Global aphasia

# Overview
The symptoms of global aphasia are those of severe Broca's aphasia and Wernicke's aphasia combined. There is an almost total reduction of all aspects of spoken and written language, in expression as well as comprehension. Improvement may occur in one or both areas (expressive and receptive) over time with rehabilitation.  What is interesting to point out is that in patients of global aphasia  other cognitive skills remain functioning - a phenomenon affirming that language faculty is indeed a separate domain.
Global aphasia is a type of aphasia that is usually associated with a large lesion in the presylvian area.  It involves a "left side blowout" which includes Broca's area, Wernicke's area and the Arcuate fasciculus.
When injury initially occurs to all of these areas, the progression starts out with Global aphasia in the first 1-2 days due brain swelling (Edema).  From there it evolves into Brocas or Wernicke's aphasia for 1-3 months (usually Broca's), then it resolves into a presidual anomic aphasia.  Studies show that spontaneous improvement, if it happens, occurs within six months, but complete recovery is rare.
Persons with global aphasia are usually mute or use repetitive vocalization.  The person frequently uses simple words such as expletives.  They are marked by a severe impairment of both understanding and expression of language. Although, they can maintain communication through gestures.

# Historical Perspective
Global aphasia was recognized to be a universal damage to both the speech receptive, and producing areas of the brain. However, it's understanding did not come into existence, until Paul Broca described Broca's aphasia(a component of Global aphasia), and Carl Wernicke described Wernicke's aphasia. A collective understanding of the two seperate components of aphasia led to the description of Global aphasia.

# Classification
According to the Cognitive Neuropsychological Model, which classifies aphasia based on the specific function lost, Global Aphasia can be classified as a non-fluent aphasia, with poor repetition, naming and auditory comprehension. This stems from diffuse global damage to both the frontal lobe, and the temporal lobe. Both areas responsible for production, and reception of speech.

# Pathophysiology
Like most forms of Aphasia, damage to the Broca's Area, in addition to Wernicke's Area, is responsible for the combination of symptoms seen in Global Aphasia. Since both areas are involved in understanding and production of speech, a cluster of symptoms encompassing both will be present. Patient can barely comprehend, or make sense, out of spoken or written language.

# Causes
Global Aphasia like most aphasias, usually results from damage to the dominant speech producing hemisphere. Massive intracerebral bleeding, tumors, and medications have been implicated as causative factors of Global Aphasia. Of them all, stroke seems to be the most common cause
- Stroke
- Cerebral Tumors 
- Infection
- Trauma
- Neurodegenerative Disease
However, stroke, seems to be the commonest cause of Global aphasia, and occurs alongside weakened limbs, which is usually an indication of other areas of the brain being involved. For this reason alone, Global Aphasia is generally more common in the elderly.

# Differentiating Global Aphasia from Other Diseases
Signs and Symptoms of Global Aphasia, can overlap, with numerous neurological conditions. These Include:
- Central Pontine Myelinosis:
- Cerebral Venous Thrombosis
- Dissection Syndromes
- Frontal Lobe syndromes
- Glioblastoma Multiforme
- Head Injury
- Multiple Sclerosis
- Pediatric Status Epilepticus
- Secondary CNS Melanoma

# Epidemiology and Demographics
Aphasia is much more prevalent in the elderly population.
Among post stroke patients: Aphasia was found to be slightly more prevalent in women, although no significant difference existed when intracerebral hemorrhage was noted
to be a cause.

# Risk Factors
- Lower education
- Higher levels of cholesterol
- Age
- Sex
- Cerebrovascular disease
Factors that indirectly increase the risk for Cerebrovascular accidents are therefore implicated as risk factors for global aphasia:
- Hypertension
- Diabetes Mellitus
- Obesity
- Tobacco
- Hyperlipidemia
- Physical inactivity

# Screening
Numerous screening tools exist for the purpose of aphasia, especially in post-stroke patients.
- Oxford Cognitive Screen : Accesses memory, language, executive function, number abilities.
- Mississippi Aphasia Screening Test: Accesses expressive and receptive language.
- Montreal Cognitive Assessment
- Boston Diagnostic Aphasia Examination: Primarily focusing on the language abilities of Aphasic patients.

# Natural History, Complications, and Prognosis

## Natural
Aphasia tends to occur following certain  risk factors, it gradually becomes progressive, affecting most mental functions.
Global cognitive decline, family history, and Genetic mutations usually worsens the outcome.

## Complications
Global aphasia in post-stroke patients can convert into Broca's aphasia over time.
- Depression
- Isolation
- Post-stroke Language and Cognitive deficits

## Prognosis
- Aphasic patients generally tend to recover with some residual deficits.
- For post-stroke patients, factors like size of lesion, location, and hemodynamic response can predict response to treatment.

# Diagnosis

## Diagnostic Study of Choice

## Study of choice
Global Aphasia is usually diagnosed by a battery of speech and cognitive tests.

## Subsequent Studies
Other investigations are usually done to rule out a secondary for example, in post stroke patients.

## History and Symptoms
- Impaired Comprehension and interpretation of language.
- Impaired understanding and Formulation of language.
- Paralysis of unilateral limbs(Stroke patients)
- Impaired pronunciation of language and certain sounds.
- Poor control of mouth, voice box, and tongue.

## Physical Examination

## Appearance of Patients
Patients typically appear normal, unless a secondary cause causing other neurologic symptoms is present.

## Skin
- Skin examination of patients usually appears normal.

## HEENT
- HEENT examination of aphasic patients is usually normal.

## Neck
- Neck examination of aphasia patients is normal.

## Lungs
- Pulmonary examination in aphasia patients is usually normal.

## Abdomen/Pelvis
- Abdominal and Pelvic examination of patients with aphasia is usually normal.

## Back
- Back examination of patients with aphasia is usually normal.

## Genitourinary
- Genitourinary examination of aphasia patients is usually normal.

## Neuromuscular
- Neuromuscular examination of aphasia patients is usually normal.

## Laboratory Findings
- Global aphasia has no specific laboratory findings.

## Electrocardiogram
- Global aphasia has no specific ECG findings.

## X-ray
- There are no positive X-ray findings in Global aphasia.

## Echocardiography and Ultrasound
Global Aphasia has no specific Echocardiographic or Ultrasound findings.

## CT scan
- CT findings only show global lesions in stroke patients, affecting Wernicke/Broca's areas.
- However, this is usually negative in other causes of aphasia.

## MRI
MRI might detect lesions in cases where vascular disease seems to be causative of aphasia.

## Other Imaging Findings
There are no other imaging findings in Global Aphasia.

## Other Diagnostic Studies
No further diagnostic studies are available in Global Aphasia

# Prognosis
Prognosis for Aphasic patients can be determined by cause of aphasia, age of patient, and presence of other co-morbidities. Older patients have a harder time recovering. Aphasia caused by stroke has a better prognosis, than that caused by a tumor, or neurodegenerative disease. Of critical importance is the ability of patients to live independently following diagnosis. This is rarely achieved, as Aphasia can persist for months to years.

# Treatment

## Medical Therapy
- Numerous medications can be used in Global aphasia and these include:
- Memantine
- Donepezil
- Levodopa
- Bromocriptine
- Galantamine

## Surgery
- There is no known surgical treatment for global aphasia but decompressive surgery can mitigate stroke, which is a risk factor for aphasia.

## Primary Prevention
No known primary preventive measures for Global aphasia

## Secondary Prevention
Multiple treatment modalities exist for Global Aphasia which includes:
1)Repetitive Transcranial  Magnetic Simulation(rTMS): Usually used in post-stroke rehabilitation.
2)Speech and Language Therapy(SLT): Has been known to be beneficial in Aphasic patients.
3) Transcranial Direct Current Simulation: When used in conjunction with speech therapy was known to be effective, rather than when used alone.
4)Piracetam: Known pharmacological agent used in global aphasia. Studies have shown little benefit in improving overall severity of aphasia, however, the writing ability of patients had a slight improvement. Overall, there has been no significant data, to support benefits of piracetam.