What is the prognosis for patients with frontotemporal dementia and motor neuron disease? A new study suggests the answer depends not on which occurs first, but whether cognitive and motor symptoms develop simultaneously.1 The study was presented at the Annual Meeting of the American Academy of Neurology.
Between 5% and 10% of patients with amyotrophic lateral sclerosis (ALS) develop frontotemporal dementia (FTD), and about the same percent of these patients develop motor neuron degeneration. There is little data available on the natural history of the combination of the 2 diseases. The dementia symptoms of the 2 disorders are very similar, according to lead study author William Hu, MD, PhD, a fellow in the department of neurology at the University of Pennsylvania, so the question arises whether the 2 disorders are actually the same. “If the survival of the 2 is different, then we have reason to make the distinction, but if it is similar, and other characteristics are similar, there may be a reason to think they are the same disease.”
Dr. Hu, along with colleagues at 5 other centers in the United States and The Netherlands, examined 87 patients with both disorders. Of these patients, 60 had developed cognitive symptoms first, 19 developed motor symptoms first, and 8 had simultaneous onset of motor and cognitive symptoms. The FTD-first and ALS-first patients were similar for both disease duration until onset of the secondary motor or cognitive symptom, and for survival after secondary onset. “The majority of these patients have very short survival, and it doesn't matter if you start with 1 symptom or the other,” Dr. Hu said.
There were 2 subgroups that had a different pattern, though. A small number of patients with FTD survived for significantly longer than the rest, although once they developed motor symptoms, they progressed at a similar rate to the main group. The second group, those who had simultaneous onset of both motor and cognitive symptoms, did much worse, progressing much more rapidly than other patients.
“We counsel our ALS patients that if they develop dementia symptoms, their prognosis is slightly poorer than if they do not,” translating to about a 1-year decrease in expected survival, Dr. Hu said. One hypothesis for the decline in survival is that compliance with 2 key supportive therapies—assisted ventilation and a feeding tube—is impaired in cognitively affected patients. “But we hypothesize there is a biological reason as well,” he said.
1. Hu W, Seelaar H, Josephs K, et al. Clinical and Survival Profiles of Patients with Frontotemporal Dementia and Motor Neuron Disease [P09.163]. Poster Session IX: Behavioral Neurology II, May 1, 2009.