Acoustic reflex contraction of the stapedius muscle stiffens the middle-ear, thus decreasing middle-ear admittance; this can be measured thanks to tympanometry. The acoustic stapedius reflex can also be recorded by means of extratympanic manometry (ETM). As the stapedius muscle is innervated by the facial nerve, a measurement of the reflex can be used to locate the injury on the nerve. If the injury is distal to the stapedius muscle, the reflex is still functional. A measurement of the reflex can also be used to suggest a retrocochlear lesion (e.g., vestibular schwannoma, acoustic neuroma). The acoustic reflex normally occurs only at relatively high
Body fat percentage be an accurate technique to measure subcutaneous fat thickness. A-mode and B-mode ultrasound systems are now used and both rely on using tabulated values of tissue sound speed and automated signal analysis to determine fat thickness. By making thickness measurements at multiple sites on the body you can calculate the estimated body fat percentage. Ultrasound techniques can also be used to directly measure muscle thickness and quantify intramuscular fat. Ultrasound equipment is expensive, and not cost-effective solely for body fat measurement, but where equipment is available, as in hospitals, the extra cost for the capability to measure body fat is