Osteoporosis Circumscripta Cranii: Its Pathogenesis and Occurrence in Leontiasis Ossea and in Hyperparathyroidism

Abstract

The pathogenesis and classification of the large, irregular, circumscribed areas of osteoporosis of the cranium first described by Schüller2 were for some time subjects of mere speculation. Schüller (14, 15) himself did not originally point out the intrinsic significance of his striking radiological findings. Soon, however, Sosman (17, 18) provided histologic observations indicating a relationship between osteoporosis circumscripta and Paget's disease. Further clinical and radiological investigation seemed to corroborate this evidence to a great extent, and osteoporosis came to be generally considered as an atypical form or precursor of Paget's disease, “probably the absorptive or destructive phase with the productive phase held in abeyance” (17). Its occurrence solely in the skulls of persons suffering from Paget's disease was thought to be related chiefly to the peculiarities of the diploic circulation, the cranial architecture, and the statics of the bones of the cranium (6). Subsequent histologic studies, however, did not unanimously support the view that circumscribed osteoporosis is without exception an early or atypical form of Paget's disease of the skull. While a group of observers (2, 16, 20) microscopically verified the identity of the two conditions in four cases, Schmorl's (13) interpretations were different. In the skulls of five persons who had been suffering from Paget's disease he saw gross as well as microscopic departures, which he identified as the results of circulatory disturbances. They seemed to resemble hemorrhagic infarctions rather than the anatomical changes characteristic of Paget's disease. In gross appearance they corresponded to the fundamentals of osteoporosis circumscripta. A similar observation was made by the present writer (20). In a verified case (Case II) of osteoporosis he saw discolored areas of deep reddish hue in the cranium, which revealed microscopically an unusual hyperemia, small hemorrhages into the bone marrow, and advanced decalcification of the bone tissue, but no signs of Paget's disease. A third group of pathological findings, reported by Schellenberg (12), and later Guillain, Ledoux-Lebard, and Lereboullet (3), bore more resemblance to osteitis fibrosa than to Paget's disease. A review of the literature shows that clinically about 60 per cent of the published cases of osteoporosis circumscripta have been associated with Paget's disease; 20 per cent, however, were connected with leontiasis ossea or bony tumors of the maxilla and not with Paget's disease. In the remaining 20 per cent the skull only was examined and not the entire skeleton; consequently, no statement can be made concerning the presence or absence of Paget's disease in these patients. It seems, therefore, that leontiasis ossea constitutes the second largest group of abnormalities in which osteoporosis circumscripta occurs, and the coincidence of these conditions is so frequent as to have definite significance.