[What's new in primary lateral sclerosis?].

Primary lateral sclerosis as a nosological entity distinct from amyotrophic lateral sclerosis has been the subject of controversy since it was first described in the nineteenth century. Primary lateral sclerosis has been defined as a rare, non-hereditary disease characterized by highly progressive spinobulbar spasticity, related to the exclusive loss of precentral pyramidal neurons, with secondary pyramidal tract degeneration and preservation of anterior horn motor neurons. We carried out a study in nine patients with a diagnosis of primary lateral sclerosis. Our clinical, electrophysiological and pathological investigations provide evidence that the disease has a heterogeneous clinical presentation and that degeneration is not restricted to the central motor system but also affects the lower motor neuron. In view of this similarity with amyotrophic lateral sclerosis, primary lateral sclerosis may represent a slowly progressive syndrome closely related to motor neuron disease and amyotrophic lateral sclerosis.