Death usually occurs within 3 years of onset from inanition, pulmonary failure, and aspiration. They are more likely to have a bulbar form of MND, which may help explain its more aggressive course. No data are available about incidence and prevalence among racial groups. Men appear to be affected slightly more frequently than women, but this difference may not be significant. The mean age of onset in sporadic cases varies among series but overall is 55-65 years.
Familial cases tend to be younger.
Some patients become strikingly disinhibited, overactive, and frankly inappropriate with emotional lability. With disease progression, even those patients manifesting disinhibition and restlessness become increasingly apathetic. Stereotypic behavior and repetitive rituals of hoarding, dressing, wandering, and toileting can be observed. Dynamic spontaneous speech output progressively declines, resulting in anarthria and mutism. Visuospatial skills are relatively spared throughout illness, but there is significant memory impairment.