The "floating door sign" in Parkinson's disease

Individuals with Parkinson's disease (PD) display micrographia. We report a new method to elicit micrographic drawing in individuals with PD and compare this to drawing in individuals with essential tremor (ET). We asked 81 individuals with PD and 19 individuals with ET to draw a house and write a sentence. We examined house height and whether vertical lines of the door connected to the house floor. If both vertical door lines failed to reach the floor by more than 1mm we designated this a "floating door sign". House height of <5 cm and letter height of <5 mm were considered micrographic drawing and writing. 45 of 81 PD patients displayed a "floating door sign" compared with only 4 of 19 ET patients (p = 0.0103). 24 of 81 PD patients compared with 1 of 19 ET patients had micrographic writing (p = 0.0224). 60 of 81 PD patients compared with 9 of 19 ET patients had micrographic drawing (p = 0.00526). The "floating door sign" correlated with micrographic writing (p = 0.0275) but not micrographic drawing. The "floating door sign" had a positive predictive value for PD but not ET. We believe it correlates with hypometeric hand movements which cause inadequate stroke size, a phenomenon described in PD.