It is not widely recognized that the pathology of Werdnig-Hoffman disease (WHD) may include cells other than the lower motor neuron. In the early infantile (acute) forms of this degenerative disease, neuropathologic involvement may extend well beyond the lower motor neuron territory to include neurons in spinal sensory ganglion and thalamus. The present report describes the neuropathologic findings of four patients with early infantile degenerative motor neuron disease, compares them to other reported patients, and discusses the relationship of these patients to those with classic WHD. We found involvement of thalamic and primary sensory neurons, although mild, to be a common finding in classic WHD. We suggest that early infantile forms of degenerative lower motor neuron disease which show prominent involvement of thalamic, primary sensory, and other neurons are but one end of the spectrum of WHD.