the differential diagnosis. Hyperechogenicity of the substantia nigra observed in Parkinson's disease has strong diagnostic predictive value, with numerous studies showing that it may precede the clinical onset of typical motor symptoms. However, it should not be associated with the duration of the disease. The purpose of this study was to submit a population of patients suffering from PD to SPECT and TCS and verify how they can be valid diagnostic support tools in clinical practice. In our study we have documented how both the SPECT exam and ultrasound represent undoubtedly useful methods in the correct diagnostic classification of PD patient. The nuclear medicine exam certainly appears more specific with regards to the localization aspect and in the correct identification of the correlation with the progression of the disability. On the contrary, the ultrasound exam, despite being less precise than the SPECT 123I-FP-CIT exam, has the indubitable advantage of being cheap, practical to perform and non-invasive. The data on SN hyperechogenicity does not appear to be associated with the clinical or demographic characteristics of the patients, the finding relating to the enlargement of the third ventricle, strictly correlated to the duration of the disease, appears to be of considerable interest also for the purpose of its possible use as biomarker in prodromal forms.