Primordial and recycled helium isotope signatures in the mantle transition zone.

Isotope compositions of basalts provide information about the chemical reservoirs in Earth's interior and play a critical role in defining models of Earth's structure. However, the helium isotope signature of the mantle below depths of a few hundred kilometers has been difficult to measure directly. This information is a vital baseline for understanding helium isotopes in erupted basalts. We measured He-Sr-Pb isotope ratios in superdeep diamond fluid inclusions from the transition zone (depth of 410 to 660 kilometers) unaffected by degassing and shallow crustal contamination. We found extreme He-C-Pb-Sr isotope variability, with high 3He/4He ratios related to higher helium concentrations. This indicates that a less degassed, high-3He/4He deep mantle source infiltrates the transition zone, where it interacts with recycled material, creating the diverse compositions recorded in ocean island basalts.

Butterfly lesion of the corpus callosum due to Schilder's disease.

A 50 year old woman developed memory impairment and confusion over a 2 week period. CT scans of the brain showed a 'butterfly lesion' of the corpus callosum extending into the frontal lobes bilaterally. Stereotactic biopsy determined the lesion to be du e to demyelination. Further diagnostic investigations and the subsequent clinical course support the diagnosis of Schilder's disease.

Bilateral optic disk pallor after unilateral internal carotid artery occlusion.

Bilateral pallor of the optic disks was observed in a 52-year-old man after dissection of an internal carotid artery. Diffuse pallor of the ipsilateral optic disk reflected infarction of the ipsilateral optic nerve and "bow-tie" atrophy of the contralateral optic disk reflected infarction of the ipsilateral optic tract. The findings were due to an occlusion of the internal carotid artery proximal to the origin of the ophthalmic artery, resulting also in insufficiency in the area of supply of the anterior choroidal artery.