dyslogia

from The Century Dictionary.

• noun Impairment of the reasoning faculties.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Difficulty in expressing ideas in speech.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun impaired ability to express ideas verbally; usually resulting from difficulties of reasoning (as in feeblemindedness or certain psychoses)