To the Editor.
—The article on "Primary Lateral Sclerosis" by Younger et al,1 in the December 1988 issue of the Archives, lists the following as part of the criteria: "Symptoms were restricted to progressive gait disorder without pain, paresthesias, sphincter symptoms, history of optic neuritis, transverse myelitis or other neurological disorder." However, in Merritt's Textbook of Neurology, seventh edition, edited by Dr Rowland (whose name is also on the article in the Archives), it states under primary lateral sclerosis, on page 552, "In contrast to ALS, upper motor neuron bladder dysfunction is common and posterior column loss may be seen." The question is, which criterion is correct?