The paper gives an update on the pathogenesis, clinical presentation, and pathomorphology of cognitive impairments (CIs) in different autoimmune, endocrine, and infectious diseases, such as systemic lupus erythematosus, Sjögren's syndrome, BehНet's disease, primary angiitis of the central nervous system, polyarteritis nodosa, cryoglobulinemic vasculitis, hypothyroidism, herpetic lesion, and neurosyphilis. These patients are observed to have ischemic-hypoxic brain damage, the causes of which are free radical-induced cell injury, oxidative stress, excitation toxicity, cell necrosis and/or apoptosis, inflammation and immune disease, molecular sequestration, and cell death. There is enhanced imbalance in the pro-oxidant and antioxidant systems as cerebrovascular insufficiency progresses; as this takes place, the nerve cells are most susceptible to the induction of free radical reactions. In these cases, antioxidants that block the effects of free radicals and may potentially improve brain perfusion, by assisting the coupling of neurons and vessels, are first-choice drugs. To improve the cognitive status and to prevent the progression of CIs, it is important to build a cognitive reserve in a patient; this is largely favored by the preservation of a proactive approach to life and social bonds, as well as intellectual work.