We report the case of a bipolar I patient who was diagnosed with frontotemporal dementia at the age of 54 during a manic episode. Her neurological state improved when this episode ended. Each subsequent thymic relapse was associated with cognitive deficits which subsided when the patient became euthymic, even though SPECT continued to show the same frontal hypoperfusion. We here discuss the hypothesis that the cognitive reserve of this patient, a former journalist, may, except during her mood episodes, have provided her with sufficient resources to meet her life demands despite her underlying neurological disorder.