If the symptoms of aphasia last longer than two or three months after a stroke, a complete recovery is unlikely. However, it is important to note that some people continue to improve over a period of years and even decades. Improvement is a slow process that usually involves both helping the individual and family understand the nature of aphasia and learning compensatory strategies for communicating.

After a traumatic brain injury (TBI) or cerebrovascular accident (CVA), the brain undergoes several healing and re-organization processes, which may result in improved language function. This is referred to as spontaneous recovery. Spontaneous recovery is the natural recovery the brain makes without treatment, and the brain begins to reorganize and change in order to recover. There are several factors that contribute to a person's chance of recovery caused by stroke, including stroke size and location. Age, sex, and education have not been found to be very predictive.

Specific to aphasia, spontaneous recovery varies among affected people and may not look the same in everyone, making it difficult to predict recovery.

Though some cases of Wernicke’s aphasia have shown greater improvements than more mild forms of aphasia, people with Wernicke’s aphasia may not reach as high a level of speech abilities as those with mild forms of aphasia.

Following are some precautions that should be taken to avoid aphasia, by decreasing the risk of stroke, the main cause of aphasia:

- Exercising regularly

- Eating a healthy diet

- Keeping alcohol consumption low and avoiding tobacco use

- Controlling blood pressure

The most common cause of Wernicke's aphasia is stroke. Strokes may occur when blood flow to the brain is completely interrupted or severely reduced. This has a direct effect on the amount of oxygen and nutrients being able to supply the brain, which causes brain cells to die within minutes. The primary classifications of stroke are hemorrhagic (ruptured blood vessel), or ischemic (blood clot reduces or completely stops blood flow). Two of the most common types of hemorrhagic stroke are subarachnoid hemorrhage and intracerebral hemorrhage. Subarachnoid hemorrhage is when an artery near the surface of the brain bursts causing blood to leak into the space between the brain and skull. Meanwhile intracerebral hemorrhage occurs when a blood vessel inside the brain bursts, causing spillage into surrounding brain tissue. Three main causes of these hemorrhagic strokes are hypertension (uncontrolled high blood pressure), aneurisms (weak spots in blood vessel walls), and arteriovenous malformations (rupture of abnormal tangle of thin-walled blood vessels). As previously noted the other major classification for a stroke is an ischemic stroke. The ischemic strokes, which are the most common form of stroke, are further broken down and can be classified as embolic or thrombotic. Embolic strokes occur when a blood clot forms away from the brain, typically in the heart. A small portion of this clot breaks away and travels through the blood vessels until eventually reaching a small enough vessel in the brain that it can no longer pass through, causing a blockage. Thrombotic strokes on the other hand are due to the formation of a blood clot directly formed in one of the arteries that supply the brain. In general, stroke is the number one leading cause of disability worldwide.,

"The middle cerebral arteries supply blood to the cortical areas involved in speech, language and swallowing. The left middle cerebral artery provides Broca's area, Wernicke's area, Heschl's gyrus, and the angular gyrus with blood". Therefore, in patients with Wernicke's aphasia, there is typically an occlusion to the left middle cerebral artery.

As a result of the occlusion in the left middle cerebral artery, Wernicke's aphasia is most commonly caused by a lesion in the posterior superior temporal gyrus (Wernicke's area). This area is posterior to the primary auditory cortex (PAC) which is responsible for decoding individual speech sounds. Wernicke's primary responsibility is to assign meaning to these speech sounds. The extent of the lesion will determine the severity of the patients deficits related to language. Damage to the surrounding areas (perisylvian region) may also result in Wernicke's aphasia symptoms due to variation in individual neuroanatomical structure and any co-occurring damage in adjacent areas of the brain.

Anomia can be genetic or caused by damage to various parts of the parietal lobe or the temporal lobe of the brain by an accident or stroke, or a brain tumor.

Although the main causes are not specifically known, many researchers have found factors contributing to anomic aphasia. It is known that people with damage to the left hemisphere of the brain are more likely to have anomic aphasia. Broca's area, the speech production center in the brain, was linked to being the source for speech execution problems, with the use of functional magnetic resonance imaging (fMRI), now commonly used to study anomic patients. Other experts believe that damage to Wernicke's area, which is the speech comprehension area of the brain, is connected to anomia because the patients cannot comprehend the words that they are hearing.

Although many experts have believed that damage to Broca's area or Wernicke's area are the main causes of anomia, current studies have shown that damage in the left parietal lobe is the epicenter of anomic aphasia. One study was conducted using a word repetition test as well as fMRI in order to see the highest level of activity as well as where the lesions are in the brain tissue. Fridrikkson, et al. saw that damage to neither Broca's area nor Wernicke's area were the sole sources of anomia in the subjects. Therefore, the original anomia model, which theorized that damage occurred on the surface of the brain in the grey matter was debunked, and it was found that the damage was in the white matter deeper in the brain, on the left hemisphere. More specifically, the damage was in a part of the nerve tract called the arcuate fasciculus, for which the mechanism of action is unknown, though it is known to connect the posterior (back) of the brain to the anterior (front) and vice versa.

New data has shown that although the arcuate fascicles' main function does not include connecting Wernicke's area and Broca's area, damage to the tract does create speech problems because the speech comprehension and speech production areas are connected by this tract. Some studies have found that in right-handed people the language center is 99% in the left hemisphere; therefore, anomic aphasia almost exclusively occurs with damage to the left hemisphere. However, in left-handed people the language center is about 60% in the left hemisphere; thus, anomic aphasia can occur with damage to the right hemisphere in left-handed people.

The most common cause of expressive aphasia is stroke. A stroke is caused by hypoperfusion (lack of oxygen) to an area of the brain, which is commonly caused by thrombosis or embolism. Some form of aphasia occurs in 34 to 38% of stroke patients. Expressive aphasia occurs in approximately 12% of new cases of aphasia caused by stroke.

In most cases, expressive aphasia is caused by a stroke in Broca's area or the surrounding vicinity. Broca's area is in the lower part of the premotor cortex in the language dominant hemisphere and is responsible for planning motor speech movements. However, cases of expressive aphasia have been seen in patients with strokes in other areas of the brain. Patients with classic symptoms of expressive aphasia in general have more acute brain lesions, whereas patients with larger, widespread lesions exhibit a variety of symptoms that may be classified as global aphasia or left unclassified.

Expressive aphasia can also be caused by trauma to the brain, tumor, cerebral hemorrhage by extradural hematoma.

Understanding lateralization of brain function is important for understanding what areas of the brain cause expressive aphasia when damaged. In the past, it has been believed that the area for language production differs between left and right-handed individuals. If this were true, damage to the homologous region of Broca's area in the right hemisphere should cause aphasia in a left-handed individual. More recent studies have shown that even left-handed individuals typically have language functions only in the left hemisphere. However, left-handed individuals are more likely to have a dominance of language in the right hemisphere.

People affected by jargon aphasia usually are elderly and/or people who have damage to the neural pathways of certain parts of the brain. This is usually the result of the following conditions[2]:

- Stroke

- Traumatic Brain Injury

- Epilepsy

- Migraine

- Brain Tumor

- Alzheimer's Disease

- Parkinson's Disease

Since jargon is associated with fluent (Wernicke’s) aphasia, it is usually caused by damage of the temporal lobe, and more specifically, Wernicke’s area. After the condition is diagnosed, a Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI) scan is typically used to determine the location and severity of the brain damage that has caused the aphasia[2].

There have been cases in which aphasia has developed after damage to only the right hemisphere of the brain. These cases are few and far between, and usually involve unique circumstances for the individual. Most commonly, these results can stem from brain organization that is different than the general population, or a heavier than normal reliance on the right hemisphere of the brain[7].

In most individuals with expressive aphasia, the majority of recovery is seen within the first year following a stroke or injury. The majority of this improvement is seen in the first four weeks in therapy following a stroke and slows thereafter. However, this timeline will vary depending upon the type of stroke experienced by the patient. Patients who experienced an ischemic stroke may recover in the days and weeks following the stroke, and then experience a plateau and gradual slowing of recovery. On the contrary, patients who experienced a hemorrhagic stroke experience a slower recovery in the first 4–8 weeks, followed by a faster recovery which eventually stabilizes.

Numerous factors impact the recovery process and outcomes. Site and extent of lesion greatly impacts recovery. Other factors that may affect prognosis are age, education, gender, and motivation. Occupation, handedness, personality, and emotional state may also be associated with recovery outcomes.

Studies have also found that prognosis of expressive aphasia correlates strongly with the initial severity of impairment. However, it has been seen that continued recovery is possible years after a stroke with effective treatment. Timing and intensity of treatment is another factor that impacts outcomes. Research suggests that even in later stages of recovery, intervention is effective at improving function, as well as, preventing loss of function.

Unlike receptive aphasia, patients with expressive aphasia are aware of their errors in language production. This may further motivate a person with expressive aphasia to progress in treatment, which would affect treatment outcomes. On the other hand, awareness of impairment may lead to higher levels of frustration, depression, anxiety, or social withdrawal, which have been proven to negatively affect a person's chance of recovery.

Global aphasia typically results from an occlusion to the trunk of the middle cerebral artery (MCA), which affects a large portion of the perisylvian region of the left cortex. Global aphasia is usually a result of a thrombotic stroke, which occurs when a blood clot forms in the brain's blood vessels. In addition to stroke, global aphasia can also be caused by traumatic brain injury (TBI), tumors, and progressive neurological disorders. The large areas in the anterior (Broca's) and posterior (Wernicke's) area of the brain are either destroyed or impaired because they are separate branches of the MCA that are supplied by its arterial trunk. Lesions usually result in extensive damage to the language areas of the left hemisphere, however global aphasia can result from damage to smaller, subcortical regions. It is well known that a lesion to the cortex can cause aphasia. However, a study by Kumar et al. (1996) suggests that lesions to the subcortical regions of the cortex such as the thalamus, basal ganglia, internal capsule, and paraventricular white matter can also cause speech and language deficits. This is due to the fact that the subcortical regions are closely associated with the language centers in the brain. Kumar et al. state that while lesions to the subcortical regions could cause certain types of aphasia, a lesion to these regions would rarely cause global aphasia. In a study performed by Ferro (1992), it was found that five different brain lesion locations were linked to aphasia. These locations include: "fronto-temporo-parietal lesions", "anterior, suprasylvian, frontal lesions", "large subcortical infarcts", "posterior, suprasylvian, parietal infarcts", and "a double lesion composed of a frontal and a temporal infarct".

Conduction aphasia is caused by damage to the parietal lobe of the brain, especially in regards to the area associated with the left-hemisphere dominant dorsal stream network. The arcuate fasciculus, which connects Broca's area and Wernicke's area (important for speech and language production and comprehension, respectively), is affected. These two areas control speech and language in the brain. The arcuate fasciculus is a thick band of fiber that connects the two areas and carries messages between them. When this area is damaged, the patient experiences damage to the auditory-motor integration system. This results in disruption to the delayed auditory feedback network, causing the individual to have difficulty correcting themselves on speech repetition tasks. Additionally, recent evidence suggests that conduction aphasia can also be caused by lesions in the left superior temporal gyrus and/or the left supramarginal gyrus.

The brain damage causing conduction aphasia is often from a stroke, which can produce both localized and widespread damage. Traumatic brain injury and tumors can also lead to localized lesions, with potential to cause conduction aphasia. Conduction aphasia can also be seen in cases of cortical damage without subcortical extensions.

In relation to other types of aphasia, TMoA occurs less frequently, so there is less information on its prognosis. In general, for individuals with aphasia, most recovery is seen within 6 months of the stroke or injury although more recovery may continue in the following months or years. The timeline of recovery may look different depending on the type of stroke that caused the aphasia. With an ischemic stroke, recovery is greatest within the first two weeks and then diminishes overtime until the progress stabilizes. With a hemorrhagic stroke, the patient often shows little improvement in the first few weeks and then has relatively rapid recovery until they stabilize.

In a study involving eight patients with border zone lesions, all patients presented with transcortical mixed aphasia initially after the stroke. Three of these patients made a complete recovery within a few days post-stroke. For three other patients with more anterior lesions, their aphasia transitioned to TMoA. All participants in the study regained full language abilities within 18 months following their stroke. This suggests a positive long-term prognosis for patients with TMoA. However, this might not be the case for all patients and more research is needed in order to solidify these findings. Another study found that prognosis of TMoA is affected by lesion size. Smaller lesions typically cause delays in speech initiation; whereas, larger lesions lead to more profound language abnormalities and difficulty with abstract language abilities.

Research has shown that treatment has a direct effect on aphasia outcomes. Intensity, duration and timing of treatment all need to be taken in to consideration when choosing a course of treatment and determining a prognosis. In general, greater intensity leads to greater improvement. For duration, longer-term treatment produces more permanent changes. As for timing, beginning treatment too early may be difficult for the system which has not recovered enough to do intensive therapy, but beginning too late may result missing the window of the opportunity in which the most change can occur. Neuroplasticity, the brain's natural ability to reorganize itself following a traumatic event, occurs best when treatment connects simultaneous events, maintains attention, taps into positive emotion, utilizes repetition tasks, and is specific to the individual's needs.

Other factors affecting prognosis includes location and site of lesion. Since the lesion that results in TMoA usually occurs in the watershed area and does not directly involve the areas of the brain responsible for general language abilities, prognosis for these patients is good overall. Other factors that determine a patient’s prognosis include age, education prior to the stroke, gender, motivation, and support.

Perseverative paraphasia is a type of paraphasia in which the previous response persists and interferes with retrieval of new responses. (See the experimental case study D.L.A published by Dennis in 1976.) It is associated with lesions in the left caudate nucleus.

When evaluating the prognosis of a patient, the main contributing participant factors that influence the extent of neuroplasticity, or the brain's ability to change are: age, lesion location, pre-existing cognitive status, motivation, age, overall health, and interaction amongst these. After brain damage, initial signs of global aphasia may appear within the first two days due to brain swelling (cerebral edema). With some time and natural recovery, impairment presentation may progress into expressive aphasia (most commonly) or receptive aphasia. Due to the size and location of the lesion associated with global aphasia, the prognosis for language abilities is poor. Research has shown that the prognosis of long-term language abilities is determined by the initial severity level of aphasia within the first four weeks after a stroke. As a result, there is a poor prognosis for persons who retain a diagnosis of aphasia after one month due to limited initial language abilities. Nonetheless, in the first year post-stroke, patients with global aphasia showed improvement in their Western Aphasia Battery (WAB) scores from baseline. When compared to individuals with Broca’s, Wernicke’s, anomic, and conduction types of aphasia, those with Broca’s aphasia showed the best rate and extent of improvement followed by global aphasia. The rate of improvement in language function was highest in the first four weeks after stroke.

Although the prognosis for persons diagnosed with global aphasia is poor, improvement in varying aspects of language is possible. For example, in 1992, Ferro performed research in which he studied the recovery of individuals with acute global aphasia, resulting from the five different lesion sites. The first lesion site was in the fronto-tempo-parietal region of the brain; patients with lesions in this location saw the least amount of gains out of all of the participants in the study, and they often never recovered from global aphasia. However, the second lesion site was the anterior, suprasylvian, frontal part of the brain; the third lesion site was the subcortical infarcts; and the fourth lesion site was the posterior, suprasylvian, parietal infarcts. Participants with lesions two, three, and four often recovered to a less severe form of aphasia, such as Broca's or transcortical. The fifth lesion site was a double lesion in both the frontal and temporal infarcts; patients with lesions at this site showed slight improvement. However, studies show that spontaneous improvement, if it happens, occurs within six months, but complete recovery is rare.

Studies have shown that persons with global aphasia have improved their verbal and nonverbal speech and language skills through speech and language therapy. One study examined the recovery of a group of individuals who were classified as having global aphasia at 3 months poststroke. The individuals received intensive speech and language intervention. The results of the study illustrated that all of the patients showed improvement. The greatest area of improvement was in auditory comprehension, and the least in the use of propositional speech. After 6 months poststroke, the individuals showed an increased use of gestures to communicate, as their communication skills remained severely impaired.

During therapy, most progress is seen within the first 3 years, but it is possible for language abilities to continuously improve at a steady rate due to long-term intensive language intervention. While improvement in language abilities is possible with intervention, only 20 percent of persons diagnosed with global aphasia achieve functional use of language. Communication of basic needs and the comprehension of simple conversations on highly familiar topics, are examples of common functional language use for this population.

Traditionally, it has been believed that conduction aphasia was the result of a lesion in the arcuate fasciculus, a deep, white matter bundle connecting the posterior temporoparietal junction with the frontal cortex. It was thought that this bundle transmitted information between Wernicke's area (responsible for language comprehension) and Broca's area (responsible for language production). Wernicke, and later Lichtheim and others, theorized that a disconnect between these two regions caused patients to fail to monitor speech and limited their ability to transfer information between comprehension and production functions, thus leading to paraphasic errors and a deficit in repetition of auditory input. This hypothesis fits well with the Wernicke-Geschwind model of language, which compartmentalizes and localizes speech comprehension and production.

Although the disconnection hypothesis explains many of the conditions associated with conduction aphasia, clinical evidence is lacking, and the Wernicke-Geschwind model has since become obsolete. There have been no known autopsy cases in which conduction aphasia was shown to be the result of a focused arcuate fasciculus lesion. Surveys of conduction aphasics with anatomical confirmation show that in nearly all patients, there was damage to portions of the cortex as well. Furthermore, there are reports of patients with severe disruption of the arcuate fasciculus who show no symptoms of conduction aphasia (although it is plausible that the contralateral hemisphere facilitated repetition in these cases).

Recent research has pointed to a different explanation for conduction aphasia, similar to Wernicke's, which is based on newer models suggesting language is facilitated by "cortically based, anatomically distributed, modular networks." Anderson et al. describe an experiment in which electrical stimulation of the left posterior superior temporal cortex in a human subject induced symptoms consistent with conduction aphasia, indicating that a deep brain disconnection is not necessary. While this study does not completely discredit the disconnection hypothesis, but does point to a system in which transmission of spoken language information involves more than just the arcuate fasciculus. Regardless of the role that the arcuate fasciculus plays in the disorder, the cortical component cannot be denied.

Wernicke's aphasia, also known as receptive aphasia, sensory aphasia, or posterior aphasia, is a type of aphasia in which individuals have difficulty understanding written and spoken language. Patients with Wernicke's aphasia demonstrate fluent speech, which is characterized by typical speech rate, intact syntactic abilities, and effortless speech output. Writing often reflects speech in that it tends to lack content or meaning. In most cases, motor deficits (i.e. hemiparesis) do not occur in individuals with Wernicke's aphasia. Therefore, they may produce a large amount of speech without much meaning. Wernicke's aphasia was named after Carl Wernicke who is credited with discovering the area of the brain responsible for language comprehension. Individuals with Wernicke's aphasia are typically unaware of their errors in speech and do not realize their speech may lack meaning. They typically remain unaware of even their most profound language deficits.

Like many acquired language disorders, Wernicke's aphasia can be experienced in many different ways and to many different degrees. Patients diagnosed with Wernicke's aphasia can show severe language comprehension deficits; however, this is dependent on the severity and extent of the lesion. Severity levels may range from being unable to understand even the simplest spoken and/or written information to missing minor details of a conversation. Many diagnosed with Wernicke's aphasia have difficulty with repetition in words and sentences, and or working memory.

Anomic aphasia (also known as dysnomia, nominal aphasia, and amnesic aphasia) is a mild, fluent type of aphasia where an individual has word retrieval failures and cannot express the words they want to say (particularly nouns and verbs). Anomia is a deficit of expressive language. The most pervasive deficit in the aphasias is anomia. Some level of anomia is seen in all of the aphasias. Individuals with aphasia who display anomia can often describe an object in detail and maybe even use hand gestures to demonstrate how the object is used but cannot find the appropriate word to name the object.

There have been no large epidemiological studies on the incidence and prevalence of the PPA variants. Though it most likely has been underestimated, onset of PPA has been found to occur in the sixth or seventh decade.

There are no known environmental risk factors for the progressive aphasias. However, one observational, retrospective study suggested that vasectomy could be a risk factor for PPA in men. These results have yet to be replicated or demonstrated by prospective studies.

PPA is not considered a hereditary disease. However, relatives of a person with any form of frontotemporal lobar degeneration, including PPA, are at slightly greater risk of developing PPA or another form of the condition. In a quarter of patients diagnosed with PPA, there is a family history of PPA or one of the other disorders in the FTLD spectrum of disorders. It has been found that genetic predisposition varies among the different PPA variants, with PNFA being more commonly familial in nature than LPA or SD.

The most convincing genetic basis of PPA has been found to be a mutation in the GRN gene. Most patients with observed GRN mutations present clinical features of PNFA, but the phenotype can be atypical.

Jargon aphasia is a type of fluent aphasia in which an individual's speech is incomprehensible, but appears to make sense to the individual. Persons experiencing this condition will either replace a desired word with another that sounds or looks like the original one, or has some other connection to it, or they will replace it with random sounds. Accordingly, persons with jargon aphasia often use neologisms, and may perseverate if they try to replace the words they can't find with sounds.

Paraphasia is associated with fluent aphasias, characterized by “fluent spontaneous speech, long grammatically shaped sentences and preserved prosody abilities.” Examples of these fluent aphasias include receptive or Wernicke’s aphasia, anomic aphasia, conduction aphasia, and transcortical sensory aphasia, among others. All of these lead to a difference in processing efficiency, which is often caused by damage to a cortical region in the brain (in receptive aphasia, for example, the lesion is in or near Wernicke’s area); lesion location is the most important determining factor for all aphasic disorders, including paraphasia - the location of the lesion can be used to hypothesize the type of aphasic symptoms the patient will display. This lesion can be caused by a variety of different methods: malfunctioning blood vessels (caused, for example, by a stroke) in the brain are the cause of 80% of aphasias in adults, as compared to head injuries, dementia and degenerative diseases, poisoning, metabolic disorders, infectious diseases, and demyelinating diseases. Lesions involving the posterior superior temporal lobe are often associated with fluent aphasias.

Transcortical sensory aphasia (TSA) is a kind of aphasia that involves damage to specific areas of the temporal lobe of the brain, resulting in symptoms such as poor auditory comprehension, relatively intact repetition, and fluent speech with semantic paraphasias present. TSA is a fluent aphasia similar to Wernicke's aphasia, with the exception of a strong ability to repeat words and phrases. The person may repeat questions rather than answer them ("echolalia").

In all of these ways, TSA is very similar to a more commonly known language disorder, receptive aphasia. However, transcortical sensory aphasia differs from receptive aphasia in that patients still have intact repetition and exhibit echolalia, or the compulsive repetition of words. Transcortical sensory aphasia cannot be diagnosed through brain imaging techniques such as functional magnetic resonance imaging (fMRI), as the results are often difficult to interpret. Therefore, clinicians rely on language assessments and observations to determine if a patient presents with the characteristics of TSA. Patients diagnosed with TSA have shown partial recovery of speech and comprehension after beginning speech therapy. Speech therapy methods for patients with any subtype of aphasia are based on the principles of learning and neuroplasticity. Clinical research on TSA is limited because it occurs so infrequently in patients with aphasia that it is very difficult to perform systematic studies.

TSA should not be confused with transcortical motor aphasia (TMA), which is characterized by nonfluent speech output, with good comprehension and repetition. Patients with TMA have impaired writing skills, difficulty speaking and difficulty maintaining a clear thought process. Furthermore, TMA is caused by lesions in cortical motor areas of the brain as well as lesions in the anterior portion of the basal ganglia, and can be seen in patients with expressive aphasia.

Agraphia is an acquired neurological disorder causing a loss in the ability to communicate through writing, either due to some form of motor dysfunction or an inability to spell. The loss of writing ability may present with other language or neurological disorders; disorders appearing commonly with agraphia are alexia, aphasia, dysarthria, agnosia, and apraxia. The study of individuals with agraphia may provide more information about the pathways involved in writing, both language related and motoric. Agraphia cannot be directly treated, but individuals can learn techniques to help regain and rehabilitate some of their previous writing abilities. These techniques differ depending on the type of agraphia.

Agraphia can be broadly divided into central and peripheral categories. Central agraphias typically involve language areas of the brain, causing difficulty spelling or with spontaneous communication, and are often accompanied by other language disorders. Peripheral agraphias usually target motor and visuospatial skills in addition to language and tend to involve motoric areas of the brain, causing difficulty in the movements associated with writing. Central agraphia may also be called aphasic agraphia as it involves areas of the brain whose major functions are connected to language and writing; peripheral agraphia may also be called nonaphasic agraphia as it involves areas of the brain whose functions are not directly connected to language and writing (typically motor areas).

The history of agraphia dates to the mid-fourteenth century, but it was not until the second half of the nineteenth century that it sparked significant clinical interest. Research in the twentieth century focused primary on aphasiology in patients with lesions from strokes.

For all practical purposes, there is no direct cure. Patients may improve if information is presented in other modalities than the damaged one. Different types of therapies can help to reverse the effects of agnosia. In some cases, occupational therapy or speech therapy can improve agnosia, depending on its cause.

Initially many individuals with a form of agnosia are unaware of the extent to which they have either a perceptual or recognition deficit. This may be caused by anosognosia which is the lack of awareness of a deficit. This lack of awareness usually leads to a form of denial and resistance to any form of help or treatment. There are various methods that can be used which can help the individual recognize the impairment in perception or recognition that they may have. A patient can be presented with a stimulus to the impaired modality only to help increase their awareness of their deficit. Alternatively, a task can be broken down into its component parts so that the individual can see each part of the problem caused by the deficit. Once the individual acknowledges their perceptual or recognition deficit, a form of treatment may be recommended. There are various forms of treatment such as compensatory strategies with alternate modalities, verbal strategies, alternate cues and organizational strategies.

Agraphia has a multitude of causes ranging from strokes, lesions, traumatic brain injury, and dementia. Twelve regions of the brain are associated with handwriting. The four distinct functional areas are the left superior frontal area composed of the middle frontal gyrus and the superior frontal sulcus, the left superior parietal area composed of the inferior parietal lobule, the superior parietal lobule and the intraparietal sulcus and lastly the primary motor cortex and the somatosensory cortex. The eight other areas are considered associative areas and are the right anterior cerebellum, the left posterior nucleus of the thalamus, the left inferior frontal gyrus, the right posterior cerebellum, the right superior frontal cortex, the right inferior parietal lobule, the left fusiform gyrus and the left putamen. The specific type of agraphia resulting from brain damage will depend on which area of the brain was damaged.

Phonological agraphia is linked to damage in areas of the brain involved in phonological processing skills (sounding out words), specifically the language areas around the sylvian fissure, such as Broca's area, Wernicke's area, and the supramarginal gyrus.

Lexical agraphia is associated with damage to the left angular gyrus and/or posterior temporal cortex. The damage is typically posterior and inferior to the perisylvian language areas.

Deep agraphia involves damage to the same areas of the brain as lexical agraphia plus some damage to the perisylvian language areas as well. More extensive left hemisphere damage can lead to global agraphia.

Gerstmann's syndrome is caused by a lesion of the dominant (usually the left) parietal lobe, usually an angular gyrus lesion.

Apraxic agraphia with ideomotor apraxia is typically caused by damage to the superior parietal lobe (where graphomotor plans are stored) or the premotor cortex (where the plans are converted into motor commands). Additionally, some individuals with cerebellar lesions (more typically associated with non-apraxic motor dysfunction) develop apraxic agraphia. Apraxic agraphia without ideomotor apraxia may be caused by damage to either of the parietal lobes, the dominant frontal lobe, or to the dominant thalamus.

Visuospatial agraphia typically has a right hemisphere pathology. Damage to the right frontal area of the brain may cause more motor defects, whereas damage to the posterior part of the right hemisphere leads predominantly to spatial defects in writing.

Organizational strategies may be extremely helpful for an individual with visual agnosia. For example, organizing clothes according to different hangers provides tactile cues for the individual, making it easier to identify certain forms of clothing as opposed to relying solely on visual cues.

Currently, the specific causes for PPA and other degenerative brain disease similar to PPA are unknown. Autopsies have revealed a variety of brain abnormalities in people who had PPA. These autopsies, as well as imaging techniques such as CT scans, MRI, EEG, single photon emission computed tomography (SPECT), and positron emission tomography (PET), have generally revealed abnormalities to be almost exclusively in the left hemisphere.

Transcortical motor aphasia (TMoA), also known as commissural dysphasia or white matter dysphasia, results from damage in the anterior superior frontal lobe of the language-dominant hemisphere. This damage is typically due to cerebrovascular accident (CVA). TMoA is generally characterized by reduced speech output, which is a result of dysfunction of the affected region of the brain. The left hemisphere is usually responsible for performing language functions, although left-handed individuals have been shown to perform language functions using either their left or right hemisphere depending on the individual. The anterior frontal lobes of the language-dominant hemisphere are essential for initiating and maintaining speech. Because of this, individuals with TMoA often present with difficulty in speech maintenance and initiation.

Damage in the watershed region does not directly harm the areas of the brain involved in language production or comprehension; instead, the damage isolates these areas from the rest of the brain. If there is damage to the frontal lobe, executive functions related to language use are often affected. Executive functions relevant to language include activating language responses, controlling syntax (grammar), and narrative discourse. Difficulties in these areas can lead to supplementary deficits involving difficulties forming complex sentences, choosing which words to use appropriately, and initiating speech in conversation.

The extent and location of the brain damage will impact the degree and variety of language functioning characteristics (i.e. damage deep to the frontal lobe and/or damage across multiple regions will greatly impair language). Right hemiparesis, or right-sided paralysis, may coincide with TMoA if the lesion in the anterior frontal lobe is large enough and extends into the posterior frontal lobe.

There are some other forms of aphasia that relate to TMoA. For instance, adynamic aphasia is a form of TMoA that is characterized by sparse speech. This occurs as a result of executive functioning in the frontal lobe. Another form of aphasia related to TMoA is dynamic aphasia. Patients with this form of aphasia may present with a contiguity disorder in which they have difficulty combining linguistic elements. For dynamic aphasia, this is most apparent when the patient is asked to sequence at the sentence level whereas for other aphasias contiguity disorder can be seen at the phoneme or word level.