Temporal bone pathology in scuba diving deaths

Histopathologic Changes of Human Vestibular Epithelia in Intralabyrinthine Hemorrhage

Objective:

To determine whether intralabyrinthine hemorrhage affects vestibular hair cells, dark cells, and transitional cells in human temporal bones.

Methods:

We examined 9 temporal bone specimens from 9 deceased donors with unilateral intralabyrinthine hemorrhage (the hemorrhage group) along with their 9 contralateral temporal bone specimens without hemorrhage (the control group). We estimated the density of type I and type II hair cells in all peripheral sensorial organs (including the cristae of the superior, lateral, and posterior semicircular canals, as well as the maculae of the saccule and utricle). We also estimated the density of dark and transitional cells in the lateral and posterior semicircular canals.

Results:

The loss of type I hair cells in the cristae of the superior, lateral, and posterior semicircular canals and in the maculae of the saccule and utricle was significantly higher in the hemorrhage group, as compared with the control group ( P < .05). The density of type II hair cells in the cristae of the superior and posterior canals and in the macula of the saccule significantly differed between the hemorrhage group and the control group ( P < .05).

Conclusion:

The loss of vestibular hair cells might be the cause of vestibular symptoms in patients with intralabyrinthine hemorrhage.

Magnetic resonance imaging in a guinea pig model of inner ear decompression sickness and barotrauma

OBJECTIVES/HYPOTHESIS

Scuba diving may cause severe hearing loss and vertigo due to inner ear barotrauma and decompression sickness. These may be difficult to differentiate clinically. Decompression sickness requires costly and potentially dangerous hyperbaric therapy, whereas such treatment may worsen barotrauma. The objective of this study was to assess the potential utility of magnetic resonance imaging to identify and distinguish blood from air in the inner ear, manifestations of barotrauma and decompression sickness, using a guinea pig model.

STUDY DESIGN

Prospective animal trial.

METHODS

Magnetic resonance of the head was performed at 3 Tesla, pre- and postinjection of 2, 4, or 10 μL of air or blood through the round window into the perilymph. With this model, 2 μL has been shown to cause hearing loss. Images were reviewed by a neuroradiologist blinded to the treatment.

RESULTS

All 14 normal ears, five of seven blood- and five of seven air-injected ears, were correctly interpreted. Two blood- and one air-injected ear were interpreted as indeterminate. One air-injected ear was incorrectly interpreted as blood.

CONCLUSIONS

Magnetic resonance reliably distinguishes small volumes of air and blood in the guinea pig inner ear. Magnetic resonance should be evaluated for its utility in the diagnosis of inner ear barotrauma and decompression sickness in scuba divers.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:2106-2109, 2016.

Endolymphatic hydrops and Ménière's disease: a lesion meta-analysis

OBJECTIVE

To determine whether the distribution of membrane lesions associated with Ménière's disease is random, as might be expected from a pervasive process such as hydrops, or orderly, as might be expected if membrane resistance is graded.

METHOD

A meta-analysis of temporal bone reports on 184 specimens demonstrating endolymphatic hydrops was undertaken to determine membrane lesion evolution and distribution.

RESULTS

Lesion distribution was found to be orderly and cochleocentric. No random scattershot lesions were reported in any study. Disease always started in the cochlear apex, even in non-symptomatic cases, and then involved the saccule, utricle, ampullae and canal system in that precise sequence as the disease progressed.

CONCLUSION

The orderly lesion progression in the otopathology associated with Ménière's disease suggests that the hydropic process has a graded non-random effect on the labyrinth. These findings suggest a pathological staging system that may be useful in temporal bone evaluation.

A model design for the labyrinthine membranes in mammals

OBJECTIVES/HYPOTHESIS

A model of the labyrinthine membranes in mammals may be useful in the study of conditions that involve membrane stress and deformation such as Meniere's disease and diving injuries.

STUDY DESIGN

Conceptual design of a model of the labyrinthine membranes in mammals.

METHODS

The model is constructed by emulating each of the several chambers of the membranous labyrinth and their connections with mathematically defined geometric shapes.

RESULTS

The model design uses a torus to emulate each semicircular canal, prolate spheroids for each ampulla, cylinders for the crus commune and utricle, an oblate spheroid for the saccule, hyperboloids of revolution for junctional zones, and a spiral torus for the cochlea membranes.

CONCLUSIONS

A complete model of the labyrinthine membranes has been designed that can serve as a platform for stress analysis when numerical dimensions are available for any particular species including man.

LEVEL OF EVIDENCE

NA.

Hyperbaric compression in the guinea pig with perilymph fistula

OBJECTIVE

The study goal was to evaluate the effects of hyperbaric therapy on the auditory and vestibular function of guinea pigs compromised by perilymph fistula (PLF).

METHODS

Twenty-four pigmented guinea pigs underwent induction of bilateral eustachian tube dysfunction before the creation of a unilateral PLF. Half of the animals were randomly assigned to receive immediate hyperbaric compression treatment of 4 "dives" each. Hearing was tested electrocochleographically, and signs of vestibulopathy were recorded before and after compression.

RESULTS

After accounting for the effects of PLF, compression was not associated with significant hearing loss (P = 0.5411). Vestibulopathy was seen only in ears with PLF, and its incidence was similar for compression and noncompression groups.

CONCLUSION

Hyperbaric compression does not compromise auditory or vestibular function in guinea pig ears with experimental PLF.

SIGNIFICANCE

Our observations support the relative safety of recompression in patients with PLF.

Inner ear barotrauma after stapedectomy in the guinea pig

OBJECTIVE

The safety of scuba diving after stapedectomy is controversial. Stapedectomy is thought to predispose to inner ear barotrauma (e.g., perilymph fistula); however, many individuals continue to scuba dive following stapedectomy without ill effects. The purpose of this study was to evaluate the cochlear effects of barotrauma, similar to that experienced with scuba diving, on inner ears previously treated with stapedectomy.

STUDY DESIGN

Prospective, controlled.

METHODS

Sixteen Hartley albino guinea pigs underwent unilateral total stapedectomy followed by hyperbaric dives on 5 consecutive days, beginning 3 weeks after stapedectomy. Cochlear effects were determined using click and tone-pip evoked electrocochleographic thresholds and cochlear hair cell counts.

RESULTS

Mean auditory thresholds increased by 29 dB after stapedectomy (P < .001), then remained stable thereafter. Mean thresholds in both the operated and control ears did not change with hyperbaric dives. Evidence of middle ear barotrauma (e.g., hemorrhage or tympanic membrane perforation) was observed in eight poststapedectomy ears and five control ears, but none demonstrated significant threshold elevation greater than or equal to 10 dB. Hair cell counts were not different between operated and control ears.

CONCLUSIONS

Stapedectomy does not appear to predispose to cochlear sequelae in the guinea pig model of diving-related barotrauma.

Update on vertigo management

Over the past decade, the treatment of vertigo has shifted from medical and surgical modalities in favor of physical therapy. When more aggressive treatment is necessary, patients may be treated with less invasive surgical modalities. This article provides an overview of recent advances.