Hereditary spastic paraplegia is a group of clinically and genetically heterogeneous disorders consisting of pure and complicated forms. A variant with the additional features of severe atrophy of the small hand muscles, dysarthria, mental retardation, and short stature has been termed Troyer syndrome (MIM#275900) after the name of Old Order Amish families suffering from these symptoms. We report here an Austrian family with two individuals who exhibit all the features of Troyer syndrome, and provide additional data on this disorder. Electrophysiological studies showed chronic denervation and reduced motor nerve conduction velocities but normal sensory potentials. Muscle biopsy revealed a neurogenic pattern while the sural nerve was normal on histological examination. Brain abnormalities on magnetic resonance imaging consisted of a thin corpus callosum with a poorly developed cingulate gyrus and mild periventricular signal hyperintensities. These findings characterize the Troyer syndrome as a disorder of the first and second motor neuron with additional damage in the brain. The morphological features observed in this family may contribute to the grouping and subsequent understanding of complicated forms of hereditary spastic paraplegia, together with similar observations in other, more recently reported families.