In recent years, a considerable number of new sporadic or hereditary small artery diseases of the brain have been detected which preferably occur in younger age, below 45 years. Cerebral microangiopathies constitute an appreciable portion of all strokes. In middle aged patients, hereditary cerebral small vessel diseases have to be separated from sporadic degenerative cerebral microangiopathy which is mainly due to a high vascular risk load. Features of the following disorders and details how to differentiate them, are reviewed here, namely CADASIL, MELAS, AD-RVLC, HEMID, CARASIL, PADMAL, FABRY, COL4A1-related cerebral small vessel diseases and a Portuguese type of autosomal dominant cerebral small vessel disease (SVDB). The symptomatic overlap of the cerebral microangiopathies include also other distinctive non-hereditary diseases like posterior (reversible) encephalopathy and Susac's syndrome which are also described. Some of the microangiopathies described here are not only seen in the young but also in the elderly. The precise diagnosis has direct therapeutic implications in several of these entities. Cerebral microangiopathies cause recurring strokes and diffuse white matter lesions leading to a broad spectrum of gait disturbances and in most of these disorders cognitive impairment or even vascular dementia in the long term. Often, they also involve the eye, the inner ear or the kidney. Several typical imaging findings from illustrative cases are presented. The order in which these diseases are presented here is not dictated by an inner logic principle, because a genetically or pathophysiologically based classification system of all these entities does not exist yet. Some entities are well established and not unusual, whereas others have only been described in a few cases in total.
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