Speech impediment
Chris has an unusual manner of speaking, between his strong regional dialect and what appear to be genuine impairments.
History
Chris's speech impediment appears to have worsened over time — he spoke clearly and normally in his earlier videos, while his stuttering has increased significantly since then.
Likely causes include troll-induced stress and the lack of conversational company not already accustomed to Chris's speaking tendencies.
Chris's problems in verbal communication potentially stem from either the extended period of "muteness" he went through during his childhood or his autism, a disorder which often results in speech difficulties. Chris's written communication generally tends to be significantly more coherent and grammatically correct than how he speaks. While writing, he has more time and freedom to determine what he says.
Non-Symptoms
Slang such as "Y'all," and "'em," and contracting the "g" of words ending in "-ing" is typical in dialects of the southeastern United States, Chris's native region.
Chris sometimes mispronounces names (such as Shigeru Miyamoto and Reggie Fils-Aimé) due to his his ignorance of their proper pronunciation rather than impairments in speaking ability.
Symptoms
Chris's diction is naturally staggered, interspersed with pauses, deep breaths, "um," "uh," and "hm." The pauses and deep breaths, used in speech therapy, suggest that Chris has had his speech impediment professionally treated at some point. Chris's protracted style of speaking seems to make it easier for him to lose his thought, stray off topic, or forget to include certain segments of his thoughts. However, in the Flipnotes he has made, his speech is surprisingly fluent, with no "ums" or "uhs". However, this is probably because he is being timed to do it, so there's little time to stop.
During the conversation with Kacey's dad, Chris claimed to pause before speaking in order to "spellcheck" what he is saying. This implies that Chris needs to consciously plan what he is going to say or else he is unable to say it; this suggests that Chris's difficulty with speech stems from poor contact between the speech centers of his brain and his cerebellum, a common characteristic of autism. Ironically, Chris clearly doesn't spellcheck his written work.
Like small children, Chris has a tendency to speak too quickly, run words into one another, and slur words. For example, Chris's pronunciation of "Ensykapeia Dramakka paysh". Chris sometimes mixes up the pieces of multiple word phrases, resulting in statements like "rell-wested." [1]
Chris has difficulty pronouncing the letter "X" and related sounds, pronouncing it as an "s" sound. This indicates trouble with consonants.