OTOSCLEROSIS

Otosclerosis is a primary disorder of the bony labyrinth and stapes known to affect only humans, leading to progressive conductive and sensorineural hearing loss [Guild SR, 1944; Schuknecht HF, 1993]. Otosclerosis is a disease particularly widespread among Caucasian populations, while it is very rare among blacks, Asians, and Native Americans [Altmann et al, 1967]. Many studies have established that the period of onset is mainly between 15 and 40 years of age, with a higher prevalence in women than in men [Gordon, 1989]. The disease is bilateral in about 75% of patients [Hueb, 1991]. The most common site is anterior to the oval window, followed by the round window niche, and the apical and medial cochlear wall, respectively [Schuknecht and Barber, 1985].

Schuknecht and Barber [Schuknecht and Barber, 1985] classified otosclerosis as clinical and histological. While clinical otosclerosis is defined as a lesion that fixes the stapes footplate, histological otosclerosis refers to cases without footplate fixation. Cochlear otosclerosis describes to cases of histological otosclerosis extensive enough to involve the endosteum of the cochlea without stapes fixation [Schuknecht, 1974].

Figure 1. This 16 year old male had a history of congenital heart disease. He also had a history of frequent nosebleeds and bruising easily. Autopsy findings included atypical complete transposition, ventricular septal defects, and pulmonary disease. This left temporal bone shows early, active otosclerosis in the anterior portion of the oval window. 

Otosclerotic bone undergoes a remodeling process in which normal bone is replaced by otosclerotic bone [Figs.]. Osteoclasts and osteoblasts can be seen within active foci of otosclerosis. Stapes fixation begins with calcification of the annular ligament joining the oval window otosclerotic lesion with the stapedial footplate. The stapes subsequently becomes fixed by the lesion [Linthicum, 1993].

Gussen [Gussen, 1975] reported loss of capillaries and pericapillary spaces in the spiral ligament and erosion of the cochlear capsular bone with a greater width of soft tissue endosteum separating the spiral ligament from the bony surface. Spiral ligament changes have been referred to as atrophy, fibrosis and thickening, especially when they are found adjacent to the endosteal bone surface [Schuknecht, 1993].

Histopathological studies suggest that certain combinations of otological diseases, e.g. otosclerosis and Meniere’s disease, can occur and may have causative links [Cawthorne,1955;  Paparella, 1984], though other associations (e.g. otitis media, or tumors of the temporal bone) are commonly only coincidental, not causative [Paparella, 1988]. Otosclerosis may cause endolymphatic hydrops by abutting the spiral ligament, resulting in a chemical disruption of ion-fluid recycling [Liston et al, 1984], obstruction of the endolymphatic duct and sac [Yoon et al, 1990], and biochemical changes [Lawrence,1966; Ghorayeb and Linthicum, 1978].

Figure 2. Cochlear otosclerosis causing hyaline degeneration of the spiral ligament and profound endolymphatic hydrops at the basal turn of the cochlea (Hematoxylin-eosin stain; original magnification x 26).

 

The differential diagnosis from Paget’s disease (osteitis deformans) should be considered. Otosclerosis differs from Paget’s disease in that it affects only the osseous labyrinth and no other bones in the body and occurs in a younger population [Ferlito,1985; Barnes and Peel, 2001].

The cause of otosclerosis is unknown, though a variety of factors involved in the development of the disease have been postulated. A gene for otosclerosis has reportedly been located in several loci, i.e. OTSC1 on chromosome 15q25-q26 [Tomek et al, 1998]; OTCS2 on chromosome 7q34-36 [Bogaert et al, 2001], and OTCS3 on chromosome 6p21.3-22.3 [Chen, 2002]. The role of measles in the pathogenesis of otosclerosis has been extensively studied [McKenna et al, 1996;Karosi et al, 2004]. Mutations of the collagen gene COL1A1 and a consequently reduced collagen type I synthesis have been observed in patients with otosclerosis [McKenna et al, 1998].

References  

1.Guild SR. Histologic otosclerosis. Ann Otol 1944; 53: 246-67.

2.Schuknecht HF. Disorders of bone. In: Schuknecht HF, editor. Pathology of the ear, 2nd edn. Philadelphia: Lea & Febiger, 1993. p. 365-414.

3. Altmann F, Glasgold A, Macduff JP. The incidence of otosclerosis as related to race and sex. Ann Otol 1967; 76: 377-92.

4. Hueb MM, Goycoolea MV, Paparella MM, Oliveira JA. Otosclerosis: the University of Minnesota temporal bone collection. Otolaryngol Head Neck Surg 1991; 105: 396-405.

5. Gordon MA. The genetics of otosclerosis: a review. Am J Otol 1989; 10: 426-38.

6. Schuknecht HF, Barber W. Histologic variants in otosclerosis. Laryngoscope 1985; 95: 1307-17.

7. Schuknecht HF, Kirchner JC. Cochlear otosclerosis: fact or fantasy? Laryngoscope 1974; 84: 766-82.

8. Linthicum FH Jr. Histopathology of otosclerosis. Otolaryngol Clin North Am 1993; 26: 335-52.

9. Gussen R. Labyrinthine otosclerosis and sensorineural deafness. Pathologic findings of the spiral ligament. Arch Otolaryngol 1975; 101: 438-40.

10. Cawthorne T. Otosclerosis. J Laryngol Otol 1955; 69: 437-56.

11. Paparella MM, Mancini F, Liston SL. Otosclerosis and Meniere’s syndrome: diagnosis and treatment. Laryngoscope 1984; 94: 1414-7.

12. Paparella MM, Schachern PA, Goycoolea MV. Multiple otopathologic disorders. Ann Otol Rhinol Laryngol 1988; 97: 14-8.

13. Liston SL, Paparella MM, Mancini F, Anderson JH. Otosclerosis and endolymphatic hydrops. Laryngoscope 1984; 94: 1003-7.

14. Yoon TH, Paparella MM, Schachern PA. Otosclerosis involving the vestibular aqueduct and Meniere’s disease. Otolaryngol Head Neck Surg 1990; 103: 107-12.

15.  Lawrence M. Possible influence of cochlear otosclerosis on inner ear fluids. Ann Otol 1966; 75: 553-8.

16. Ghorayeb BY, Linthicum FH Jr. Otosclerotic inner ear syndrome. Ann Otol 1978; 87: 85-90.

17. Ferlito A. Orecchio. In: Lanza G, editor. Anatomia patologica sistematica, 2nd edn, vol. II. Padova: Piccin, 1985. p. 2286-307.

18. Barnes L, Peel RL. Diseases of the external auditory canal, middle ear, and temporal bone. In: Barnes L editor. Surgical pathology of head and neck, 2nd edn, vol. I. New York: Marcel Dekker, 2001. p. 557-99.

19. Tomek MS, Brown MR, Mani SR, Ramesh A, Srisailapathy CR, Coucke P, Zbar RI, Bell AM, McGuirt WT, Fukushima K, Willems PJ, Van Camp G, Smith RJ. Localization of a gene for otosclerosis to chromosome 15q25-q26. Hum Mol Genet 1998; 7: 285-90.

20. Van Den Bogaert K, Govaerts PJ, Schatteman I, Brown MR, Caethoven G, Offeciers FE, Somers T, Declau F, Coucke P, Van de Heyning P, Smith RJH, Van Camp G. A second gene for otosclerosis, OTSC2, maps to chromosome 7q34-36. Am J Hum Genet 2001; 68: 495-500.

21. Chen W, Campbell CA, Green GE, Van Den Bogaert K, Komodikis C, Manolidis LS, Aconomou E, Kyamides Y, Christodoulou K, Faghel C, Giguere CM, Alford RL, Manolidis S, Van Camp G, Smith RJH. Linkage of otosclerosis to a third locus (OTSC3) on human chromosome 6p21.3-22.3. J Med Genet 2002; 39: 473-7.

22. McKenna MJ, Kristiansen AG, Haines J. Polymerase chain reaction amplification of a measles virus sequence from human temporal bone sections with active otosclerosis. Am J Otol 1996; 17: 827-30.

23. Karosi T, Konya J, Szabo LZ, Sziklai I. Measles virus prevalence in otosclerotic stapes footplate samples. Otol Neurotol 2004; 25: 451-6.

24. McKenna MJ, Kristiansen AG, Bartley ML, Rogus JJ, Haines JL. Association of COL1A1 and otosclerosis: evidence for a shared genetic etiology with mild osteogenesis imperfecta. Am J Otol 1998; 19: 604-10.