|
Cortical blindness is the total or partial loss of vision in a normal-appearing eye caused by damage to the brain's occipital cortex.〔(Dictionary of Eye Terminology )〕 Cortical blindness can be acquired or congenital, and may also be transient in certain instances. Acquired cortical blindness is most often caused by loss of blood flow to the occipital cortex from either unilateral or bilateral posterior cerebral artery blockage (ischemic stroke) and by cardiac surgery.〔 In most cases, the complete loss of vision is not permanent and the patient may recover some of their vision (Cortical visual impairment).〔 Congenital cortical blindness is most often caused by perinatal ischemic stroke, encephalitis, and meningitis.〔http://www.hadley.edu/SeminarDownload/Cortical_Visual%20Impairment_and_Blindness-PPT-Hadley.ppt〕 Rarely, a patient with acquired cortical blindness may have little or no insight that they have lost vision, a phenomenon known as Anton–Babinski syndrome. Cortical blindness and cortical visual impairment (CVI), which refers to the partial loss of vision caused by cortical damage, are both classified as subsets of neurological visual impairment (NVI). NVI and its three subtypes—cortical blindness, cortical visual impairment, and delayed visual maturation—must be distinguished from ocular visual impairment in terms of their different etiologies and structural foci, the brain and the eye respectively. One diagnostic marker of this distinction is that the pupils of individuals with cortical blindness will respond to light whereas those of individuals with ocular visual impairment will not. ==Causes== The most common cause of cortical blindness is ischemia (oxygen deprivation) to the occipital lobes caused by blockage to one or both of the posterior cerebral arteries.〔 However, other conditions have also been known to cause acquired and transient cortical blindness, including: * Bilateral lesions of the primary visual cortex 〔 * Side effect of some anti-epilepsy drugs (AEDs) * Creutzfeldt–Jakob disease, in association with a rapid onset of dementia * Infection 〔http://www.aph.org/cvi/define.html〕 * Head trauma to the occipital lobe of the brain 〔 * Congenital abnormalities of the occipital lobe 〔 * Eclampsia and, rarely, pre-eclampsia * Hyperammonemia The most common causes of congenital cortical blindness are: * Traumatic brain injury (TBI) to the occipital lobe of the brain 〔 * Congenital abnormalities of the occipital lobe 〔 * Perinatal ischemia 〔 * Encephalitis 〔 * Meningitis 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cortical blindness」の詳細全文を読む スポンサード リンク
|