Negex trigger not recognized as ContextAnnotation

["Glover, Jessica" <Je...@ssa.gov>]

Hello,

I am running the cTAKES (with YTEX) CVD with an analysis engine that uses NegexAnnotator.

When I process the text "No tremor was evident.", "No" is correctly annotated as a ContextAnnotation with FocusText = "tremor" and Scope = "[PREN]", so that "tremor" as a SignSymptomMention has polarity = -1. As you would expect.

However, if I change the text to:

"EXTREMITIES: No lower extremity edema is present. NEUROLOGIC: I was unable to elicit deep tendon reflexes. No tremor was evident. LABORATORY DATA: Most recent laboratory tests include a TSH of 3.4 with a free T4 of 1.0."

the "No" from "No tremor was evident" is not annotated as a ContextAnnotation, and "tremor" has polarity=0.

I have looked through the negation triggers list,  read what I could find about the Negex algorithm, and I cannot determine why the "No" in question isn't getting picked up as a [PREN]. The bolded terms "No" and "free" are picked up as [PREN] and [POST] triggers, respectively.

My only clue is that the "No" in question is picked up when it is one of only two negation triggers in the text, e.g.

"I was unable to elicit deep tendon reflexes. No tremor was evident. LABORATORY DATA: Most recent laboratory tests include a TSH of 3.4 with a free T4 of 1.0."
                Or
"EXTREMITIES: No lower extremity edema is present. NEUROLOGIC: I was unable to elicit deep tendon reflexes. No tremor was evident."

So perhaps it has something to do with the way it is sandwiched between a [PREN] and a [POST]?

Could anyone more familiar with the Negex algorithm as it is implemented in YTEX help me understand this phenomenon?

Thank you,
Jessica