Behavioral variant frontotemporal dementia (bvFTD)

bvFTD is the most common FTD syndrome. It is characterized by alterations in social decorum and personal regulation including disinhibition, apathy, overeating, emotional blunting, personality changes toward coldness and submissiveness, repetitive motor behaviors, and impairment in judgment and insight. With these behavioral changes, deficits in executive control emerge and patients have problems with planning, organizing, shifting patterns and generating ideas.

As bvFTD may be misconstrued as a midlife problem of adjustment or a psychiatric disorder, patients often do not reach the neurologist until they have profound lapses in financial or interpersonal judgment. Unlike in AD, where family and acquaintances are often sympathetic to the patient due to the sparing of social decorum, colleagues and family may resent patients with bvFTD because of their rudeness, coldness and deficits in social modulation.

Approximately 15% of patients develop ALS, and extrapyramidal deficits are common, particularly as the disease progresses. Both structural and functional imaging are helpful and typically show greater abnormalities in the right than the left frontal regions. The ventral and medial frontal and insular regions are hit early in bvFTD, driving the disinhibition, apathy and eating disorder. This atrophy is usually evident by the time that the patient presents to the office.

Semantic dementia (SD)

SD is a temporally predominant syndrome that attacks asymmetrically either the left or the right anterior temporal lobe involving the amygdala. In our experience, left-sided cases are more commonly recognized than are cases that begin on the right-side. In classical SD, patients show problems with word finding, often with nouns more than verbs. Speech remains fluent, but anomia worsens and patients show trouble both in naming and recognizing words. Compulsive interest in visually appealing objects is common, sometimes leading to repetitive playing of card games such as solitaire. As SD spreads to the right side, patients begin to have problems recognizing emotions in others. Eventually prosopagnosia and multimodality agnosia for objects develop.

Progressive non-fluent aphasia (PNFA)

A disorder that begins with deficits in speech or language, PNFA has an insidious onset. Often, the patient becomes aware of his or her deficits before others have noticed changes. Nonfluent aphasia emerges associated with decreased word output, while soon thereafter, shortened phrase length and deficits in articulation develop. The use of nouns remains intact, but deficits in the understanding of grammar and the use of verbs are common. Many patients exhibit speech apraxia, which is characterized by a deficit in articulatory planning resulting in an inability to command the speech musculature to produce sounds in a proper sequence. Social decorum remains intact throughout most of the illness, although some patients evolve to a bvFTD syndrome. Motor disorders characteristic of corticobasal degeneration (CBD) or progressive supranuclear palsy (PSP) are common several years after the onset of PNFA. Some patients evolve from PNFA to classical CBD or PSP over a fairly short period of time. Most patients with PNFA show tau pathology at autopsy.

FTD with motor neuron disease

In addition to the three subtypes of FTD, frontotemporal dementia can present in the context of motor disturbances as well. Three other disorders that commonly overlap with FTD are: corticobasal degeneration (CBD), progressive supranuclear palsy (PSP) and FTD with motor neuron disease (FTD-MND).

Traditionally, CBD was defined by the presence of asymmetric parkinsonism with dystonia, rigidity, limb apraxia and a “useless or alien” limb. Pathological examination demonstrates neuronal inclusions with tau present in astrocytes and neurons.

PSP has been described as a movement disorder associated with falls, ophthalmoplegia, axial rigidity and a frontal dementia. Like CBD, tau inclusions are seen postmortem. Recently, it has become evident that most patients with PNFA show PSP or CBD postmortem.

Patients with FTD-MND generally start with dementia symptoms, primarily behavioral changes such as disinhibition. Shortly after the onset of dementia, patients develop weakness and wasting of limb muscles. Typically, the respiratory complications of bulbar palsy are the cause of death, and patients live approximately 1.4 years after diagnosis.