Introduction
Akinetopsia is derived from a Greek word: a for not, kine for move, and opsia for see. Akinetopsia means motion blindness. It is a higher visual processing disorder that results due to extra-striate lesions. The patient has difficulty perceiving objects in motion, with variable severity. This condition is rare, and very few cases have been reported in the literature. Several etiologies have been suggested to have caused this condition. Patients with akinetopsia say that smooth movements of objects appear as discontinuous freeze-frame images. The patients might have difficulty pouring tea into a cup as the tea will appear frozen, just like a glacier. Thus, a better understanding is required to manage this condition successfully.
What Is Akinetopsia?
Akinetopsia is a rare visual perception disorder. It is mainly occurring due to problems in the brain rather than the eyes, which is why it is at times also known as cerebral akinetopsia. It affects the person's ability to perceive motion within their visual field. Some people with akinetopsia might see things in stop-action motion. For others, the objects may reappear after being vanished. Normal motion perception allows the brain to perceive things when in motion, but this perception gets disrupted in akinetopsia. It is a visual processing disorder that affects how the brain processes what a person sees. The brain has difficulty understanding the information taken through the eyes. Motion blindness might occur in varying degrees. Motion blindness can impact a person's daily activity like:
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Cooking
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Reading.
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Playing sports.
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Driving.
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Watching television.
What Causes Akinetopsia?
It occurs due to impairment in the part of the brain responsible for visual motion processing. The possible causes of damage to the part of the brain include stroke, lesions in the brain, side effects of medications, traumatic brain injury, and neurodegenerative disorders like Alzheimer's disease, epilepsy, etc.
What Are the Types of Akinetopsia?
Akinetopisa has been classified depending on the condition’s severity and its effect on motion perception. Two primary forms have been found:
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Frozen Frames: This type has been referred to as cinematographic vision or inconspicuous akinetopsia. Such an individual with cinematographic vision sees motion like a movie reel. Strobe-like effects may also occur. It is the most common type and the least severe.
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Vanishing Objects: This is the second type, also known as gross akinetopsia. This is the most severe type and refers to the invisibility of moving objects. It involves the inability to perceive objects. The objects may vanish once they move. This is a very rare condition.
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Akinetopsia vs. Zeitraffer Phenomenon: The Zeitraffer phenomenon is similar and affects motion perception. It affects the brain's ability to determine the speed at which objects in the visual fields are moving; in this condition, the objects may appear to move in slow motion.
What Are the Symptoms of Akinetopsia?
The symptoms of akinetopsia include the following:
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Impaired Motion Perception: Inability to recognize or perceive motion. The moving objects appear frozen or fragmented rather than a smooth and continuous motion.
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Difficulty Tracking Moving Objects: People need help visually tracking objects in motion. It affects activities like sports, driving, and walking in crowded environments.
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Motion-Induced Discomfort: Patients may experience discomfort and disorientation when exposed to moving stimuli such as watching a movie or being in a busy environment.
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Challenges with Depth Perception: Individuals find it difficult to distance themselves from moving objects.
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Inability to Recognize Facial Expressions: Struggle to perceive dynamic changes in facial perceptions.
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Balance Issues: Balance and coordination issues are especially important when visual input is crucial, such as navigating the terrain and walking.
Who Is at Risk of Akinetopsia?
Those people who present with the below-mentioned condition are at increased risk of developing akinetopsia:
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Brain Lesions or Tumors: Akinetopsia is associated with damage to specific brain areas, the visual motion area (Area MT or V5), or the posterior parietal cortex. Brain lesions or brain tumors in these regions can disrupt motion information processing.
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Head Trauma: Traumatic brain injuries, particularly those affecting the visual brain areas, may lead to akinetopsia. Head injuries result in damage to the occipital and parietal lobes, thereby disrupting the normal brain functioning in that area.
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Stroke: Affects the area of the brain responsible for processing motion in the brain. The interruption of blood supply in this region can result in damage and subsequent motion perception deficits.
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Neurological Disorders: Certain neurological disorders, such as cortical blindness or other visual processing disorders, may be associated with akinetopsia. Disorders affecting the visual pathways or higher-order visual processing areas can increase the risk.
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Infection or Inflammatory Conditions: Infections or inflammatory conditions affecting the brain, such as encephalitis or multiple sclerosis, may contribute to akinetopsia. Inflammation and damage to the visual processing areas can disrupt motion perception.
What Part of the Brain Is Affected by Akinetopsia?
The specific area involved in the brain is known as the visual area, V5, and the middle temporal cortex (V5/MT), which is the part of the brain’s visual cortex located in the posterior part of the brain in the outer layer. The visual cortex is located on both sides of the brain. Mostly, the damage caused by akinetopsia involves both sides, known as bilateral lesions. However, in some cases, the damage could be on only one side, known as unilateral lesions. Different areas of the visual cortex are responsible for processing specific visual information. The V5/MT area is important in visual perception and integration. It also helps in eye movements.
How Is This Condition Diagnosed?
A thorough physical examination is performed, along with obtaining a medical history. The doctor inquires about medication use, injury in the head, and other related medical conditions. Other neuroimaging, such as computed tomography (CT) and magnetic resonance imaging (MRI) may also be advised to rule out other conditions.
What Are the Treatment Options for Akinetopsia?
The treatment is challenging as this condition is rare. The underlying cause determines the management. Vestibular and visual rehabilitation is controversial and does not offer any strong evidence. There is no currently approved medication for this condition, although the seizures can be treated with Carbamazepine 200/mg per day.
Conclusion:
It is essential to note that Akinetopsia is a rare condition, and not everyone with the mentioned risk factors will develop it. Additionally, the specific causes and risk factors may vary among individuals. Diagnosis and evaluation by a medical professional, typically by a neurologist or ophthalmologist, is essential for identifying the underlying cause of motion perception deficits and deploying appropriate management strategies. If someone is experiencing symptoms suggestive of Akinetopsia, they must seek medical attention and a comprehensive evaluation.
