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Several studies have reported an increased risk to develop Parkinson's disease (PD) in essential tremor (ET) populations. Hyperechogenicity of the substantia nigra (SN) is a common transcranial sonography (TCS) finding in PD and has been suggested as a PD risk-marker in nonparkinsonian subjects. This study compared SN areas of 44 ET patients with 100 controls and 100 PD patients. Sixteen percent of ET patients had SN hyperechogenicity as compared with 3% of controls and 75% of PD patients. These findings might correspond to an increased risk of ET patients to develop PD. Long-term follow-up will show if those with hyperechogenic SN develop PD, while these without will not.
Stockner et al. (Tue,) studied this question.