The presenting symptom of dementia with Lewy bodies is often cognitive dysfunction, though dementia eventually occurs in all individuals with DLB. In contrast to Alzheimer's disease (AD), in which memory loss is the first symptom, those with DLB first experience impaired attention, executive function, and visuospatial function, while memory is affected later. These impairments present as driving difficulty, such as becoming lost, misjudging distances, or as impaired job performance. In terms of cognitive testing, individuals may have problems with figure copying as a result of visuospatial impairment, with clock-drawing due to executive function impairment, and difficulty with serial sevens as a result of impaired attention. Short-term memory and orientation to time and place remain intact in the earlier stages of the disease.

While the specific symptoms in a person with DLB may vary, core features include: fluctuating cognition with great variations in attention and alertness from day to day and hour to hour, recurrent visual hallucinations (observed in 75% of people with DLB), and motor features of Parkinson's disease. Suggestive symptoms are rapid eye movement (REM)-sleep behavior disorder and abnormalities detected in PET or SPECT scans. REM sleep behavior disorder (RBD) often is a symptom first recognized by the patient's caretaker. RBD includes vivid dreaming, with persistent dreams, purposeful or violent movements, and falling out of bed. Benzodiazepines, anticholinergics, surgical anesthetics, some antidepressants, and over-the-counter drug cold remedies may cause acute confusion, delusions, and hallucinations.

Tremors are less common in DLB than in Parkinson's disease. Parkinsonian features may include shuffling gait, reduced arm-swing during walking, blank expression (reduced range of facial expression), stiffness of movements, ratchet-like cogwheeling movements, low speech volume, sialorrhea, and difficulty swallowing. Also, DLB patients often experience problems with orthostatic hypotension, including repeated falls, fainting, and transient loss of consciousness. Sleep-disordered breathing, a problem in multiple system atrophy, also may be a problem.

One of the most critical and distinctive clinical features of the disease is hypersensitivity to neuroleptic and antiemetic medications that affect dopaminergic and cholinergic systems. In the worst cases, a patient treated with these medications could become catatonic, lose cognitive function, or develop life-threatening muscle rigidity. Some commonly used medications that should be used with great caution, if at all, for people with DLB, are chlorpromazine, haloperidol, or thioridazine.

Visual hallucinations in people with DLB most commonly involve perception of people or animals that are not there, and may reflect Lewy bodies or AD pathology in the temporal lobe. Delusions may include reduplicative paramnesia and other elaborate misperceptions or misinterpretations. These hallucinations are not necessarily disturbing, and in some cases, the person with DLB may have insight into the hallucinations and even be amused by them, or be conscious they are not real. People with DLB also may have problems with vision, including double vision, and misinterpretation of what they see, for example, mistaking a pile of socks for snakes or a clothes closet for the bathroom.

Progressive supranuclear palsy (PSP) is a form of dementia that is characterized by problems with eye movements. Generally the problems begin with difficulty moving the eyes up and/or down (vertical gaze palsy). Since difficulty moving the eyes upward can sometimes happen in normal aging, problems with downward eye movements are the key in PSP. Other key symptoms of PSP include falls backwards, balance problems, slow movements, rigid muscles, irritability, apathy, social withdrawal, and depression. The person may also have certain "frontal lobe signs" such as perseveration, a grasp reflex and utilization behavior (the need to use an object once you see it). People with PSP often have progressive difficulty eating and swallowing, and eventually with talking as well. Because of the rigidity and slow movements, PSP is sometimes misdiagnosed as Parkinson's disease.

On scans of the brain, the midbrain of people with PSP is generally shrunken (atrophied), but there are no other common brain abnormalities visible on images of the person's brain.

The symptoms of dementia vary across types and stages of the diagnosis. The most common affected areas include memory, visual-spatial, language, attention and problem solving. Most types of dementia are slow and progressive. By the time the person shows signs of the disorder, the process in the brain has been happening for a long time. It is possible for a patient to have two types of dementia at the same time. About 10% of people with dementia have what is known as "mixed dementia", which is usually a combination of Alzheimer's disease and another type of dementia such as frontotemporal dementia or vascular dementia. Additional psychological and behavioral problems that often affect people who have dementia include:

- Balance problems

- Tremor

- Speech and language difficulty

- Trouble eating or swallowing

- Memory distortions (believing that a memory has already happened when it has not, thinking an old memory is a new one, combining two memories, or confusing the people in a memory)

- Wandering or restlessness

- Perception and visual problems

- "Behavioral and psychological symptoms of dementia" (BPSD) almost always occur in all types of dementia. BPSDs may manifest as:

When people with dementia are put in circumstances beyond their abilities, there may be a sudden change to crying or anger (a ""catastrophic reaction"").

Psychosis (often delusions of persecution) and agitation/aggression also often accompany dementia.

The first symptoms are often mistakenly attributed to ageing or stress. Detailed neuropsychological testing can reveal mild cognitive difficulties up to eight years before a person fulfils the clinical criteria for diagnosis of AD. These early symptoms can affect the most complex activities of daily living. The most noticeable deficit is short term memory loss, which shows up as difficulty in remembering recently learned facts and inability to acquire new information.

Subtle problems with the executive functions of attentiveness, planning, flexibility, and abstract thinking, or impairments in semantic memory (memory of meanings, and concept relationships) can also be symptomatic of the early stages of AD. Apathy can be observed at this stage, and remains the most persistent neuropsychiatric symptom throughout the course of the disease. Depressive symptoms, irritability and reduced awareness of subtle memory difficulties are also common.

The preclinical stage of the disease has also been termed mild cognitive impairment (MCI). This is often found to be a transitional stage between normal ageing and dementia. MCI can present with a variety of symptoms, and when memory loss is the predominant symptom, it is termed "amnestic MCI" and is frequently seen as a prodromal stage of Alzheimer's disease.

The disease course is divided into four stages, with a progressive pattern of cognitive and functional impairment.

The symptoms of DLB overlap clinically with those of Alzheimer's disease and Parkinson's disease, but are associated more commonly with the latter. Because of this overlap, early DLB is often misdiagnosed. The overlap of neuropathological and presenting symptoms (cognitive, emotional, and motor) may make an accurate differential diagnosis difficult. In fact, DLB often is confused in its early stages with Alzheimer's disease and/or vascular dementia (multi-infarct dementia). However, while Alzheimer’s disease usually begins gradually, DLB frequently has a rapid or acute onset, with an especially rapid cognitive and physical decline in the first few months. Thus, DLB tends to progress more rapidly than Alzheimer’s disease. Despite the difficulty, a prompt diagnosis is important because of the risks of sensitivity to certain neuroleptic (antipsychotic) medications and because appropriate treatment of symptoms may improve life for both the person with DLB and the person's caregivers.

Dementia with Lewy bodies is distinguished from the dementia that sometimes occurs in Parkinson's disease by the time frame in which dementia symptoms appear relative to Parkinson symptoms. Parkinson's disease with dementia (PDD) would be the diagnosis when the onset of dementia is more than a year after the onset of Parkinsonian symptoms. DLB is diagnosed when cognitive symptoms begin at the same time or within a year of Parkinson symptoms.

FTD is traditionally difficult to diagnose due to the heterogeneity of the associated symptoms. Signs and symptoms are classified into three groups based on the functions of the frontal and temporal lobes:

- Behavioural variant frontotemporal dementia (BvFTD) is characterized by changes in social behavior and conduct, with loss of social awareness and poor impulse control.

- Semantic dementia (SD) is characterized by the loss of semantic understanding, resulting in impaired word comprehension, although speech remains fluent and grammatically faultless.

- Progressive nonfluent aphasia (PNFA) is characterized by progressive difficulties in speech production.

However, the following abilities in the person with FTD are preserved:

- Perception

- Spatial Skills

- Memory

- Praxis

In later stages of FTD, the clinical phenotypes may overlap. FTD patients tend to struggle with binge eating and compulsive behaviors. These binge eating habits are often associated with abnormal eating behavior including overeating, stuffing oneself with food, changes in food preferences (cravings for more sweets, carbohydrates), eating inedible objects and snatching food from others. Recent findings from structural MRI research have indicated that eating changes in FTD are associated with atrophy (wasting) in the right ventral insula, striatum, and orbitofrontal cortex.

Patients with FTD show marked deficiencies in executive functioning and working memory. Most FTD patients become unable to perform skills that require complex planning or sequencing. In addition to the characteristic cognitive dysfunction, a number of primitive reflexes known as frontal release signs are often able to be elicited. Usually the first of these frontal release signs to appear is the palmomental reflex which appears relatively early in the disease course whereas the palmar grasp reflex and rooting reflex appear late in the disease course.

In rare cases, FTD can occur in patients with motor neuron disease (MND) (typically amyotrophic lateral sclerosis). The prognosis for people with MND is worse when combined with FTD, shortening survival by about a year.

The most recognizable symptoms in Parkinson's disease are movement ("motor") related. Non-motor symptoms, which include autonomic dysfunction, neuropsychiatric problems (mood, cognition, behavior or thought alterations), and sensory (especially altered sense of smell) and sleep difficulties, are also common. Some of these non-motor symptoms may be present at the time of diagnosis.

Because CBD is progressive, a standard set of diagnostic criteria can be used, which is centered on the disease’s evolution. Included in these fundamental features are problems with cortical processing, dysfunction of the basal ganglia, and a sudden and detrimental onset. Psychiatric and cognitive dysfunctions, although present in CBD, are much less prevalent and lack establishment as common indicators of the presence of the disease.

Some of the most prevalent symptom types in people exhibiting CBD pertain to identifiable movement disorders and problems with cortical processing. These symptoms are initial indicators of the presence of the disease. Each of the associated movement complications typically appear asymmetrically and the symptoms are not observed uniformly throughout the body. For example, a person exhibiting an alien hand syndrome (explained later) in one hand, will not correspondingly display the same symptom in the contralateral limb. Predominant movement disorders and cortical dysfunctions associated with CBD include:

- Parkinsonism

- Alien hand syndrome

- Apraxia (ideomotor apraxia and limb-kinetic apraxia)

- Aphasia

The movement difficulties found in PD are called "parkinsonism" and a number of different disorders feature parkinsonism. "Parkinsonism" is defined as bradykinesia (slowness in initiating voluntary movements, with progressive reduction in speed and range of repetitive actions such as voluntary finger-tapping) in combination with one of three other physical signs: muscular (lead-pipe or cogwheel) rigidity, tremor at rest, and postural instability.

Parkinson's disease is the most common form of parkinsonism and is sometimes called "idiopathic parkinsonism", meaning parkinsonism with no identifiable cause. Identifiable causes of parkinsonism include toxins, infections, side effects of drugs, metabolic derangement, and brain lesions such as strokes. Several neurodegenerative disorders also may present with parkinsonism and are sometimes referred to as "atypical parkinsonism" or "Parkinson plus" syndromes (illnesses with parkinsonism plus some other features distinguishing them from PD). They include multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, and dementia with Lewy bodies (DLB).

Scientists sometimes refer to Parkinson’s disease as a synucleiopathy (due to an abnormal accumulation of alpha-synuclein protein in the brain) to distinguish it from other neurodegenerative diseases, such as Alzheimer's disease where the brain accumulates tau protein. Considerable clinical and pathological overlap exists between tauopathies and synucleinopathies. In contrast to Parkinson's disease, Alzheimer's disease presents most commonly with memory loss, and the cardinal signs of Parkinson's disease (slowness, tremor, stiffness, and postural instability) are not normal features of Alzheimer's.

Dementia with Lewy bodies is another synucleinopathy and it has close pathological similarities with PD, especially with the subset of PD cases with dementia. The relationship between PD and DLB is complex and incompletely understood. They may represent parts of a continuum with variable distinguishing clinical and pathological features or they may prove to be separate diseases.

Frontotemporal dementia (FTD) is the clinical presentation of frontotemporal lobar degeneration, which is characterized by progressive neuronal loss predominantly involving the frontal or temporal lobes, and typical loss of over 70% of spindle neurons, while other neuron types remain intact.

It was first described by Arnold Pick in 1892 and was originally called "Pick's disease", a term now reserved for Pick disease, one specific type of frontotemporal dementia. Second only to Alzheimer's disease (AD) in prevalence, FTD accounts for 20% of young-onset dementia cases. Signs and symptoms typically manifest in late adulthood, more commonly between the ages of 55 and 65, approximately equally affecting men and women.

Common signs and symptoms include significant changes in social and personal behavior, apathy, blunting of emotions, and deficits in both expressive and receptive language. Currently, there is no cure for FTD, but there are treatments that help alleviate symptoms.

Symptoms include mental deterioration, language disorder, transient ischemic attack, muscle ataxia, and impaired movements including change of walk, slowness of movements, and change in posture. These symptoms usually coincide with multiple falls, epilepsy, fainting, and uncontrollable bladder.

Because Binswanger’s disease affects flow processing speed and causes impaired concentration, the ability to do everyday tasks such as managing finances, preparing a meal and driving may become very difficult.

Differentiating the different dementia syndromes can be challenging, due to the frequently overlapping clinical features and related underlying pathology. In particular, Alzheimer's dementia often co-occurs with vascular dementia.

People with vascular dementia present with progressive cognitive impairment, acutely or subacutely as in mild cognitive impairment, frequently step-wise, after multiple cerebrovascular events (strokes). Some people may appear to improve between events and decline after more silent strokes. A rapidly deteriorating condition may lead to death from a stroke, heart disease, or infection.

Signs and symptoms are cognitive, motor, behavioral, and for a significant proportion of patients also affective. These changes typically occur over a period of 5–10 years. Signs are typically the same as in other dementias, but mainly include cognitive decline and memory impairment of sufficient severity as to interfere with activities of daily living, sometimes with presence of focal neurologic signs, and evidence of features consistent with cerebrovascular disease on brain imaging (CT or MRI). The neurologic signs localizing to certain areas of the brain that can be observed are hemiparesis, bradykinesia, hyperreflexia, extensor plantar reflexes, ataxia, pseudobulbar palsy, as well as gait and swallowing difficulties. People have patchy deficits in terms of cognitive testing. They tend to have better free recall and fewer recall intrusions when compared with patients with Alzheimer's disease. In the more severely affected patients, or patients affected by infarcts in Wernicke's or Broca's areas, specific problems with speaking called dysarthrias and aphasias may be present.

In small vessel disease, the frontal lobes are often affected. Consequently, patients with vascular dementia tend to perform worse than their Alzheimer's disease counterparts in frontal lobe tasks, such as verbal fluency, and may present with frontal lobe problems: apathy, abulia, problems with attention, orientation, and urinary incontinence. They tend to exhibit more perseverative behavior. VaD patients may also present with general slowing of processing ability, difficulty shifting sets, and impairment in abstract thinking. Apathy early in the disease is more suggestive of vascular dementia.

Rare genetic disorders which result in vascular lesions in the brain have other patterns of presentation. As a rule, they tend to present earlier in life and have a more aggressive course. In addition, infectious disorders, such as syphilis, can lead to arterial damage, strokes, and bacterial inflammation of the brain.

Tauopathy belongs to a class of neurodegenerative diseases associated with the pathological aggregation of tau protein in neurofibrillary or gliofibrillary tangles in the human brain. Tangles are formed by hyperphosphorylation of a microtubule-associated protein known as tau, causing it to aggregate in an insoluble form. (These aggregations of hyperphosphorylated tau protein are also referred to as paired helical filaments). The precise mechanism of tangle formation is not completely understood, and it is still controversial as to whether tangles are a primary causative factor in the disease or play a more peripheral role. Primary tauopathies, i.e., conditions in which neurofibrillary tangles (NFT) are predominantly observed, include:

- Primary age-related tauopathy (PART)/Neurofibrillary tangle-predominant senile dementia, with NFTs similar to AD, but without plaques.

- Chronic traumatic encephalopathy, including dementia pugilistica

- Progressive supranuclear palsy

- Corticobasal degeneration

- Frontotemporal dementia and parkinsonism linked to chromosome 17

- Lytico-Bodig disease (Parkinson-dementia complex of Guam)

- Ganglioglioma and gangliocytoma

- Meningioangiomatosis

- Postencephalitic parkinsonism

- Subacute sclerosing panencephalitis

- As well as lead encephalopathy, tuberous sclerosis, Hallervorden-Spatz disease, and lipofuscinosis

Neurofibrillary tangles were first described by Alois Alzheimer in one of his patients suffering from Alzheimer's disease (AD), which is considered a secondary tauopathy. AD is also classified as an amyloidosis because of the presence of senile plaques.

The degree of NFT involvement in AD is defined by Braak stages. Braak stages I and II are used when NFT involvement is confined mainly to the transentorhinal region of the brain, stages III and IV when there's also involvement of limbic regions such as the hippocampus, and V and VI when there's extensive neocortical involvement. This should not be confused with the degree of senile plaque involvement, which progresses differently.

In both Pick's disease and corticobasal degeneration, tau proteins are deposited as inclusion bodies within swollen or "ballooned" neurons.

Argyrophilic grain disease (AGD), another type of dementia, is marked by an abundance of argyrophilic grains and coiled bodies upon microscopic examination of brain tissue. Some consider it to be a type of Alzheimer's disease. It may co-exist with other tauopathies such as progressive supranuclear palsy and corticobasal degeneration, and also Pick's disease.

Huntington's disease (HD): a neurodegenerative disease caused by a CAG tripled expansion in the Huntington gene is the most recently described tauopathy (Fernandez-Nogales et al. Nat Med 2014). JJ Lucas and co-workers demonstrate that, in brains with HD, tau levels are increased and the 4R/3R balance is altered. In addition, the Lucas study shows intranuclear insoluble deposits of tau; these "Lucas' rods" were also found in brains with Alzheimer's disease.

Tauopathies are often overlapped with synucleinopathies, possibly due to interaction between the synuclein and tau proteins.

The non-Alzheimer's tauopathies are sometimes grouped together as "Pick's complex" due to their association with frontotemporal dementia, or frontotemporal lobar degeneration.

Pick's disease is a term that can be used in two different ways. It has traditionally been used as a term for a group of neurodegenerative diseases with symptoms attributable to frontal and temporal lobe dysfunction. Common symptoms that are noticed early are personality and emotional changes, as well as deterioration of language. This condition is now more commonly called frontotemporal dementia by professionals, and the use of "Pick's disease" as a clinical diagnosis has fallen out of fashion. The second use of the term (and the one now used among professionals) is to mean a specific pathology that is one of the causes of frontotemporal lobar degeneration. These two uses have previously led to confusion among professionals and patients and so its use should be restricted to the specific pathological subtype described below. It is also known as Pick disease and PiD (not to be confused with pelvic inflammatory disease (PID) or Parkinson's disease (PD)). A defining characteristic of the disease is build-up of tau proteins in neurons, accumulating into silver-staining, spherical aggregations known as "Pick bodies".

The symptoms of Pick's disease include difficulty in language and thinking, efforts to dissociate from family, behavioral changes, unwarranted anxiety, irrational fears, CBD (Compulsive buying disorder, or oniomania), impaired regulation of social conduct (e.g., breaches of etiquette, vulgar language, tactlessness, , misperception), passivity, low motivation (aboulia), inertia, over-activity, pacing and wandering. It is a characteristic of Pick’s disease that dysfunctional, argumentative, or hostile social conduct is initially exhibited towards family members and not initially exhibited in a workplace or neutral environment. The changes in personality allow doctors to distinguish between Pick's disease and Alzheimer's disease. Pick's disease is one of the causes of the clinical syndrome of frontotemporal lobar degeneration which has three subtypes. Pick's disease pathology is associated more with the frontotemporal dementia and progressive nonfluent aphasia subtypes than the semantic dementia subtype.

Binswanger's disease, also known as subcortical leukoencephalopathy, is a form of small vessel vascular dementia caused by damage to the white brain matter. White matter atrophy can be caused by many circumstances including chronic hypertension as well as old age. This disease is characterized by loss of memory and intellectual function and by changes in mood. These changes encompass what are known as executive functions of the brain. It usually presents between 54 and 66 years of age, and the first symptoms are usually mental deterioration or stroke.

It was described by Otto Binswanger in 1894, and Alois Alzheimer first used the phrase "Binswanger's disease" in 1902. However, Olszewski is credited with much of the modern-day investigation of this disease which began in 1962.

Vascular dementia, also known as multi-infarct dementia (MID) and vascular cognitive impairment (VCI), is dementia caused by problems in the supply of blood to the brain, typically a series of minor strokes, leading to worsening cognitive decline that occurs step by step. The term refers to a syndrome consisting of a complex interaction of cerebrovascular disease and risk factors that lead to changes in the brain structures due to strokes and lesions, and resulting changes in cognition. The temporal relationship between a stroke and cognitive deficits is needed to make the diagnosis.

The main symptom resulting from PCA is a decrease in visuospatial and visuoperceptual capabilities. Because the posterior region of the brain is home to the occipital lobe, which is responsible for visual processing, visual functions are impaired in PCA patients. The atrophy is progressive; early symptoms include difficulty reading, blurred vision, light sensitivity, issues with depth perception, and trouble navigating through space. Additional symptoms include apraxia, a disorder of movement planning, alexia, an impaired ability to read, and visual agnosia, an object recognition disorder. Damage to the ventral, or “what” stream, of the visual system, located in the temporal lobe, leads to the symptoms related to general vision and object recognition deficits; damage to the dorsal, or “where/how” stream, located in the parietal lobe, leads to PCA symptoms related to impaired movements in response to visual stimuli, such as navigation and apraxia.

As neurodegeneration spreads, more severe symptoms emerge, including the inability to recognize familiar people and objects, trouble navigating familiar places, and sometimes visual hallucinations. In addition, patients may experience difficulty making guiding movements towards objects, and may experience a decline in literacy skills including reading, writing, and spelling. Furthermore, if neural death spreads into other anterior cortical regions, symptoms similar to Alzheimer's disease, such as memory loss, may result. PCA patients with significant atrophy in one hemisphere of the brain may experience hemispatial neglect, the inability to see stimuli on one half of the visual field. Anxiety and depression are also common in PCA patients.

There are 3 main histological subtypes found at post-mortem:

- FTLD-tau is characterised by tau positive inclusions often referred to as Pick-bodies. Examples of FTLD-tau include; Pick's disease, corticobasal degeneration, progressive supranuclear palsy.

- FTLD-TDP (or FTLD-U ) is characterised by ubiquitin and TDP-43 positive, tau negative, FUS negative inclusions. The pathological histology of this subtype is so diverse it is subdivided into four subtypes based on the detailed histological findings:

Two physicians independently categorized the various forms of TDP-43 associated disorders. Both classifications were considered equally valid by the medical community, but the physicians in question have jointly proposed a compromise classification to avoid confusion.

- FTLD-FUS; which is characterised by FUS positive cytoplasmic inclusions, intra nuclear inclusions, and neuritic threads. All of which are present in the cortex, medulla, hippocampus, and motor cells of the spinal cord and XIIth cranial nerve.

Dementia lacking distinctive histology (DLDH) is a rare and controversial entity. New analyses have allowed many cases previously described as DLDH to be reclassified into one of the positively defined subgroups.

Mild cognitive impairment (MCI), also known as incipient dementia and isolated memory impairment, is a neurological disorder that occurs in older adults which involves cognitive impairments with minimal impairment in instrumental activities of daily living. MCI involves the onset and evolution of cognitive impairments beyond those expected based on the age and education of the individual, but which are not significant enough to interfere with their daily activities. It may occur as a transitional stage between normal aging and dementia. Causation of the syndrome in and of itself remains unknown, as, therefore, do prevention and treatment.

For diagnostic purposes, magnetic resonance imaging (MRI) and ([18F]fluorodeoxyglucose) positron emission tomography (FDG-PET) are applied. They measure either atrophy or reductions in glucose utilization. The three clinical subtypes of frontotemporal lobar degeneration, frontotemporal dementia, semantic dementia and progressive nonfluent aphasia, are characterized by impairments in specific neural networks. The first subtype with behavioral deficits, frontotemporal dementia, mainly affects a frontomedian network discussed in the context of social cognition. Semantic dementia is mainly related to the inferior temporal poles and amygdalae; brain regions that have been discussed in the context of conceptual knowledge, semantic information processing, and social cognition, whereas progressive nonfluent aphasia affects the whole left frontotemporal network for phonological and syntactical processing.

Posterior cortical atrophy (PCA), also called Benson's syndrome, is a form of dementia which is usually considered an atypical variant of Alzheimer's disease (AD). The disease causes atrophy of the posterior part of the cerebral cortex, resulting in the progressive disruption of complex visual processing. PCA was first described by D. Frank Benson in 1988.

In rare cases, PCA can be caused by dementia with Lewy bodies and Creutzfeldt–Jakob disease.

PCA usually affects people at an earlier age than typical cases of Alzheimer's disease, with initial symptoms often experienced in people in their mid-fifties or early sixties. This was the case with writer Terry Pratchett (1948-2015), who went public in 2007 about being diagnosed with PCA. In "The Mind's Eye", neurologist Oliver Sacks examines the case of concert pianist Lilian Kallir (1931–2004), who suffered from PCA.

Neurodegeneration is the progressive loss of structure or function of neurons, including death of neurons. Many neurodegenerative diseases – including amyotrophic lateral sclerosis, Parkinson's, Alzheimer's, and Huntington's – occur as a result of neurodegenerative processes. Such diseases are incurable, resulting in progressive degeneration and/or death of neuron cells. As research progresses, many similarities appear that relate these diseases to one another on a sub-cellular level. Discovering these similarities offers hope for therapeutic advances that could ameliorate many diseases simultaneously. There are many parallels between different neurodegenerative disorders including atypical protein assemblies as well as induced cell death. Neurodegeneration can be found in many different levels of neuronal circuitry ranging from molecular to systemic.