These later disorders overlap with a disorder previously known as Pick's disease.
These subtypes are connected by very complex clinical and, more importantly, pathological underpinnings, but also share substantial overlaps which, in reality, create a continuum of disease expression, especially as the disorders unfold over time.
This article will focus upon the behavioral variant. This area of clinical neuroscience is among the most complicated and dynamic arenas in all of neuroscience.
Symptoms and Etiology
The frontal lobes in Homo sapiens act to create truly advanced "social" animals; they shape goal-directed behaviors, motivation and our innate awareness of ourselves and those around us. The first symptoms in bvFTD are variable although most patients show dramatic changes in executive control (planning / executing adaptive behaviors) or personality.
Characteristic behaviors are an acquired change in social interactions, which tend to exclude the well being of those around the affected person (manifested as indifference, lack of concern and/or loss of insight).
Antisocial behaviors-including theft, reckless driving, and indecent exposure-can lead the FTD patient to be arrested. Some patients become socially withdrawn, leading to a misdiagnosis of depression. Apathy, overeating, disinhibition, hypersexuality and repetitive compulsive behaviors are common early features driven by degeneration of specific areas of the brain which modulate these activities. Ad- diction-related behaviors-including alcoholism, suicide, schizophrenia, sociopathy and bipolar disorder-are common initial diagnoses for individuals with FTD.
The bvFTDs are among the most challenging, and to a certain extent, devastating degenerative disorders seen on a routine basis by specialists. Many patients with bvFTD are considered initially to have purely psychiatric disorders, as basic cognitive skills may be well preserved in the first few years. Some individuals tragically end up within the legal system (e.g. incarceration) due to socially unacceptable behaviors. Other domains of the mind, such as cognitive capacities (e.g. language, memory, visuospatial functioning, etc.), invariably become impaired as the disorder progresses.
Diagnosis and Treatment
In experienced hands, characteristic bvFTD is readily diagnosed by routine clinical methods, including detailed neuropsychological testing. As the disorder progresses, brain imaging demonstrates the expected loss of tissue in the affected regions. Genetic testing is available on a research basis. Unfortunately, as with all the primary de- generative dementias, no disease-modifying interventions have been developed to date. However, a select number of medications (in particular the SSRI-class agents) can modulate unacceptable behaviors.
The FTD group of disorders, although uncommon and not a major health problem numerically in relationship to AD and other more common forms of dementia, have created a rapidly evolving scientific test-bed for understanding the basis of acquired brain degeneration. Researchers have now discovered that related (connected) brain circuits appear to "degenerate" in concert. The same processes we see in normal early brain development demonstrate a reverse process or "unraveling" due to the accumulation of misfolded, native structural or signaling proteins within specific nerve cells.
It now appears that all the common dementias share this property. Thus, developments in one research arena will undoubtedly impact another. In a quiet way, the very complex arena of the FTDs may unlock keys to combating the impending tsunami of dementias, which will inevitably descend upon our long-living human populations. From a basic research standpoint, understanding the most unique and complex part of our own legacy, the frontal lobes, remains a rewarding endeavor in itself.