The blood supply system of the optic chiasma was studied in 85 fresh human specimens using various histological and anatomical methods. Computer image analysis and ultrastructural examinations of the microvessel in 58...The blood supply system of the optic chiasma was studied in 85 fresh human specimens using various histological and anatomical methods. Computer image analysis and ultrastructural examinations of the microvessel in 58fetal specimens were also conducted. The authors found that the medial portion of the chiasma is a weak point in the microcirculation network. This weak point is apt to be disturbed first and become ischemic. causing disorders of the crossing optic nerve fibers and resulting in characterestic bitemporal visual field defects. SEM studies showed no ultrastructural difference between the capillaries at the medial and lateral portions of the chiasma. It was concluded that: 1) No special artery supplies the median chiasma the weak point of microcirculation at the median chiasma is due to its relatively scanty capillary distribution; 2) 'lateral chiasma arteries' could provide a better blood supply to the lateral fibers and thus the nasal quadrantic visual field could be preserved in many late stages of visual field defect in sellar region tumors, 3) cases with pituitary microadenoma which is not sufficiently large to press the chiasma but involves bitemporal visual field defect are due to the tumor recieving “shunt-flow” (stealing blood) from the chiasma through the peri-infundibulum plexus.展开更多
BACKGROUND Nonketotic hyperglycemia(NKH)is characterized by hyperglycemia with little or no ketoacidosis.Diverse neurological symptoms have been described in NKH patients,including choreoathetosis,hemiballismus,seizur...BACKGROUND Nonketotic hyperglycemia(NKH)is characterized by hyperglycemia with little or no ketoacidosis.Diverse neurological symptoms have been described in NKH patients,including choreoathetosis,hemiballismus,seizures,and coma in severe cases.Homonymous hemianopia,with or without occipital seizures,caused by hyperglycemia is less readily recognized.CASE SUMMARY We describe a 54-year-old man with NKH,who reported seeing round,colored flickering lights with right homonymous hemianopia.Cranial magnetic resonance imaging demonstrated abnormalities in the left occipital lobe,with decreased T2 signal of the white matter,restricted diffusion,and corresponding low signal intensity in the apparent diffusion coefficient map.He responded to rehydration and a low-dose insulin regimen,with improvements of his visual field defect.CONCLUSION Patients with NKH may present focal neurologic signs.Hyperglycemia should be taken into consideration when making an etiologic diagnosis of homonymous hemianopia.展开更多
Palinopsia is the recurrence or persistence of visual images after cessation of the stimulus. Palinopsia has been associated with a wide variety of etiologies and mechanisms such as drug induced, seizures, migraine, p...Palinopsia is the recurrence or persistence of visual images after cessation of the stimulus. Palinopsia has been associated with a wide variety of etiologies and mechanisms such as drug induced, seizures, migraine, psychiatric conditions, head trauma and structural lesions in the brain. We report a case of occipital stroke who presented with oscillating palinopsia. Sudden-onset palinopsia is a very rare symptom of stroke, but it must be recognized early as it is a highly time dependent, and potentially treatable condition. A 57-year-old woman with a history of poorly controlled type 2 diabetes, hyperlipidemia, and hypertension presented with sudden onset right sided palinopsia with images of her face and right forearm with hand, occurring several times in a day, lasting for a few minutes each time, and appearing in the same location each time. There are few case reports in literature secondary to stroke and what makes it interesting also is that she reported persistence of image even when her eyes are closed. Moreover, the sudden onset is not common in literature. The Magnetic Resonance Imaging (MRI) of the brain showed evidence of left Posterior Cerebral Artery (PCA) territorial (Fusiform gyrus) subacute ischemic infarction. Visual field assessment showed a right homonymous hemianopia. She was treated with aspirin and clopidogrel. The frequency and intensity of palinopsia reduced subsequently. The face image disappeared in the first week while the forearm image disintegrated gradually over the next few weeks. Palinopsia may be a rare presenting symptom of stroke. It is important for the clinician or emergency room doctors to be alert to the possibility of undiagnosed structural neurological lesions like occipital stroke and differentiate it from non-organic causes, as prompt management may reduce the risk of visual or motor disability.展开更多
The mechanism of bitemporal hemianopia arising as a result of chiasmal compression is unknown.In this study,we combined an ex vivo experiment and finite element modelling(FEM)to investigate its potential mechanism.A c...The mechanism of bitemporal hemianopia arising as a result of chiasmal compression is unknown.In this study,we combined an ex vivo experiment and finite element modelling(FEM)to investigate its potential mechanism.A cadaveric human optic chiasm was scanned using micro-CT before and after deformation by inflation of Foley catheter,to simulate tumour growth from beneath.The geometry of the same chiasm was reconstructed and simulated using finite element analysis.Chiasmal deformations were extracted from the simulation and compared with those observed during micro-CT scanning.In addition,nerve fibre models examining variation in local fibre distribution patterns of the chiasm were incorporated to investigate the strain(deformation)distributions of the chiasm at an axonal level.The FEM model matched the micro-CT scans well both qualitatively and quantitatively.Compression of the chiasm induced high strains in the paracentral portions of the chiasm where the crossing optic nerve fibres are located.At an axonal level,the magnitude of strains affecting crossed fibres were greater than those affecting uncrossed fibres.The high strains in the paracentral portions of the chiasm,combined with the differences in strain between crossed and uncrossed nerve fibres,are consistent with a biomechanical explanation for the pattern of visual field loss seen in chiasmal compression.展开更多
文摘The blood supply system of the optic chiasma was studied in 85 fresh human specimens using various histological and anatomical methods. Computer image analysis and ultrastructural examinations of the microvessel in 58fetal specimens were also conducted. The authors found that the medial portion of the chiasma is a weak point in the microcirculation network. This weak point is apt to be disturbed first and become ischemic. causing disorders of the crossing optic nerve fibers and resulting in characterestic bitemporal visual field defects. SEM studies showed no ultrastructural difference between the capillaries at the medial and lateral portions of the chiasma. It was concluded that: 1) No special artery supplies the median chiasma the weak point of microcirculation at the median chiasma is due to its relatively scanty capillary distribution; 2) 'lateral chiasma arteries' could provide a better blood supply to the lateral fibers and thus the nasal quadrantic visual field could be preserved in many late stages of visual field defect in sellar region tumors, 3) cases with pituitary microadenoma which is not sufficiently large to press the chiasma but involves bitemporal visual field defect are due to the tumor recieving “shunt-flow” (stealing blood) from the chiasma through the peri-infundibulum plexus.
基金The fund of Department of Education Zhejiang Province Scientific Research Project,No.Y201839721Zhejiang Province Medical Science and Technology Project,No.2017174708,No.2020RC061,and No.2018273034+2 种基金the Zhejiang Provincial Natural Scientific Foundation of China,No.LGF20H090011 and No.LY18H090002Zhejiang public welfare Technology Application Research Project,No.LGF20H090011the Medical and Health Science and Technology Program of Zhejiang Province,No.2018273034.
文摘BACKGROUND Nonketotic hyperglycemia(NKH)is characterized by hyperglycemia with little or no ketoacidosis.Diverse neurological symptoms have been described in NKH patients,including choreoathetosis,hemiballismus,seizures,and coma in severe cases.Homonymous hemianopia,with or without occipital seizures,caused by hyperglycemia is less readily recognized.CASE SUMMARY We describe a 54-year-old man with NKH,who reported seeing round,colored flickering lights with right homonymous hemianopia.Cranial magnetic resonance imaging demonstrated abnormalities in the left occipital lobe,with decreased T2 signal of the white matter,restricted diffusion,and corresponding low signal intensity in the apparent diffusion coefficient map.He responded to rehydration and a low-dose insulin regimen,with improvements of his visual field defect.CONCLUSION Patients with NKH may present focal neurologic signs.Hyperglycemia should be taken into consideration when making an etiologic diagnosis of homonymous hemianopia.
文摘Palinopsia is the recurrence or persistence of visual images after cessation of the stimulus. Palinopsia has been associated with a wide variety of etiologies and mechanisms such as drug induced, seizures, migraine, psychiatric conditions, head trauma and structural lesions in the brain. We report a case of occipital stroke who presented with oscillating palinopsia. Sudden-onset palinopsia is a very rare symptom of stroke, but it must be recognized early as it is a highly time dependent, and potentially treatable condition. A 57-year-old woman with a history of poorly controlled type 2 diabetes, hyperlipidemia, and hypertension presented with sudden onset right sided palinopsia with images of her face and right forearm with hand, occurring several times in a day, lasting for a few minutes each time, and appearing in the same location each time. There are few case reports in literature secondary to stroke and what makes it interesting also is that she reported persistence of image even when her eyes are closed. Moreover, the sudden onset is not common in literature. The Magnetic Resonance Imaging (MRI) of the brain showed evidence of left Posterior Cerebral Artery (PCA) territorial (Fusiform gyrus) subacute ischemic infarction. Visual field assessment showed a right homonymous hemianopia. She was treated with aspirin and clopidogrel. The frequency and intensity of palinopsia reduced subsequently. The face image disappeared in the first week while the forearm image disintegrated gradually over the next few weeks. Palinopsia may be a rare presenting symptom of stroke. It is important for the clinician or emergency room doctors to be alert to the possibility of undiagnosed structural neurological lesions like occipital stroke and differentiate it from non-organic causes, as prompt management may reduce the risk of visual or motor disability.
基金Supported by National Natural Science Foundation of China(12002025)This study was approved by the ACT Health Human Research Ethics Committee(ETH 1.14.020).
文摘The mechanism of bitemporal hemianopia arising as a result of chiasmal compression is unknown.In this study,we combined an ex vivo experiment and finite element modelling(FEM)to investigate its potential mechanism.A cadaveric human optic chiasm was scanned using micro-CT before and after deformation by inflation of Foley catheter,to simulate tumour growth from beneath.The geometry of the same chiasm was reconstructed and simulated using finite element analysis.Chiasmal deformations were extracted from the simulation and compared with those observed during micro-CT scanning.In addition,nerve fibre models examining variation in local fibre distribution patterns of the chiasm were incorporated to investigate the strain(deformation)distributions of the chiasm at an axonal level.The FEM model matched the micro-CT scans well both qualitatively and quantitatively.Compression of the chiasm induced high strains in the paracentral portions of the chiasm where the crossing optic nerve fibres are located.At an axonal level,the magnitude of strains affecting crossed fibres were greater than those affecting uncrossed fibres.The high strains in the paracentral portions of the chiasm,combined with the differences in strain between crossed and uncrossed nerve fibres,are consistent with a biomechanical explanation for the pattern of visual field loss seen in chiasmal compression.
