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Medical Forum / General / Vision / March 2006Vasoconstriction in Occipital
Hi: Lets say that each and every artery, arteriole, and capillary supplying the right division of the part of occipital lobe in my cerebral cortex were to go into vasospasm [leading to complete constriction] instantly and remain like that for a week. What symptoms would I experience in the first minute? What symptoms would I experience in the 15 minutes? What about in a day? In a week? Would there be any visual hallucinations in any of these time periods? Unilateral or bilateral? Thanks, Radium > Lets say that each and every artery, arteriole, and capillary supplying > the right division of the part of occipital lobe in my cerebral cortex > were to go into vasospasm [leading to complete constriction] instantly > and remain like that for a week. > > What symptoms would I experience in the first minute? It's logical to think you might experience zig-zag C-shapes or heat waves like migraine aura. But most people with posterior cerebral artery strokes don't report hallucinations. Their chief complaint is they bump into things. > Unilateral or bilateral? "Bilateral homonymous hemianopsia" is the characteristic field defect for PCA occlusion. The visual field defects are drawn with two black "D"s occluding the RIGHT field of each eye, if the LEFT brain was involved. Often some vision in the center (macula) is spared, otherwide the defect is characterized by a straight line down the middle. If it's the RIGHT field, reading is very difficult. In real life, the effect is not black, but "grayish" or "absent" more than any particular shade. They bump into things. Phantom hallucinations, like phantom limb pain, are called Charles Bonnet syndrome (bo-NAY). -MT, OD > > Lets say that each and every artery, arteriole, and capillary supplying > > the right division of the part of occipital lobe in my cerebral cortex [quoted text clipped - 27 lines] > > -MT, OD Under what conditions would the visual auras affect the left half of the left eye? Under what conditions would these disturbances get worse as you go more left in the left half of the left eye and less severe as you reach the middle of the left eye? Has there ever been a case in any migraine aura patient, where the patient reports blindness in the left half of the left eye getting more severe at the left end of his/her eye? Has there ever been a case in any migraine aura patient, where the patient reports visual hallucinations [or PSEUDOhallucinations if the patient knows visual effects are not real] in the left half of the left eye getting more vivid at the left end of his/her eye? Can the visual hallucinations/distortions present in migraine auras make the victim dizzy even if the inner ears and parts of the brain directly concerned with balance are not affected by the vasoconstriction? > Under what conditions would the visual auras affect the left half of > the left eye? "Classic" migraine never involves one eye only. If it's cortical, it's in both eyes. If it's in one eye only, it isn't migraine, except for very rare instances of "retinal migraine" or other forms that affect arteries other than the PCA. > Under what conditions would these disturbances get worse > as you go more left in the left half of the left eye and less severe as > you reach the middle of the left eye? The further you go out the vascular tree, the more anoxia. > Has there ever been a case in any migraine aura patient, where the > patient reports blindness in the left half of the left eye getting more > severe at the left end of his/her eye? Again, if it is just one eye, it isn't typical migraine. If it's just one eye you'd suspect a problem in the optic nerve or retina, somewhere anterior to the pituitary gland. > Has there ever been a case in any migraine aura patient, where the > patient reports visual hallucinations [or PSEUDOhallucinations if the > patient knows visual effects are not real] in the left half of the left > eye getting more vivid at the left end of his/her eye? Migraine auras can be more vivid in the peripheral vision. But they're usually dynamic, changing over time. > Can the visual hallucinations/distortions present in migraine auras > make the victim dizzy even if the inner ears and parts of the brain > directly concerned with balance are not affected by the > vasoconstriction? Migraine can involve more than one vessel. But lots of stressful events produce "dizzy" sensations. -MT > > Under what conditions would the visual auras affect the left half of > > the left eye? > "Classic" migraine never involves one eye only. If it's cortical, it's in > both eyes. I thought the right visual cortex recieves info the the left eye and the the left visual cortex receives from the right eye. > If it's in one eye only, it isn't migraine, except for very rare instances > of "retinal migraine" or other forms that affect arteries other than the [quoted text clipped - 19 lines] > > patient knows visual effects are not real] in the left half of the left > > eye getting more vivid at the left end of his/her eye? > Migraine auras can be more vivid in the peripheral vision. But they're > usually dynamic, changing over time. True. But can certain parts of the visual field be more in the "hallucinatory world" while leaving other regions of the visual field in touch with reality and the same time? > > Can the visual hallucinations/distortions present in migraine auras > > make the victim dizzy even if the inner ears and parts of the brain [quoted text clipped - 3 lines] > Migraine can involve more than one vessel. But lots of stressful events > produce "dizzy" sensations. I guess "cerebellar migraine auras" would consist of dizziness and other disruptions involving the sense of balance. > I thought the right visual cortex recieves info the the left eye and > the the left visual cortex receives from the right eye. Nope. The right _field_ in each eye goes to the left brain. Google the term "optic chiasm." > True. But can certain parts of the visual field be more in the > "hallucinatory world" while leaving other regions of the visual field > in touch with reality and the same time? I've never asked. -MT > "Classic" migraine never involves one eye only. If it's cortical, it's in > both eyes. But are the hallucinations different in each eye? Or does the patient hallucinate the same thing in both eyes? > What symptoms would I experience in the 15 minutes? I forgot to mention - after 15 minutes without oxygen or glucose, most cortex would be irretrievable. Migraine spasm isn't "complete constriction". -MT Radium, you asked about burns over in the Chronic Pain Group this past week...May I ask just why are you asking these questions?  SignatureRonnie -- *When one candle burns out.. Another is lit* > Hi: > [quoted text clipped - 17 lines] > > Radium > Radium, you asked about burns over in the Chronic > Pain Group this past week...May I ask just why are > you asking these questions? I guess I am just interested in very wierd science. Ummmmmmm, I'm not a physician, but if each and every blood vessel in a section of your brain because completely constricted, you'd have a major stroke in a very short period of time. Teri > Hi: > [quoted text clipped - 17 lines] > > Radium |
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