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. 2010 Aug;143(2):269-73.
doi: 10.1016/j.otohns.2010.03.001.

Endolymphatic pseudohydrops of the cochlear apex

Andres Makarem  1 , Jose N Fayad, Fred H Linthicum Jr
Affiliations

Endolymphatic pseudohydrops of the cochlear apex

Andres Makarem et al. Otolaryngol Head Neck Surg. 2010 Aug.

Abstract

Objective: To demonstrate that what appears to be endolymphatic hydrops of the apical scala media is normal anatomy.

Study design: Computer-generated three-dimensional reconstruction of the cochlear apex and tabulation of the number of cases with arched Reissner's membranes (pseudohydrops) versus flat membranes.

Setting: Temporal bone laboratory consisting of 809 documented pairs of temporal bones.

Subjects and methods: Archival temporal bone sections from 107 bones (65 patients) were used to determine the percentage of arched (pseudohydrops) versus flat Reissner's membranes. Two bones, one of each membrane shape, were randomly selected for computer-generated three-dimensional reconstructions showing the cochlear apical anatomy.

Results: An arched Reissner's membrane was found in 48.6 percent of bones. In the cochlear apex, Reissner's membrane appears to be distended, simulating hydrops, due to its transition from a conical structure to a triangle bounded by the basilar membrane with the organ of Corti, the stria vascularis, and Reissner's membrane. Membrane findings were similar in both ears in 73.8 percent of the bilateral cases studied. There were no significant relationships between membrane type and clinical characteristics.

Conclusion: What appears to be endolymphatic hydrops of the cochlear apex is the transition area of the cochlear duct from a conical shape at the extreme apex to the triangular shape found in the rest of the cochlea. The appearance of distension is dependent upon the cochlear length and the level of the microscopic section.

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Figures

Figure 1
Figure 1
(A) Midmodiolar section of the human cochlea showing arched Reissner’s membrane of the apical segment (arrow). X20, Hematoxylin and eosin (H&E). (B) Arched Reissner’s membrane in rabbit and (C) guinea pig, X 40 (H&E)
Figure 1
Figure 1
(A) Midmodiolar section of the human cochlea showing arched Reissner’s membrane of the apical segment (arrow). X20, Hematoxylin and eosin (H&E). (B) Arched Reissner’s membrane in rabbit and (C) guinea pig, X 40 (H&E)
Figure 1
Figure 1
(A) Midmodiolar section of the human cochlea showing arched Reissner’s membrane of the apical segment (arrow). X20, Hematoxylin and eosin (H&E). (B) Arched Reissner’s membrane in rabbit and (C) guinea pig, X 40 (H&E)
Figure 2
Figure 2
A demonstration of the varying orientation of the apical segment in two of the eight temporal bones cut in the coronal plane. The yellow indicates the organ of Corti on the white basilar membrane. X10
Figure 3
Figure 3
(A) The cochlear duct (a) occupies the entire area of the most apical aspect of the cochlea. (b) The scala media in the middle cochlear segment. (B) A few microns away from the apex, Reissner’s membrane begins to separate from the cochlear wall (arrow). (a) Indicates endolymphatic spaces. (C) Final triangular configuration of the scala media, but still showing some slight outward bulging of Reissner’s membrane. (H&E X 40)
Figure 3
Figure 3
(A) The cochlear duct (a) occupies the entire area of the most apical aspect of the cochlea. (b) The scala media in the middle cochlear segment. (B) A few microns away from the apex, Reissner’s membrane begins to separate from the cochlear wall (arrow). (a) Indicates endolymphatic spaces. (C) Final triangular configuration of the scala media, but still showing some slight outward bulging of Reissner’s membrane. (H&E X 40)
Figure 3
Figure 3
(A) The cochlear duct (a) occupies the entire area of the most apical aspect of the cochlea. (b) The scala media in the middle cochlear segment. (B) A few microns away from the apex, Reissner’s membrane begins to separate from the cochlear wall (arrow). (a) Indicates endolymphatic spaces. (C) Final triangular configuration of the scala media, but still showing some slight outward bulging of Reissner’s membrane. (H&E X 40)
Figure 4
Figure 4
Computer-assisted three-dimensional reconstruction of the cochlear apex showing the conical configuration of the scala media apex. green = Reissner’s membrane, red = stria vascularis, yellow = organ of Corti, white = basilar membrane and osseous spiral lamina, grayish blue = boundaries of perilymph spaces. X 20
Figure 5
Figure 5
Computer-aided reconstruction of a routine sectioned cochlear apex in which Reissner’s membrane appears flat due to the variation in cochlear lengths. However, at the apex of the cochlea, the cochlear duct is a blunted cone. light blue = perilymph, red = stria vascularis, green = Reissner’s membrane, dark blue = endolymph, yellow = organ of Corti, white= osseous spiral lamina. X20
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