Behavioral Variant Frontotemporal Dementia (BvFTD)
BvFTD occurs when FTLD affects mainly the frontal lobes. Early symptoms in bvFTD usually include problems with social and emotional dysfunction. These can include loss of interest in previously enjoyed activities (apathy), loss of empathy, loss of knowledge about how to behave in social situations (often called disinhibition), and fixations or obsessions about certain topics or ideas to the exclusion of other activities and topics. There can sometimes be changes in eating habits in bvFTD, including being fixated on certain foods or overeating and craving sweet and starchy food. Cognitive problems in bvFTD often include difficulty with prioritizing and organizing, and getting easily distracted. BvFTD can be caused by either tau or TDP-43 protein dysfunction/accumulation, and can be either genetic (f-bvFTD) or sporadic (s-bvFTD).
Semantic Variant of PPA (SvPPA)
SvPPA occurs when FTLD affects the temporal lobes, especially in the left hemisphere of the brain. Symptoms of svPPA usually begin with trouble finding words for objects and people (including people well-known to the person) and early symptoms usually also include some trouble recognizing words (a person may ask, “what does that word mean?”). As the problem worsens, speech becomes more empty, with non-specific words like “thingie” being substituted for more specific words. Trouble recognizing faces of people who are well known can sometimes be an early symptom of svPPA. Most patients with svPPA also develop some of the social-emotional symptoms of bvFTD (see above), usually within a couple of years of the language symptoms, or sometimes before the language symptoms. SvPPA is usually caused by TDP-43 protein dysfunction/accumulation.
Non-fluent variant of PPA (NfvPPA)
NfvPPA occurs when FTLD affects the frontal lobe in the left hemisphere of the brain. Symptoms of nfvPPA usually begin with trouble finding pronouncing and articulating words, so that the person sounds as if they are stuttering or “tripping” over the words, and early symptoms may also include trouble thinking of the words one wants to say. This problem makes people slow down their speaking, and often they appear to have to think very hard and concentrate while speaking. Understanding other people is usually not a problem early in nfvPPA. NfvPPA is often caused by tau protein dysfunction/accumulation, but can also be caused by TDP-43 or other proteins.
Progressive Supranuclear Palsy (PSP)
PSP is a syndrome (sometimes called “Richardson’ssyndrome” after Dr. Richardson who first described it) where patients have difficulty with movement in combination with other problems including social-emotional function, cognitive functions, or language, depending on which parts of the brain are involved. The movement problems are due to involvement of the brainstem, and include stiffness and slowness of the body, poor balance with falling, and trouble with moving the eyes. Because of the eye movement trouble, patients with PSP can complain of visual problems such as reading or looking down to see things right in front of them (for instance looking down at their plate while eating). Family members may notice they do not make eye contact. The movement trouble can often be confused with the symptoms of Parkinson’s disease, although patients with PSP usually fall more often than patients with Parkinson’s disease. Patients with PSP may have social-emotional problems and cognitive similar to those in bvFTD, and language problems similar to those seen in nfvPPA. If they have problems with judgement, they may be unable to change their behavior to avoid falls. While PSP is defined by the movement problems in the body and eyes, it is now recognized that the other social-emotional, cognitive and language problems may be the earliest symptoms in PSP and the movement problems can emerge later. PSP is almost always caused by tau protein dysfunction/accumulation.
Corticobasal Syndrome (CBS)
CBS is similar to PSP in that it is another syndrome where patients have difficulty with movement in combination with other problems including social-emotional function, cognitive functions, or language. In contrast to PSP, there are no major problems with eye movement, and falling is much less of a problem. Early features in many patients with CBS include worsening stiffness affecting one side of the body (arm or leg), and this can be associated with any of the language, other cognitive, or social-emotional problems seen in bvFTD and PPA, sometimes in milder forms. Unusual sensations can be noted in the affected side of the body, and patients can sometimes complain of a feeling that the affected part of the body behaves in unwanted ways (moves unintentionally or even gets in the way of other movements). As in PSP, the cognitive, social-emotional or language problems can occur early and only be followed later by the movement trouble, so that a patient may initially get a diagnosis of nfvPPA, for instance, and later recognized as having CBS when movement trouble develops. CBS can often be difficult to distinguish from PSP if eye movement trouble develops only later in the illness. CBS is often caused by tau protein dysfunction/accumulation, but can also be caused by TDP-43, and Alzheimer’s disease.
Amyotrophic Lateral Sclerosis (ALS)
ALS, often called Lou Gehrig’s disease, is a caused by neurodegeneration in the nerves in the brain and spinal cord that control the muscles of the body. Because of the types of nerve cells involved, ALS is part of a group of disorders called motor neuron diseases (MND). The main symptoms of ALS are weakness, twitching and atrophy (shrinking) of the muscles of the limbs, torso, neck and face, usually starting in one part of the body and spreading to others. There is also stiffness of the limbs. ALS was not well recognized as being related to FTLD until it was discovered in the 2000’s that ALS is caused by TDP-43, one of the proteins that causes other FTLD syndromes. Although for most ALS patients, the main problem is with strength and movement, many have subtle problems with cognitive function, judgement and social-emotional function, and in some these problems are severe enough to be called bvFTD or PPA (these syndromes are often called FTD-MND).