Neurological symptoms cover a whole host of ailments in snakes. They include:

- OPMV
- Meningitis
- Septicemia
- Various viral and bacterial infections
- Issues with metabolism/organ disfunction
- Exposure to extreme temperatures
- Previous head injuries
- Previous exposure to toxins
- Inherited genetic issues
..and IBD.

The fact that he can climb and perch and do other things that require coordination is fairly encouraging. The only advice I think is worth it's salt is to QT him and take him to a Vet.