Dr David Tuller: Shaky Evidence for Signs of Functional Neurological Disorders


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Trial By Error: Shaky Evidence for Signs of Functional Neurological Disorders

30 DECEMBER 2019

By David Tuller, DrPH

One of my goals next year is to write more about so-called “medically unexplained symptoms,” also known as MUS. The term MUS might be useful as a descriptive name for the large category of phenomena that lack a proven pathophysiological pathway. But in the medical literature, and in the minds of those who present themselves as experts in the field, it is framed as an actual diagnosis that can be delivered with full confidence rather than a provisional construct based on the current state of medical understanding.

Different specialties have their own sub-categories of MUS. In neurology, these are called “functional neurological disorders,” or FND. This term has generally replaced older ones for this concept, including “conversion disorders” and “psychogenic disorders.” As with MUS overall, the evidence for these conditions has resided primarily in the absence of standard signs indicating organic dysfunction. The phrases “conversion disorder” and “psychogenic disorder” mean exactly what they say–the idea is that unexpressed psychological distress is transformed into physical symptoms, although how this “conversion” would occur is not really clear.

In contrast, FND is considered a kindler, gentler phrase. It does not automatically convey the notion of a psychiatric disorder, so the presumption is that the diagnosis is more likely to be acceptable to patients, who can resist being told they do not have an organic illness.
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