Thursday, 25 April 2013

Heating effect on nerve conduction in MS

The science behind heat-sensitivity in MS #MSBlog #MSResearch

"This study looks at the effect of heat stress on the function of central nerves in MSers, compared to controls. No surprises regarding the headline results; heat stress affects the function of MSers more than it does healthy controls. The main reason for this is that demyelinated and/or remyelinated nerves malfunction when exposed to temperatures above normal. Heat sensitivity is a common problem in MSers. We have previously posted on this and have done surveys in the past highlighting this issue. This is why there have been studies on cooling suits in the past and why so many MSers find cooler environments more bearable. What is your experience?"



Epub: White et al. Effect of passive whole-body heating on central conduction and cortical excitability in multiple sclerosis patients and healthy controls. J Appl Physiol. 2013 Apr 18.

Background: Heat stress is associated with increased fatigue perception and decrements in function for individuals with MS. Similarly, healthy individuals experience decrements in exercise performance during hyperthermia. Alterations in central nervous system (CNS) function during hyperthermia include reduced voluntary activation of muscle and increased effort perception. 

Objective: The purpose of this investigation was to test the hypothesis that passive heat exposure in MSers will produce increased subjective fatigue and impairments in physiologic measures of central conduction and cortical excitability compared to healthy individuals. 

Methods: Eleven healthy individuals and 11 MS patients completed a series of transcranial magnetic stimulation (TMS) studies to examine central conduction and cortical excitability under thermoneutral (TN) and heat-stressed (HS) conditions at rest and after a fatiguing thumb abduction task. Passive heat stress resulted in significantly greater fatigue perception and impairments in force production in MSers. 

Results: Central motor conduction time (CMCT) was significantly shorter during HS in controls; however, in MS patients normal increases in conduction velocity with increased temperature were not observed centrally. MSers also exhibited decreased cortical excitability during HS, evidenced by significant increases in resting motor threshold, decreased MEP amplitude, and decreased recruitment curve slope. Both groups exhibited post-exercise depression of MEP amplitude, but the magnitude of these decrements was amplified in MSers during HS. 

Conclusions: Taken together, these results suggest that CNS pathology in MSers played a substantial role in reducing cortical excitability during HS.

Other posts of interest:

03 Dec 2012
Humidity impacts on your body's ability to lose heat; i.e. it reduces the rate at which you can perspire (human) or sweat (animal), which is one of the most brilliant cooling systems ever invented. If you are interested in ...
26 Nov 2012
Research: heat and excersise. Epub: Skjerb├Žk et al. Heat sensitive persons with multiple sclerosis are more tolerant to resistance exercise than to endurance exercise. Mult Scler. 2012 Nov. BACKGROUND: Heat sensitivity is ...
04 Dec 2012
More on heat sensitivity or Uhthoff's phenomenon. #MSBlog: More on temperature sensitivity; how temperature blocks conduction in demyelinated axons! Stutzer & Kesselring. Wilhelm Uhthoff: a phenomenon 1853 to 1927.
03 Jun 2012
Results: MSers showed a significantly (P=0.002) higher core body temperature than the controls following the heat stress. Performances in walking (P<0.001), chair rise (P=0.005) and functional reach (P=0.04) were poorer in ...

14 Mar 2012
RESULTS: More patients with MS reported heat sensitivity for fatigue, compared to patients with UC (53.4% vs 35.5%, respectively, P = 0.016). However, heat-sensitive patients were equally fatigued as heat-insensitive ...
12 Aug 2012
Simply, unbearable. If this is how MSers feel in more moderate temperatures I really feel for them. I am now more determined than ever to try and do something for MS-related fatigue and heat sensitivity. I have some ideas.
11 Mar 2012
MS symptoms and heat. Epub: Leavitt VM, Sumowski JF, Chiaravalloti N, Deluca J. Warmer outdoor temperature is associated with worse cognitive status in multiple sclerosis Neurology 2012 March 7. OBJECTIVE: Patients ...
28 Jul 2011
I suspect that MS'ers with heat sensitivity or fatigue-related conduction block will be more likely to be fampridine responders you are definitely right. In this case. Having been on fampridine for nine weeks now. It is a revelation ...

03 May 2012
The are quite a few post on the blog concerning the influence of heat and MS. With the good old British ... Heat really is quite cruel for 4-5 months of the year where I live, suffice to say my home is air-conditioned. ReplyDelete ...

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