Worry will not help, and I know how it is, you want to know right now exactly what is going on. Call the pediatrician and get strarted on the process.
It is likely that the same motor issues that are causing the articulation errors you took him to be evaluated for are also casuing his other motor concerns, but speech and langauge issues also accompany neurological conditions too.
By "neurological" she probably was refering to nuerodevelopmental issues which range from mild to severe, and I would take comfort that you only worried about the speech issue and your pediatrician did not notice this at all, and assume for now that his issue is on the mild side. Think more in terms of fine motor control issue for now, and keep your mind off the scary idea that it is some deeply rooted nuerological condition, disorder, or syndrome. Try not to borrow trouble and go looking for every condition that could fit his motor issues, it probably won't be helpful and will just make you worry more. If you need to know the details about something serious, it will find you once you start the evaluation process.
I am assuming that this is a school based evaluation (from your last post) and that the speech therapist will be bringing in the OT, PT and maybe a psychologist to evaluate his developmental level in a little more depth, is that right? If it is, consult with your pediatrician about private evaluations for all these areas, and for the medical attention that he needs as well. The school is required to identify his needs and to evaluate all areas of his disablity, but they are not diagnostic, and you should not be relying on them to diagnose or provide all the services that he needs. Even for speech, OT, and PT, you should get private evaluations so that you maximize his progress, becasue the school is only required to make him functional in the classroom, and you will want far more than that. You probably will need a consultation with a Neurologist and an evaluation with a Developmental Pediatrician, a Speech therapist, an Occupational Therapist, and a Physical Therapist (all these areas will be run through a Developmenta Pediatrician's office, and all the peices of the evaluation will be covered, and explained to you in one report from the Developmental Pediatrician.)
I have been where you are. You thought that your son just danced to his own drummer, and needed a little therapy, and BOOM, people start saying things that make little sense, and you think that they are not telling you something becasue they don't want to scare you, and by not just saying what they think, they actually scare you more. It will be OK. Ask them to write down the words for you, and get explainations for any you do not understand. The speech therapist may be worried about how you will respond to what she suspects, and I would try to stay as calm as you can, because if a school noticed an issue, it is something you should take seriously. Schools actually have a huge tendancy to under identify, so there is something there and you probably will be receiving public serivces to help him. Just don't skimp on the private services! His medical condition and all services that make him more than "functional" are your responsiblity; know that this is true, even if they say otherwise.
Do not feel bad that you did not notice this yourself. Shame on your doctor (if the same one has been seeing him and screening for development all along.)
It will be OK.
M.