A method of prognosing a course of disease progression and/or survival time in a subject diagnosed with ALS or FTD is disclosed. The method comprising: (a) detecting a level of miR-181 in a biological sample of the subject; and (b) determining the disease progression and/or survival time based on the level of the miR-181, wherein: (i) when the level of miR-181 is higher than that in a control sample, it is indicative of a rapid disease progression and/or poor survival; or (ii) when the level of miR-181 is about the same or lower than that in the control sample, it is indicative of a slow disease progression and/or good survival. Methods of prognosing a stage of disease in a subject diagnosed with ALS or FTD are also disclosed.