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Defining Executive Function

Posted Jun 25 2010 10:26am

A deficit in a person’s executive function can be of the first signs of the onset of Parkinson’s disease (PDD).

The term executive function describes a set of that control and regulate other abilities and behaviors. Executive functions are necessary for goal-directed behavior. They include the ability to initiate and stop actions, to monitor and change behavior as needed, and to plan future behavior when faced with novel tasks and situations. Executive functions allow us to anticipate outcomes and adapt to changing situations. The ability to form concepts and think abstractly are often considered components of executive function.

So, how is executive dysfunction manifested in PDD?

The dementia associated with Parkinson’s disease has an insidious onset and slow progression and is characterized by cognitive and motor slowing, executive dysfunction, and impairments in memory retrieval and flexibility.

And what have I been noticing?  Let’s talk about this morning’s shower.

I got the water going, made sure my shower seat was where it was supposed to be, put my washcloth over the faucet, placed the towel on the toilet seat (after first closing the toilet seat), pulled down the shower nozzle and sat down to scrub myself.

So far, so good.  I leaned over, switched off the shower, then realized there was one part of my body that I hadn’t washed yet, and I would have to wash that standing up.  So I turned the water back on, got it to the correct temperature, put the shower nozzle back on its hook and finished washing myself.

OK, so the shower was done.  I dried myself.  I have to do this systematically now to make sure I don’t forget to dry any part of myself.  I start with the face, the head, and work my way down.  I have gotten out of the shower before after drying one arm and not the other, one leg and not the other, leaving my back wet.  Now, I have to give conscious effort to section off my body in my mind and dry each portion in a set order.

Over to the sink.  I look at all the stuff there and for a moment have to think about what to do next.

Ah!  The pre-shave lotion.  I grab the bottle, poot a generous portion of the lotion onto my hand, rub it into my face and scalp.

OK, that’s done.  Now, while allowing the pre-shave to work, I brush my teeth.  I can do this pretty much automatically as the toothbrush and toothpaste are close together on the sink.  Where I tend to screw up is in the area of mouthwash.  More than once, I’ve caught myself reaching for the after shave, unscrewing the top and ALMOST pouring it into a glass before I realize I’m about to gargle with cologne.  I put the top back on the bottle, grab the Listerine, and do the job properly.

Shaving goes pretty well, although it’s a slow process to buzz my head and face and do a good job of it.

The point is… things that used to be automatic now require thought.  When I’m at the computer and I need to shift from one task to another, I find myself looking at the icons on my screen wondering just what the hell was I supposed to do.  Even working on the blog, if I see a correction that needs to be made, I will go to the edit screen and completely forget where the mistake was, what kind of mistake it was, was it a typo or a format error…

I find my focus wandering.  I find my ability to pay attention wavering.  And I’m seeing what my doc calls “illusions.”  Yesterday, sitting here at my desk, there were two different instances of something dashing under the table from my left… about the size of a mouse.  Didn’t get a good look.  And one of the dogs was under the table at the time and would have CERTAINLY been alerted by the presence of a mouse.  If there was one.  Which there wasn’t.

And all of these are symptomatic of the onset of Parkinson’s disease dementia.

My doctor and I talked about this at my last visit, and he felt I was still relatively early in that process and that the side effects of the drugs he could offer would probably not be worth the relief I’d get.

The appearance of PDD, even at a low level at this point, does not bode well .  Here’s an abstract from a scholarly article on the subject.

Several recent studies have shown that dementia is common in Parkinson’s disease (PD), and that in some patients, cognitive impairment occurs even at the time of diagnosis. The point prevalence of dementia in PD is close to 30% and the incidence rate is increased 4–6 times as compared to controls. The cumulative prevalence is very high, at least 75% of PD patients who survive for more than 10 years will develop dementia. The mean time from onset of PD to dementia is approximately 10 years. However, there are considerable variations, and some patients develop dementia early in the disease course. Earlier onset of dementia is associated with more structural brain changes. The most established risk factors for early dementia are old age, severity of motor symptoms, in particular postural and gait disturbances, mild cognitive impairment and visual hallucinations. The genetic contributions to dementia are currently not clear and need to be explored in future studies.

From the article itself…(subscription required)

Several have confirmed that patients with more severe and advanced have a higher risk for dementia than those with less advanced PD. More interesting, an association between specific motor symptoms and dementia has been reported in several studies. Symptoms such as rigidity, postural instability and gait disturbance predict more rapid cognitive decline and time to dementia. In one study, speech and axial impairment, indicative of predominantly non-dopaminergic deficiency, were found to predict incident dementia, whereas dopaminergic symptoms such as rigidity and were not.  Several studies have found an association between postural instability and gait disorder (PIGD) motor subtype to be associated with dementia. Of note, the motor profile differs with time, the most common change being from tremor-dominant to PIGD type. We recently showed that in nearly all dementia cases, dementia was preceded by PIGD dominant, or by the transfer from tremor-dominant to PIGD type PD. Similar findings were reported in another study . In the CamPaign study of incident PD, non-tremor type (i.e. mixed or PIGD type) motor symptom severity was associated with a higher risk for dementia independent of age.

I have the PIGD type of Parkinson’s.  I have never had any real tremor to speak of.  Now that my DBS is working right, rigidity is under control, but not postural instability or my gait.  I’m having problems with speech and some with swallowing.

Visual hallucinations (VH) are among the most characteristic neuropsychiatric features of PD, and may even aid in the differentiation of PD from other parkinsonian disorders. VH are common in PD, particularly in patients with dementia. In a longitudinal, community-based study, we found visual hallucinations to be associated both with a higher rate of cognitive decline  as well as a higher risk for development of dementia . The association of VH with dementia is probably related to VH being associated both with Lewy body pathology in the temporal lobe as well as with cholinergic deficits.

According to Wikipedia, “cholinergic” refers to the neurotransmitter “acetylcholine” which is a chemical you need in the thinking parts of your brain to work properly.  PD patients, as well as Alzheimer patients suffer from a lack of this chemical.

Oh well.  According to the literature , folks who are diagnosed at 45 have an average life expectancy of 21 years.  Dementia cuts into that somewhat.    Everything from here on in is gravy, I s’pose.

So, in other words, I have nothing to worry about.  As long as I don’t step in front of a bus.  Or think I’m chasing a rabbit and fall and break my hip.  Or swallow incorrectly and drown or get pneumonia.

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