Double dorsiflexion sign (DDFS) and double finger tap sign (DFTS): More tricks in the neurologist's bag for assessing non-physiological weakness?
Butt R, Shah K, Miller D, and Schultz L. Double dorsiflexion sign (DDFS) and double finger tap sign (DFTS): More tricks in the neurologist's bag for assessing non-physiological weakness? Neurology 2018; 90(15 Suppl 1):P5.333.
Objective: Testing accuracy of DDFS and DFTS in identifying inorganic paresis. Background: While physical exam maneuvers, such as the Hoover's and Abductor sign, can aid in differentiating patients with organic and non-organic weakness, many patients inevitably undergo intracranial imaging for evaluation. We propose two new physical exam techniques, DDFS and DFTS, which can assist in this differentiation. For DDFS, the patient dorsiflexes against resistance in both ankles individually, and then both simultaneously. Both groups of patients will have paresis in the affected limb when individually tested; however, during simultaneous testing, the inorganic patients will have transient improvement in the affected limb, followed by “give way” weakness in both limbs. For DFTS, the patient taps their index finger and thumb together in each hand individually, and then, simultaneously. Both groups of patients will have reduced speed in the affected hand when tested individually; however, during simultaneous testing, non-organic patients will have fluctuating speeds and amplitudes in both hands. Design/Methods: A prospective observational study of patients examined in a single center from 10/2016 - 10/2017. Patients were divided into controls (suspected organic weakness) and cases (suspected in organic weakness). DDF, DFT, Hoover and Abductor signs were performed. The exam findings were cross-verified using CT and MRI imaging, along with, attending assessments. Accuracy of the signs was analyzed using sensitivity and specificity along corresponding 95% confidence intervals. Results: 19 patients were enrolled, of which 16 were cases and 3 controls. DDFS identified inorganic paresis in 87.5% of patients (14/16) while DFTS identified inorganic paresis in 100% of the patients (11/11). All tests revealed high sensitivity with 100% specificity. Conclusions: In this selected group of patients, DDFS and DFTS appear a reliable method to screen between organic and non-organic paresis. Larger studies are warranted to further assess their validity in isolation, and in conjunction with the other established maneuvers.
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