The Trill symbiote would change its appearance from when it initially appeared here to how it would appear on Star Trek: Deep Space Nine (1993). In this case, the symbiote's appearance was made to resemble a caterpillar with the head of an octopus. According to Make-Up Supervisor Michael Westmore, the symbiote was re-made for DS9 to be more "streamlined" to make it easier to handle. Also the appearance of the Trill hosts would change as well. Here, the Trill hosts had semi-ridged foreheads and no body spots, but on DS9 they have smooth foreheads and body spots.
The increased eosinophilia in the cerebral spinal fluid and elevated sedimentation rate discussed by Nurse Ogawa and Dr. Crusher when examining Odan would, in fact, be expected findings with a parasite in the spinal canal.
The graphic on Picard's monitor before he has his conversation with Odan is the Tyken's Rift from Night Terrors (1991).
First appearance of the conjoined symbiotic race of the Trill and only TNG appearance. The Trill would appear regularly on Star Trek: Deep Space Nine (1993), primarily with the characters of the Dax line of lives.