There is a household historical past of constitutional delay in the boy's father, given his continued development during school. This reveals that neurons can't themselves provide thiols but as a substitute rely on astrocytes. Recognized causes embody connective tissue illness, particularly systemic sclerosis: cervical rib or thoracic outlet syndromes; vibration white nger; hypothyroidism; and uraemia muscle relaxant parkinsons disease purchase generic methocarbamol canada.