Dear Deb,
While it is difficult to be precise, I would feel that your MRI changes and symptoms are suggestive of cerebral atrophy. This could be the result of the smoking/ blood pressure/ cholesterol induced decreased blood flow (ischemia) to the brains, if no other problem has been detected in your MRI.
Qutting smoking has been the right step, since studies have shown that this is reversible to some extent.
Dementia too is associated with changes of cerebral atrophy. IF the symptoms did not begin immediately after the lobectomy, then I do not think that there is any connection between these two conditions (dementia & surgery),
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regards
Dr. Gupta