Hi doctor my mother has a condition where she's not able to raise her left arm above shoulder level since childhood. She can pull the hand till stomach level on her own however she could never pull it above or move it. The hand functions normally and there is no pain. However she has never been able to pull that hand above shoulder level on her own but if someone else holds her hand and then pulls it up it goes up. But she cannot do it on her own ! Can anyone guide me why this is happening ? Is it a neurological disorder or something related to bone ? Would really appreciate some guidance or any kind of top of the head info on this.