Continuing on the TEASC's report on their evaluation of Lyn, I'm quoting the actual report below. Most of the interjections in parentheses are in the report. Mine are in italics:
1. Dementia, mild. Probable Alzheimers type.
2. Anxiety disorder, most consistent with agoraphobia (anxiety when out of home or in crowded situations)
Discussion: Sundowner syndrome generally appears at the same time that significant dementia/cofnitive decline is noted. The development of evening anxiety (when out of the home) that began 15 years ago is more likely to be a specific form of anxiety (such as agoraphobia), which can have many symptoms in common with sundowning.
Diagnosing dementia in individuals with developmental disability can be challenging. Traditional IQ and many other neuropsychological tests done may not reflect actual abiliies. It is more helpful to keep track of independent activities of daily living and basic activities, monitoring functional changes over time. It is also critical to get labs and other tests to rule out medical causes. (The workup done in 2011 was quite thorough). Since being seen by (neurologist) and (clinician who performed the neuropsych eval) a year ago, Lyn has continued to have more functional decline. Her general mood is good, and there is no indication per family of any depression. Anxiety appears to be specific to being out in the evenings or in new situations, especially with groups of people. This would argue against "pseudo dementia". Her decline is most consisten with dementia. However, anxiety does not appear to be restricting both Lyn and her family from doing things they used to do together (i.e., have people over, take trips, etc.).
The reason for using IQ tests Normed on a "normal" population is to gauge how much an individual's intellectual functioning is different from the functioning of other individuals their age (children or adults). Comparing results with a normal population is what allows us to determine that a person is functioning lower than average, within average range, or higher than average.
I found this diagnosis to be very interesting for a couple of reasons. First, it is good to have confirmation from the multi-disciplinary TEASC team that we really are looking at dementia. Second, the offering up of agoraphobia is an interesting conclusion that we've never had suggested or considered previously. Finally, the last paragraph provides an explanation as to why tests used for the normal population are used in connection with the intellectually disabled population. We have previously questioned this and it is nice to have a logical reason.