Hello Lansy and welcome to HealthBoards,
A single episode could be your neurologists way of say a first neurological event and could be considered part of the McDonald Criteria or it could simply be you had a single episode of tonic spasms with no known cause at this time.
L'Hermittes can be caused by any damage to the spine (injuries, MS, other conditions) so until you have the MRI it is difficult to know if L'Hermittes is MS caused or if their is another reason for the L'Hermittes.
MS is a clinical diagnosis and there is no single test, by it's self, that can give you a diagnosis of MS. There is not a symptom of MS that is unique to the disease so it is important to rule out any other cause for a patient's symptoms.
Do you have MS? Only time and testing will tell. Good luck with the cervical MRI