I think you can know that this is a thalamic stroke rather than cortical because a cortical stroke occurring only in the postcentral gyrus (primary sensory cortex) and involving the entire homunculus without affecting the nearby precentral gyrus (primary motor cortex) is very unlikely.
I had no idea this was central Stroke Syndrome. But got it right with this logic. Vibration (Posterior column) and pain (spinothalamic) both ultimately synapse in the VPL thalamus. Symptoms on the right side means that the lesion is contralateral in the brain due to decussation rules. so Left thalamus was the origin. Discussed in table FA'18 page 493
submitted by โtinydoc(276)
Neuropathic Pain after stroke is central Post stroke pain Syndrome
caused by contralateral thalamic lesions
Pg. 504 FA19