Cerebral atrophy

Cerebral atrophy is a common feature of many of the diseases that affect the brain. Atrophy of any tissue means a decrement in the size of the cell, which can be due to progressive loss of cytoplasmic proteins. In brain tissue, atrophy describes a loss of neurons and the connections between them. Brain atrophy can be classified into two main categories: generalized and focal atrophy. Generalized atrophy occurs across the entire brain whereas focal atrophy affects cells in a specific location. Structural changes continue during adulthood as brain shrinkage commences after the age of 35, at a rate of 0.2% per year. The rate of decline is accelerated when individuals reach 70 years old. By the age of 90, the human brain will have experienced a 15% loss of its initial peak weight. Besides brain atrophy, aging has also been associated with cerebral microbleeds.

Diseases and disorders

thumb|Pick's disease showing brain atrophy,

Alzheimer's disease; high resolution MRI scans have shown the progression of cerebral atrophy in Alzheimer's disease
Cerebral palsy, in which lesions (damaged areas) may impair motor coordination
Senile dementia, fronto-temporal dementia, and vascular dementia
Pick's disease, causes progressive destruction of nerve cells in the brain
Huntington's disease, and other genetic disorders that cause build-up of toxic levels of proteins in neurons
Leukodystrophies, such as Krabbe disease, which destroy the myelin sheath that protects axons
Multiple sclerosis, which causes inflammation, myelin damage, and lesions in cerebral tissue
Epilepsy, in which lesions cause abnormal electrochemical discharges that result in seizures
GLUT1 deficiency syndrome
Anorexia nervosa, bulimia nervosa, and other eating disorders
Malnutrition, caused by lack or excess of nutrition from foods
Type II diabetes, where the body does not use insulin properly resulting in high blood sugar
Bipolar disorder, significant loss of brain tissue during manic episodes; however it's not verified whether the episodes cause brain tissue loss or vice versa
Schizophrenia is associated with brain tissue volume loss.
Mitochondrial encephalomyopathies, such as Kearns–Sayre syndrome, which interfere with the basic functions of neurons
Posterior cortical atrophy: in the most posterior area of the brain lies the visual cortex, the area of the brain where visual information is received and processed. When cortical atrophy occurs in this brain area due to neurodegeneration, the first symptom is impairment in vision. A common vision impairment seen in patients with posterior cortical atrophy is simultanagnosia, where a person is unable to see multiple locations at once or to quickly shift attention between these locations. When looking at images of a brain with posterior cortical atrophy, one can see a loss in volume of the dorsal and ventral visual pathways, where visual stimuli is brought to the visual cortex and integrated information is sent back out to other areas of the brain. Because this disorder results in visual impairments, there is often a missed or delayed diagnosis, as the assumption is that there is a problem is in the eyes when the reality is that the problem is all the way in the back of the brain.
Prion diseases, a group of invariably fatal encephalopathies that cause the progressive death of neurons.

Infections

An infectious agent or the inflammatory reaction to it can destroy neurons and their axons. These include:

Encephalitis, acute inflammation in the brain
Neurosyphilis, an infection in the brain or spinal cord
AIDS, disease of the immune system

Drug-induced

Alcohol (partially reversible): Standardized MRI evidence suggest chronic alcoholism (alcohol use disorder) is associated with widespread cortical atrophy and major brain changes. In contrast to healthy controls, macrostructural findings indicate alcoholic brains are smaller in mass and volume. Neuroimaging studies also show that cortical shrinkage in "uncomplicated alcoholism" is most severe in the frontal lobe in comparison to the other divisions of the cerebral cortex. In addition, neurological diseases that co-occur with excessive alcohol consumption—such as Wernicke–Korsakoff syndrome (WKS)—are characterized by substantial volume deficits of the diencephalon structures.
Antipsychotic use. However, untreated psychosis is associated with decreases in brain volume also.

Diagnosis

Neurofilament light chain

Cerebrospinal fluid (CSF) is a fluid that is found exclusively in the brain and spinal cord that circulates between sections of the brain offering an extra layer of protection. Studies have shown that biomarkers in the CSF and plasma can be tracked for their presence in different parts of the brain—and their presence can tell us about cerebral atrophy. One study took advantage of biomarkers, namely one called neurofilament light chain (NFL), in patients with Alzheimer's disease. Neurofilament light chain is a protein that is important in the growth and branching of neurons—cells found in the brain. In Alzheimer's Disease, neurons will stop working or die in a process called neurodegeneration. By tracking NFL, researchers can see this neurodegeneration, which this study showed was associated with brain atrophy and later cognitive decline in Alzheimer's patients. Other biomarkers like Ng – a protein important in long-term potentiation and memory – have been tracked for their associations with brain atrophy as well, but NFL had the greatest association.

Measures

thumb|400px|[[Computed tomography of the head|Brain CT with different grading systems of cerebral atrophy (seen as decreased size of gyri and secondary increased size of sulci):

- Medial temporal lobe atrophy (MTA)

- Posterior atrophy (PA)

- Frontal cortical atrophy (fGCA)]]

CT and MRI are most commonly used to observe the brain for cerebral atrophy. A CT scan takes cross sectional images of the brain using X-rays, while an MRI uses a magnetic field. With both measures, multiple images can be compared to see if there is a loss in brain volume over time.

Difference from hydrocephalus

Cerebral atrophy can be hard to distinguish from hydrocephalus because both cerebral atrophy and hydrocephalus involve an increase in cerebrospinal fluid (CSF) volume. In cerebral atrophy, this increase in CSF volume comes as a result of the decrease in cortical volume. In hydrocephalus, the increase in volume happens due to the CSF itself.

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File:Normal pressure hydrocephalus versus atrophy.jpg

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! Normal pressure hydrocephalus !! Brain atrophy

| Preferable projection ||colspan=2| Coronal plane at the level of the posterior commissure of the brain.

| Modality in this example || CT || MRI

| CSF spaces over the convexity near the vertex (red ellipse 20px) || Narrowed convexity ("tight convexity") as well as medial cisterns || Widened vertex (red arrow) and medial cisterns (green arrow)

| Callosal angle (blue V) || Acute angle || Obtuse angle

| Most likely cause of leucoaraiosis (periventricular signal alterations, blue arrows 25px)

| Transependymal cerebrospinal fluid diapedesis

| Vascular encephalopathy, in this case suggested by unilateral occurrence

Treatment

Prevention of cerebral atrophy depends on preventing the conditions driving it. Some steps that can be taken to reduce the risk:

controlling blood pressure
a healthy balanced diet including omega-3's and antioxidants
staying active mentally, physically, and socially.

Reversibility of cerebral atrophy

While most cerebral atrophy is said to be irreversible, there are recent studies that show this is not always the case. A child who was treated with ACTH originally showed atrophy, but four months after treatment the brain was seemingly normal again.

As previously mentioned, chronic alcoholism is known to be associated with significant brain damage.