To the Editor.
—The case of Sydenham's chorea reported by Dr Swedo1 was an interesting and well-presented lesson. However, I wish to take issue with one sentence: "An electroencephalogram [EEG] revealed diffuse posterior cortical slowing." This is a confusing description of the EEG. Was the slowing pathologic or the normal posterior slowing of youth? Was the slowing in the θ or δ range? Was it constant or intermittent? Was the slowing seen only during drowsiness (which would be a normal finding)? Did it attenuate with eye opening? Were the results of the EEG otherwise normal? Since EEGs, generally speaking, measure cortical function, the term "cortical slowing" is troublingly redundant. In addition, "diffuse posterior" is self-contradictory; was the abnormality seen diffusely, bilaterally in the posterior head regions, bisynchronously, or independently?Approximately half the patients with Sydenham's chorea will have abnormal findings on EEGs. Pathologic slowing ranges from mild background slowing
Jeret JS. Sydenham's Chorea. JAMA. 1995;274(4):304. doi:10.1001/jama.1995.03530040030032