allochiria

   Also known as allocheiria. Both terms stem from the Greek words allos (other) and cheir (hand), translating loosely to 'other hand'. The term allochiria was introduced in or shortly before 1882 by the Austrian neuroanatomist and neuropathologist Heinrich Obersteiner (1847—1922) to denote a "confusion of sides", or a mislocation of sensory stimuli to the corresponding opposite half of the body. Allochiria has been observed mainly in the context of neglect, which is usually due to a lesion affecting the right parietal lobe. It has also been described in conditions such as tabes dorsalis and other myelopathies, in diffuse organic brain syndromes, in parieto-occipital tumours, and in hysteria. The majority of cases of allochiria are related to the tactile sense, but allochiric responses can occur in other sensory modalities as well. In * auditory allochiria, a person speaking from one side is responded to as if someone were speaking from the other side. In *visual or *optical allochiria, stimuli presented within one hemifield of vision are attributed to a source on the contralateral side. Allochiric responses have also been described in the sensory modalities of pain, pro-priocepsis, temperature, smell, and taste, as well as in reflex electrical movements. Conceptually as well as phenomenologically, allochiria is related to * allachaesthesia. The American neurologists Kimford Meador et al. have drawn attention to the original descriptions and word derivations of allochiria and allachaesthesia, identifying the work of the Welsh neurologist and psychoanalyst Alfred Ernest Jones (1879—1958) as the principal source of confusion in this matter. As Meador et al. point out, in 1907 Jones redefined both notions in an attempt to increase their diagnostic specificity, depicting both conditions as a positive indication of the presence of hysteria. Today allochiria is generally considered a variant or subset of allachaesthesia, and neither condition is now associated exclusively with hysteria. As Meador et al. recapitulate in their 1991 paper on the subject, "Allachaesthe-sia is a condition in which a sensory impression is mislocated to a remote position, and allochiria denotes mislocations to the corresponding opposite half of the body or space." Another condition phenomenologically related to allochiria is * spinal cord damage-induced synaesthesia. It is unlikely, however, that the two phenomena are related in a pathophysiological sense as well.

   References

   Obersteiner, H. (1882). On allochiria. Brain,4, 153—163.

   Meador, K.J., Allen, M.E., Adams, R.J., Loring, D.W. (1991). Allochiria vs allesthesia. Is there a misperception? Archives of Neurology, 48, 546—549.