Hemineglect and Hemianopia-Unaware Of, Or Blind To, One Side Of The Body
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Lesions of the brain are fascinating, and as complex, as the organ itself. The fact that the brain is basically two separate organs held together in the middle, and that each half controls the opposite side of the body, even makes the manifestations of brain injuries more bizarre and interesting. Understanding this basic principle– that each half of the brain controls the opposite side of the body: the right hemisphere, for instance, controls the left side of the body– is key to understanding how certain brain lesions– be it a stroke, or a tumour — may make one completely unaware of one side of his body, or unable to see things happening in one-half of his field of vision.
In hemineglect, a stroke in the region of the middle cerebral artery, or a tumour compressing the temporal lobe of the brain, could make one unable to recognize that one side of their body belongs to them. In severe cases, such a person may be doing any of the following :
- shaving only one-half of their beard.
- combing only one side of their hair.
- wearing shoes on just one foot.
- a lady may only manicure just the fingers of a hand, apply make up to just one side of her face, and adorn just one-half of her body.
There have even been cases where a patient threw themself out of the hospital bed, because they woke up, saw one of their legs, and- thinking it belonged to a stranger, they tried to push the intruder out of their bed.
In this, due to compression of the optic tract, or perhaps stroke involving the primary visual cortex, one is able to perceive only what one-half of either eye is seeing. Usually, it happens in such a way that similar halves of both eyes are what is affected. For instance, the right half of the right eye, and the right half of the left eye [see the picture below]. When images from both eyes are superimposed in the brain, the person would only be able to see what is happening in just half of the visual field. This is somehow “worse” than being blind in one eye entirely. Close an eye, and you’d see that you’ll still be able to see a little bit of what is happening on the other side. In homonymous hemianopia, however, the person would not, unless they turn their heads to the said side. Thus, it may manifest in any of the following ways:
- inability to see an arm extended for a handshake if said arm is on the side of the visual field where the person has lost vision.
- colliding with objects, or bumping into people, on one side, while walking.
- eating just half of the food given to them, or serving food on just one-half of the plate, if they were the ones dishing it out.
- on the road, it could be a disaster: a car driver may ram into another car, or knockdown someone on the sidewalk, simply because he can’t see them.
Does, “I don’t know where he appeared from o” after a car accident, sound familiar to you?Right! The worst part is that, if the lesion is cortical, the person may also have visual anosognosia [ Anton-Babinski Syndrome], and may not even know that they’re not seeing what is happening on one-half of their visual field!
Sometimes, it may be difficult to tell which a patient is having, of these two. The expertise of a neurologist, and neuroimaging, is usually needed to tell which is which..Just a weird phenomenon you should be aware of.