Neurological Signs: Mirror Phenomena
Posted in Clinical Review Article on 22nd Sep 2015
The speaker of these lines is an ageing Chinese academic, Old Gisors, who habitually smokes opium, a habit which might possibly be relevant to his strange sensory experiences. A number of mirror phenomena are described in the neurological literature,2 of which those with a cognitive flavour are briefly considered here (i.e. neither mirror movements nor the “mirror dystonia” sometimes encountered in writer’s cramp are discussed).
Mirror Sign and Mirrored Self-Misidentification
The experience reported by Old Gisors, a failure to recognise ones’ own reflection in a mirror, may be described as the “mirror sign”. In addition to this failure, patients may sometimes develop a delusional belief that their reflection is in fact that of a stranger, which has been termed “mirrored self-misidentification”,3 a response which might contribute to the “phantom boarder sign” (the belief that there is someone else living in the house).
Rather little seems to have been published on these signs, but the articles which have appeared generally indicate that it is a reflection (no pun intended!) of cognitive decline,3 for example in Alzheimer’s disease (AD)4,5 or dementia with Lewy bodies.6 Mirror sign may perhaps be a consequence of visual agnosia, and has been noted in a patient with the posterior cortical atrophy variant of AD who also had visual hallucinations.7 Unusually mirror sign may occur as a focal deficit at the onset of a progressive dementing illness, indicative of non-dominant hemisphere dysfunction. In addition to perceptual (face processing) impairments, affective and reasoning deficits may also contribute to the pathogenesis of mirror sign.8 Dementia is not, however, a sine qua non: mirrored self-misidentification has also been noted in an elderly patient with a right dorsolateral frontal infarct, bilateral frontal encephalomalacia consistent with previous head trauma, and posterior periventricular ischaemic lesions but without dementia. Based on these observations, the authors suggested that the right dorsolateral prefrontal cortex may be important for self-recognition.9
Mirror Agnosia, Mirror Apraxia, Mirror Ataxia
Mirror agnosia and mirror apraxia are related phenomena, as may be mirror ataxia.
Mirror agnosia is a deficit in which patients are unable to use mirror knowledge when interacting with mirrors (a definition which might also encompass mirror sign and mirrored self-misidentification). Also sometimes known as the “looking glass syndrome”, or “Ramachandran’s sign” after the first description,10 patients are unable to point to the real object when it is seen in a mirror. They may attempt to reach “into” the mirror even when the actual location of the target has been shown, suggesting an inability to distinguish between the real and virtual images. This reaching for the virtual object has been termed mirror apraxia.11 Reaching for the real object but with increased errors of direction has been termed mirror ataxia.12 Parietal lobe lesions with associated hemispatial neglect may underlie these signs, with dissociation of retinotopic (allocentric) space and body schema (egocentric space). A lesion study suggested different areas of parietal lobe might underpin mirror ataxia (postcentral sulcus) and mirror agnosia (posterior angular gyrus and superior temporal gyrus).12
The visual hallucination of seeing ones’ own face, autoscopy, has been termed mirror hallucination since there is left-right reversal as in a mirror image. This has been described in association with epilepsy, migraine, and parieto-occipital space-occupying lesions.13
Mirror writing is a mirror image of normal writing, hence in English it runs from right to left with characters back to front. In double mirror writing (écriture en double mirroir) script is also inverted top to bottom (script goes up the page) as well as being mirror reversed. Mirror writing may occur spontaneously, more often in left-handers, as well as in a variety of pathological situations, mostly associated with left hemisphere damage. Leonardo da Vinci is perhaps the most celebrated historical mirror writer.14
Mirror writing should perhaps not be included here since it is most probably a motor phenomenon, akin to mirror movements, rather than a cognitive phenomenon, although it is reported to occur on occasion in the context of cognitive impairment or dementia. That said, in my experience of asking people with cognitive complaints to write sentences (e.g. when administering the Mini-Mental State Examination or the Addenbrooke’s Cognitive Examination and its subsequent iterations, ACE-R and ACE-III) I do not recall ever having seen a mirror sentence produced.
- Malraux A. Man’s Fate. London: Penguin Modern Classics, 2009 :42.
- Larner AJ. A dictionary of neurological signs (3rd edition). New York: Springer, 2011:222-5.
- Connors MH, Coltheart M. On the behaviour of senile dementia patients vis-à-vis the mirror: Ajuriaguerra, Strejilevitch and Tissot (1963). Neuropsychologia 2011;49:1679-92.
- Kumakura T. The mirror sign in presenile and senile dementias (especially in Alzheimer-type dementias) [in Japanese]. Seishin Shinkeigaku Zasshi 1982;84:307-35.
- Mulcare JL, Nicolson SE, Bisen VS, Sostre SO. The mirror sign: a reflection of cognitive decline. Psychosomatics 2012;53:188-92.
- Gil-Ruiz N, Osorio RS, Cruz I et al. An effective environmental intervention for management of the “mirror sign” in a case of probable Lewy body dementia. Neurocase 2013;19:1-13.
- Yoshida T, Yuki N, Nakagawa M. i Acta Psychiatr Scand 2006;114:62-65.
- Breen N, Caine D, Coltheart M. Mirrored-self misidentification: two cases of focal onset dementia. Neurocase 2001;7:239-54.
- Villarejo A, Martin VP, Moreno-Ramos T et al. Mirrored self-misidentification in a patient without dementia: evidence for right hemispheric and bifrontal damage. Neurocase 2011;17:276-84.
- Ramachandran VS, Altschuler EL, Hillyer S. Mirror agnosia. Proc Biol Sci 1997;264:645-7.
- Binkofski F, Butler A, Buccino G et al. Mirror apraxia affects the peripersonal mirror space. A combined lesion and cerebral activation study. Exp Brain Res 2003;153:210-19.
- Binkofski F, Buccino G, Dohle C, Seitz RJ, Freund HJ. Mirror agnosia and mirror ataxia constitute different parietal lobe disorders. Ann Neurol 1999;46:51-61.
- Brugger P. Reflective mirrors; perspective taking in autoscopic phenomena. Cogn Neuropsychiatry 2002;7:179-94.
- Schott GD. Mirror writing: neurological reflections on an unusual phenomenon. J Neurol Neurosurg Psychiatry 2007;78:5-13.
ACNR 2015;15(4):14. Online 21/09/2015Download this Article