There is a syndrome that perplexes both patients and doctors alike -- one where weakness is the primary complaint but there is absolutely no identifiable reason why this should exist at all. The key word here is "identifiable" -- for there is most likely some kind of reason, but it is not overt. A full physical and neurological examination has been done to no avail. And the symptoms cannot simply be due to fatigue or pain even if these are present. What is this syndrome and how can we begin to think about this?
Earlier this year, a group of researchers in Edinburgh, Scotland defined a syndrome called "functional weakness " . They sought to identify how common this was and what distinguished this group of people from those who were similar, but whose weakness could be explained by neurological illness. This second group were referred to as the controls. They found that there were 3.9 new cases per 100,000 people per year -- comparable with prior statistics that were around 5 per 100,000 and even higher in new neurology patients.
These researchers then compared the patients with "functional weakness" with the control subjects. They found that people with functional weakness had more pain and a higher frequency of depression, generalized anxiety disorder, panic disorder and somatization disorder (a psychiatric term for physical symptoms without identifiable physical cause). However, both groups were similar in their self assessments of depression and anxiety. Much of this was not that remarkable and up to this point, informational and interesting.
However, what was remarkable was the following finding: People with functional weakness were less likely to agree that stress was a possible cause of their illness but twice as likely as controls to report that they were not working because of their symptoms. Both of the latter findings were statistically significant. While people with functional weakness appear to be every bit as disabled as people with weakness due to neurological disease, why would they be so much less likely to attribute their symptoms to psychological factors?
The paradox here is that people with neurologic disease recognize psychological causality whereas those with psychological disease do not. The literal possible reasons are manifold, but the possibility of psychological denial of symptoms is intriguing. This study concluded that denial was more likely than secondary gain -- that is, that people with functional weakness were not likely to be missing work because it suited them, or seeking attention because they wanted it. There seemed to be other factors at play.
One important factor was the greater panic disorder in people with functional weakness. This group of patients appeared to have non-fearful panic -- that is, their anxiety may have been largely unconscious. Several studies have now shown quite convincingly that fear can be registered outside of conscious awareness in the brain  and I have dedicated a chapter to this phenomenon in my book "Life Unlocked: 7 Revolutionary Lessons To Overcome Fear" .
One intriguing parallel not mentioned in this article is that of the similarity between psychological denial and physical denial. When people have a stroke in the parietal region of the brain, and if you ask them to move the paralyzed leg, they are unaware that they cannot move the leg because they are paralyzed. They may even answer: "I have arthritis" or "I don't feel like it" . They are completely in denial of their physical paralysis.
Similarly, some people who have functional weakness may also be in denial of their psychological illness. I believe that this could be due to the unseen effects of panic disorder. For one, people with panic disorder have brain abnormalities that are similar to those with somatoform disorders (physical symptoms due to psychological vulnerabilities) . Secondary, deficits in the parietal lobe have been reported in patients with panic disorder [6-8]. This same region has been implicated in denial of physical symptoms.
Thus, if you have weakness, fatigue and pain with no identifiable physical or psychological cause, your unconscious brain may be wreaking havoc on your insight due to the anxiety that you cannot feel as anxiety, but which nonetheless impacts your brain in very significant ways.
1.Stone, J., C. Warlow, and M. Sharpe, The symptom of functional weakness: a controlled study of 107 patients. Brain, 2010. 133(Pt 5): p. 1537-51.
2.Whalen, P.J., et al., Masked presentations of emotional facial expressions modulate amygdala activity without explicit knowledge. J Neurosci, 1998. 18(1): p. 411-8.
3.Pillay, S., Life Unlocked: 7 Revolutionary Lessons To Overcome Fear. 2010, New York: Rodale.
4.Ramachandran, V.S., The evolutionary biology of self-deception, laughter, dreaming and depression: some clues from anosognosia. Med Hypotheses, 1996. 47(5): p. 347-62.
5.Koh, K.B., et al., Shared neural activity in panic disorder and undifferentiated somatoform disorder compared with healthy controls. J Clin Psychiatry, 2010.
6.Lai, C.H. and Y.Y. Hsu, A subtle grey-matter increase in first-episode, drug-naive major depressive disorder with panic disorder after 6 weeks' duloxetine therapy. Int J Neuropsychopharmacol: p. 1-11.
7.Hasler, G., et al., Altered cerebral gamma-aminobutyric acid type A-benzodiazepine receptor binding in panic disorder determined by [11C]flumazenil positron emission tomography. Arch Gen Psychiatry, 2008. 65(10): p. 1166-75.
8.Eren, I., et al., Evaluation of regional cerebral blood flow changes in panic disorder with Tc99m-HMPAO SPECT. Psychiatry Res, 2003. 123(2): p. 135-43.