This is by no means a study, and I'm by no means a vet, but I've had 4 spinal cord injured tomcats, at least 2 of whom had trouble with urinary crystals. Buddy (who'd been hit by a car) developed a weird neurological spasm at the neck of his bladder in response to crystals, which eventually got him PTS because he couldn't pee. Koi, who'd been shot in the spine, leaked pee when he slept but was never diagnosed with crystals. Ace, who is a tail pull boy, recently started peeing in his sleep, and, come to find out, had crystals. I upped the amount of the special urinary food I was giving the herd (they don't like it, so I was mixing it with blue Cat Chow), and within 2 days no more peeing everywhere! Even though the special food is more expensive than most, even at Walmart, it might be worth considering having all SCI tomcats eat it for prevention.