190 CLINICAL APPLIED ANATOMY. 



the lateral ventricle they terminate in the occipital cortex. Some 

 of the fibres possibly pass to the angular region, but the optic 

 radiation lies immediately subjacent to this part of the parietal 

 lobe, and may be indirectly injured by lesions in this situation 

 even if it do not in part terminate here. (Fig. 16.) 



The optic radiation may be damaged by softening, haemorrhage, 

 tumour or injury of the optic thalamus, or the posterior part of 

 the internal capsule. In such cases hemianaesthesia or hemiplegia 

 may be associated with homonymous hemianopia. Lesions in 

 the occipital lobe, the occipital cortex, and possibly in the parietal 

 lobe, may also damage the tract. 



The blood supply of the occipital visual cortex is derived from 

 the occipital branch of the posterior cerebral artery. This branch 

 also supplies the optic radiation. Sight may be impaired as the 

 result of embolism or thrombosis of this vessel, hemianopia 

 resulting. The parieto-occipital and the calcarine branches of 

 this occipital artery lie in the superior and inferior limiting sulci 

 of the cuneal lobule and the parieto-occipital branch supplies a 

 secondary cuneal branch which lies in a fissure in the cuneus 

 parallel to the calcarine artery. 



Since the posterior cerebral artery supplies the temporal lobe 

 in part, lesions of this lobe may be associated with lesions of the 

 occipital visual centres. 



The angular region of the cortex lies in the area of distribution 

 of the middle cerebral artery. 



The visual portion of the thalamus is supplied by the posterior 

 perforating branches of the posterior cerebral artery. (Fig. 10, 

 p. 165.) 



The superior quadrigeminal and the external geniculate bodies 

 are also supplied by the posterior cerebral artery. 



OPHTHALMOPLEGIA. 



Anatomically considered ophthalmoplegia may be divided into 

 supranuclear, nuclear and intranuclear varieties. 



Supranuclear ophthalmoplegia. Areas of the frontal lobes 

 and possibly also of the parietal and occipital lobes are connected 



