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Agnosia

The inability to recognize people, shapes, smells or objects even though the concerned basic sensory modality is intact is termed as agnosia. Agnosia is classified as a neuro psychological disorder. The term is coined from the Greek word meaning 'not knowing'.


Visual agnosia: A person with visual agnosia might not be in a position to recognize an object though he/she may identify the shape, etc. The object is viewed but the person cannot meaningfully relate it to anything. In simple words it can be put as inability to visually recognize objects. Visual agnosia is related to as a neurological disorder. Visual agnosia can manifest in the following types:

Apperceptive visual agnosia: patient is unable to identify any object.

Associative visual agnosia: patient can register the image but cannot define the object.

Integrative visual agnosia: can register the image but cannot put the pieces together to make complete sense of the image.

The different types of visual agnosia also include:

Agnostic alexia: Inability to recognize text

Color agnosia: Inability to differentiate colors and as a result cannot name any color

Object agnosia: Inability to name objects

Prosopagnosia: Inability to identify the face of people, even if the person is known to the patient

Simultanagnosia: Inability to recognize an image as a whole even though the individual details can be listed out

The commonly reported causes for agnosia are stroke, neurological disorders, dementia, brain injury or brain infection, injury to the occipital lobe of the brain or heriditary factors. After a thorough physical examination, the medical practitioner might ask for the following:

1. Brain imaging using CT or MRI to pinpoint the area of damage and the extent of injury.
2. Neuropsychological testing by asking the patient to identify objects.

Alzheimer's disease

Alzheimer's disease is a progressive mental disorder that brings about changes in the brain slowly leading to dementia. Named after the German physician Alois Alzheimer, Alzheimer's disease has 2 characteristic neuronal changes : Loss of cholinergic cells in the basal forebrain and the development of neuritic plaques in the cerebral cortex. Neurofibrillary tangles can also occur due to Neuritic plaques.

Here the brain cells degenerate and die thus causing a decline in the mental functioning and memory of a person. Alzheimer's disease (AD) or Presenile dementia as it was earlier known as, is one of the primary causes of dementia. The levels of the brain neurotransmitters serotonin, norepinephrine and acetylcholine are found to be low in AD. This kind of brain disorder causes loss of social and intellectual skills of a person. In severe cases it interferes with the day-to-day activities of a person.


Alzheimer's disease causes

  • Most scientists believe that Alzheimer's disease is caused due to increase in production and accumulation of a protein called beta-amyloid protein. The accumulation of this protein leads to nerve cell death.
  • Environment factors that causes a change in the brain's functioning can also lead to Alzheimer's disease
  • Genetic causes
  • Abnormal levels of elements like aluminum and lead
  • Chronic cerebrovascular condition resulting from high blood pressure can lead to cerebral microbleeds. These microbleeds over a long period can result in mild cognitive impairment.
  • Head injury
  • Some viruses
  • Lifestyle changes that causes change in the brain's functioning can also lead to Alzheimer's disease


There are 4 major cognitive deficits arising out of AD :

1. Amnesia : Memory loss is probably the most common symptoms of Alzheimer' disease.
2. Aphasia : Loss of Language - Failure to recollect names of objects
3. Apraxia : Inability to perform voluntary movements
4. Agnosia : Inability to recognize people and places


Alzheimer's disease symptoms
  • Forgetfulness, unusual difficulty in remembering things
  • Mild confusion
  • Occasional memory lapse
  • Disorientation day, date, etc.
  • Problem with speaking and writing
  • Problem in thinking and reasoning
  • Decision making problems
  • Depression, anxiety, mood swing and many such behavioral problems
  • Problems with cognitive skills like calculating, judgment, etc


Alzheimer's disease diagnosis

1. A physical examination and a neurological examination to check:


  • Muscle tone and strength
  • Sense of touch and sight
  • Reflexes
  • Balance
  • Coordination, etc.

2. Brain imaging (CT scans, MRI) to check for tumors, etc.
3. Lab tests for thyroid etc so as to rule out other possibilities for memory loss


Treating Alzheimer's disease

As this disease is of degenerative nature, there is no permanent cure. Early diagnosis and changes in lifestyle can slow down its progression or improve the quality of life for the afflicted.


  • Drugs to deal with cognitive changes and memory symptoms
  • Drugs to increase acetylcholine or butylcholine levels. eg; Donepezil hydrochloride or rivastigmine, a cholinergic agonist or Cholinesterase inhibitor.
  • Vitamin E combined with Cholinesterase inhibitors
  • Alternate medicines like Ginkgo Biloba, Brahmi, Gotu kola, Ginseng and St. John's Wort
  • Exercise
  • Well balanced and nutritious food
  • Lifestyle changes that help deal with and improve the current condition

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Collection of Pages - Last revised Date: October 19, 2017