The x-ray appearance and incidence of calcified nodules on the habenular commissure.

Abstract

The shadow cast by a calcified pineal gland in a roentgenogram of the lateral aspect of the head is commonly in two parts—a large posterior part and a small cap-like anterior part (Figs. 4, 5, and 6). The cap-like anterior portion is a supplementary opacity which is contributed by calcified nodules of neuroglia located on the habenular commissure. These nodules were observed and described by Quercy, de Lachaud, and Durand in 1938. The present study was undertaken to obtain further information concerning these nodules which might be of value to the radiologist. Material and Method The brains of 123 individuals, 75 males and 48 females, all free of intracranial disease and ranging in age from twenty to eighty-two years, were obtained at autopsy and fixed in 10 per cent formaldehyde for several months. The cerebral hemispheres, the meninges, and the roof of the third ventricle were then removed to permit inspection of the pineal gland and the lining of the third ventricle. Each gland and the whole habenular commissure, to which it is attached, was then removed from the brain in one piece and roentgenograms were obtained from both the lateral and the superior aspects. Observations Structure, Location and X-Ray Appearance of the Nodules: The neurogliar nodules, as described by Quercy, de Lachaud, and Durand, are formed by a localized thickening of the neuroglia between the commissure and the overlying ependyma. These masses of neuroglia attain a thickness of 1 mm. and cover an irregularly shaped area 5 mm. or less across. Several such nodules may be present when they are small, but as they enlarge they unite and form a single large nodule which may cover the whole ventricular surface of the habenular commissure. In the present study of 123 brains, these nodules were found only on the habenular commissure. No anatomical peculiarity of this site was observed to account for this. The histologic picture of calcification in the neurogliar nodules is similar to that in the pineal gland proper. In both instances, in hematoxylin and eosin stained sections, purple granules are present in the spaces between the neurogliar fibers, and in heavily calcified regions these are large and crowded together into large mulberry-like masses. Figure 1 is a photograph of the dorsal aspect of the forebrain of a specimen with the roof of the third ventricle removed to show two small nodules on the habenular commissure. Figure 2 is a similar preparation in which there is a single large nodule that covers the greater part of the habenular commissure. Figure 3 is a mid-sagittal section to show the thickness and the extent of such a nodule in the median plane. The pineal recess, the extension of the third ventricle into the stalk of the pineal gland, has the habenular commissure in its upper wall and the posterior commissure in its lower wall.