The follow-up of eight Japanese children with Langerhans cell histiocytosis (LCH)-related neurodegenerative central nervous system (ND-CNS) disease who were treated with intravenous immunoglobulin (IVIG) for >3 years is described. The patients developed ND-CNS disease at a median age of 5.2 (range 3.5-10.0) years and received IVIG treatment for a median duration of 6.5 + (range 3.7 to 10+) years. After a median follow-up period of 11.6 + (8.3+ to 13.9+) years after ND-CNS disease diagnosis, the median Expanded Disability Status Scale (EDSS) score of the eight patients was 4.0 (range 2.0-9.5). At the last follow-up as of March 2014, three patients have low EDSS scores (<3.0) and can walk without any assistance. Another three patients have EDSS scores of 3.5-4.5 and can walk by themselves, albeit occasionally with supports. However, the remaining two patients are wheelchair bound or bed ridden. The school performance of seven of the eight patients was below average. IVIG appeared to be most beneficial when it was administered soon after ND-CNS disease diagnosis when the EDSS scores were low (1.0-2.5). The patients who began receiving IVIG when their high EDSS scores were higher (4.5-7.0) appeared to obtain less benefit. To prevent progression of ND-CNS disease in patients with LCH, it is recommended to introduce IVIG early and to continue this therapy for >3 years.