Asomatognosia

Asomatognosia is the inability to feel, recognize, or be conscious of one's own specific body parts or bodily conditions (Whishaw, 2015). Generally, asomatognosia often arises from damage to the right parietal lobe (Whishaw, 2015). Evidence indicates that damage to the right hemisphere often results from a stroke or pre-existing hemispatial neglect, or inattention to the left visual field (Antoniello, 2016) (Keenan, 2004). Individuals who suffer from somatoparaphrenia, a specific form of asomatognosia, ignore or deny ownership of a body part contralateral to the brain lesion (Feinberg, 1990). Although this condition can affect one or both sides of the body, most patients exhibit the inability to recognize limbs/body parts (i.e., arm, leg, head, breast) on the left side of their body as their own (Keenan, 2004). While individuals with asomatognosia typically suffer large lesions across several temporoparietal sectors, those with somatoparaphrenia also suffer lesions in the right medial and orbitofrontal regions of the brain (Feinberg 2010).

History

In 20th century literature, asomatognosia was often distinguished from the closely related somatoparaphrenia. According to Gerstmann's (1942) definition, asomatognosia was described as the "imperception of the affected limbs or body half, in various degrees from simple forgetting to obstinate denial of their existence." Critchley (1953) numbered various deficits of body image, including somatoparaphrenia and the rare loss of awareness of one body half corresponding to asomatognosia or hemidepersonalization. He stated that these (as well as other bodily) phenomena are not "sharply demarcated" and that it is not uncommon for one condition to merge into another. In Hécaen (1972) hemiasomatognosia and disownership were also distinguished but closely linked. Feinberg and colleagues (1990, 2010) forwarded a different definition, according to which verbal asomatognosia was defined as the denial of ownership, while somatoparaphrenia as a subtype of asomatognosia where patients also display delusional misidentification and complex confabulation.

The term asomatognosia was coined from the Greek: a (without), soma (stem somat– body or bodily), and gnosis (knowledge), thus defined as the "lack of awareness [of ownership] of one's body parts". The word Somatoagnosia (constructed from the same roots) is sometimes also used instead.