Anton syndrome

Anton syndrome
Anton syndrome
Specialty	Neurology
Named after	Gabriel Anton

Last updated November 13, 2023

Anton syndrome, also known as Anton-Babinski syndrome and visual anosognosia, is a rare symptom of brain damage occurring in the occipital lobe. Those who have it are cortically blind, but affirm, often quite adamantly and in the face of clear evidence of their blindness, that they are capable of seeing. Failing to accept being blind, people with Anton syndrome dismiss evidence of their condition and employ confabulation to fill in the missing sensory input. It is named after the neurologist Gabriel Anton. Only 28 cases have been published.^[1]

Presentation

Anton syndrome is mostly seen following a stroke, but may also be seen after head injury. Neurologist Macdonald Critchley describes it thusly:

The sudden development of bilateral occipital dysfunction is likely to produce transient physical and psychological effects in which mental confusion may be prominent. It may be some days before the relatives, or the nursing staff, stumble onto the fact that the patient has actually become sightless. This is not only because the patient ordinarily does not volunteer the information that he has become blind, but he furthermore misleads his entourage by behaving and talking as though he were sighted. Attention is aroused however when the patient is found to collide with pieces of furniture, to fall over objects, and to experience difficulty in finding his way around. He may try to walk through a wall or through a closed door on his way from one room to another. Suspicion is still further alerted when he begins to describe people and objects around himself which, as a matter of fact, are not there at all.
Thus we have the twin symptoms of anosognosia (or lack of awareness of defect) and confabulation, the latter affecting both speech and behaviour.^[2]

Anton syndrome may be thought of ideally as the opposite of blindsight, blindsight occurring when there is degraded vision resulting in part of the visual field not consciously being experienced, but some reliable perception does in fact occur.^[3]

Causes

It is not known why patients with Anton syndrome deny their blindness, although there are many theories. One hypothesis is that damage to the visual cortex results in the inability to communicate with the speech-language areas of the brain. Visual imagery is received but cannot be interpreted; the speech centers of the brain confabulate a response.^[4] Another possibility is that in Anton syndrome, lesions cause a disconnection between internal visual representations in visual association cortex, metacognitive processing in the cingulate cortex and memory-associated structures including the hippocampus. Anosognosia occurs because visual inputs cannot be meta-cognitively compared to priors stored in memory to recognize a deficit.^[5]

Patients have also reported visual anosognosia after experiencing ischemic vascular cerebral disease. A 96-year-old man, who was admitted to an emergency department complaining of a severe headache and sudden loss of vision, was discovered to have had a posterior cerebral artery thrombosis with consequent loss of vision. He adamantly claimed he was able to see despite an ophthalmologic exam proving otherwise. An MRI of his brain proved that his right occipital lobe was ischemic. Similarly, a 56-year-old woman was admitted to the emergency department in a confused state and with severely impaired psychomotor skills. Ocular movements and pupil reflexes were still intact, but the patient could not name objects and was not aware of light changes in the room, and seemed unaware of her visual deficit.^{[ citation needed ]}

Diagnosis

Though the patient is blind, they will behave and talk as if they have normal vision. Attention is aroused, however, when the patient is found to collide with pieces of furniture, to fall over objects, and to experience difficulty in finding their way around. They may try to walk through a wall or a closed door on their way from one room to another. Suspicion is still further alerted when they begin to describe people and objects around them who do not exist. Mental confusion may also be seen. Patients with ABS may give excuses for their blindness. They may explain that their inability to see is because of the lack of proper lighting, and they may try their best to prove that they are not blind, thereby putting themselves in danger.^[6] Differential diagnosis' include: Cerebral visual impairment, delayed visual development, homonymous hemianopia, lack of facial recognition, visual agnosia, visual neglect, and visual perceptual disorder. ^[7]

History

Anton syndrome was first reported by an Austrian psychiatrist and neurologist in 1895, Gabriel Anton described the case of Juliane Hochriehser. Juliane Hochriehser was a 69-year-old who experienced anosognosia with cortical deafness that stemmed from lesions on both of her temporal lobes. After this initial finding, Gabriel Anton went on to describe other individuals who had similar experiences of objective blindness and deafness but denied their deficiencies.^{[ citation needed ]} Although cases of Anton syndrome are mostly reported in adults, there was a notable case of a young child experiencing it. The European Journal of Neurology published an article in 2007 that examines a case study of a six-year-old child with Anton syndrome and early stages of adrenoleukodystrophy. The child reportedly had abnormal eye movements, would often fall, and would reach for things and often miss his target. When his sight was tested at 20/20 he was still unable to read the large letters on the chart. He denied having headaches, diplopia, or eye pain and seemed unconcerned and unaware of his poor eyesight. Upon examination, his pupils were equal in shape, round, and reactive to light. His mother commented that he developed unusual eye movements and that they had a "roving quality".^[8]

Culture and society

Anton syndrome was first described in writing by Michel de Montaigne, a Renaissance French writer. In the second book of his Essais, near the final of the twelfth chapter, Montaigne describes a nobleman who experienced visual anosognosia but denied his own blindness. ^[9]

Anton syndrome was featured in a two-part episode of the television series House M.D. , titled "Euphoria", although it was ascribed to primary amoebic meningoencephalitis, a disease that usually does not cause the syndrome in real life. The syndrome features prominently in the Rupert Thomson novel The Insult . It is also mentioned in the science fiction novel Blindsight , by Peter Watts.

It is mentioned frequently as "Anton's Blindness" as one of the primary metaphors in Raj Patel's The Value of Nothing . In Lars von Trier's film Dogville , the character Jack McKay acts as if he can see but gives many signs he cannot.

The syndrome is also the main theme of the Malaysian movie Desolasi (Desolation), where the patients live in their own world of imagination, while unable to see the real world. It is also mentioned in Oliver Sacks's An Anthropologist on Mars .

Related Research Articles

<span class="mw-page-title-main">Agnosia</span> Medical condition

Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.

Blindsight is the ability of people who are cortically blind to respond to visual stimuli that they do not consciously see due to lesions in the primary visual cortex, also known as the striate cortex or Brodmann Area 17. The term was coined by Lawrence Weiskrantz and his colleagues in a paper published in a 1974 issue of Brain. A previous paper studying the discriminatory capacity of a cortically blind patient was published in Nature in 1973. The assumed existence of blindsight is controversial, with some arguing that it is merely degraded conscious vision.

The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ob, 'behind', and caput, 'head'.

Anosognosia is a condition in which a person with a disability is cognitively unaware of having it due to an underlying physical or psychological condition. Anosognosia can result from physiological damage to brain structures, typically to the parietal lobe or a diffuse lesion on the fronto-temporal-parietal area in the right hemisphere, and is thus a neuropsychiatric disorder. A deficit of self-awareness, it was first named by the neurologist Joseph Babinski in 1914. Phenomenologically, anosognosia has similarities to denial, which is a psychological defense mechanism; attempts have been made at a unified explanation. Anosognosia is sometimes accompanied by asomatognosia, a form of neglect in which patients deny ownership of body parts such as their limbs. The term is from Ancient Greek ἀ- a-, 'without', νόσος nosos, 'disease' and γνῶσις gnōsis, 'knowledge'. It is also considered a disorder that makes the treatment of the patient more difficult, since it may affect negatively the therapeutic relationship.

Visual release hallucinations, also known as Charles Bonnet syndrome or CBS, are a type of psychophysical visual disturbance in which a person with partial or severe blindness experiences visual hallucinations.

<span class="mw-page-title-main">Pulvinar nuclei</span>

The pulvinar nuclei or nuclei of the pulvinar are the nuclei located in the thalamus. As a group they make up the collection called the pulvinar of the thalamus, usually just called the pulvinar.

Joseph Jules François Félix Babinski was a French-Polish professor of neurology. He is best known for his 1896 description of the Babinski sign, a pathological plantar reflex indicative of corticospinal tract damage.

<span class="mw-page-title-main">Bálint's syndrome</span> Medical condition

Bálint's syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments: inability to perceive the visual field as a whole (simultanagnosia), difficulty in fixating the eyes, and inability to move the hand to a specific object by using vision. It was named in 1909 for the Austro-Hungarian neurologist and psychiatrist Rezső Bálint who first identified it.

Cortical blindness is the total or partial loss of vision in a normal-appearing eye caused by damage to the brain's occipital cortex. Cortical blindness can be acquired or congenital, and may also be transient in certain instances. Acquired cortical blindness is most often caused by loss of blood flow to the occipital cortex from either unilateral or bilateral posterior cerebral artery blockage and by cardiac surgery. In most cases, the complete loss of vision is not permanent and the patient may recover some of their vision. Congenital cortical blindness is most often caused by perinatal ischemic stroke, encephalitis, and meningitis. Rarely, a patient with acquired cortical blindness may have little or no insight that they have lost vision, a phenomenon known as Anton–Babinski syndrome.

Visual agnosia is an impairment in recognition of visually presented objects. It is not due to a deficit in vision, language, memory, or intellect. While cortical blindness results from lesions to primary visual cortex, visual agnosia is often due to damage to more anterior cortex such as the posterior occipital and/or temporal lobe(s) in the brain.^[2] There are two types of visual agnosia: apperceptive agnosia and associative agnosia.

The inferior temporal gyrus is one of three gyri of the temporal lobe and is located below the middle temporal gyrus, connected behind with the inferior occipital gyrus; it also extends around the infero-lateral border on to the inferior surface of the temporal lobe, where it is limited by the inferior sulcus. This region is one of the higher levels of the ventral stream of visual processing, associated with the representation of objects, places, faces, and colors. It may also be involved in face perception, and in the recognition of numbers and words.

Cerebral achromatopsia is a type of color blindness caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina. It is often confused with congenital achromatopsia but underlying physiological deficits of the disorders are completely distinct. A similar, but distinct, deficit called color agnosia exists in which a person has intact color perception but has deficits in color recognition, such as knowing which color they are looking at.

Hemianopsia, or hemianopia, is a visual field loss on the left or right side of the vertical midline. It can affect one eye but usually affects both eyes.

<span class="mw-page-title-main">Gabriel Anton</span> Austrian neurologist and psychiatrist

Gabriel Anton was an Austrian neurologist and psychiatrist. He is primarily remembered for his studies of psychiatric conditions arising from damage to the cerebral cortex and the basal ganglia.

The Riddoch syndrome is a term coined by Zeki and Ffytche (1998) in a paper published in Brain. The term acknowledges the work of George Riddoch who was the first to describe a condition in which a form of visual impairment, caused by lesions in the occipital lobe, leaves the sufferer blind but able to distinguish visual stimuli with specific characteristics when these appear in the patient's blind field. The most common stimuli that can be perceived consciously are the presence and direction of fast moving objects ; in his work these moving objects were described as "vague and shadowy". Riddoch concluded from his observations that "movement may be recognized as a special visual perception".

<span class="mw-page-title-main">Posterior cortical atrophy</span> Medical condition

Posterior cortical atrophy (PCA), also called Benson's syndrome, is a rare form of dementia which is considered a visual variant or an atypical variant of Alzheimer's disease (AD). The disease causes atrophy of the posterior part of the cerebral cortex, resulting in the progressive disruption of complex visual processing. PCA was first described by D. Frank Benson in 1988.

Amorphosynthesis, also called a hemi-sensory deficit, is a neuropsychological condition in which a patient experiences unilateral inattention to sensory input. This phenomenon is frequently associated with damage to the right cerebral hemisphere resulting in severe sensory deficits that are observed on the contralesional (left) side of the body. A right-sided deficit is less commonly observed and the effects are reported to be temporary and minor. Evidence suggests that the right cerebral hemisphere has a dominant role in attention and awareness to somatic sensations through ipsilateral and contralateral stimulation. In contrast, the left cerebral hemisphere is activated only by contralateral stimuli. Thus, the left and right cerebral hemispheres exhibit redundant processing to the right-side of the body and a lesion to the left cerebral hemisphere can be compensated by the ipsiversive processes of the right cerebral hemisphere. For this reason, right-sided amorphosynthesis is less often observed and is generally associated with bilateral lesions.

Disconnection syndrome is a general term for a collection of neurological symptoms caused – via lesions to associational or commissural nerve fibres – by damage to the white matter axons of communication pathways in the cerebrum, independent of any lesions to the cortex. The behavioral effects of such disconnections are relatively predictable in adults. Disconnection syndromes usually reflect circumstances where regions A and B still have their functional specializations except in domains that depend on the interconnections between the two regions.

Cerebral diplopia or polyopia describes seeing two or more images arranged in ordered rows, columns, or diagonals after fixation on a stimulus. The polyopic images occur monocular bilaterally and binocularly, differentiating it from ocular diplopia or polyopia. The number of duplicated images can range from one to hundreds. Some patients report difficulty in distinguishing the replicated images from the real images, while others report that the false images differ in size, intensity, or color. Cerebral polyopia is sometimes confused with palinopsia, in which multiple images appear while watching an object. However, in cerebral polyopia, the duplicated images are of a stationary object which are perceived even after the object is removed from the visual field. Movement of the original object causes all of the duplicated images to move, or the polyopic images disappear during motion. In palinoptic polyopia, movement causes each polyopic image to leave an image in its wake, creating hundreds of persistent images (entomopia).

The visual pathway consists of structures that carry visual information from the retina to the brain. Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way:
Retina→Optic nerve→Optic chiasma →Optic tract→Lateral geniculate body→Optic radiation→Primary visual cortex

References

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↑ Critchley M (1979). "Modes of reaction to central blindness". The Divine Banquet of the Brain and Other Essays. Raven Press. p. 156. ISBN 978-0-89004-348-6.
↑ Derrien D, Garric C, Sergent C, Chokron S (2022-10-14). "The nature of blindsight: implications for current theories of consciousness". Neuroscience of Consciousness. 2022 (1): niab043. doi:10.1093/nc/niab043. PMC 8884361 . PMID 35237447.
↑ Prigatano GP, Schacter DL (1991). Awareness of deficit after brain injury: clinical and theoretical issues. Oxford [Oxfordshire]: Oxford University Press. pp. 53–60. ISBN 978-0-19-505941-0.
↑ Kletenik I, Gaudet K, Prasad S, Cohen AL, Fox MD (September 2023). "Network Localization of Awareness in Visual and Motor Anosognosia". Annals of Neurology. 94 (3): 434–441. doi:10.1002/ana.26709. PMC 10524951. PMID 37289520. S2CID 259119253.
↑ Das MJ, Naqvi IA (2022). "Anton Syndrome". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID 30844182 . Retrieved 2023-02-03.
↑ M Das, Joe; Naqvi, Imama A. (2023), "Anton Syndrome", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30844182 , retrieved 2023-10-21
↑ Trifiletti RR, Syed EH, Hayes-Rosen C, Parano E, Pavone P (February 2007). "Anton-Babinski syndrome in a child with early-stage adrenoleukodystrophy". European Journal of Neurology. 14 (2): e11–e12. doi:10.1111/j.1468-1331.2006.01581.x. PMID 17250706. S2CID 26141348.
↑ Bernoulli, René (1990-11-21). "Michel de Montaigne (1533-1592) : Bericht über einen Fall des Nichtwahrnehmens der eigenen Blindheit". Gesnerus. 47 (1): 13–20. doi:10.1163/22977953-04701004. ISSN 0016-9161.