Otosclerosis. A further investigation of inorganic constituents by neutron activation analysis

Composition of the otosclerotic stapes: electron microprobe analyses

For the first time, otosclerotic stapes have been distinguished from unafflicted controls at a high level of significance by using a spectrum of elements measured by energy-dispersive spectrometer-electron probe microanalyses (EDS/EPMA). Discriminant analyses of the maximum concentration of 13 elements measured at several sites within each of 32 stapes differentiated otosclerotic from unafflicted individuals well above the 95% confidence level. Eight of the 9 control (unafflicted) and 21 of the 23 afflicted stapes were correctly classified. In descending order of contribution to the discriminant function, the elements are Zn > Cr > K > Ca > Si > Mn > Na > Al > Mg > P > Fe > S > Ti. Zinc and chromium account for much of the difference, but discriminant analyses excluding them still distinguish the two groups at the 95% confidence level. These results are consistent with previous reports of high levels of alkaline phosphatase, a zinc-containing enzyme, in afflicted stapes. But the broad spectrum of elements capable of distinguishing otosclerotic stapes warrants study of additional zinc-containing and other metal-containing or metal-activated moieties.

Distribution of structural and trace elements in human temporal bone

This study was undertaken to evaluate a systematic analysis of mineral and trace elements of individual functionally determined parts of adult temporal bone. Marked differences were observed in basic structural elements (Ca, P, Mg, and Zn) among different bone regions. The more so, molar Ca/P ratio was significantly different in various regions, being highest in the hammer and vestibular regions. Taxonomic analysis revealed specific differences in the mineral ratio between the two petrous bone regions believed to develop from various embryonal bases. According to results, the observed differences in mineral trace element composition of particular regions of human temporal bone might be explained by their developmental specificities and functional adaptation.

Vitamin D deficiency and otosclerosis

A prospective study of 47 patients with otosclerosis was undertaken to investigate the possible etiologic role of vitamin D undernutrition. The population comprised 27 women and 20 men, with a mean age of 46.4 years (range 21 to 79). The disease was bilateral in 43 patients, and cochlear involvement was present in 84.4%. The mean duration of symptoms was 17.1 years. Vitamin D status was evaluated by measuring the plasma 25-hydroxy vitamin D3 (25-OHD), which is the main storage metabolite. Abnormally low 25-OHD levels were found in 10 patients (21.7%) and borderline low levels in another two. Raised serum alkaline phosphatase levels were present in 32.6%, calcium in 6.5%, and inorganic phosphate in 4.3%. Calcium and vitamin D replacement therapy resulted in significant hearing improvement in 3 of 16 patients; these data support a causal correlation. Vitamin D deficiency is probably a factor in the etiology of some cases of otosclerosis and is important, since the deafness resulting from cochlear involvement may be reversible.

Histomorphometric analysis of iliac trabecular bone in otosclerosis

With the aim of investigating whether patients with otosclerosis suffer from a generalized bone disorder, a histomorphometric analysis of trabecular bone from the iliac crest was performed. Iliac crest biopsies from 10 patients with otosclerosis and 20 normal controls were obtained after tetracycline double labelling and examined by histomorphometry. No significant differences were found in the estimates of density and remodeling of bone between patients and sex and age-matched normal controls. Qualitatively the bone specimens showed no signs of any generalized bone disorder.

Mineral and collagen content of human ossicles

With increased use of human otologic homograft tissue for implantation, different preservation techniques and products are used for storing and preserving the grafts before surgery. Preserved ossicles may, according to some authors, already exhibit signs of decalcification after 2 weeks. Therefore, the mineral (calcium, phosphorus) and collagen content of human ossicles (incus) and mastoid cortex and the influence of different storage techniques was biochemically investigated. No significant mineral or collagen-concentration changes were observed after a 6-week storage in pH-7 formaldehyde or in cialit, in either the ossicles or in the cortical bone. These biochemical findings are in agreement with histologic observations and with similar experiments using the photon absorptiometry technique.

Mineral content of skeletal bones in otosclerosis

In 63 patients with otosclerosis confirmed by operation, the bone mineral content was determined by photon absorptiometry. The bone mineral content and bone mineral concentration were found to be normal, which lends support to the assumption that otosclerosis is a localized disease and not a manifestation of a generalized disorder of the skeletal system.