Functional Neurologic Disorder, <i>La Lésion Dynamique</i>

Functional neurologic disorder is common and a significant cause of disability and stress in neurologic patients. The nature of this disorder has been unclear. Originally called hysteria, the disorder interested Charcot who postulated that a functional lesion, <i>la lésion dynamique</i>, was responsible. Recent studies of functional neurologic disorders now allow us to understand what <i>la lésion dynamique</i> is and identifies these disorders without ambiguity as arising from the brain. Functional neurologic disorders are best understood as a multifactorial process with a biopsychosocial model. There can be a genetic predisposition. Commonly there is early life trauma that leads to a developmental abnormality of the amygdala, including loss of inhibition. This abnormality can be considered a predisposing factor. When stressed, the amygdala becomes hyperactive, driving the limbic system to cause widespread network dysfunction in the brain. This dysfunction can improve, correlating with clinical improvement. Network dysfunction is becoming recognized as an important pathologic process in neurology and psychiatry, as real as any other pathology. We should be able to make progress in helping patients with functional neurologic disorders with this understanding of <i>la lésion dynamique</i>.