Frontotemporal dementia (FTD) is a progressive, degenerative brain disease that gradually destroys the ability to behave appropriately, empathize with others, learn, reason, make judgments, communicate and carry out daily activities. In people under age 60, FTD is the most common cause of dementia and affects as many people as Alzheimer’s disease in the 45-64 age group. Men are affected more commonly than women. There are several forms of the disease that lead to slightly different behavioral, language and/or motor symptoms. Due to the symptoms, FTD can be mistaken for Alzheimer’s disease, Parkinson’s disease or a primarily psychiatric disorder like depression, manic-depression, obsessive-compulsive disease or schizophrenia. There is no treatment or cure yet that can reverse the damage, but medications and lifestyle changes can help relieve the symptoms. FTD is not contagious.
Forms of Frontotemporal Dementia
Based on the distinct patterns of signs and symptoms, three different clinical syndromes have been grouped together under the category of “frontotemporal dementia” (FTD):
- Behavioral-variant frontotemporal dementia (bvFTD)
- Semantic dementia (SD) and
- Progressive non-fluent aphasia (PNFA).
Previously, researchers sometimes used “FTD” to refer only to bvFTD, which has also been called “frontal variant FTD” (fvFTD) or Pick’s Disease. The language variants (SD and PNFA) are sometimes grouped together under the term “primary progressive aphasia” (PPA). PPA has since been split into three subgroups: progressive non-fluent aphasia, semantic dementia and logopenic progressive aphasia (LPA). At autopsy, patients with LPA are often found to have Alzheimer’s disease, not FTLD. SD was previously referred to at times as “temporal variant FTD” (tvFTD).
A small number of people affected by FTD also develop motor neuron disease (FTD/MND), (sometimes called FTD with amyotrophic lateral sclerosis or FTD/ALS).
Corticobasal degeneration (CBD), also called corticobasal syndrome or corticobasal ganglionic degeneration, and progressive supranuclear palsy (PSP) are two related diseases that are not classified as FTD but often share some symptoms with FTD.
Image Brain MRI scans from a patient with behavioral variant frontotemporal dementia.
a | MRI scan of the case patient taken on initial presentation
b | MRI scan taken 2 years after initial presentation showing more-severe frontal atrophy. © 2010 Nature Publishing Group.
Behavioral Variant Frontotemporal Dementia (bvFTD)
Behavioral variant frontotemporal dementia (bvFTD) has also been referred to as “frontal variant FTD” (fvFTD) or “Pick’s disease.” Approximately 60% of people with any form of FTD have bvFTD. By definition, this form of FTD affects social skills, emotions, personal conduct, and self-awareness. Deficits in these functions most often reflect damage to specific regions within the frontal and temporal lobes. With damage to these areas, people may show mood and behavior changes including stubbornness, emotional coldness or distance, apathy and selfishness. Unlike Alzheimer’s disease, which affects a different area of the brain, many people with bvFTD don’t show any confusion or forgetfulness about where they are or what day it is, at least at first.
Semantic Dementia (SD)
Semantic dementia, which has also been called “temporal variant FTD,” accounts for 20% of FTD cases. Language difficulty, the predominant complaint of people with SD, is due to the disease damaging the left temporal lobe, an area critical for assigning meaning to words. The language deficit is not in producing speech but is a loss of the meaning, or semantics, of words. At first, you might notice someone substituting a word like “thingy” for more unusual words, but eventually a person with SD will lose the meaning of more common words as well. For example, early in the illness a patient might lose the word for a falcon, later-on forget the word for a chicken, then call all winged creatures “bird” and eventually call all animals “things.” Not only do they lose the ability to recall the word, but the concept of these words is also lost. “What is a bird?” might be a typical response for a patient with advanced SD. Reading and spelling usually decline as well, but the person may still be able to do arithmetic and use numbers, shapes or colors well. Names of people, even good friends, can become quite difficult for people with SD. Like the behavioral variant, memory, an understanding of where they are, and sense of day and time tend to function as before. Muscle control for daily life and activities tends to remain good until late in the disease. Some of these skills may seem worse than they actually are because of the language difficulty people with SD have when they try to express themselves.
When SD starts in the right temporal lobe, people in the early stages have more trouble remembering the faces of friends and familiar people. Additionally, these people show profound deficits in understanding the emotions of others. The loss of empathy is an early, and often initial, symptom of patients with this right-sided form of SD. Eventually people with right-sided onset progress to the left side and then develop the classical language features of SD. Similarly, left-sided cases progress to involve the right temporal lobe and then the person experiences difficulty recognizing faces, foods, animals and emotion. SD patients eventually develop classical bvFTD behaviors including disinhibition, apathy, loss of empathy and diminished insight. The time from diagnosis to the end is longer than for those with bvFTD, typically taking about six years.
Progressive Nonfluent Aphasia (PNFA)
PNFA accounts for only about 20% of all people with FTD. Unlike semantic dementia where the person maintains the ability to speak but loses the meaning of the word, people with PNFA have difficulty producing language fluently even though they still know the meaning of the words they are trying to say. The person may talk slowly, having trouble saying the words, and have great trouble with the telephone, talking within groups of people or understanding complex sentences. In recent years it has become apparent that many patients with PNFA go on to develop severe Parkinsonian symptoms that overlap with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) such as an inability to move the eyes side-to-side, muscle rigidity in the arms and legs, falls, and weakness in the muscles around the throat.
FTD with Motor Neuron Disease
Approximately 15% of patients with FTD also develop motor neuron disease (FTD-MND). Most often, this combination occurs in patients with bvFTD, and only rarely does MND arise in patients with SD or PNFA. MND affects motor nerve cells in the spinal cord, the brain stem (which sits on top of the spinal cord), and the cerebral cortex. Because the brainstem was once referred to as the “bulb”, you may hear some MND symptoms described as “bulbar symptoms”. The most common type of MND is amyotrophic lateral sclerosis (ALS), also called Lou Gehrig’s disease, which can occur as a purely motor disorder. More often, however, patients with ALS also have behavioral or cognitive problems similar to those seen in FTD. MND symptoms include slurring of speech, difficulty swallowing, choking, limb weakness or muscle wasting. In patients with FTD-MND, there is often (but not always) a family history of the disease, and scientists are getting closer to identifying gene mutations that cause the illness.