Anton syndrome is a rare neurological disorder in which a person has cortical blindness but denies or is unaware of their loss of vision. Despite being unable to see, the patient may claim to perceive their surroundings normally and may even describe scenes that they are not actually seeing.
This condition typically occurs following bilateral lesions of the occipital lobes, particularly as a consequence of a stroke affecting the posterior cerebral circulation.
What is Anton syndrome?
Anton syndrome is a form of anosognosia, meaning a lack of awareness of one’s own neurological deficit.
In this condition, the impairment affects vision. Although the eyes and anterior visual pathways may function normally, the brain loses its ability to process visual information due to damage to the occipital cortex.
As a result, the patient develops cortical blindness but typically denies the presence of any visual impairment.
Why does Anton syndrome occur?
Anton syndrome occurs when both occipital lobes, which are responsible for processing visual information, are damaged.
In addition to cortical blindness, there is disruption of the brain networks involved in awareness of one’s own neurological deficits, which explains why the patient may insist that they can see normally.
Causes
The most common causes include:
- Bilateral posterior cerebral artery stroke.
- Intracerebral hemorrhage.
- Traumatic brain injury.
- Hypoxic-ischemic encephalopathy.
- Brain tumors.
- Central nervous system infections.
- Rare neurodegenerative diseases.
Stroke is the most common cause in adults.
Symptoms of Anton syndrome
The most characteristic clinical manifestations include:
- Cortical blindness.
- Denial of visual loss.
- Inaccurate descriptions of the surroundings (confabulation).
- Difficulty with spatial orientation.
- Colliding with objects while walking.
- Inconsistent responses to visual stimuli.
- Preservation of pupillary reflexes in many cases.
The combination of cortical blindness and lack of awareness of the visual deficit is the hallmark of Anton syndrome.
Association with stroke
Most cases occur following bilateral posterior cerebral artery infarction.
When both occipital lobes are affected, visual processing is impaired. If the brain networks involved in awareness of neurological deficits are also damaged, the patient may completely deny their loss of vision.
How is Anton syndrome diagnosed?
Diagnosis is based on neurological examination and neuroimaging studies.
The most commonly used diagnostic techniques include:
- Brain magnetic resonance imaging (MRI).
- Computed tomography (CT).
- CT angiography (CTA).
- Magnetic resonance angiography (MRA).
- Neuro-ophthalmological examination.
Clinical assessment can confirm the presence of cortical blindness despite the patient reporting that their vision is normal.
Treatment
Treatment depends on the underlying condition responsible for the brain lesion.
When the cause is a stroke, management follows established stroke treatment protocols. Subsequently, rehabilitation may include strategies aimed at improving the patient’s functional adaptation and addressing the limitations resulting from vision loss.
Treatment should always be individualized according to the specific characteristics of each case.
Prognosis
The prognosis depends on factors such as:
- The extent of the brain lesion.
- The underlying cause.
- The time to diagnosis.
- The treatment received.
- The degree of recovery of the affected brain tissue.
In some patients, awareness of the deficit may improve over time, although visual recovery will depend on the extent of the underlying brain damage.
Conclusion
Anton syndrome is a rare neurological disorder characterized by the combination of cortical blindness and a lack of awareness of vision loss. It typically occurs following bilateral damage to the occipital lobes, particularly as a consequence of stroke. Recognizing this syndrome is important for understanding certain visual and cognitive impairments that may occur following brain injury.
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