soldiers demonstrating a sternal rub A central stimulus is one which can only be successfully found if the brain is involved in the response to the pain (as opposed to peripheral stimuli, which can induce a result as a result of
reflex. The four commonly used central pain stimuli are: • the
trapezius squeeze - which involves gripping and twisting a portion of the
trapezius muscle in the patient's shoulder •
sternal rub - this involves creating a turning pressure (akin to a grinding motion with a pestle and mortar) on the patient's
sternum however it has been suggested that central stimuli are less suitable for the assessment of eye opening, compared to peripheral stimuli, as they can cause grimacing. There is also a statistical reason behind central pain stimuli being inaccurate, especially regarding the GCS, which depending on the patient's eye response, the total score, and thus severity of patients' condition, can be altered with varying prognostic accuracy. If the patient reacts to the central pain stimulus normally, then a peripheral stimulus is unlikely to be required, unless there is suspicion of localised
paresthesia or
paralysis in a particular limb. It has been claimed that supraorbital pressure and trapezius squeeze are more effective than the sternal rub or peripheral stimulation, but sternal rub remains the most common. Supraorbital and mandibular pressure may not be suitable for patients with head injuries, or those with periorbital swelling. ==Peripheral stimuli==