Marcy White and her husband Andrew Trossman appeared on ABC's "Nightline" on behalf of their son Jacob, 4, who has Pelizaeus-Merzbacher (PMD), a rare degenerative neurological disorder that cannot be treated with any proven medication. Jacob's case came to the attention of Dr. Jim Garbern, a neurology professor and PMD researcher at Wayne State's School of Medicine. Garbern has begun testing a drug used for spinal cord injuries on PMD symptoms, using mice, and has received some positive results in the last month. "Where the mice that would normally, without any treatment, have a very exaggerated tremor in their hind limbs when they're walking, the animals, after about a day of treatment, had much better control of their limbs," said Garbern. "I'm guardedly optimistic that it's working, but I want to make absolutely sure of that before we review all of our data and present it to the pharmaceutical company," he said.