Help Me Understand This?

[HopeSprings]

This is exactly the type of testing I'm interested in. If only I could understand the results! Maybe I need to read it laying down. LOL. My understanding is that the author concludes that brain blood flow is not impaired in POTS patients and therefore is NOT the cause of cognitive issues, but they DO find cognitive problems. If it's not brain blood flow, then what is it?? Or have I misunderstood?

Thanks.

Increasing orthostatic stress impairs neurocognitive functioning in Chronic Fatigue Syndrome with Postural Tachycardia Syndrome.

Ocon AJ, Messer Z, Medow M, Stewart J.

Abstract

Chronic Fatigue Syndrome (CFS) is commonly co-morbid with Postural Tachycardia Syndrome (POTS). Individuals with CFS/POTS experience unrelenting fatigue, tachycardia during orthostatic stress, and ill-defined neurocognitive impairment, often described as mental fog. We hypothesized that orthostatic stress causes neurocognitive impairment in CFS/POTS related to decreased cerebral blood flow velocity (CBFV). 16 CFS/POTS and 20 control subjects underwent graded tilt table testing (at 0, 15, 30, 45, 60, and 75°) with continuous cardiovascular, cerebrovascular, and respiratory monitoring and neurocognitive testing using a N-back task at each angle. The N-back task tests working memory, concentration, attention, and information processing. The N-back imposes increasing cognitive challenge with escalating (0, 1, 2, 3, and 4-back) difficulty levels. Subject dropout due to orthostatic presyncope at each angle was similar between groups. There were no N-back accuracy or reaction time differences between groups while supine. CFS/POTS subjects responded less correctly during the N-back and had greater normalized reaction time at 45, 60, and 75°. Further, at 75° CFS/POTS subjects responded less correctly and had greater normalized reaction time than controls during the 2, 3, and 4 back tests. Changes in CBFV were not different between the groups and were not associated with N-back scores. Thus, we concluded that increasing orthostatic stress combined with a cognitive challenge impairs the neurocognitive abilities of working memory, accuracy, and information processing in CFS/POTS, but that this is not related to changes in CBFV. Individuals with CFS/POTS should be aware that orthostatic stress may impair their neurocognitive abilities.

PMID: 21919887 [PubMed - as supplied by publisher]

http://www.ncbi.nlm.nih.gov/pubmed/21919887

[HopeSprings]

Now wait a minute - are these same people contradicting themselves in a previous study? Now I'm really confused.

Am J Physiol Heart Circ Physiol. 2009 Aug;297(2):H664-73. Epub 2009 Jun 5.

Decreased upright cerebral blood flow and cerebral autoregulation in normocapnic postural tachycardia syndrome.

Ocon AJ, Medow MS, Taneja I, Clarke D, Stewart JM.

SourceDepartment of Physiology, The Center for Hypotension, New York Medical College, Valhalla, New York 10532, USA.

Abstract

Postural tachycardia syndrome (POTS), a chronic form of orthostatic intolerance, has signs and symptoms of lightheadedness, loss of vision, headache, fatigue, and neurocognitive deficits consistent with reductions in cerebrovascular perfusion. We hypothesized that young, normocapnic POTS patients exhibit abnormal cerebral autoregulation (CA) that results in decreased static and dynamic cerebral blood flow (CBF) autoregulation. All subjects had continuous recordings of mean arterial pressure (MAP) and CBF velocity (CBFV) using transcranial Doppler sonography in both the supine supine position and during a 70 degrees head-up tilt. During tilt, POTS patients (n = 9) demonstrated a higher heart rate than controls (n = 7) (109 +/- 6 vs. 80 +/- 2 beats/min, P < 0.05), whereas controls demonstrated a higher MAP than POTS (87 +/- 2 vs. 77 +/- 3 mmHg, P < 0.05). Also during tilt, mean CBFV decreased 19.5 +/- 2.6% in POTS patients versus 10.3 +/- 2.0% in controls (P < 0.05). We then used a transfer function analysis of MAP and CFBV in the frequency domain to quantify these changes. The low-frequency (LF; 0.04-0.15 Hz) component of CBFV variability increased during tilt in POTS patients (supine: 3 +/- 0.9 vs. tilt: 9 +/- 2, P < 0.02). In POTS patients, there was an increase in LF and high-frequency coherence between MAP and CBFV, an increase in LF gain, and a lack of significant change in phase. Static CA may be less effective in POTS patients compared with controls, since immediately after tilt CBFV decreased more in POTS patients and was highly oscillatory and autoregulation did not restore CBFV to baseline values until the subjects became supine. Dynamic CA may be less effective in POTS patients because MAP and CBFV during tilt became almost perfectly synchronous. We conclude that dynamic and static autoregulation of CBF are less effective in POTS patients compared with control subjects during orthostatic challenge.

http://www.ncbi.nlm.nih.gov/pubmed/19502561

[sue1234]

I don't understand either(apparently not enough CBF!).

[juliegee]

Hmmmm, looks like the same group sans Taneja & Clarke in the most recent study. I would guess that the first study you listed, 2011, reflects their current understanding. You're right- they are doggedly testing the same hypothesis with different results. I find it encouraging that they acknowledge the cognitive deficits most of us experience- they just don't know WHY...

Guess we should stay tuned for study number three