The intrastitial blood supply of the lateral geniculate body

Characterization of the blood oxygen level dependent hemodynamic response function in human subcortical regions with high spatiotemporal resolution

Subcortical brain regions are absolutely essential for normal human function. These phylogenetically early brain regions play critical roles in human behaviors such as the orientation of attention, arousal, and the modulation of sensory signals to cerebral cortex. Despite the critical health importance of subcortical brain regions, there has been a dearth of research on their neurovascular responses. Blood oxygen level dependent (BOLD) functional MRI (fMRI) experiments can help fill this gap in our understanding. The BOLD hemodynamic response function (HRF) evoked by brief (<4 s) neural activation is crucial for the interpretation of fMRI results because linear analysis between neural activity and the BOLD response relies on the HRF. Moreover, the HRF is a consequence of underlying local blood flow and oxygen metabolism, so characterization of the HRF enables understanding of neurovascular and neurometabolic coupling. We measured the subcortical HRF at 9.4T and 3T with high spatiotemporal resolution using protocols that enabled reliable delineation of HRFs in individual subjects. These results were compared with the HRF in visual cortex. The HRF was faster in subcortical regions than cortical regions at both field strengths. There was no significant undershoot in subcortical areas while there was a significant post-stimulus undershoot that was tightly coupled with its peak amplitude in cortex. The different BOLD temporal dynamics indicate different vascular dynamics and neurometabolic responses between cortex and subcortical nuclei.

Bilateral Isolated Lateral Geniculate Body Lesions in a Patient with Pancreatitis and Microangiopathy

An 18-year-old woman developed pancreatitis and a thrombotic microangiopathy but no electrolyte abnormalities. She required intubation hours after admission and was not able to communicate for 8 days. Upon recovering consciousness, she reported severely impaired vision in both eyes, but ophthalmologic evaluation and neuroimaging were not obtained until several days later. Ophthalmologic examination documented retinal infarcts and profound binocular vision loss with hourglass bilateral homonymous hemianopic visual field loss. MRI showed signal abnormalities restricted to the area of the lateral geniculate bodies (LGBs) with characteristics most suggestive of hemorrhagic infarction. Very few cases of isolated bilateral LBG lesions have been reported. Damage has been attributed to myelinolysis from osmotic demyelination or to infarction from microvascular occlusion. This case conforms more to microvascular infarction. The vulnerability of the LGB to selective microvascular infarction may be based on a combination of its unique architecture and high metabolic demand.

Microvascularization of thalamus and metathalamus in common tree shrew (Tupaia glis)

The microangioarchitecture of the thalamus and metathalamus in common tree shrew (Tupaia glis) was studied using vascular corrosion cast/stereomicroscope and SEM technique. The arterial supply of the thalamus and metathalamus was found to originate from perforating branches of the posterior communicating artery, the posterior cerebral artery, the middle cerebral artery, and the anterior choroidal artery. These perforating arteries gave rise to numerous bipinnate arterioles which in turn, with decreasing vessel diameters, branched into a non-fenestrated capillary bed. Venous blood from the superficial parts of the thalamus and metathalamus was collected into the thalamocollicular vein, whereas venous blood from internal aspects of the thalamus was conveyed to the internal cerebral vein. Some venous blood from the most rostral part of the thalamus flowed into tributaries of the middle cerebral vein before draining into the cavernous sinus. Further, the thalamic and metathalamic vascular arrangement was found to be of centripetal type. In addition, thalamic arterial anastomosis was rarely observed. Thus, obstruction of thalamic blood supply could easily lead to thalamic infraction.

Sectorial optic atrophy and homonymous, horizontal sectoranopia: a lateral choroidal artery syndrome?

Two patients with sectorial optic atrophy and homonymous, horizontal sectoranopia are described. Neuroradiological investigations localised the visual pathway lesion to the lateral geniculate body. The peculiar nature of the field defect and the optic atrophy appeared explicable in terms of ischaemia in the territory of the lateral choroidal artery.