We say "have amnesia", not "have an amnesia". Being an uncountable noun, the word amnesia doesn't take the article "an".
We say "have amnesia", not "have an amnesia".
The doctor said she has amnesia.
The doctor said she has an amnesia.
Being an uncountable noun, the word amnesia doesn't take the article "an".
Having amnesia does not mean that a person’s awareness is affected.
If you have retrograde amnesia, you may be unable to recall past information.
When someone has anterograde amnesia, they cannot remember new information.
Follow the same practice with the expressions "cause amnesia", "treat amnesia", "cure amnesia", etc.
Brain trauma can cause amnesia.
How can you treat amnesia?
Be aware, however, that you can use a possessive pronoun (my, your, his, her, etc.)
If your amnesia is caused by a terrible experience, therapy can be helpful.
The word amnesia can also be an adjective. In this situation, use the articles a/an according to the conventional rules.
I read an amnesia case study recently.
He pretends to be an amnesia patient.
A partial list of diseases and symptoms that do not take a/an: