33 巻 (2016) 1 号 p. 9-18
Autoimmune encephalopathies are clinically and immunologically heterogeneous disorders. Over time, many different types of autoimmune encephalopathy have been discovered. In such clinical situations, we often recognize that patients with autoimmune encephalopathy are often misdiagnosed as exhibiting functional psychogenic movement, conversion, or somatoform disorders. We clinically analyzed 63 patients (14 males and 49 females; age range, 15–79 years) diagnosed with autoimmune encephalopathy in our hospital from 2013 to 2015. Throughout this period we diagnosed almost no conversion disorders in our department. These patients were diagnosed using the diagnostic criteria for each disease, following clinical features showing neurological symptoms of brain origin, responsiveness to immunosuppressive therapy, the existence of known pathological antibodies, and/or history of human papilloma virus (HPV) vaccination. Fourty–two patients showed motor disturbance (weakness, paresis of extremities, or slower pinching) and 35/42 (83.3％) patients showed give–way weakness, indicating disruption of continuous muscle contraction. Fourty–four patients showed sensory abnormalities such as strong pain, deep muscle pain, dysesthesia, paresthesia, or fast neurologic pain. Surprisingly, most pain was distributed in manner that was not explainable anatomically, while some patients also showed patchy, stocking–glove, or localized pain. Seventeen patients exhibited involuntary movements such as tremor entrainment, dystonia, or coarse involuntary movement. In most patients, such motor, sensory, or involuntary movements were markedly improved with immunosuppressive therapies such as prednisolone, azathioprine, or immune adsorption therapy. We observed memory loss, PNES (psychogenic non–epileptic seizure), dissociative amnesia, hyperventilation, opsoclonus, epilepsy, or autonomic symptoms amongst our patients. Although give–way weakness, anatomically unexplainable pain/abnormal sensation, and strange involuntary movements were thought to be psychogenic, the presence of one of these three symptoms was indicative of autoimmune encephalopathy. As autoimmune encephalitis exhibits diffuse involvement with the whole brain, these symptoms were entirely understandable. Except for the presence of organic disease, most patients were classified into somatoform disorders (DSM–IV, ICD–10) or functional movement disorders. Without first excluding autoimmune encephalopathy, we propose that physicians should not diagnose somatoform disorders. Since autoimmune encephalopathy patients often possess so–called psychogenic signs, it is possible that such signs might be generated by autoimmune encephalopathy instead of somatoform disorders. In conclusion, we propose that give–way weakness and anatomically unexplainable pain/abnormal sensation are key symptoms of autoimmune encephalopathy. We hope that many patients with autoimmune encephalopathy will now be identifiable using our new neurological examination and that each patient can be given an exact diagnosis and therefore be administered with the appropriate treatments.