Jonathan Edwards
Senior Member (Voting Rights)
I will try to summarise a few points on anatomy and physiology, as I understand them.
1. CSF is produced by choroid plexus within fluid spaces called ventricles deep inside the brain and flows out of the brain at the fourth ventricle into the subdural space between the brain and skull. The CSF around the spinal cord is a dead end and not involved in any directional flow.
2. Therefore, cervical spine stenosis has no effect on CSF flow in the skull so does not affect intracranial pressure. It is irrelevant to any theory of raised intracranial pressure.
3. The same almost certainly applies to craniocervical instability since it does not interfere with circulation of CSF. Unless there is associated Chiari Malformation, in which case it is the Chiari that is the problem.
4. Chiari Malformation, if major, can lead to compression of the cerebellum on to the brainstem, which can block the outflow of CSF from the inner ventricles to the brain/skull space. This can lead to raised pressure within the brain but should not raise the pressure of CSF outside the brain. Such an effect is visible on an ordinary CT or MRI scan as an increase in size of ventricles relative to the brain/skull subdural CSF space. As far as I am aware nobody has said anything about such an appearance in any cases of ME/CFS.
5. Chiari Malformation comes in all degrees and over diagnosis of mild 'Chiari' is something that has been a concern for decades.
6. As far as I can establish the consensus view is that Chiari is not associated with EDS. The suggestion of an association comes from the Bolognese group in 2007. However, at that time the EDS criteria were even vaguer than they ae since 2017. Moreover, the report is based on a cohort of 'Chiari' cases attending a tertiary referral centre. It may be of note that they found that the combination of 'EDS' and Chiari was eight times more common in women. As far as I know EDS is not more common in women but 'hypermobility' as judged by Beighton score is much commoner in women because it does not have a different scale by gender and women have more mobile joints (elbows in particular). Everything points to the 'EDS' cases in this study being polygenic hypermobility and since the rate was only about 10%, which is normal, I doubt anything was found more than expected by chance. Which suggests that the consensus view is correct - there is no association with EDS.
7. The population based studies I have seen do not indicate any association between EDS and ME/CFS.
8. Idiopathic intracranial hypertension (IIH) is essentially unrelated to any of the above because the problem is failure to resorb CSF in the subdural brain/skull space. There is no blockage to flow. I do not know the detail of the imaging but I would not expect increase in ventricle size relative to subdural space. That may be why optic nerve oedema has been used to judge raised pressure in these cases.
9. Optic nerve oedema can occur with both an obstructive cause of high pressure and IIH. Note, however, that we cannot say that raised pressure may have been missed in CTD cases because the optic nerve is protected from oedema if the only evidence of raised pressure is optic nerve oedema. (And we have no reason to think CTD cases are relevant to ME.)
These are some of the reasons why I have said the anatomy and physiology do not add up.
One particular issue that worries me is that this group has chosen to send patients to a clinic in London that is highly controversial in terms of its interpretation of findings. There are fully competent neuroradiologists in Sweden, I am quite sure.
1. CSF is produced by choroid plexus within fluid spaces called ventricles deep inside the brain and flows out of the brain at the fourth ventricle into the subdural space between the brain and skull. The CSF around the spinal cord is a dead end and not involved in any directional flow.
2. Therefore, cervical spine stenosis has no effect on CSF flow in the skull so does not affect intracranial pressure. It is irrelevant to any theory of raised intracranial pressure.
3. The same almost certainly applies to craniocervical instability since it does not interfere with circulation of CSF. Unless there is associated Chiari Malformation, in which case it is the Chiari that is the problem.
4. Chiari Malformation, if major, can lead to compression of the cerebellum on to the brainstem, which can block the outflow of CSF from the inner ventricles to the brain/skull space. This can lead to raised pressure within the brain but should not raise the pressure of CSF outside the brain. Such an effect is visible on an ordinary CT or MRI scan as an increase in size of ventricles relative to the brain/skull subdural CSF space. As far as I am aware nobody has said anything about such an appearance in any cases of ME/CFS.
5. Chiari Malformation comes in all degrees and over diagnosis of mild 'Chiari' is something that has been a concern for decades.
6. As far as I can establish the consensus view is that Chiari is not associated with EDS. The suggestion of an association comes from the Bolognese group in 2007. However, at that time the EDS criteria were even vaguer than they ae since 2017. Moreover, the report is based on a cohort of 'Chiari' cases attending a tertiary referral centre. It may be of note that they found that the combination of 'EDS' and Chiari was eight times more common in women. As far as I know EDS is not more common in women but 'hypermobility' as judged by Beighton score is much commoner in women because it does not have a different scale by gender and women have more mobile joints (elbows in particular). Everything points to the 'EDS' cases in this study being polygenic hypermobility and since the rate was only about 10%, which is normal, I doubt anything was found more than expected by chance. Which suggests that the consensus view is correct - there is no association with EDS.
7. The population based studies I have seen do not indicate any association between EDS and ME/CFS.
8. Idiopathic intracranial hypertension (IIH) is essentially unrelated to any of the above because the problem is failure to resorb CSF in the subdural brain/skull space. There is no blockage to flow. I do not know the detail of the imaging but I would not expect increase in ventricle size relative to subdural space. That may be why optic nerve oedema has been used to judge raised pressure in these cases.
9. Optic nerve oedema can occur with both an obstructive cause of high pressure and IIH. Note, however, that we cannot say that raised pressure may have been missed in CTD cases because the optic nerve is protected from oedema if the only evidence of raised pressure is optic nerve oedema. (And we have no reason to think CTD cases are relevant to ME.)
These are some of the reasons why I have said the anatomy and physiology do not add up.
One particular issue that worries me is that this group has chosen to send patients to a clinic in London that is highly controversial in terms of its interpretation of findings. There are fully competent neuroradiologists in Sweden, I am quite sure.
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