Pathology of neuroepithelial suprastructures of the human inner ear

Original Contributions Am J Otolaryngol 3: 77-90, 1982

Pathology of Neuroepithelial Suprastructures of the Human Inner Ear LARS-GORAN JOHNSSON, M.D.,* ROLAND C. ROUSE, PH.D.,~"CHARLES G. WRIGHT, PH.D.,$ PAMELAJ. HENRY,B.S.,']" ANDJOSEPHE. HAWKINS,JR., PH.D., D.Sc.+ Neuroepithelial suprastructures in abnormal human inner ears were studied by light microscopy, scanning electron microscopy, and x-ray diffraction. The most common abnormality was calcification, which selectively affected the gelatinous membranes (otoconial, cupular, and tectorial) and the secretory tissues (stria vascularis and utricular dark cells). The structures most frequently affected were the otoconial membranes. The minerals invotved were apatite, octacalclum phosphate, and vaterite, replacing the normal layer of calcium carbonate in the form of calcite crystals. The first two of these substances were sometimes mixed with calcite. In the saccule such abnormal otoconial deposits were usually associated with a collapsed saccular wall. Formation of abnormal otoconia is characterized as primary (no pre-existing normal calcite otoconia) or secondary (formed after the destruction of normal otoconia). Such deposits probably depend upon an abnormal composition of the endolymph, especially upon an elevated concentration of phosphate ions. It is inferred that a normal endolymphatic microhomeostasis is necessary to maintain the functional state of the neuroepithelial suprastruetures.

otoconia in man, largely because the crystals tend to dissolve during the decalcification process used in conventional temporal bone histology." They are also easily dislodged during normal handling 3 and during the process of dissection. The structure and mineralogic composition of normal h u m a n otoconia (Fig. 1) are now well-established? -~ The crystals are composites of calcite, which is the trigonal polymorph of CaCO,, and an organic matrix, which may be composed of glycoprotein. Aggregates of otoconia are held together in v i v o by an organic substance, which may be identical in composition to the otoconial matrix, and form a flexible crystalline layer, which rests upon a gelatinous membrane. 7 The crystalline and gelatinous layers together constitute the otoconial membrane, With increasing age, the crystals are often reduced in number, especially in the saccule, leaving the otoconial membrane almost bare and translucent. 7-9 Before an otoconium disintegrates it becomes hollow and assumes a characteristic fibrous, skeletal appearance ~ (Fig. 2). This p h e n o m e n o n is a part of the regular labyrinthine aging process and does not represent otoconial abnormality in the same sense as

Each of the sensory neuroepithelia of the inner ear is surrounded by a special membranous suprastructure, w h i c h is u s u a l l y described as gelatinous, although Iurato I has reported that the protein involved appears to be related to keratin, epidermin, myosin, and fibrinogen, rather than to collagen or elastin. The utricular and saccular maculae have an overlying mineral layer or otoconial mass, consisting of crystals of calcium carbonate in the form of calcite. The tectorial membrane of Corti's organ and the cupulae of the ampullar cristae are normally devoid of any mineral layer. The otopathologic literature contains only limited information about abnormalities of the Received September 9, 1981. Accepted for publication November 27, 1981. Supported by USPHS Research Grants NS 05o65, NS 16238, NS 11672, NS 12706, and Program Project Grant NS 05785, and by a grant from the Research Fund of the AmericanOtological Society. * Department of Otorhinolaryngology, University of Helsinki Central Hospital, He|sinki, Finland. + Kresge Hearing Research Institute, Department of Otorhinolaryngology,Universityof MichiganMedicalSchool, Ann Arbor, Michigan48109. $ Collier Center for CommunicationDisorders, University of Texas at Dallas, Dallas, Texas 75235. Address correspondence and reprint requests to Dr. Hawkins.

0196-0709182J030010077 $02.80 (~) W. B. Saunders Co. 77

INNEREAR NEUROEPITHELIALSUPRASTRUCTURES does the material presently described. Likewise, intergrowths of several otoconia, as in Figure 3, and calcite crystals of anomalous shape often occur in small numbers o n an otherwise normal otoconial membrane. Despite their sometimes bizarre appearance, such deviant crystals should not be taken as evidence of vestibular disease. We p r e v i o u s l y r e p o r t e d s e v e r a l cases of grossly abnormal h u m a n otoconia consisting of apatite, Ca5 (PO4,CO3]3 (OH,F,C1), ~~and vaterite, w h i c h is the hexagonal polymorph of CaCO3 L1 {Fig. 4). In a d d i t i o n , r e p o r t s of a b n o r m a l otoconia associated with chronic otitis media s and congenital absence of otoconia ~ have appe&red. In contradistinction to the paucity of reported human cases, there is a rather extensive l i t e r a t u r e on a b n o r m a l o t o c o n i a in c e r t a i n species of laboratory animals, most of w h i c h have genetic abnormalities. 1~-~5 Our present k n o w l e d g e of pathology of the tectoria[ membrane and the cupulae in m a n is equally limited. Both structures shrink and become distorted u n d e r the influence of fixatives. The cupulae are also easily dislodged during the process of dissection. Therefore, abnormalities of the tectorial membrane and the cupulae are e v e n more likely to go u n d e t e c t e d than are abnormalities of the otoconial membrane. Findings in h u m a n temporal bone studies hy us and other investigators show that w h e n Reissner's membrane is collapsed or its integrity severely compromised, as in hydrops labyrinthi, the tectorial membrane is severely altered. Schuknecht "2 and Antoli-Candela '6 have, i n fact, demonstrated local distortion of the rectorial membrane spatially related to a r u p t u r e of Reissner's memb r a n e . w J o h n s s o n t7 h a s s u g g e s t e d t h a t in Meni~re's disease a t t a c k s the tectorial membrane shrinks u n d e r t h e influence of a n increased sodium concentration, thereby causing auditory dysfunction and fluctuant hearing loss. The tectorial membrane is rolled up and distorted in endolymphatic labyrinthitis of viral origin. ~a Similar abnormalities are likely to occur in other forms of labyrinthitis as well. Only four cupular abnormalities have been reported to date: cupulolithiasis, 2 malformation of the cupula, s distortion of the cupula due to hemorrhage and possible toxic effect of blood on the cupula, ~9 and calcification of cupulae. ~'~~ The neutral buoyancy of the cupula apparently can

AmericQn Journal of OtolQryngo[ogy 78

wIn Dalmatian dogs that have hereditary deafness, Reissnet's membrane is often collapsed, and the tectorial membrane is alwaysseverely distorted {Johnssonet al., in preparation).

be altered by alcohol, heavy water,"' and other substances/2 but such alterations presumably do not involve gross changes in its structure. MATERIALS AND METHODS The specimens used in this study were from a large group of t e m p o r a l b o n e s d e s c r i b e d elsewhere. 9,2~ They were processed using the technique of microdissection and surface preparation, w h i c h has been described in detail by Hawkins and Johnsson. 24 In selected cases the vestibular neuroepithelia were critical pointdried, gold-coated, and surveyed with a JSM-U3 scanning electron microscope (Japan Electron Optics Corporation) operated at 15 kV. In most cases the otoconial membranes were similarly treated, except that they were allowed to dry in air. Qualitative chemical analyses were performed on crystalline samples while they were in the scanning electron microscope, using voltages of 15 or 25 kV and a solid-state x-ray detector (Kevex Corporation) coupled to a multichannel analyzer (Tracer Northern Scientific, Model 710}. Identification of the minerals composing the crystalline deposits was a c c o m p l i s h e d by powder x-ray diffraction using 114.6 and 57.3 m m diameter Debye-Scherrer cameras. The resuiting diffraction patterns were carefully measured to detect any' weak lines signifying the presence of minor constituents. RESULTS The results of this study are summarized in Table 1. In the sections that follow we describe some of our observations in greater detail and comment upon their significance. Otoconial Abnormalities in the Saccule

COLLAPSED SACCULAR WALL. The most common otoconia] abnormality was associated w i t h a complete or portia[ collapse of the membranous walt of the saccule, a s exemplified by specimens from patients 1, 2, 4, 5, 7, 9, and 10. In the specimens from patients 4, 5, 7, and 9 the collapse of the saccule was presumably secondary to cochleo-saccular hydrops. In these specimens the saccule had a characteristic appearance, w h i c h is illustrated in Figure 5. The lumen of the saccule was absent or reduced to a pocket along the superior and medial margin of the macula, where large areas of the membranous saccular wall are normally attached to the o u t s i d e of the utricular macula. This a t t a c h m e n t apparently

JOHNSSON ET AL.

Figure 1 (above, left).

Normal calcite otoconia from the saccule of a 6-year-old child,

Figure 2 (above, right), Typical age-related degeneration of the saccular otoconia from a 74-year-old man, Figure 3 (right), One of the common types of otoeonial intergrowths, showing two crystals interpenetrating at about go ~ From the case illustrated in Figure 1.

Figure 4,

Lenticular vaterite crystals from the utricle of a fetus, estimated age 175 days. The hollowing out of many of the crystals suggests that these a b n o r m a l o t o c o n i a are degenerating much like the normal calcite otoconia in Figure 2,

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INNER EAR NEUROEPITHELIAL SUPRASTRUCTURES T A B L E 1.

Results MINERALOGY

Otosclerosis Patient 1

RACE, SEX, AGE (YEARS)

SIDE

W, M, 70

R, L

MAIORLABYRINTHINEABNORMALITIES ANDGENERALINFORMATION Bilateral small anterior loci of otosclerosis. Collapse of saccular wall in both ears and crust of crystals on saccular maculae. Marked loss of utricular otoconia, Hypothyroidism. Gentamicin, tobramycin for gram-negative pneumonia. Died of renal insufficiency, presumably secondary to nephrotoxicity.

PHASES

MORPHOLOGY

L saccule: apatite

Spherulites

L utricle: calcite

Normal otoconia

R saccule: apatite

Spherulites

Tectorial membrane: bilateral, more or less symmetrically located proteinaceous mass adherent to underside of membrane in the basal turn, Patient 2

W, M, 62

R

Extensive capsular otosclerosis with multiple loci. Formation of bone in scala tympani. Partial collapse of saccular wall. Thick crust of crystals on maculae.

Patient 3

W, M, 68

R, L

Large bilateral anterior loci of otosclerosis, Left ear: Partial loss of saccular oto-

conia. Numerous large crystals remain, several attached to the wall. Utricle covered by incomplete thin layer of huge translucent crystals. Right ear: Condition of otoconia unknown,

L saccule: calcite L utricle: calcite

Malformed otoconia

R utricle: calcite

Normal otoconia

L utricle: calcite plus apatite R,L saccules: no deposits L cochlea: apatite

Spherulites

Fenestration of right side. Stapedectomy on left side. No history of obvious dizziness. Patient 4

W, F, 73

R, L

Large bilateral anterior loci of otosclerosis. In both ears invasion of small areas of basflar membrane adjacent to foci. Left ear: cochlear hydrops. Reissner's membrane mostly collapsed, but herniating through helicotrema. Saccular wall collapsed. A narrow space along the striola contains the otoconial membrane, which is dislodged from the neuroepithelium, wrinkled, devoid of otoconia. Saccular otoconia absent also on right side. Utricular otoeonia present on both sides.

Spherulites

Sepsis after surgery for abdominal aneurysm. Poor hearing deteriorated further after tobramycin and gentamiein treatment. Became completely deaf. Patient 5

Patient 6

American Journal of OtoJaryngoJogy 80

W, M, 78

W, M, 71

R, L

R, L

Bilateral extensive multiple foci of otosclerosis. Right ear: Saccule completely collapsed. Left ear: Hydrops, Reissner's membrane partially collapsed, saccule completely collapsed. Utricle partially collapsed. Concretions on the bastlar membrane and at the site of the atrophic stria. Profound bilateral hearing loss for more than 14 years, progressed to complete deafness. In both ears crust of crystals in saccule. Extensive capsular otosclerosis with multiple loci. Bilateral hydrops most severe on left side. Saccule ruptured on the right side with remaining walls erect and partially covered with crystals. Left side had no otoconia. Meni~re's disease.

R saccule and utricle: apatite

Spherulites

L saccule and utricle: apatite

Spherulites

R saccnla: apatite plus calcite

Spherulites

JOHNSSON ET AL. TABLE 1--Continued

MINERALOGY

RACE, SEX, AGE (YEARS)

SIDE

W, M, 62

R, L

MAJORLABYRINTHINEABNORMALITIES ANDGENERALINFORMATION

PHASES

MORPHOLOGY

Meni~re's disease Patient 7

Patient 8

W, M, 85

R

Severe hydrops with Reissner's membrane R saccule: bulging into the vestibule and the semi- apatite circular canals indenting all three membranous ampullae. Membranous wall Apatite of saccule partially collapsed. Crust of crystals in saccule.

Hollow granular otoconia Spherulites

Severe hydrops as above, except that wall of saccule bulges, causing the ampullary indentation. No saccular otoconia present,

Hydrops, acquired syphilis Patient 9

W, M, 63

R,L

Severe cochlear hydrops with more or L saccule: less complete collapse of saccular wall apatite plus on left side. Had received cochlear im(?) calcite plants, Crust of crystals in saccule. No saccuIar otoconia on right side. No utricular otoconia on either side,

R,L

Patient and her brother and sister deaf since btrth. About once a month spells of dizziness,

Hereditary congenital deafness Patient 10

W, F, 58

Left eat': Severe cochleo-saccular hydrops, Reissner's membrane bulging

into the vestibule, Concretions on basilar membrane and at site of atrophic stria, Crust of otoconia in saccule and utricle, All three capulae petrified,

R utricle, calcite

Etched normal otoconia

R cochlea: apatite octacalcium phosphate

Spherulites

Right ear: Slight hydrops. Saccule parL saccule: calcite tially collapsed. Accumulation of crysapatite tals in scala media of apical turn. Concretions on basilar membrane and at site of atrophic stria. L utricle: apatite plus calcite All cupulae: otacalcium phosphate plus apatite

Etched normal otoconia Spherulites Spherulites

Spherulites

L cochlea: apatite Viral labyrinthitis Patient 11

F, [1 me]

R

Cytomegalovirus labyrinthitis. Saccule collapsed. Both maculae covered by thick crust.

Patient 12

W, F, 63

R

Chickenpoxin childhood caused profound deafness, Severe sensorineural degeneration, Both maculae covered by thick crust.

Patient 13

W, F, [6 mo]

R

Rubella syndrome. Labyrinthine hemorrhage. Otoconial membrane of right saccule displaced by blood clot and adherent to the membranous wall,

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Figure 5. Characteristic appearance o[ a collapsed saccule, patient 1, right ear. A t h i n white crust of apatite on t h e anterior half of the macula can be s e e n through the collapsed membranous wall. The darker area at the lower right, below the curved line indicating its border, is the collapsed reinforced portion of the wall. The defect in the wall at the upper right c o r r e s p o n d s to the a~ea that was attached to the macula utriculi. O s m i u m tetroxide.

American Journal

of Otolaryngology 82

retards or prevents collapse of the wall in this region. In some s p e c i m e n s the thicker, semilunar-shaped area of the membranous saccular wall described by P e r l m a n "-'5 h a d not caved in completely, so that a second small pocket was formed along the inferior margin of the macula. In all specimens but one (that of patient 4) the membranous wall was adherent to a crystalline mass or crust resting on the neuroepithelium. The crusts were always whitish in color, thin, quite rigid, and appeared more or less immobile in relation to the neuroepithelium. No obvious gelatinous layer was seen under the crystalline mass. In each case the crust had an abnormal mineralogic composition consisting of either apatite, w h i c h is chemically related to octacalcium p h o s p h a t e [CasH2(PO4)6" 5H20], 2~ or a mixture of apatite and calcite. The shape of the calcium phosphates was invariably spherulitic. In an infant (patient 11) with viral labyrinthitis the abnormal crystalline covering had a different appearance, the crust being m u c h thicker than in the cases described above. Usuatly only about a fourth to a third of each macula was covered with a crystalline mass, ex-

cept in the specimens from patients 2, 5, 11, and 12, where a l m o s t the e n t i r e s u r f a c e of the n e u r o e p i t h e l i u m was c o v e r e d w i t h a crust, which was also much thicker than those in the other specimens. In most cases the crystalline c o v e r i n g was not a t t a c h e d to t h e n e u r o e p ithelium except in minute areas b e n e a t h the center of the crust. In the specimen from patient 2, however, two large areas of crust were attached to the neuroepithelium, so that epithelial artifacts were formed w h e n the mass was lifted off. In the specimens from patients 2, 4, and 7, no circumscribed loss of sensory ceils under the crystalline mass was observed by scanning electron microscopy. The hair cell loss was severe but diffuse. Giant stereocilia were present in the specimen from patient 7 (Meni~re's disease), where they appeared to have been formed by fusion of several normal-sized stereocilia. This specimen was unique in that the otoconia were hollow, with wails composed of very small apatite granules (Fig. 6). INTACT OR EXPANDED SACCULAR WALL. In the

specimen from patient 8 (Meni~re's disease) the

IOHNSSON ET AL. wall was expanded b u t had no visible defect. That from p a t i e n t 10 ( h e r e d i t a r y deafness) showed marked saccular hydrops in the left ear, with the maculae covered by aggregates of apatite spherulites (Fig. 7) or n o r m a l otoconia showing age-related etching. The right saccule was partially collapsed onto a macule covered with more of the etched, but otherwise normallooking, calcite otoconia. These and other interesting features of t h e specimen from patient 10 have been described in detail elsewhere. 2~ RUPTURED SACCULAR WALL.

In the specimen

from patient 6, w h i c h showed hydrops labyrinthi, the saccule in the right ear was ruptured. The remnants of the wall were partly lined with crystals and were s t a n d i n g erect around the macula, which was partially covered with an abnormal crystalline mass.

Otoconial Abnormalities in the Utricle

Abnormalities of the otoconia in the utricle often cannot be evaluated as completely as those of the saccule because utricular otocanial membranes are not infrequently displaced, damaged, or lost during the process of dissection. Such artifacts sometimes occurred in our specimens. Collapse of the utricular wall had occurred only in the specimen from patient 4. We did not observe this p h e n o m e n o n in o u r p r e v i o u s studies. :J.~7.':~The membranous wall of the utricle was studied only by light microscopy, and it was difficult to evaluate changes in it. There was usually a decreased number of osmiophilic ceils in tile wall, but w h e t h e r this finding implies changes in the dark cells "7 is not clear. In tile specimens from patients 4 (hydrops) and 10 (hereditary deafness), and in those from two cases of viral labyrinthitis (Fig. 8), abnormal otoconia were found in the utricle in one ear. The abnormality was obvious and could be seen under the dissection microscope. The crystals on the macule formed a thick crust, which covered the entire macula and could be lifted off in one piece. In the specimen from patient 4 the crust proved to be spherulitic apatite similar to that in the saccule of the specimen from patient 10 (Fig. 7). Again, no separate gelatinous layer could be found under the crystalline mass, which was not attached to the neuroepithelium and appeared immobile in relation to it. The specimen from patient 3 showed a different otoconial abnormality. Here, only about a third of the gelatinous part of the otoconial membrane in the utricle of the left ear was c o y -

Figure 6. Hollow otoconiacomposed of granules of apatite from the right saecute of patient 7. In shape they resemb[e the hollow degenerating atocania in Figure 2. ered with crystals. These proved to be discrete crystals of calcite, w h i c h were t r a n s l u c e n t , sparsely distributed, and of extraordinary size (Fig. g). Giant calcite otoconia of similar or even larger sizes have been found in the maculae of normal guinea pigs. ~5 Abnormalities of the Cupula and Tectorial Membrane

In a 10-day-old infant with a cyanotic type of congenital heart disease, the left utricle contained a single, loosely tangled, gelatinous band, which occupied a large part of the utricular space above the macula. This band appeared to have a structure similar to that of a normal cupula {Fig. 10}. We believe that this structure represents a dysplasia of the cupula of the superior or posterior ampulla. The horizontal ampulla appeared to be normal. Unique tectorial m e m b r a n e a b n o r m a l i t i e s were found in the specimen from 7g-year-old man, patient 1, who had died of subarachnoid hemorrhage with antecedent causes listed as hypothyroidism and acute renal failure in the

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INNER EAR NEUROEPITHELIAL SUPRASTRUCTURES

Figure 7 (above). P a r t of t h e aggregate of apatite s p h e r u l i t e s covering the left saccular otocon i a l m e m b r a n e of p a t i e n t 10. Notice the pock-marked surfaces of some of the spherulites (lower

right).

Figure 8. Abnormal crystalline covering consisting of a t h i c k r i g i d c r u s t of a p a t i t e o n t h e macula utriculi of p a t i e n t a2, right ear. The usual features of the surface of a normal otoconial membrane are lacking, e.g., t h e r e is no snowdrift line a n d a d e e p groove can be seen in the crust to t h e u p p e r r i g h t . O s m i u m tetroxide.

American Journal of O,olaryngology 84

IOHNSSON ET AL.

Figure 9. Abnormal otoconial covering on the macula utriculi of patient 3, left ear. The otaeonia are greatly reduced in number, and only a few huge translucent crystals remain. Osmium tetroxide.

:I(

autopsy report. He had a long history of urinary tract infections and ha d been treated with tobramycin a n d gentamicin. The most p r o m i n e n t pathologic feature found in the cochlea on both sides was a structureless, transparent, lightly-stained mass, which was at tached to a relatively circumscribed area of the undersurface of the tectorial membrane in the middle of the basal turn. The length of the lesion was approximately 3.4 ram. The changes in the two ears looked identical, except that the lesion was located about 2 m m more apically in the left ear. The mass was smooth and drop-shaped, as if it had flowed d o wn along Corti's organ under the influence of gravity (Fig. 11). The hair cells in the left ear were counted, revealing a complete sensory cell loss in the first 5 mm of the cochlea. Above that point the cytocochleogram was relatively flat, with approximately 40 to 60 per cent of th e outer hair cells and 80 per cent of the inner hair cells remaining. There was a slight dip in the cytocochleogram for the outer hair cells in the 9- to 17-mm region of the basilar membrane, but the loss was not clearly related to the pathologic ch an ges in the tectariaI membrane, There were no significant strial or vascular changes in either ear.

Among the many abnormalities in the specim en from patient 10 were the petrification of all three cupulae in the left ear and the calcification of part of the rectorial membrane in the right ear. On both sides the membrane was shrunken and r e t r a c t e d t o w a r d s the i n n e r s u l c u s . T h e s e changes h a v e b e e n m ore ful l y d e s c r i b e d by ]ohnsson et al. "~ DISCUSSION Dystrophic calcification, i.e., d e p o s i t i o n of calcium salts in dead and degenerating tissues, is the most common form of pathologic calcification, occurring in a variety of organs. Conceivably the calcification associated with strial atrophy could have been the result of such a process. Calcifications at other sites such as those described here, however, are probably closely related to the special conditions existing in the labyrinth. Mineral deposits composed of spherulitic calcium phosphates occur in other parts of the h u m a n body; in fact, this material is of general occurrence in many biologic calcifications, normal as well as abnormal. Spherulitic apatite has been found in such diverse e n v i r o n m e n t s as cal-

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INNER EAR NEUROEPITHELIAL SUPRASTRUCTURES

Figure 10. Tangle of gelatinous material found in the utricle of a lO-day-old infant with congenital heart disease, probably representing cupular dysplasia. InseL: normal cupula. Notice the striations in both structures. Osmium tetroxide.

American Journal

of Ololaryngology 86

cifying rat cartilage, 2s c o w and monkey teeth, "9 neoplastic h u m a n bone, :'~ human pineal calcifications, ~' and h u m a n u r i n a r y calculi. :~2 The spherulites go under a variety of names, including calcospherites, bone nodules, acervuli, and spherical mineral clusters. In normal calcified tissues such as b o n e a n d d e n t i n the apatite spherulites always occur along so-called "mineralizing fronts, ''2:~ w h e r e they are associated with the early stages of mineral formation. The calcium phosphate spherulites described in this report are not the first examples of such materials to be found in the vertebrate inner ear. CarlstrSm ~3 found that in the cyclostomes, the most primitive of the living vertebrate classes, the otoconia normally consist entirely of apatite spherulites. Also, the embryos of certain species of sharks reportedly contain spherulitic amorp h o u s calcium p h o s p h a t e otoconia, although these deposits are resorbed postnatally and the adult forms synthesize aragonite (orthorhombic CaCOz) for the purpose. 34 In man, Lim and Sounders 3'~ found "calcospherites" at the sites of new bone formation in otosclerotic stapes, and simi-

lar structures occur in the middle ear in association with tympanosclerosis2 6 An important generalization that can be made from the present study is that under pathologic conditions certain anatomic structures of the labyrinth are preferentially mineralized, or the composition of their normal mineral covering is drastically altered. The susceptible structures are 1) the gelatinous membranes, namely the saccular and utricular otoconial membranes with their otoconia, the tectorial membrane, and the cupulae; and 2) the secretory tissues, including the stria vascularis and the dark cell region of the utricule. Of these the otoconial membranes are by far the most c o m m o n l y affected. Although Table 1 contains only two examples of strial concretions, such formations commonly a c c o m p a n y strial atrophy. 23"~7-'~9 Apatite was found deposited over the dark cell region of the utricular wall in the specimen from patient 10. Deposits of calcite otoconia c o m m o n l y occur in this region in guinea pigs. 1~ In the p r e s e n t s t u d y t h e r e w a s only one specimen with calcified cupulae. The relation-

JOHNSSON ET AL.

Figure 11. Proteinaceousmaterial (arrow and inset) attached to the urLdarsideof the tectorial membranein the right ear from a 70-year-old man with hypothyroidism (patient 1). OC = organ of Corti; OL = osseous spiral lamina. Osmium tetroxlde.

ship of this condition to cupulolithiasis is not clear. We did not find deposits attached to the cupula, as reported to occur in cupulolithiasis.'-' Otoconia can become dislodged artifactually from the macule utriculi in the course of dissection or storage, and may appear anywhere in the interior of the utricle and in the posterior ampulla. Apparently this type of displacement can be found in conventional sections as welh 4~Such otoconia are usually numerous, loose, and not attached to any specific structures. Because of the possibility of such artifacts, it is difficult to judge to what extent loose otoconia found in the posterior ampulla "'4' r epr e s ent in v i v o conditions or postmortem artifacts, Crystalline deposits observed in the cochleas of man and ex p er im e nt a l animals have been taken a priori for displaced otoconia. On the basis of our observations, it appears unlikely that such deposits could consist of otoconia that have become dislodged from the macu[a sacculi and have found their way through the ductus reuniens into the cochlea. Rather, the crystals d'escribed had probably been formed in the cochlea

de nova and were perhaps similar in composition to those in our cases. Having established that calcium phosphates in the m e m b r a n o u s l a b y r i n t h in m a n r e s e m b l e t h o s e in o t h e r c a l c i f i e d t i s s u e s , a n d t h a t labyrinthine calcification is a highly selective process, the question of the genesis of these deposits arises. However, before i n q u i r i n g into possible causes, we first consider w h e t h e r the deposits are p r i m a r y or secondary. That is, were the phosphates formed d e n o v a at a site where no m i n e r a l phase was p r e s e n t , or d i d t h e y supplant pre-existing normal calcite otoconia, which had somehow been eliminated from their normal sites of deposition? O b v i o u s l y , m i n e r a l d e p o s i t s in or on all structures other than the otoconial membranes must be primary, since such structures are normally unmineralized. There is no unequivocal evidence for primary otoconial calcium phosphates, only the fact that if primary deposition can occur in places such as the cochlear duct (specimen from patient 10), there is no obvious reason w h y it could not occur on the otoconial mem-

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American Journal of Otola ryngology 88

branes as well. Examples of agenesis of normal otoconia in infants are k n o w n ) I'''-' Perhaps some of the patients in Table 1 had abnormalities of this type prior to the formation of phosphate minerals on their otoconial membranes. Turning to the possibility that some of the abnormal deposits are secondary, three alternative (but not mutually exclusive) explanations are proposed: 1] A layer of secondary calcium phosphates was deposited over an aggregate of normal calcite otoconia. 2) Pre-existing calcite otoconia were removed by solution, that process being followed by calcium phosphate deposition. 3] Calcite otoconia were transformed in situ into apatite by reaction with phosphate ions. Borrowing a term from the geochemical literature, we shall call this chemical replacement process "phosphatization." Again, the available evidence is mostly ambiguous. In the specimen from patient 7 the right saccule contained structures strongly resembling normal otoconia hollowed out by agerelated degenerative processes s but composed entirely of apatite. The specimen from patient 10 yielded the three petrified cupulae, in which both the overall shape and the surface striation of normal cupulae were preserved. These observations would seem to support the phosphatization hypothesis, although in the latter case it was soft tissue rather than calcite that was phosphatized. Also in the specimen from patient 10 the " s n o w d r i f t " line was p r e s e r v e d in the apatite-calcium mixture on the left utricular otoconial membrane. This finding is, of course~ also consistent with alternative I above. Supporting alternative 2 is the general observation that in most specimens from the elderly patients listed in Table 1 the phosphate deposits covered only a small portion of the saccular otoconial membranes, suggesting that phosphate deposition occurred there only after the normal otoconia had been greatly reduced in number or eliminated as the patient advanced in age. In infants the abnormal saccular deposits always covered the entire surface of the maculae. Experiments in vitro provide support for the replacement origin of otoconial calcium phosphate deposits. Ames '~2found that calcite placed in 0.3 M sodium phosphate solutions was spontaneously transformed into apatite over a period of time, but the morphologic integrity of the original calcite was preserved in the end product. This would explain the observations in the specimens from patients 7 and 10. Simpson 4a'44 performed similar experiments in 0.05 to 0.4 g sodium and potassium phosphate solutions, At pH values of 7 or greater the reaction products

were apatite and o c t a c a l c i u m p h o s p h a t e , in w h i c h the morphologic integrity of the preexisting calcite was not preserved. This observation might account for the spherulitic apatite deposits, which bear no resemblance to normal otoconia. The rather common occurrence of apatitecalcite mixtures (with the former mineral usually strongly predominant) in the cases in Table I is consistent with both primary and secondary origins for the apatite. Bachra et al. ''~ found that under physiologic conditions the precipitation of calcium phosphates from calcium phosphate carbonate solutions is often followed by the precipitation of small amounts of calcium carbonates. Both solids are t h u s p r i m a r y phases. Simpson 'l'~ found small amounts of unreacted calcite in the secondary apatite formed by phosphatization of calcite, Of course, the otoconial apatite-calcite mixtures could also result from deposition of an apatite layer over a b o d y of calcite otoconia, as previously mentioned. Both possibilities are consistent with the fact that such. m i x t u r e s almost a l w a y s s h o w e d only spherulitic apatite on the surface of the mass when studied by scanning electron microscopy. Whatever the exact chemical mechanism, it seems certain that the formation of phosphate minerals in the membranous labyrinth requires an abnormal composition of the endolymph, in particular, an abnormally high phosphate content, w h i c h may in turn be associated with structural defects in the membranous walls of the vestibular organs. The correlation between the incidence of such defects and the presence of abnormal otoconia is too strong to be mere coincidence. 82In most specimens examined the saccular wall was drastically altered, whereas changes in the utricular wall were more subtle. It could also be argued that degeneration of the neuroepithelium is responsible for otoconial abnormalities. The integrity of the tectorial membrane depends upon a normal ionic environment. 4s The structure of the membrane appears to be unaffected by sensory degeneration alone; even in the complete absence of Corti's organ the membrane appears normal by light microscopy. It may well be that all epithelial suprastructures d e p e n d u p o n normal homeostasis of the endolymph. It is not unreasonable to assume that changes in the composition of vestibular end o l y m p h could alter otoconial structure, al82The association between collapse of the saccular wall and abnormalcalcium phosphate deposits on the otoconial membranes also occurs in deaf Dalmatiandogs [lohnssonet al., in preparation).

JOHNSSON ET AL,

though the vestibular organs are more resistant to insults than is Corti's organ. We previously postulated that changes in the walls of the vestibular organs could also involve the cupulae in Meni~re's disease, 1~ but at present there are no unequivocal histologic findings to support that notion. The association of otosclerosis and abnormal otoconia raises the question whether the two conditions could have a common cause, such as an a b n o r m a l i t y of c a l c i u m m e t a b o l i s m , or whether otosclerosis affects the membranous walls of the vestibular organs. Otosclerotic loci, at least in their active phase, are likely to release lysosomal enzymes and ions, which could act upon the otoconia directly as well as indirectly, by affecting the membranous walls of the vestibular organsY The f u n c t i o n a l s i g n i f i c a n c e of abnormal otoconia is unclear. In the present material the extent of general involvement of the macular organs was so great that the presence of abnormal otoconia appears to have been of secondary importance. It is important to note, however, that abnormal otoconia commonly occurred in the utricle, even though the walls of that organ were not collapsed, Conceivably, early changes in the otoconia before the onset of large-scale involvement of the walls and the neuroepithelia could of themselves cause macular dysfunction and dysequilibrium. The substitution of a rigid crust of apatite for the n o r m a l flexible layer of otoconia may render the suprastructure unresponsive to the forces of linear acceleration, such response being needed for postural control. On the other hand, the fact that abnormal otoconia were associated with hydrops labyrinthi and Meni~re's disease does not to us imply that such deposits are responsible for vertigo in Meni&re's disease. Although abnormal otoconia could cause some symptoms, the spells of true vertigo characteristic of Meni~re's disease probably have a cause other than otoconial dysfunction. The tangle of gelatinous material found in the utricle of one specimen from a patient with congenital heart disease (Fig. 10) probably represents an unusual dysplasia of the cupula. The finding of the structureless material adhering to the tectorial membrane in another specimen (Fig. 11) is unique and difficult to explain. Apparently the mass was proteinaceous. The patient had hypothyroidism and had been treated with aminoglycosides. Mechanical stimulation of the sensory cells must have been altered, at least in the area covered by the proteinaceous mass. A highly abnormal rectorial membrane has been f o u n d in the c o c h l e a s of offspring of

hypothyroid mice, in which the membrane was distorted, thick, and not in contact with the hair cells. 4s Those changes were clearly different from what was observed in the present case, in which the membrane itself appeared normal in light microscopy. The similarity of the appearances of this localized lesion in the two ears is also perplexing, and raises the possibility of bilateral cochlear insult being involved in its pathogenesis. The lesion was located just above the 4 kHz area in the left ear, but this abnormality has never been associated with exposure to noise or acoustic trauma, either in man or in experimental animals; nor is aminoglycoside ototoxicity known to damage the tectorial membrane. In the past, abnormalities of the suprastructures in the labyrinth such as those we have described have been largely ignored. It is hoped that this report will increase awareness of this type of pathologic change, which is more common that hitherto believed.

References I. Iurato S: Functional implications of the nature and submicroscopic structure of the tectorial and basilar membranes. ] Acoust Sea Am 34: 1381-1395, 1962 2. Schuknecht HF: Pathology of the Ear. Cambridge, Harvard University Press, 1974 3. Wright CG, Hubbard DG: Observations of otoconial membranes from human infants. Acta Otolaryngo[ (Stockh) 68: 185-194, 1978 4. Carlstrthm D, Engstr6m H, Hjorth S: Electron microscopic and x-ray diffraction studies of statoconia. Laryngoscope 63: 1052-1057, 1953 5. Carlstrhm D, Engstr6m H: The ultrastructure of statoconia. Acta Otolaryngol (Stockh) 45: 14-18, 1955 6. Ross MD, Johnsson L-G, Peacor D, et al: Observations on normal and degenerating human otoconia. Ann Otol Rhinol Laryngol 85: 310-326, 1976 7. Johnsson L-G, Hawkins JE Jr: Otolithic membranes of the saccule and utricle in man. Science 157: 1454-1456, 1967 S. Johnsson L-G: Degenerative changes and anomalies of the vestibular system in man. Laryngoscope 81: 1682-1694, 1971 9, Johnsson L-C, Hawkins IE Jr: Sensory end neural degeneration with aging as seen in microdissections of the human inner ear. Ann Otol Rhinol Laryngol 81: 179-193, 1972 10. Johnsson L-G, and Hawkins fE Jtr: Hydrops and cupulolithiasis as seen in microdissections of human temporal bones, in: Pulec IL (ed.): Meni~re's Disease. Proceedings of the Fourth Extraordinary Meeting of the B~r~ny Society. Anaheim, California, Palisades Publishing Company (in press} 11. Wright CG, Rouse RC, Johnsson L-G, et ah Vaterite e t e c o n i a in two cases of otoconial membrane dysplasia. Ann Otol Rhinel Laryngol (in press} 12. Wright CG, Hubbard DG, Graham JW: Absence of otoconia in a human infant. Ann Oral Rhinol Laryngol 88: 779-783, 1979 13. Pnrichia N, Erway LC: Effects of dichlorophenamide, zinc, and manganese on otolith development in mice. Dev Biol 27: 395-405, 1972 14. Lira DI, Erway LC: Influence of manganese on geneti-

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