Regarding the treatment of vestibular migraines; overtime does an ssri become less effective due to tolerance and a switch to a tca become necessary?

Use both cautiously.: Vestibular migraines is a variant of migraine in general accompanied b dizziness especially when moving and sometimes voices seem muffled. Ssri's are effective . If the medications are less effective, you may ask your doctor to bump the dosage up or use a tricyclic in conjunction with the ssri instead of changing the medication all together.

Neither my choice: I have not found great value with either category for vestibular migraine or even any of the migraine variants. Some nsaid's such as Indocin or Naproxen may help, but drugs such as beta-blockers, calcium channel blockers, topamax (topiramate) or Depakote work far better. Otc preps such as riboflavin, butterbur, co-q10, feverfew might be tried. Botox seems to be useful in selected cases. Find a headache doc.