Bulbo-spinal lower motor neuron disease. Accumulation of neurofilaments in perikarya and axons

Two sporadic adult cases of bulbo-spinal lower motor neuron disease are reported. In the first patient, the disease lasted 8 months and was characterized by a bulbar onset followed by a progressive cephalocaudal involvement of the lower motor neurons in the spinal cord. In the second case of 14 months duration, the cervical spinal cord was affected at first while medulla oblongata and lower limbs were involved later on. There was a slight increase of the protein contents in the CSF. Postmortem examination confirmed the selective involvement of the lower motor neurons in medulla oblongata and spinal cord with severe loss at cervico-medullary level in case 1 and more diffuse loss in case 2, in keeping with the clinical signs. Bodian silver staining and electron microscopy showed the accumulation of neurofilaments in anterior born cells' perikarya and in proximal axonal dilatations. The nosology of the disorder and the comparison with lesions found in various types of motor neuron disease in humans and animals are discussed.