Functional weakness

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Functional weakness is a neurological term used to describe patients who feel weak in an arm or a limb but on testing no signs of objective weakness are found. It is generally not caused by damage to the wiring of the central nervous system but can result from plasticity within the cortex in response to injury elsewhere in the body. Feelings of weakness and fatigue are common in many illnesses and are not in themselves objective symptoms or signs. Despite this the feeling of weakness has been found to be associated with positive autoantibodies to CHRM1 in patients with myalgic encephalomyelitis. It can also be associated with postural hypotension and postural orthostatic tachycardia (POTS- a mild form of neuropathy). Patients with low flow POTS are especially prone to regional variations in blood flow and associated weakness. Neurologists however continue to see the "feeling" of weakness as a sign of psychosomatic distress. The term functional is generally used as an attempt to improve doctor patient relationships. Most patients with functional weakness find terms such as conversion disorder or hysterical weakness offensive.

References

• A web based journal for patients can be found at www.conversiondisorder.co.uk
• International Journal of Medicine 2003 Aug 112(2): 2225-30 [1]
• A Leg To Stand On- Oliver Sacks
• The Postural Tachycardia Syndrome- Marvin S. Medow, PhD, and Julian M. Stewart, MD, PhDCardiology in Review 2007;15: 67–75
• What should we say to patients with symptoms unexplained by disease? The "number needed to offend" Stone et al. [2]