Clearing Up Some Confusing Terms
What are amnesia, aphasia, anomia, alexia, agraphia, acalculia, (relatively commonly used terms) and agnosia, apraxia, anosagnosia, anosadiaphoria (relatively uncommonly used terms)? Wow, I have been doing behavioral neurology for over 25 years and I know I missed a few of the "a" words here....In numerous previous blogs I have frequently referred to disorders of thinking and memory and occasionally I have used the term cognition. I have also briefly mentioned some of the terms above, such as aphasia. I believe it is time to be a little more specific about what some of these terms mean. I will try in this blog to describe some specific terms that are commonly used in discussing Alzheimer's disease and related disorders.
In the previous blog this month, I tried to describe the common brain imaging tests that may be associated with an evaluation of a patient with Alzheimer's disease. As the evaluation progresses and the patient is seen by a psychiatrist, neurologist, neuropsychologist, psychologist or other health care professional, one or more of the "a" terms or related terms may be used. They are convenient shorthand for conveying an accurate description of a patient's ability of disability. As indicated some of these terms are commonly used and some are uncommonly used. We will review the common terms.
Thinking and Memory: These two words may be loosely translated into "cognition."
Cognition: Cognition is a term that includes the various brain abilities that enable a person to perform complex interactions with the environment (including other people). It includes all of and more than the terms that will be discussed below.
Amnesia: This is an impairment of the cognitive function memory. In clinical neuroscience (neurology, psychiatry, psychology etc), when the letter "a" is applied to the front of a word or term, the "a" indicates an impairment of that ability. Amnesia may be applied to any type of memory loss, including loss of language related information (verbal amnesia) or spatial information (spatial amnesia). When patients with Alzheimer's disease cannot remember what day it is, where they are, who is President, or where the closest drug store is, they are demonstrating amnesia.
Aphasia: This is an impairment of language, especially spoken language. It includes the ability to speak with the appropriate words and grammar, understand spoken language, repeat spoken language and say names of objects or people. When patients with Alzheimer's disease cannot speak in grammatically correct sentences, convey accurate information, name objects or people or understand what is being said to them, they are demonstrating aphasia.
Anomia: This is an impairment in the ability to accurately say the name of something. It is not because the patient cannot recognize the item but because something disrupts the brain's ability to produce the correct word. When patients with Alzheimer's disease say the wrong name (calling a "penguin" a "parrot"), they are demonstrating anomia.
Alexia and agraphia: These terms describe disorders of reading and writing respectively. The reading impairment may include the ability to read aloud or for understanding (comprehension). The writing impairment may include the ability to spell correctly or write the correct letters. When patients have impaired reading and writing, they have alexia and agraphia. The simultaneous occurrence of these two disorders is more likely in patients with stroke than in patients with Alzheimer's disease.
Acalculia: This describes an impairment of ability to do mathematics. When patients are making errors on their check books or do not know how much change they should be getting when they go to the store, they are demonstrating acalculia.
Spatial disorientation: This is an impairment in the understanding of relationships in space. When patients cannot figure out where there rooms are located or where known locations are when they are traveling, they are demonstrating spatial disorientation.
At this point, I would like to make a couple of comments. Many of you who have read the above descriptions carefully, may have noticed that many of these terms describe conditions that may overlap with other terms. Examples include the possibility that spatial disorientation (getting lost) might occur due to spatial amnesia (not remembering what things look like) and that reading, writing and speech are strongly related. Pure alexia (impaired reading without any other disturbance), pure agraphia (impaired writing), and pure anomia (impaired ability to name) all exist. However, the most likely situation is for two or three of these to occur together.
Also, many of you may know that the prefix "dys" may also be used with the word roots discussed here. The use of the prefix "dys" rather than "a." reflects a convention. The convention is that "dys" is used to indicate a problem from birth, (i.e., dyslexia is trouble reading because of a developmental problem) and "a" is used to indicate a problem that came on after birth (i.e. alexia is trouble reading because of a brain injury, such as stroke, Alzheimer's disease, or traumatic injury).
I have addressed some of the more common terms that you might hear in discussions or read in reports about Alzheimer's disease and patients with it. It is hoped that this discussion will enable you to better appreciate what is being said or written.