This study will examine the effectiveness of G-CSF in treating patients with amyotrophic lateral sclerosis (ALS) - a fatal neurological degenerative disease that causes adult-onset, progressive motor neurons loss in the spinal cord, brain stem and motor cortex. Patients develop progressive wasting and weakness of both upper and lower limbs, bulbar and respiratory muscles. Usually death from respiratory failure typically is within 3-5 years of diagnosis. Although there are various treatments for ALS, riluzole is the only approved treatment to delay the disease progression. G-CSF is an approved drug that is used to increase white blood cell counts. Moreover, G-CSF and its receptor are expressed by neurons. It acts anti-apoptosis by activating several protective pathways, stimulates neuronal differentiation of adult neural stem cells in the brain, and improves long-term recovery. G-CSF is a novel neurotrophic factor, and a highly attractive candidate for the treatment of neurodegenerative conditions such as ALS.