USMLE World Neuroanatomy Flashcards
Location of lesion and possible causes of a monocular scotoma
Partial lesion in the retina, optic disk, or optic nerve
Macular degeneration, optic neuritis
Location of lesion and possible causes of a right anopia
Right optic nerve
Retinal artery or central retinal vein occlusion
Location of lesion and possible causes of a bitemporal hemianopia
Optic chiasm
Pressure exerted by a pituitary tumor, craniophayngioma, aneurysm of ACA
Location of lesion and possible causes of a right nasal hemianopia
Right perichiasmal lesion
Calcification or aneurysm of the internal carotid artery impinging on uncrossed lateral retinal fibers
Location of lesion and possible causes of a left homonymous hemianopia
Right optic tract or optic radiation
Optica tract: occlusion of anterior choroidal artery
Optic radiation: occlusion of a MCA branch OR lesion involving posterior limb of internal capsule
Location of lesion and possible causes of a left homonymous superior quadrantanopia (pie in the sky)
Right temporal lobe (Meyer’s loop)
Lesion or stroke involving temporal lobe
Typically what artery?
Location of lesion and possible causes of a left homonymous inferior quadrantanopia (pie on the floor)
Right parietal lobe (dorsal optic radiation)
Lesion or stroke involving parietal lobe
Typically what artery?
Location of lesion and possible causes of a left homonymous hemianopia with macular sparing
Right primary visual cortex (occipital lobe
Occlusion of PCA. Macula is spared due to collateral blood from the MCA.
Pupillary light reflex involves what structures?
Ipsilateral optic nerve –> bilateral pretectal nucleus –> bilateral Edinger-Westphal nuclei –> bilateral ciliary ganglion –> bilateral pupillary sphincter muscles (parasympathetic nervous system)
What is a relative afferent (Marcus Gunn) pupillary defect?
Lesion of afferent limb of pupillary light reflex;
Light in affected eye -> neither constricts;
Light in normal eye –> both constrict;
Light back to affected eye –> apparent dilation of both pupils because stimulus carried through that optic nerve is weaker; seen in MS
Symptoms of CN IX lesion:
Loss of gag reflex (afferent limb); loss of sensation in the upper pharynx, posterior tongue, tonsils, and middle ear cavity; and loss of taste in posterior tongue.
