Haemangioblastomas are a rare form of brain tumor composed of blood vessel cells. They develop slowly as cysts, typically in the cerebellum, and are mostly noncancerous. Symptoms may include headache, vomiting, nystagmus (abnormal jerky eye movements), and ataxia (lack of muscle coordination) if the tumor is located in the cerebellum. Surgical removal is often feasible for most haemangioblastomas.