Many disorders commonly cause focal or diffuse abnormalities of the central nervous system. This may lead to sensory, motor, or autonomic dysfunction of body parts that have connections to the involved areas, or abnormalities of cognition, emotion, or consciousness if there is involvement of certain areas of the brain, particularly the cerebral cortex. Many types of pathology commonly cause focal syndromes of the central nervous system, including idiopathic, vascular, epileptic, immune, mechanical, and neoplastic disorders. Many types of pathology commonly cause diffuse syndromes of the brain, mostly affecting widespread areas of cerebral cortex on both sides; these include genetic, idiopathic, vascular, epileptic, mechanical, metabolic, infectious, environmental, nutritional, and toxic disorders. Because the central nervous system performs many functions and may be affected by many disorders, a large number of syndromes may occur with central lesions, often making the diagnosis of these disorders challenging.