The disease is still common in some parts of India and Africa. In these districts, during periods of famine when wheat and other grains are in short supply, the diet may for months consist of flour made of the grass pea. In individuals so exposed, a gradual weakening of the legs accompanied by spasticity and cramps occurs. Paresthesias, numbness, formication in the legs, and frequency and urgency of micturition, erectile dysfunction, and sphincteric spasms are added. The upper extremities may exhibit coarse tremors and involuntary movements. These symptoms, once established, are more or less permanent but not progressive, and most of the patients live out their natural life span.
Only two reports on the neuropathology of lathyrism were known to Dastur, one by Buzzard and Greenfield in England, the other by Filiminoff in Russia. Both of their patients had been in a stationary paraplegic state for years. Greenfield noted a loss of ascending and descending tracts in the spinal cord, particularly the corticospinal and direct spinocerebellar tracts. Filiminoff observed a loss of myelinated fibers in the lateral and posterior columns. Unlike the cases of Spencer and colleagues, there had been a loss of pain and thermal sensation in the upper extremities. The larger Betz cells had disappeared, while anterior horn cells were unaffected. Gliosis and thickening of blood vessels was seen in the degenerated tracts.
The toxic nature of this disease, long suspected, was confirmed by Spencer and colleagues. They extracted a neuroexcitatory amino acid, beta-N-oxalylaminoalanine (BOAA), from grass peas and were able to induce corticospinal dysfunction in monkeys by giving this substance with a nutritious diet. Subsequently, Hugon and coworkers produced a primate model of lathyrism by feeding monkeys a diet of L. sativus in addition to an alcoholic extract of this legume. These findings tend to negate the importance of several other factors that had been thought to be causative, namely, malnutrition, ergot contamination, and toxins derived from Vicia sativa, the common vetch that grows alongside the lathyrus species.
The African acute spastic paraplegia called konzo has a similar toxic pathogenesis; it is caused by cyanide-like compounds in flour made from cassava.
These are described in Chap. 37 but should be considered in cases of chronic and progressive syndromes of the cauda equina and conus medullaris.
Familial Spastic Paraplegia (See Chap. 38)
There are several familial forms of progressive spastic paraplegia, some beginning in childhood, others in adult life. The pattern of inheritance in almost all our adult cases has been autosomal dominant. A lack of sensory symptoms and signs and sparing of sphincteric function until late in the illness are important diagnostic features. A number of adult cases are “complicated” in the sense that the spastic paraplegia is associated with cerebellar ataxia or dementia. By contrast, primary lateral sclerosis, a sporadic form of degenerative disease of the motor system, is characterized by a pure spastic paraplegia and bulbar spastic palsy either initially or with progression, the result of changes that are confined to the corticospinal pathways. These disorders are discussed extensively with the heredodegenerative diseases in Chap. 38, and the myelopathy associated with adrenoleukodystrophy, in Chap. 36.
This syndrome is most often attributable to developmental syringomyelia, that is, a central cavitation of the spinal cord of undetermined cause, but a similar clinical syndrome may be observed in association with other pathologic states such as intramedullary cord tumors, traumatic myelopathy, postradiation myelopathy, infarction (myelomalacia), bleeding (hematomyelia), and, rarely, with extramedullary tumors, cervical spondylosis, spinal arachnoiditis, and cervical necrotizing myelitis.