Transcranial sonography findings in Parkinson’s disease and essential tremor: cases report* Achados de ultrassonografia transcraniana na doença de Parkinson e no tremor essencial: relato de casos

eases coursing with parkinsonian symptoms, particularly PD and ET. TCS is harmless, low-cost, performed with widely available equipment and does not require patient sedation. The greatest limitation of this technique is dependence on the temporal acoustic window to allow the ultrasound waves to overcome the bone barrier and generate two-dimensional images of intracranial structures. This accounts for 10% to 20% of failure of the method to obtain useful diagnostic images. Many authors reported key TCS finding in PD patients – expanded area of SN echogenicity > 0.20 cm –, in up to 90% of cases. In the Hospital Universitário Clementino Fraga Filho da Universidade Federal do Rio de Janeiro (HUCFF-UFRJ), a study is currently going on about the usefulness of the method for the diagnosis of PD in the Brazilian population. In a pilot study, 88% of the PD patients presented expanded area of SN echogenicity, corroborating the good sensitivity of the method for detecting the disease. However, the finding of the marker in individuals within the control group (false-positive results), reduced the technique specificity to approximately 82%. Recent prospective ditions present distinctive clinical courses – PD is more severe –, as well as distinctive therapeutic approaches. For that reason, neuroimaging studies such as brain computed tomography and magnetic resonance imaging are requested, however without providing a sure diagnosis of neither of the two entities, restricting the role of those imaging methods to that of ruling out causes of secondary parkinsonism, such as hydrocephalus, cerebrovascular disease, etc.. Functional neuroimaging, such as positron emission tomography (PET) or single-photon emission tomography (SPECT), might play a relevant role in the differential diagnosis because of their capability of identifying reduced striatal dopaminergic activity; but their high cost and limited availability outside of the large Brazilian research centers make their routine utilization unfeasible. Research on transcranial sonography (TCS) started in 1995 when investigators observed increased echogenicity at the mesencephalic substantia nigra (SN) site in patients with PD. The technique has been studied in several countries, with a high number of publications validating its usefulness in the differential diagnosis of disINTRODUCTION