Acquired brain injury (ABI) means brain damage caused by events after birth, rather than as part of a genetic or congenital disorders. Those with ABI suffer from cognitive, physical, or behavioral impairments limiting their activity and participation in society. ABI results from traumatic or non-traumatic brain injury due to internal or external source (e.g. infection, brain tumor, hypoxia). Preclinical studies regarding cell therapy in animal models of ABI showed improvements of neurological dysfunction. UCB possess various stem or progenitor cells and is known to secrete neurotrophic factors to repair injured brain. This clinical research aims to determine the safety and efficacy of allogeneic UCB for patients with ABI.