Apperceptive agnosia
Each patient that suffers from apperceptive agnosia does not have brain damage in exactly the same area. However, brain damage in proximity to the occipital lobe is largely correlated with the patterns of deficit seen in apperceptive agnosics. For example, patient JB suffered extensive damage to the parietal-occipital areas to the left cerebral hemisphere leading to his deficit in the ability to name distinguish between structurally similar object.
Cerebral hypoxia
Cerebral hypoxia can be caused by any event that severely interferes with the brain's ability to receive or process oxygen. This event may be internal or external to the body. Mild and moderate forms of cerebral hypoxia may be caused by various diseases that interfere with breathing and blood oxygenation. Severe asthma and various sorts of anemia can cause some degree of diffuse cerebral hypoxia. Other causes include status epilepticus, work in nitrogen-rich environments, ascent from a deep-water dive, flying at high altitudes in an unpressurized cabin without supplemental oxygen, and intense exercise at high altitudes prior to acclimatization.