Blink reflex recovery cycle distinguishes essential tremor with resting tremor from de novo Parkinson's disease: an exploratory study.

An increased R2 recovery component of the blink reflex (R2-BRrc) has been observed in Parkinson's disease (PD), cranio-cervical dystonia, dystonic tremor and essential tremor with associated resting tremor (rET), while the BRrc was reported normal in patients with essential tremor (ET). Distinguishing rET from tremor dominant PD (tPD) may be challenging especially in the first stages of the diseases, in the absence of DAT-SPECT investigation. We evaluated the possible usefulness of BRrc for differentiating subjects with de novo tPD from those with rET. We investigated R2-BRrc at interstimulus intervals (ISI) of 100, 150, 200, 300, 400, 500 and 750 ms in 11 participants with tPD, 10 with rET and 20 healthy controls. All participants underwent DAT-SPECT and cardiac MIBG scintigraphy. R2 recovery was significantly enhanced in tPD compared to controls at all investigated ISIs (p < 0.001), while in subjects with rET patients BRrc was significantly increased compared to controls at ISI 150, 200, 300, 400, 500 and 750 ms (p < 0.001). At ISI 100 R2-BRrc distinguished patients participants with de novo tPD from those with rET with a sensitivity, specificity and accuracy of 100%. Our findings demonstrate the usefulness of BRrc for differentiating de novo tPD from rET.