A practical approach to the late effects of Polio
Charlotte Leboeuf

5 WHAT CAUSES THE LATE EFFECTS OF POLIO?

It is not clear exactly what causes the late effects of polio. There may even be several causes or a set of circumstances which favours the development of new symptoms. Some recent scientific concepts are explained below.

• Some think that the abnormal wear and tear associated with residual polio explains the symptoms of the late effects of polio. In other words, they do not consider this a "new" condition but a logical consequence of the "old" symptoms. Opponents to this concept have pointed out that even those who were mildly affected by polio or who had no obvious residual effects can experience its late effects (4).

  
  

• Others think that, due to the diminished number of motor neurones after paralytic polio, signs of ageing become more apparent in people who previously had polio. An argument against this notion is that the late effects of polio can start at any age and commonly well before the age of 60, when the number of motor neurones starts to diminish in all of us (5). However, for people past the age of 60, the combination of the two will need to be taken into account.

• One of the early concerns was that the polio infection had come back again; that the polio virus had become reactivated. This reaction is understandable, since some of the "new" symptoms resemble the "old" ones (such as pain, weakness and respiratory distress). Tests have failed to detect the polio virus in people who experience the late effects of polio and it is unlikely that it can remain active in the nervous system for so long (6). There is usually no need to worry about a new polio infection and the late effects of polio are not contagious.

• There is some evidence that the immune status is changed in people who previously had polio (7). An autopsy study of spinal cords from people who had polio many years prior to death showed signs of inflammation (8). This was an unexpected finding. In another study inflammatory changes were also found in fully recovered and originally spared muscles (9). Other researchers have failed to confirm these findings of immunological and inflammatory processes (7), so there are still many question marks in this area.

• Some people with symptoms of the late effects of polio have been, mistakenly, told by their doctor that they have the progressive motor neurone disease, amyotrophic lateral sclerosis (ALS). To receive such a diagnosis would be devastating, since ALS has a rapid and fatal course. Luckily, there are several important differences between these two conditions, the most important probably being that the LEOP is relatively slow and mild, and, unless there are important respiratory problems, it is certainly not life threatening. The present scientific literature makes a clear distinction between these two entities.

• The most common concept is that the deficient post-polio neuromuscular complex is prone to overuse because there are fewer nerve cells, fewer active muscle fibres and deficient circulation in areas which were affected by the polio virus (10). Excessive use of post-polio muscles and nerves appears to precede their deterioration. "Excessive" use is of course relative. Overuse is likely to occur faster in deficient areas because muscles and nerves must work harder to keep up with the requirements of daily living. Post-polio muscles have also been shown to need longer time to recover from activity than normal muscles.
  Overuse fatigue is a common complaint and it can occur in all muscles; those of the trunk (including the chest), the throat and mouth as well as arms and legs.

  
  

© Copyright The Lincolnshire Post-Polio Network 1997 1998 1999 2000

This document comprises an index, introduction and sixteen other sections or subdocuments. Permission for printing copies is granted only on the basis that ALL sections are printed in their entirety and kept together as a single document.

Document preparation: Chris Salter, Original Think-tank, Cornwall, United Kingdom.
Document Reference: <URL:http://www.zynet.co.uk/ott/polio/lincolnshire/library/australia/paleop/sectn_05.html>
Created: 30th December 1997
Last modification: 6th June 2000