A clinical examination technique for mild upper motor neuron paresis of the arm

Recognizing subtle upper motor neuron arm paresis is fundamental to the neurologic examination.1 Although the pronator drift test is widely used, others have contributed observations: Souque (see reference 2) described abduction of all fingers in the outstretched paretic hand; Wartenberg3 observed finger spreading in a single patient asked to press down with his paretic hand; Alter4 described the digiti quinti sign (isolated little finger abduction with outstretched hands, palms downward). Although these signs are useful, there are inconsistencies concerning their elicitation and utility.

To achieve a rigorous examination technique, 50 consecutive patients (“training set”) with mild unilateral arm weakness were prospectively evaluated by the author. Mild weakness was defined as minimal reduction in strength inapparent to the patient’s family and coworkers but manifesting as subtle difficulty in routine activities. Patients were excluded if they had weakness from a peripheral nerve lesion and were included only after imaging demonstrated an appropriate CNS lesion. …