PSN Library Files

August 28, 2006

Electrophysiological findings in a cohort of old polio survivors. [Part I – The Article]
Sorenson EJ, Daube JR, Windebank AJ.
Department of Neurology, Mayo Clinic, Rochester, MN, USA.
J Peripher Nerv Syst. 2006 Sep;11(3):241-6.

A population-based cohort of poliomyelitis survivors was established and followed for 15 years (mean time since polio was 40 years). Over time, the cohort demonstrated a modest decline in summated compound muscle action potential amplitudes (CMAP) and a moderate decline in the summated motor unit number estimates (MUNE). There was no association between symptoms of late deterioration and magnitude of decline. Rather, the presence of these symptoms was associated with the magnitude of the residual deficits. Two patterns of neuron loss were modeled (linear and proportional decline). The summated MUNE was a more sensitive measure of loss of motor units than was the summated CMAP and appears to be a more valid measure of attritional loss of anterior horn cells. Of these two models of neuron loss, the proportional loss of motor neurons was a better fit of the data than a linear loss.

[Links below open in new windows]

Link to Abstract at journal site. Full text requires a subscription to journal or one-off payment of US$39 (at the time of writing).

Link to US National Library of Medicine (NLM) PubMed entry PMID: 16930286.
https://www.ncbi.nlm.nih.gov/pubmed/16930286?dopt=AbstractPlus

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August 28, 2006

Survivors of childhood polio do well decades later as they age. [Part II – The Press Release]

ROCHESTER, Minn. — Mayo Clinic researchers have found that years after experiencing childhood polio, most survivors do not experience declines greater than expected in their elderly counterparts, but rather experience only modest increased weakness which may be commensurate with normal aging.

“Other researchers have suggested that polio is a more aggressive condition later in life, but we’ve actually found it to be relatively benign,” says Eric Sorenson, M.D., Mayo Clinic neurologist and lead study researcher. “Our results suggest that polio survivors may not age any differently than those in the normal population — they’re not doing too badly compared to their peers. This tells us that the cause for the decline in muscle strength in polio survivors may be aging alone.”

Polio is a contagious, viral illness that peaked in the United States in 1952, when 3,000 people died of the disease. Mass immunizations in the mid-1950s began to slow the spread of the disease, and the last case of polio not caused by a vaccine occurred in the United States in 1979. The three major types of polio include spinal polio, a paralytic polio that attacks nerve cells in the spinal cord; bulbar polio, in which the virus attacks motor neurons in the brainstem; and bulbospinal polio, a combination of spinal and bulbar polios. The effects of polio run the gamut from a complete return to normal function to paralysis of limbs to acute death. Following the illness, most patients are worried about their long-term prognoses, according to Dr. Sorenson.

To conduct this study, the researchers randomly selected a group of 50 polio survivors from the general population of Olmsted County, home of Mayo Clinic, and followed them for 15 years. The average age of participants at the study’s start was 53, and the patients were an average of 40 years past their childhood experience with polio. The researchers measured strength and loss of neurons at the beginning of this period, and then again five and 15 years later with electrophysiological testing, strength testing and timed tests of performing basic functions. They found modest declines. Each patient also completed questionnaires about symptoms of progressive weakness at the beginning and end of the study period. Though the majority complained of progressive weakness during the time they were studied, these symptoms did not correspond with their actual magnitudes of decline over time. Rather, the researchers found patients’ symptoms experienced were associated with the degree of residual weakness immediately following their polio infections.

“Overall, we found that strength changed very little in these polio survivors as they grew older, and we discovered the neurons dropped off at a rate comparable to other non-polio survivors as they aged,” says Dr. Sorenson. “We concluded this was normal aging on top of their old deficits. Very few had to change their homes or add adaptive equipment. Those who had weakness problems during our study had a larger deficit at the end of their childhood disease, making them more likely to develop symptoms. So, as deficits at the end of the disease increase, the probability of experiencing post-polio symptoms increases.”

The discrepancy between what some of the patients experienced with growing weakness and their actual measurements of strength and neuronal loss likely is due to increased sensitivity due to their disease experiences, according to Dr. Sorenson.

“Patients feel their weakness progressing, but when you measure it, it’s very modest,” he says. “Likely, they lost so much strength at the time of their illness that any change is very noticeable to them. Though the likelihood is high that patients who have had childhood polio will complain of weakness later in life, they can expect years of stability without the need for major lifestyle modifications.”

Other Mayo Clinic researchers involved in this study include Anthony Windebank, M.D., and Jasper Daube, M.D. To obtain the latest news releases from Mayo Clinic, go to www.mayoclinic.org/news. MayoClinic.com (www.mayoclinic.com) is available as a resource for your health stories.

Contact: Lisa Lucier
newsbureau@mayo.edu
507-284-5005
Mayo Clinic

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EurekAlert | Survivors of childhood polio do well decades later as they age. [Part II – The Press Release]
Public release date: 21-Aug-2006.

The original of the above article can be found at [link opens in new window]
http://www.eurekalert.org/pub_releases/2006-08/mc-soc081506.php.

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August 28, 2006

‘No Polio effects’ in later life / Many Polio Survivors Faring Well. [Part III – The Media]

Opening Paragraphs + Extract:

People who survive polio in childhood will not suffer further effects later in life, say US researchers.

The Mayo Clinic team looked at 50 people who had had the disease as children and found most did not suffer any polio-related decline when older.

Polio has been wiped out in most places but remains a threat, particularly in India, Pakistan and Nigeria.

Experts said the Journal of the Peripheral Nervous System paper offered reassurance to polio survivors.

…

Dr Eric Sorenson, who led the study, said: “Other researchers have suggested that polio is a more aggressive condition later in life, but we’ve actually found it to be relatively benign.

“Our results suggest that polio survivors may not age any differently than those in the normal population – they’re not doing too badly compared to their peers.”

He added that the findings should be comforting to people worried about polio-related decline later in life.

“Though the likelihood is high that patients who have had childhood polio will complain of weakness later in life, they can expect years of stability without the need for major lifestyle modifications.”

———

BBC News | Health | ‘No Polio effects’ in later life.
Last Updated: Saturday, 26 August 2006, 23:55 GMT 00:55 UK.

The full text of the above article can be found at [link opens in new window]
http://news.bbc.co.uk/1/hi/health/4799725.stm.

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November 11, 2006

Dr. Sorenson responds to “Polio Survivors throw doubt on Study”. [Part VI – The Author’s Response]

[P&PPNews Editor: Dr. Sorenson’s numbered comments reference corresponding comments in “Polio Survivors throw doubt on Study”. Published with Dr. Sorenson’s permission.]

Dear Ms. Boone,

Thank you for your correspondence and your comments. Many of the points you raised are valid criticisms. I would make the following comments:

The study population was chosen to be a random, population based sample. This was done because this method of sampling is the least biased. There are always questions about whether or not: A) the sample cases are representative of the population from which they are drawn, and B) is the population that is sampled, representative of the diseased population as a whole. You mention that our sample is skewed with an over-representation of those more severely affected. Actually, if our sampled is biased it is biased towards those less affected. Approximately 40% of our subjects had only minimal neurological deficits. I’m not sure how you arrived at the 90% being severe. Only about 20% of our subjects would we have classified as severe.
In our study we did find that the polio subjects did weaken modestly with time, but the degree of this weakness did not correlate with whether or not they were symptomatic. The only correlation with symptoms was with the severity of their residual deficits after polio. I am only aware of one other large prospective study on polio from the Netherlands that over a 6 year period found similar results (Nollet F. et. Al. Perceived health and physical functioning in postpoliomyelitis syndrome: a 6-year prospective follow-up study. Archives of Physical Medicine & Rehabilitation. 84(7):1048-56, 2003).

You may very well be correct that there is a subset of subjects that do more poorly than the group as a whole. Our polio cohort, as a whole, was fairly normally distributed in their magnitude of change over the course of the study. The majority of our cohort had only a modest decline in strength, however, there was a small minority that changed more and a small minority that didn’t change at all. In our cohort we did not identify any baseline variables that predicted the rate of change. Predictor variables may exist but we did not identify any.
I am not sure how to comment on this point. We have not presented any data with an intent to mislead or misrepresent.
I do not believe that anyone who sees polio patients questions the existence of the post-polio syndrome. I have not made any such claims. I believe the controversy is over our theory that the normal process of aging may be the root cause. It is true that we did not include a normal aging control group at the onset of our cohort study and this remains our speculation. A normal age matched control group has not been done in any previous long term study of polio survivors that I am aware of. This theory however has been erroneously interpreted that we are suggesting that polio survivors are merely getting older. In contrast, we propose that there is an attritional loss of motor neurons, muscle mass and strength in normal subjects. Because normal subjects have a considerable reserve capacity, they are not aware of these effects. Polio survivors however, who have already lost a number of motor neurons, no longer have that reserve capacity and the same attritional loss in them results in larger problems and progressive weakness. This would explain why those who with the largest residual deficits are more likely to be symptomatic; and why the polio group as a whole appears to decline in a relatively normally distributed fashion.
The issues related to the reliability and validity of MMT are valid. Because of this we did not only complete the MMT but also completed quantitative strength tests using a series of strain gauges resulting in specific force measurements in the muscle groups tested. It is difficult to translate these force measurements into an overall global measure of strength which can be done and has been validated with the NDS-w scale (MMT). In looking at the quantitative force measurements the results were the same as those with the NDS-w scores providing internal validity to our findings.
As you point out responses to questionnaires can be misleading. One of the drawbacks of questionnaire research is the subjectivity and the interpretation of the respondent. We asked a number of questions including specific questions such as: What gait aids do you use? What braces or orthotics do you use? What modifications have you made to your home? Etc. to minimize the subjectivity and variability of the respondents.
You are correct that it is often difficult to assess the extent of polio survivors residual effects by talking to or merely observing them. I am often struck by how polio survivors have adapted to their deficits. This is why it was important that we did our timed functional tasks, strength testing and electrophysiology testing at baseline and followed the group prospectively. Otherwise it is very difficult to determine this in a retrospective fashion. Even our baseline assessments were years after maximal recovery in all cases. What the polio subjects’ true maximal recovery was cannot be known for certain, and must be inferred.
I am sorry if our work has provided you or your colleagues difficulty or distress, none was intended.

Sincerely,

Eric J. Sorenson, MD Department of Neurology Mayo Clinic Rochester, MN 55905

END

Polio Survivors throw doubt on Study | Hilary Boone [PDF 157KB] | Minor Revisions 11th November 2006.
https://www.lincolnshirepostpolio.org.uk/downloads/extra/poliosurvivorsdoubtstudy.pdf

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September 23, 2006

Three reviews of ‘Electrophysiological findings in a cohort of old polio survivors’ (E. J. Sorenson, et al). [Part V – The Dissection]

The following articles consist of three separate reviews of the recently published ‘Electrophysiological findings in a cohort of old polio survivors’ [Sorenson EJ, Daube JR and Windebank AJ (2006) Journal of the Peripheral Nervous System, Vol 11:241-246].

In “MUNE data review”, Dr. Mavis Matheson discusses significant inconsistencies in the math. “I’ve reviewed the article and if the math is done correctly, one gets entirely different results.”

MUNE data review | Dr. Mavis Matheson [PDF 102KB].
https://www.lincolnshirepostpolio.org.uk/downloads/extra/munedatareview.pdf

In the second article “The Mayo Clinic haunts postpolio patients again”, Dr Ruth Bridgens discusses a number of aspects including the cohort’s applicability to the wider population of polio survivors, the limitations of the measures chosen and the interpretation of their findings.

The Mayo Clinic haunts postpolio patients again | Dr Ruth Bridgens [PDF 149KB] | Updated 26th September 2006.
https://www.lincolnshirepostpolio.org.uk/downloads/extra/mayohauntsagain.pdf

Finally, in the third and last article of this set, “Polio Survivors throw doubt on Study”, Hilary Boone has applied a retrospective comparative analysis to all the major articles arising from this study published over its 15 year period. Based on that analysis, seven issues are raised which “we believe need to be taken into account before conclusive statements can be made regarding findings from Sorenson et al s research report.”

Polio Survivors throw doubt on Study | Hilary Boone [PDF 157KB] | Updated 11th November 2006.
https://www.lincolnshirepostpolio.org.uk/downloads/extra/poliosurvivorsdoubtstudy.pdf

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November 11, 2006

Dr. Sorenson responds to “Polio Survivors throw doubt on Study”. [Part VI – The Author’s Response]

[P&PPNews Editor: Dr. Sorenson’s numbered comments reference corresponding comments in “Polio Survivors throw doubt on Study”. Published with Dr. Sorenson’s permission.]

Dear Ms. Boone,

Thank you for your correspondence and your comments. Many of the points you raised are valid criticisms. I would make the following comments:

The study population was chosen to be a random, population based sample. This was done because this method of sampling is the least biased. There are always questions about whether or not: A) the sample cases are representative of the population from which they are drawn, and B) is the population that is sampled, representative of the diseased population as a whole. You mention that our sample is skewed with an over-representation of those more severely affected. Actually, if our sampled is biased it is biased towards those less affected. Approximately 40% of our subjects had only minimal neurological deficits. I’m not sure how you arrived at the 90% being severe. Only about 20% of our subjects would we have classified as severe.
In our study we did find that the polio subjects did weaken modestly with time, but the degree of this weakness did not correlate with whether or not they were symptomatic. The only correlation with symptoms was with the severity of their residual deficits after polio. I am only aware of one other large prospective study on polio from the Netherlands that over a 6 year period found similar results (Nollet F. et. Al. Perceived health and physical functioning in postpoliomyelitis syndrome: a 6-year prospective follow-up study. Archives of Physical Medicine & Rehabilitation. 84(7):1048-56, 2003).

You may very well be correct that there is a subset of subjects that do more poorly than the group as a whole. Our polio cohort, as a whole, was fairly normally distributed in their magnitude of change over the course of the study. The majority of our cohort had only a modest decline in strength, however, there was a small minority that changed more and a small minority that didn’t change at all. In our cohort we did not identify any baseline variables that predicted the rate of change. Predictor variables may exist but we did not identify any.
I am not sure how to comment on this point. We have not presented any data with an intent to mislead or misrepresent.
I do not believe that anyone who sees polio patients questions the existence of the post-polio syndrome. I have not made any such claims. I believe the controversy is over our theory that the normal process of aging may be the root cause. It is true that we did not include a normal aging control group at the onset of our cohort study and this remains our speculation. A normal age matched control group has not been done in any previous long term study of polio survivors that I am aware of. This theory however has been erroneously interpreted that we are suggesting that polio survivors are merely getting older. In contrast, we propose that there is an attritional loss of motor neurons, muscle mass and strength in normal subjects. Because normal subjects have a considerable reserve capacity, they are not aware of these effects. Polio survivors however, who have already lost a number of motor neurons, no longer have that reserve capacity and the same attritional loss in them results in larger problems and progressive weakness. This would explain why those who with the largest residual deficits are more likely to be symptomatic; and why the polio group as a whole appears to decline in a relatively normally distributed fashion.
The issues related to the reliability and validity of MMT are valid. Because of this we did not only complete the MMT but also completed quantitative strength tests using a series of strain gauges resulting in specific force measurements in the muscle groups tested. It is difficult to translate these force measurements into an overall global measure of strength which can be done and has been validated with the NDS-w scale (MMT). In looking at the quantitative force measurements the results were the same as those with the NDS-w scores providing internal validity to our findings.
As you point out responses to questionnaires can be misleading. One of the drawbacks of questionnaire research is the subjectivity and the interpretation of the respondent. We asked a number of questions including specific questions such as: What gait aids do you use? What braces or orthotics do you use? What modifications have you made to your home? Etc. to minimize the subjectivity and variability of the respondents.
You are correct that it is often difficult to assess the extent of polio survivors residual effects by talking to or merely observing them. I am often struck by how polio survivors have adapted to their deficits. This is why it was important that we did our timed functional tasks, strength testing and electrophysiology testing at baseline and followed the group prospectively. Otherwise it is very difficult to determine this in a retrospective fashion. Even our baseline assessments were years after maximal recovery in all cases. What the polio subjects’ true maximal recovery was cannot be known for certain, and must be inferred.
I am sorry if our work has provided you or your colleagues difficulty or distress, none was intended.

Sincerely,

Eric J. Sorenson, MD Department of Neurology Mayo Clinic Rochester, MN 55905

END

Polio Survivors throw doubt on Study | Hilary Boone [PDF 157KB] | Minor Revisions 11th November 2006.
https://www.lincolnshirepostpolio.org.uk/downloads/extra/poliosurvivorsdoubtstudy.pdf

Hilary Boone and Dr Sorenson

Lancet

Study Throws Doubt on PPS

Dr Windebeck

Polio Survivors Throw Doubt on Study

Hilary Boone, Lincolnshire Post-Polio Network

 

‘Survivors of childhood polio do well decades later as they age’ [a],

‘Polio Survivors faring well’ [b],

‘‘No polio effects’ in later life’ [c]

 

The above three press statements were made in sequence during the last ten days of August 2006. The initial statement, on the 21st August 2006, was the announcement by the Newsbureau of the Mayo Clinic in Rochester, Minnesota, [a] of the research findings reported in an article in the Journal of the Peripheral Nervous System, ‘Electrophysiological findings in a cohort of old polio survivors’ by Eric J. Sorenson, Jasper R. Daube, and Anthony J. Windebank. Their research used a cohort of patients that they had been studying over the last 15 years. [1,2,3,3a,4,5] A cohort of 50, reduced over the 15 years to 38 ‘old polio survivors’. Within days the findings had been reported by other media and by the time it was on the BBC News – Health there were ‘No polio effects in later life’. [c]

 

Polio Survivors who are NOT doing well decades after recovery; who do have polio effects in later life; who have been presenting with well documented new symptoms – including considerable functional decline in actions of daily living – to recognised Post Polio Clinics and Specialists during the last 25 years are once again disappointed that this cohort continues to be used as representative of the polio population. In the authors’ own words in the 1996 article ‘…we believe that our findings can be extrapolated to the whole population of polio survivors in the United States.’[4]

 

McCarthy reviewed the 1996 article [4] in the Lancet in February 1996 [8] with the heading

 

Study throws doubt on post polio syndrome

 

Helena Edwards of the Leicestershire Post-Polio Network in her rebuttal stated, ‘We, in the UK, heard from people whose doctors were assuring them that PPS did not exist, and in some cases the doctors mentioned that their information came from an article they had read recently.’ [9]

 

We present the following issues that we believe need to be taken into account before conclusive statements can be made regarding findings from Sorenson et al’s research report. Authors who raise other issues with this research, and the way findings have been presented, are included in References at the end of this paper [d,e,f,g].

 

1. We believe the people in Sorenson et al’s study cannot be extrapolated to the ‘polio

population’, because 90% of their cohort is towards one end of the scale, towards

more severe deficits.

2. There are important facts from 10% [5 of 50 subjects] of their study group that appear

to have been dismissed when in fact they appear to show what is happening at the

other end of the scale, those of us presenting to PPS specialists and PPS Clinics;

polio survivors who recovered well and now have new symptoms and considerable

functional decline in activities of daily living.

3. Their use of numbers and phrases can easily be misinterpreted without the full facts

from previous articles.

4. Sorenson et al make several statements of caution, regarding comparing studies with

the normal population, then appear to proceed to ‘overcome’ or ‘ignore’ them in this

article. Yet just eighteen months earlier they stated ‘the effects of normal aging in this

cohort cannot be commented on.’ [5]

5. We question the validity and reliability of Manual Muscle Testing to grade muscles.
6. We question the reliability of a YES/NO questionnaire. Ask 50 Polio Survivors “Can

you do x?” and the vast majority will say “Yes”. Ask the same number “How do you do

x?” and you are likely to get a huge variety of answers.

7. The extent of recovery from paralytic polio experienced by many polio survivors is

often not realised.

 

Issue 1

Quite simply, in the authors own words, from two of the articles, the cohort used is weighted towards people whose polio residuals were more visible

 

• ‘we selected those survivors from the original cohort [223] who currently reside in

Rochester and the surrounding area’ [2]

• ‘we also randomly selected an equal number from those who were complaining of

deterioration and those who were not.’ This intentionally biases the study toward

those with difficulty… At this time, 31 patients have completed the study.’ [2]

• ‘From the 247 survivors, we selected 50 subjects.’ [3 – Abstract]
• ‘Fifty survivors who lived closest to Rochester were selected for the study. This group

was likely to stay in the area and be available for follow-up study.’’ [3]

• ‘58 subjects were called in order to recruit fifty’ [3]
• ‘Those evaluated showed a trend towards more severe deficits’ [3]
• ‘There may be a tendency for more handicapped residents to remain geographically

closer to our clinic.’ [3]

• ‘These subjects were not seeking medical attention; they were invited to participate

on the basis of their having had polio.’ [3]

 

Issue 2

Important facts in their study actually relate to the other end of the scale, of polio survivors who are experiencing new symptoms and functional decline, do not seem to have been given equal attention. Again using the authors own words. [3]

 

• ‘that 5 subjects who had made the greatest recovery were all experiencing new

difficulties’

• ‘One of the two nearing retirement who had made an occupation change because of

leg weakness was a surgeon. He had significant progressive leg weakness so that

ambulation had deteriorated from requiring no aids to needing a cane and then a

walker and finally a wheelchair for distances’

• ‘that nine limbs that were newly symptomatic that had not been paralyzed during the

acute illness were in 4 subjects.

Three of the four had purely bulbar polio but now complained of limb symptoms. The fourth had paralysis involving the legs and now complained of arm pain’

• ‘That in no case did they find new complaints in a limb that showed no electrophysical

evidence of having been affected by the original disease.’

 

Issue 3

The use of numbers and phrases in their articles can easily be misinterpreted without reading all previous articles relating to the study. For instance the article that triggered the recent press releases, ‘Electrophysiological findings in a cohort of old polio survivors’, stated:-

 

• Fifty representative subjects were randomly chosen from 298 patients with a

documented history of paralytic poliomyelitis residing in Olmsted County at the time of

the infection. [6]

 

Compare that statement with the following quotes from the progression of articles from 1984 to 2005, referenced [1,2,3,4,5], relating to this study group. We accept that these quotes are taken in isolation and not the full context, but they do not appear to be consistent.

 

1984     Patients were required to have had established residence in Rochester prior to diagnosis for inclusion in this study.’

‘Of the 316, 201 had paralytic polio and 115 had nonparalytic polio.’

‘23 died in the acute phase of the illness…. 7 deaths in subsequent years.’

… ‘a questionnaire was circulated in April 1984 to all traceable patients who had had paralytic poliomyelitis.’

‘Of 171 potential respondents… 23 people remain untraced at the time of presentation of this data’

‘Replies have been received from 128.., three persons were unwilling to participate.’ ‘Of the 125 remaining, 97 patients indicated stability and 28 indicated deterioration since their maximal recovery from polio.’

‘This questionnaire was supplemented by a detailed telephone interview for those who indicated deterioration since their maximal functional recovery from polio.’ [1]

 

1987     ‘This group has subsequently been expanded to include all residents of Olmstead

County, who had paralytic polio between 1935 and 1959. Two hundred eighty six subjects were identified, and 276 have been located for follow-up.

‘Thirty people (10.5%) died in the acute phase of the illness, and 23 died in later years.’

‘The remaining 233 formed the cohort for the follow-up. Two hundred twenty-three have been located’.

‘At this time, 31 patients have completed the study. Ten individuals reported no difficulties of any kind… Seventeen reported new, perceived, specific limb weakness.’ [2]

 

1991     ‘We identified a cohort of 300 individuals who had paralytic polio between 1935 and 1955. All lived in Olmstead County, Minnesota.’

‘Two hundred ninety-three of the 300 cases were traced. Of the 300 subjects, 53 were known to have died’.

‘Fifty survivors who lived closest to Rochester were selected for the study. This group was likely to stay in the area and be available for follow-up study.’

‘58 subjects were called in order to recruit 50.’

In response to the questionnaire, 32 individuals complained of some new difficulty (Table 4)

Table 4 – No new symptoms 18. *Types of complaints reported by 32 of the subjects with paralytic polio.

More subjects (21 of 33) complained of lower limb difficulty than upper limb problems (nine of thirty)

The cause of the symptoms is unclear but they are not attributable to age alone because the population is still relatively young (median age 49 years) [3]

 

1995     ‘Of the 300 cases, 298 identified for follow-up. 53 had died;’

‘From the population of 300, 50 survivors were chosen on the basis of proximity of residence to Rochester. This group was chosen because they were likely to stay in the area and be available for detailed repeated measurements.’

‘Detailed comparisons between 50 and the other 197 survivors to ensure that the cohort was representative.’

‘This group of subjects was then reconstructed after five years. All gave information about their present status, and 46 underwent again the complete battery of tests described above.’

‘The number of subjects reporting new symptoms of weakness, pain, or fatigue remained constant over the five year interval. Of 30 individuals who had symptoms at the first study point, 23 continued to have symptoms and 7 did not. Six individuals who did not have symptoms at the first time point did have symptoms after five years.’

‘..(Table 1), the distribution remained similar except that more patients were likely to be complaining of all three symptoms at the second evaluation.’ [3a]

 

1996     ‘Three hundred individuals met the criteria for paralytic poliomyelitis. 298 of whom were available for follow-up; (n.b. 53 had died) we chose a representative cohort of 50 individuals for prospective, sequential evaluations. They were chosen because they represented the whole cohort…’

‘Of the 50 patients, 46 completed the detailed 5 year study. Four patients declined to complete the tests but were contacted by telephone; all four reported that they were asymptomatic and did not want to participate in further detailed physiologic testing.’’ [4]

 

2005     ‘In 1987, we began a population-based cohort study of 50 subjects with a remote history of paralytic poliomyelitis.’

‘Fifty representative subjects were chosen from 298 patients who previously had well documented paralytic poliomyelitis, living in Olmstead County at the time of the infection.’ (n.b. 53 had died)

Of the original 50 subjects of the cohort, three subjects died during the 15 year follow up period. Nine of the remaining 47 refused further participation.’

‘Thirty-one of the 38 subjects whom we followed for 15 years reported symptoms of progressive weakness during the study period. Only seven subjects remained asymptomatic.’ [5]

Issue 4

Sorenson et al make several statements of caution when comparing their study to others then appear to proceed to ‘overcome’ or ‘ignore’ them. E.g. Regarding the McComas study Sorenson states ‘Without such a control group, one cannot reliably compare the changes in the polio group with those in a normal aging population.’ [6]

 

The first paragraph of their Press Release on 21st August 2006 states:-

‘Survivors of Childhood Polio Do Well Decades Later As They Age’

ROCHESTER, Minn. Mayo Clinic researchers have found that years after experiencing childhood polio, most survivors do not experience declines greater than expected in their elderly counterparts, but rather experience only modest increased weakness which may be commensurate with normal aging.’ [a]

 

Compare that to the statement in their 15 year follow-up article published in March 2005, just eighteen months earlier.

 

‘How the changes identified in our polio cohort compare with those of a normal aging population remains unknown. We did not include a normal control group at the inception of the cohort. In the absence of a normal control population, the effects of normal aging in this cohort cannot be commented on.’[5]

 

Issue 5

Manual Muscle Testing – How valid and reliable is this as a form of grading muscles?

 

Professor W.J.W. Sharrard – a world renowned Polio Professor from the 1950’s, who wrote ‘Muscle recovery in Poliomyelitis’ [10], studied polio patients at autopsy and found that ‘muscle grades of 3 were given to individuals with 85% denervation of the muscles. In other words, profound muscle weakness must be evident before abnormal grades are given.’

 

The Mayo Clinic states that Manual Muscle Testing and Isometric testing across different joints were used to grade muscles. They have not used the normal MRC grading scale but used the following scale, which they state ‘has the advantage that numbers can be handled additively for additional analysis’ [2]

 

0             Normal strength

1             25% loss of strength

2             50% loss of strength

3             75% loss of strength

4             100% loss of strength

 

The issue with Manual Muscle Testing – most often performed as a single action – is that it will not tell the health professional how long the patient can sustain that action, repeat that action, or how they use that action in a pattern of movement. According to Westbrook in her rebuttal of the 5 year study [9] Windebank et al derived their “Neurological Disability Score” from the results of manual muscle testing, a method that is notorious for overestimating polio muscle strength.[11] Polio survivors developed many trick movements; use other muscles instead of or to assist weakened ones. Important evidence of reported new weakness and compensatory strategies can be missed unless people are observed performing actions of daily living over a period of time.

 

Polio Survivors, who have often taken months or even years before presenting new weakness to a health professional, report again and again that ‘They say I am strong, that I have nothing wrong with me. Then why can I no longer do the things I used to a few years ago?’ To ensure this is not misinterpreted as age loss; such comments are coming from individuals in their 40’s and 50’s. The following are two responses to the Lincolnshire Post-Polio Network in May 2002:

 

“Regarding the MMT you are correct. If done only a single time, it can give an erroneous idea of the true muscle strength and endurance. In a way, the key word here is “endurance” which reflects muscle strength on multiple contractions. Many polios will have good strength on a single contraction only to get weaker on repeated contractions.” Lauro S. Halstead M.D. Director of Post-Polio Program, National Rehabilitation Hospital, Washington DC, USA.

 

“You have done a brilliant job of describing a real problem for polio survivors and professionals that is, the limitations of the Manual Muscle Testing (MMT) scheme (a British invention, circa 1950, by the way). I quite agree with your comments and observations”. Fred Maynard, M.D. Marquette, Michigan, USA – President Board of Directors, Post-Polio Health International.

 

Issue 6

Each participant completed a questionnaire of 337 items enquiring about limb and bulbar weakness, pain, fatigue and activities of daily living, in a YES/NO format.

 

There is an issue here that is well recognised and reported on in medical articles, [12] that polio survivors are strong willed, determined, highly capable people, who, regardless of level of disability/ability, do not need any help thank you. They are reluctant to admit that they are having new symptoms, new functional decline, and even when admitted and/or confirmed by testing, it can still be some time before they take the advice to pace and rest and use aids and equipment. Using a yes/no questionnaire does not necessarily allow polio survivors to convey to the health professional HOW they actually perform the action in question. ‘Independently and with ease’ for ‘I could/can manage a small flight of stairs (about 10 steps) might turn out to be going up backwards sitting on their bottom.

 

Sorenson et al recognised ‘that it had been difficult to ascertain whether limbs, apparently uninvolved by the original disease process, might become affected by progressive symptoms years later. This is because of the reliance of the memories of an illness that occurred 30 to 50 years earlier.’

 

The mean age at polio onset was variously reported as 9, 12 or 13 with the youngest age at one year or less. Not only is it difficult for affected individuals and family members to remember, it must also be taken into account that the youngest patients had limited language levels at the time of their polio.

 

Issue 7

The high levels of recovery from Paralytic Polio of some polio survivors, including some who were in iron lungs, is often not realised. Many have competed in professional or high level amateur sports, some have joined the police and armed forces, or had other highly physical jobs. The damage from their polio was not easily visible externally.

 

Following a presentation at St. Thomas Hospital in London by Dr. Windebank on the results of the first five years study [4], Hilary Boone asked “How many of the 50 did sport?” Dr. Windebank replied that “one man could manage three holes of golf.” When asked, ‘No swimmers, athletes, rugby referees, people in the police or armed forces?’ he emphatically replied, ‘these people had paralytic polio’. Hilary Boone replied, ‘so did the people I am talking about, including myself. They all had paralytic polio and some were even in iron lungs’. The seminar restarted and Dr. Windebank did not answer a follow-up letter.

 

Conclusion

We believe the above throws doubt on the methods used in this study and the conclusions the authors made and continue to make from this research. The cohort steered towards those

• who had more severe deficits following recovery, [Method and Results 1991 – 3]
• who geographically still lived near to the clinic, [Method and Results 1991 – 3]
• ‘These subjects were not seeking medical attention; they were invited to participate

on the basis of their having had polio’ [Discussion 1991 – 3]

 

It is highly possible that this cohort is not representative of the 608 residents of Olmstead County who had acute polio between 1935 and 1960. The results of the 50, now 38, people in this study cannot be extrapolated to the polio population of the United States. Sorenson et al’s conclusions, based on a study of patients who have been chosen/selected, without a control group, believed by them to be representative of the ‘polio population’, can in fact be misleading.

 

Sorenson et al state, ‘There are no confirmatory tests to reliably distinguish between the effects of the old disease from new progressive difficulties. It is a clinical diagnosis following history taking, physical examination, and test results.’ [3] Therefore we believe it is essential that any study group mentioned in a polio/post polio medical article is more clearly defined to allow readers to make comparisons with their patients.

 

More and more polio survivors who recovered to the greatest degree from paralytic polio are now presenting to health professionals with new symptoms of weakness, pain, fatigue and considerable functional decline in actions of daily living. These are people who have often led active lives, have competed at amateur and professional sports, and who have had highly physically demanding jobs. They now find they have to:-

 

• Change their occupation and often medically retire early
• Return to using/start using aids and orthotics
• Go back to/start using canes, crutches, walkers, electric scooters and wheelchairs.
• Modify their homes and/or move to single story homes
• Be prescribed or purchase electrically operated chairs and beds
• Recommence using/start using respiratory aids
• Go from being very fit and active to being less able than their parents

 

In fact the results of this study can and should only be compared to those polio survivors who match the level of ability, disability, symptoms and lifestyle of the 50 participants, now 38.

 

This cohort has also been used in another article in Neurology in 2005. [7]

 

Where do we go from here?

Terminology: Are reported symptoms related to the late effects of polio, post polio syndrome, post polio sequelae, unstable polio, post-polio muscular atrophy, another medical condition; or a combination?

 

To be perfectly frank Polio Survivors already experiencing new and unexpected symptoms and functional decline do not care what label they are given so long as:-

 

• All our reported symptoms are accurately assessed and recorded.
• Other conditions are checked for as there are no diagnostic tests.
• We are given the medical and financial support to manage our lives.

 

The Mayo Clinic have been aware for ten years since publishing the results of the 5 year level of their study that other health professionals and post polio support groups do not entirely agree with all the statements made regarding their Olmstead County Polio research. It is regrettable that following such critique, they did not extend their study to include more polio survivors who had recovered like the surgeon and were now experiencing considerable new difficulties.

 

It is a sorry state of affairs when polio survivors around the world must give up hours of their time to research their medical condition. To have to continually question and research the results of testing that do not corroborate your reported symptoms because of the way it has been carried out or recorded is unjust. Struggling on year after year, often deteriorating through incorrect advice and treatment or lack of it, has to come to an end.

 

Polio Survivors – a strong willed, determined, highly motivated, hard working group of people – want to live for as long as possible, doing as much as possible. We need a full and accurate base line assessment that takes into account the endurance of our weakening muscles. We need advice, and the understanding that it takes time to accept that we have to change our lifestyle. We need treatment where it is available, appropriate aids and equipment, and benefits so that we can financially cope in this world where anything ‘disabled’ has a high price label.

 

References – available from PSN on request admin@poliosurvivorsnetwork.org.uk