A Single Center Pilot Study to Assess the Intra-observer Reliability of Measuring Muscle Strength Using a Hand Held Dynamometer in Children and Adults With Neurofibromatosis Type 1 (NF1) and Type 2 (NF2)

Strength of one weak muscle group and of the biceps of the dominant arm will be measured using a hand-held dynamometer. An average of three readings will be used as one observation. Three observations per patient will be obtained on one day with a minimum of 15 minute rest period between each observation.