There are several interesting links and videos in this post - hope you enjoy!
Some patients suffering from cortical blindness can not see stationary objects, however are able to see moving ones - although often having difficulty to see their colour and shape. This phenomenon is called Riddoch phenomenon. Another symptom sometimes associated with cortical blindness is Anton-Babinski syndrome, in which a cortically blind patient denies being blind. In some cases, patients may also suffer from hallucinations.
Cortical blindness may occur for many reasons. Occipital cortex may be damaged due to head trauma or to lesions, which may be caused by neurodegenerative diseases, tumours, meningitis etc. It is also a side effect of the long term use of some anticonvulsants: drugs used to treat epileptic seizures.
When cortical blindness is not total, it is referred to as a cortical visual impairment (CVI). The symptoms may be aversion to light, discrepancy in visual ability between the eyes (in which case the depth perception may be impaired), photophobia or narrow vision field.
Inability to perceive a picture as a whole, instead seeing only its separate parts. For example, when looking at a picture of a house, a person would perceive a wall, a door, a window etc. - but not the house in its entirety.
2. Oculomotor apraxia
Defect or complete absence of a controlled eye movement, i.e. ability to focus. Patients would have to turn their head in order to follow an object. The term apraxia is debatable in relation to this impairment; apraxia is typically an inability to perform a skilled or learned action, while eye movements are not considered to be neither.
3. Optic ataxia
Inability to reach accurately for an object in front of a patient. It makes it hard for patients to rely on their visual function in order to navigate in space, and they have to use other senses instead. For example, they might have to hold on to a sink in a bathroom in order to know where it is.
Balint Syndrome is caused by a damage to both parietal lobes, most commonly due to two or more subsequent strokes; other causes might be neurodegenerative diseases (e.g. Alzheimer's) or tumour.
There is no treatment available for Balint's syndrome, partly to the complicated combination of three seemingly independent symptoms. The patients normally undergo Occupational Therapy, during which they learn to cope with everyday life situations. In case with Balint Syndrome, techniques used for blind people are often in use - such as learning to use audiobooks instead of reading, etc.
Achromatopsia can be either acquired or congenital. The cause for the acquired condition is most commonly a damage to the thalamus or cerebral cortex (tumour or head trauma are the most frequent causes). Congenital achromatopsia is normally caused by a malfunction of a retinal phototransduction pathway, which means that cones fail to respond to the light input properly.
The condition is very rare, thus misdiagnosis is common. Public awareness of the condition increased sinceOliver Sacks published his book The Island of the Colorblind, which then was made into a film. All of it is available on YouTube for free, first part HERE.
Currently, there is no treatment for achromatopsia. In 2003, a device called eye-borg was introduced, which allows achromats to 'see' colours through the sound waves. As it senses the colours in front of it, it converts them into sound waves; a person memorises a particular sound for each colour. The first one to use the device was the artist Neil Harbisson (follow the link to visit his website, its awesome! Some argue he should officially be recognised as a cyborg..). Watch his TED talk below, fascinating!
1. Agraphia/dysgraphia: total loss or impairment of writing ability
2. Acalculia/dyscalculia: loss or impairment ability to understand calculation or arithmetics
3. Finger agnosia: inability to identify fingers on the one's hand
4. Inability to distinguish right from left.
In addition, many patients also experience some level of aphasia (impairment of speech comprehension or production).
Gerstmann Syndrome occurs when the left parietal lobe in the region of the angular gyrus is damaged. It most commonly occurs due to a stroke or in association with damage to the parietal lobe.
For unknown reasons, a variant of Gerstmann Syndrome called Developmental Gerstmann Syndrome is sometimes diagnosed in children, normally when they reach school age. Children with the disorder exhibit poor handwriting and spelling skills, and difficulty with math functions, including adding, subtracting, multiplying, and dividing. An inability to differentiate right from left and to discriminate among individual fingers may also be apparent. In addition, many children also suffer from constructional apraxia, an inability to copy simple drawings.
There is no treatment for Gerstmann Syndrome, however occupational and speech therapies might help to minimise the negative effects of apraxia and dysgraphia.