Influence of stimulus location and limb position on motor responses in the comatose patient

Motor responses to standardized stimuli were evaluated in 18 comatose patients with abnormal motor reactions. Painful stimuli were applied to three areas: the supraorbital, sternal, and medial aspects of the arm. Stimulations were carried out with the upper limbs first flexed and then extended. The initial position of the arm significantly influenced the posturing pattern. With the arm initially flexed there was a significantly higher percentage of abnormal flexor reactions, and the opposite occurred with the arm initially extended. Supraorbital stimulation yielded a significantly higher number of extensor responses. Arm stimulation, instead, caused a higher percentage of abnormal flexor reactions. When painful stimulation was applied to an arm initially flexed, the percentage of extensor responses was extremely low. Conversely, supraorbital stimulation with the arms extended yielded the highest percentage of extensor responses. The study shows that, within the frame of abnormal motor responses, the same patient can exhibit different reactions according to the site of stimulation and initial position of the upper extremities. These patterns are fairly constant and should be borne in mind in the evaluation of comatose patients.