Food for thought.  My hardest job is with a man struggling with a mental diagnosis that prevents understanding and limits his communication.  WOW.  I feel like leaving him every day.  But MAN serving him is difficult.  

He has aphasia.

A comprehension and communication (reading, speaking, or writing) disorder resulting from damage or injury to the specific area in the brain.
Very common (More than 3 million cases per year in US)
 
Treatments can help manage condition, no known cure
 
Requires lab test or imaging
 
A lifelong condition
 
Common for ages 60 and older