Lack of a recognizable head http://www.healthline.com/symptom/poor-muscle-tone http://www.healthline.com/symptom/poor-muscle-tone http://www.healthline.com/symptom/poor-muscle-tone What Causes Poor Muscle Tone? http://www.healthline.com/symptom/poor-muscle-tone hypotonia http://www.healthline.com/symptom/poor-muscle-tone