[Transcranial sonography (TCS) in evaluation of patients with essential tremor]

Essential tremor is one of the most common movement disorders characterized by combination of postural bilateral action tremor with frequency 4-12MHz. Diagnosis is based on clinical examination, while neuroimaging methods so far have limited role. Recent reports showed that substantia nigra (SN) hyperechogenicity detected by transcranial sonography (TCS) is a specific finding of Parkinsons disease (PD). Usefulness of TCS in distinguishing some basal ganglia disorders is well documented. However, only a few studies showed its usage in the differentiation of the ET as a potential misdiagnosis of the PD. The aim of this study was to determine the reliability of TCS in the differentiation of patients with ET, PD and healthy controls. TCS and clinical examination was performed on 120 individuals, including 40 PD patients, 40 patients suffering from ET and 40 matched controls. Bilateral SN hyperechogenicity over the margin of 0.20 cm2 was found in 90% of PD patients, 10% of healthy subjects and in 17% patients with ET. Interobserver agreement for this method was significant. TCS may serve as a practical and sufficiently sensitive neuroimaging tool in ET diagnosing and in distinguishing it from PD, its repeatability and accuracy might add to its practical value.