Does anyone know where to find information about infantile spasms causing autism?

Not correct. Infantile spasms will not cause autism. Infantile spasms are usually the result of an underlying brain abnormally, which may result in autism like symptoms.
It's not the spasms. Any brain pathology causes greater risk of autism. Underlying causes are found in > 75% of infants with west syndrome. Almost 50% of infants with ws have a prenatal cause like abnormal development of the cortex of the brain, metabolic syndromes, or genetic syndromes. Tuberous sclerosis can cause both west syndrome & autism. West syndrome itself can cause regression or arrest of development.