How accurate is a complete office neurological exam on detecting brain tumor ?

Depends: A neurological exam can help to localize a lesion, but determination of the etiology of the lesion (the diagnosis) depends on the history and a diagnostic work-up (imaging, labs, etc) if indicated. Location and rate of growth of brain tumors are factors in how they first manifest. See a neurologist for evaluation if you're concerned. http://www.nlm.nih.gov/medlineplus/ency/article/003191.htm