ABSTRACT
Motor neuron disease (MND) is a chronic, progressive, and fatal disorder, predominantly involving the motor cortex, the corticospinal tract, lower cranial nerve nuclei, and spinal anterior horn cells. The Western Pacific Foci consist of the Mariana Islands (including Guam), the Kii peninsula of Japan, and the West Irian region of New Guinea. The diagnosis of MND is based on identification of the clinical syndrome and its progression over time. Some infrequent MND-like syndromes can be excluded by laboratory tests or nerve biopsy. The two types of diagnostic errors in epidemiologic investigations are underdiagnosis and overdiagnosis. Their presence may lead to inaccurate measurements of disease frequency in population surveys, or selection bias and misclassification for outcome in cohort or case-control studies. The presence of overdiagnosis is better known and can be controlled, at least for living patients, through assessment by clinicians. Special investigations of overdiagnosis were reported in 7 of 21 surveys of MND.
