Dong-Han Lee; Do-Won Kwon; Minho Jang; Jung Eun Shin; Chang-Hee Kim

doi:10.21790/rvs.2025.011

Articles

Page Path: HOME > Res Vestib Sci > Volume 24(2); 2025 > Article

Case Report
Positional nystagmus in pneumolabyrinth: a case report: Dong-Han Lee, Do-Won Kwon, Minho Jang, Jung Eun Shin, Chang-Hee Kim; Research in Vestibular Science 2025;24(2):107-112.
DOI: https://doi.org/10.21790/rvs.2025.011
Published online: June 15, 2025

Department of Otorhinolaryngology-Head and Neck Surgery, Konkuk University Medical Center, Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, Korea

Corresponding author: Chang-Hee Kim Department of Otorhinolaryngology-Head and Neck Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, 120-1 Neungdong-ro, Gwangjin-gu, Seoul 05030, Korea. E-mail: ryomachang@gmail.com

• Received: May 17, 2025 • Revised: June 7, 2025 • Accepted: June 9, 2025

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

2,432 Views
22 Download

prev next

Full Article

Download PDF

Abstract
INTRODUCTION
CASE REPORT
DISCUSSION
ARTICLE INFORMATION
SUPPLEMENTARY MATERIALS
REFERENCES

Abstract

This report describes a patient with left-sided pneumolabyrinth following a temporal bone fracture and demonstrates characteristic positional nystagmus observed in this condition along with a discussion of its mechanism. A previously healthy 38-year-old man presented with left-sided hearing loss, tinnitus, and positional vertigo after blunt head trauma. Temporal bone computed tomography revealed pneumolabyrinth in the ampulla of the left lateral semicircular canal (LSCC). Pure tone audiometry showed mixed hearing loss on the left (bone, 13.8 dB; air, 42.5 dB). Video Frenzel examination revealed direction-changing positional nystagmus: persistent left-beating nystagmus in the bow position, right-beating nystagmus upon moving from bowing to leaning, and persistent left-beating nystagmus in the left head-roll position only. We propose that in pneumolabyrinth involving the LSCC, changes in head position shift the air bubble, generating a buoyant force that indents the endolymphatic membrane and deflects the cupula, producing positional nystagmus. The direction of nystagmus may vary depending on the bubble’s location.
Keywords: Skull fractures; PLabyrinth; Positional nystagmus; Vertigo; Hearing loss

INTRODUCTION

Pneumolabyrinth indicates the presence of air in the inner ear organs, such as the cochlea, semicircular canals, or vestibules due to an abnormal connection between the middle ear and inner ear [1]. Head trauma is known to be the most common cause of pneumolabyrinth, and symptoms can include sensorineural hearing loss, conductive hearing loss, aural fullness, and dizziness. The dizziness in patients with pneumolabyrinth can exhibit a variety of vestibular symptoms such as motion intolerance, disequilibrium, or rotatory vertigo according to the size and location of the air bubbles. Although many studies on pneumolabyrinth have reported vestibular symptoms, a detailed description of nystagmus findings, especially that of positional nystagmus, has not been conducted. In the present study, we demonstrate positional nystagmus in a patient with pneumolabyrinth and discuss the mechanisms underlying positional nystagmus.

CASE REPORT

A 38-year-old male patient visited the emergency department complaining of left-sided hearing loss, tinnitus, and dizziness, which had developed 7 days prior to the hospital visit after blunt head trauma. The patient demonstrated clear consciousness and no weakness of motor or sensory function in the extremities. Neurological examination revealed no focal neurologic deficit. The bedside head impulse test showed no catch-up saccade. Otoendoscopic examination showed an intact tympanic membrane without perforation on both sides, but mild hemotympanum was noted on the left side. Temporal bone computed tomography (TBCT) demonstrated a linear fracture in the squamous and mastoid segments of the left temporal bone and soft tissue density in the left mastoid and middle ear cavities. There was also a suspicious fracture involving the tegmen of the left temporal bone and left facial canal. Small low-density lesions were observed in the ampulla of the left lateral semicircular canal (LSCC) suggesting pneumolabyrinth (Fig. 1, red arrow), and in the left middle cranial fossa suggesting pneumocephalus (Fig. 1, yellow arrow). Pure tone audiometry (PTA) revealed mixed hearing loss with an average bone conduction threshold of 13.8 dB and an average air conduction threshold of 42.5 dB on the left side (Fig. 2A). Video Frenzel goggle examination demonstrated left-beating spontaneous nystagmus with very low amplitude and direction-changing positional nystagmus. In a bow position, persistent nystagmus beating toward the left side was observed (Supplementary Video 1, Fig. 3A). Changing the head position from bowing to leaning evoked transient right-beating nystagmus, and subsequent change to a supine position elicited no further change in nystagmus direction (Supplementary Video 2, Fig. 3B). Then, the head was turned to the right approximately 90° in a supine position, and no change in nystagmus pattern was noted (Supplementary Video 3, Fig. 3C). In the left head-roll position, persistent left-beating nystagmus was observed (Supplementary Video 4, Fig. 3D). Under the diagnosis of temporal bone fracture with pneumolabyrinth and pneumocephalus, the patient received conservative treatment, including absolute bed rest, prophylactic intravenous antibiotics, a stool softener and systemic corticosteroids. Positional vertigo dramatically improved the day after admission, and hearing loss recovered gradually, demonstrating a PTA threshold of 10 dB on the left side 4 months after head trauma (Fig. 2B).

This study was approved by the Institutional Review Board of Konkuk University Medical Center (No. 2022-08-028) with a waiver of informed consent. All image and video data used in this study contained no personally identifiable information.

DISCUSSION

Perilymph fistula refers to an abnormal connection between the inner ear and the middle ear, and pneumolabyrinth can occur when air bubbles are trapped in the inner ear structures as a result of a fracture of the labyrinthine bone, subluxation of the stapes into the vestibule or a fracture of the stapedial footplate [2,3]. Vestibular symptoms in perilymph fistula can include postural instability with positional vertigo and induced by loud sound (Tullio phenomenon) or pressure changes (Hennebert’s sign) [4]. Vertigo in pneumolabyrinth can be attributed to an injury to the inner ear and displacement of the fluid spaces by an air bubble in addition to the manifestation of a perilymph fistula itself. Positional nystagmus in pneumolabyrinth has rarely been described [2,5]. It is conjectured that air bubbles, which are trapped in inner ear structures, are moved into the semicircular canals by a head position change, eliciting positional nystagmus [2,5]. Mandalà et al. [5] reported a case of pneumolabyrinth involving the vestibule, superior and posterior semicircular canals, and cochlea on the left side. Horizontal left-beating nystagmus was observed in a leaning position, and the nystagmus direction was reversed in a bowing position. When the patient’s head was tilted 30° forward in a seated position, the nystagmus disappeared. In supine head-roll positions, direction-changing positional apogeotropic nystagmus, which was stronger on the right side, was observed [5]. It was hypothesized that traumatic detachment of otoconial particles floating into the LSCC was responsible for the development of positional nystagmus. Ederies et al. [3] reported a case of a pneumolabyrinth on the left side with positional nystagmus. Right-beating nystagmus was observed in the sitting and both head hanging positions, and the nystagmus was changed to a left-beating nystagmus upon sitting from a supine position. The movement of the air bubble by head position change, along with the occurrence of vertigo and nystagmus, was demonstrated on TBCT, and the authors presumed that air movement within the vestibular labyrinth caused cupular displacement, leading to positional nystagmus [2].

In the semicircular canals, the perilymphatic space is tightly separated from the endolymphatic space by a thin endolymphatic membrane, and it appears that the endolymph is completely immersed in the perilymph fluid. The endolymphatic membrane is very thin and deformable, and deformability of the endolymphatic space may affect semicircular canal function [6-11]. It has been shown that mechanical indentation of the endolymphatic membrane can drive the endolymph toward the cupula [9,11], and mathematical simulations have predicted that acceleration-driven perilymph flow may drive cupula displacement via pressure-driven endolymphatic duct deformation [10]. As shown in TBCT in our patient (Fig. 1), the air bubble was trapped within the perilymphatic space in the LSCC ampulla, adhering to the endolymphatic membrane by the effect of gravity because this area is most gravity-dependent in a seated position (Fig. 3). The endolymphatic space assumes an eccentric position in contact with the outer surface of the bony canals of the LSCC, and the endolymphatic membrane is attached to the region of the sensory epithelium and the opposing wall in the ampulla (Fig. 3) [12]. Because the density of the air bubble is lower than that of inner ear fluids, a buoyant force is continuously imposed on the air bubble, causing indentation of the endolymphatic membrane. The endolymphatic space is known to be separated into medial and lateral to the cupula by the adhesion between the cupula and ampullary wall. Thus, the buoyant force, which causes indentation of the endolymphatic membrane, can be delivered to the LSCC cupula, resulting in cupular deflection. The endolymphatic membrane at the left LSCC ampulla is utriculopetally indented in a bowed position (Fig. 3A), eliciting persistent left-beating nystagmus (Supplementary Video 1). Upon changing positions from bowing to leaning, the air bubble moves to the uppermost part of the LSCC perilymphatic space, recovering the indentation of the endolymphatic membrane (Fig. 3B), which elicits transient right-beating nystagmus (Supplementary Video 2). A subsequent change to the supine position provokes no further movement of the air bubble, resulting in no change in the nystagmus pattern. When the head is rolled to the right, the air bubble may move utriculofugally to settle in an uppermost part (Fig. 3C) and impose no direct buoyant force on the ampullary endolymphatic membrane, eliciting no specific change in the nystagmus pattern (Supplementary Video 3). When the head is rolled to the left, the buoyant force moves the air bubble to the ampullary region, causing continuous indentation of the endolymphatic membrane and utriculopetal deflection of the LSCC cupula (Fig. 3D). In this position, persistent left-beating nystagmus is observed (Supplementary Video 4).

In the present study, we investigated the mechanism of positional nystagmus in pneumolabyrinth and hypothesized that indentation of the endolymphatic membrane is caused by the buoyant force, which is imposed on the air bubble, eliciting cupular deflection and positional nystagmus. However, the nystagmus in pneumolabyrinth should be comprehensively interpreted because this positional nystagmus is superimposed by the nystagmus caused by the perilymph fistula itself and/or unilateral vestibular hypofunction in the affected ear. Furthermore, the pattern of positional nystagmus may vary according to the location and size of air bubbles.

In conclusion, vertigo in a perilymph fistula complicated by pneumolabyrinth is commonly incapacitating. In pneumolabyrinth involving the LSCC, a buoyant force imposed on the air bubble by position change can elicit indentation of the endolymphatic membrane of the LSCC ampulla, causing deflection of the LSCC cupula and positional nystagmus.

ARTICLE INFORMATION

Funding/Support

This report was supported by Konkuk University in 2024.

Conflicts of Interest

No potential conflict of interest relevant to this article was reported.

Availability of Data and Materials

The datasets are not publicly available but are available from the corresponding author upon reasonable request.

Authors’ Contributions

Conceptualization, Funding acquisition, Methodology, Project administration, Visualization: Kim CH; Data curation, Formal analysis: All authors; Writing–Original Draft: All authors; Writing–Review & Editing: All authors.

All authors read and approved the final manuscript.

SUPPLEMENTARY MATERIALS

Supplementary materials can be found via https://doi.org/10.21790/rvs.2025.011.

Supplementary Video 1.

Persistent Left-Beating Nystagmus in Bow Position. In a bow position, persistent left-beating nystagmus was observed.

Supplementary Video 2.

Transient Right-Beating Nystagmus During Bowing → Leaning → Lying-Down Transition. Transient right-beating nystagmus was observed on changing from bowing to leaning position, and no change of nystagmus was elicited by the subsequent lying-down position.

Supplementary Video 3.

No Nystagmus in Right Head-Roll. The right head-roll maneuver elicited no typical unidirectional positional nystagmus.

Supplementary Video 4.

Persistent Left-Beating Nystagmus in Left Head-Roll. In the left head-roll position, persistent left-beating nystagmus was observed.

Fig. 1.

Axial (A) and coronal (B) views of temporal bone computed tomography show pneumolabyrinth in the ampulla of the left lateral semicircular canal (red arrows). A small pneumocephalus is demonstrated in the left middle cranial fossa (A, yellow arrow).

Fig. 2.

(A) Pure tone audiometry reveals a normal hearing threshold on the right side and mixed hearing loss (HL) on the left side on the day of head trauma. (B) The HL on the left side was alleviated 4 months after head trauma except for high-frequency HL.

Fig. 3.

A mechanism explaining the characteristic positional nystagmus in pneumolabyrinth involving the left lateral semicircular canal. (A) In a bowed position, the air bubble, which is located at the canal-side ampulla in the perilymphatic space, is floated by the effect of gravity. The continuous buoyant force is utriculopetally applied to the endolymphatic membrane (arrowheads), causing cupula deflection (arrows), which elicits persistent left-beating positional nystagmus. (B) Upon changing the head position from bowing to leaning, the air bubble moves to the most gravity-dependent location by a buoyant force. The endolymphatic membrane returns to the original position (arrowheads), causing transient right-beating positional nystagmus. (C) In the right head-roll position, the air bubble moves to the canal side by a buoyant force, eliciting no typical horizontal positional nystagmus. (D) In the left head-roll position, the continuous buoyant force is utriculopetally applied to the endolymphatic membrane (arrowheads), causing cupula deflection (arrows) and persistent left-beating positional nystagmus. U, utricle.

REFERENCES

1. Botti C, Castellucci A, Crocetta FM, et al. Pneumolabyrinth: a systematic review. Eur Arch Otorhinolaryngol 2021;278:4619–4632. Article PubMed PDF
2. Ederies A, Yuen HW, Chen JM, Aviv RI, Symons SP. Traumatic stapes fracture with rotation and subluxation into the vestibule and pneumolabyrinth. Laryngoscope 2009;119:1195–1197. Article PubMed PDF
3. Tsubota M, Shojaku H, Watanabe Y. Prognosis of inner ear function in pneumolabyrinth: case report and literature review. Am J Otolaryngol 2009;30:423–426. Article PubMed
4. Merchant SN, Rosowski JJ. Conductive hearing loss caused by third-window lesions of the inner ear. Otol Neurotol 2008;29:282–289. Article PubMed PMC
5. Mandalà M, Colletti L, Carner M, et al. Pneumolabyrinth and positional vertigo after stapedectomy. Auris Nasus Larynx 2011;38:547–550. Article PubMed
6. Kim CH, Shin JE, Yoo MH, Park HJ. Direction-changing and direction-fixed positional nystagmus in patients with vestibular neuritis and Meniere disease. Clin Exp Otorhinolaryngol 2019;12:255–260. Article PubMed PMC PDF
7. Kim CH, Pham NC. Density difference between perilymph and endolymph: a new hypothesis for light cupula phenomenon. Med Hypotheses 2019;123:55–59. Article PubMed
8. Kim CH, Shin JE, Park JH. Dialysis disequilibrium syndrome revisited: feeling “disequilibrated” due to inner ear dyshomeostasis? Med Hypotheses 2019;129:109262. Article PubMed
9. Rabbitt RD, Boyle R, Highstein SM. Mechanical amplification by hair cells in the semicircular canals. Proc Natl Acad Sci U S A 2010;107:3864–3869. Article PubMed PMC
10. Iversen MM, Rabbitt RD. Wave mechanics of the vestibular semicircular canals. Biophys J 2017;113:1133–1149. Article PubMed PMC
11. Dickman JD, Reder PA, Correia MJ. A method for controlled mechanical stimulation of single semicircular canals. J Neurosci Methods 1988;25:111–119. Article PubMed
12. Curthoys IS, Oman CM. Dimensions of the horizontal semicircular duct, ampulla and utricle in the human. Acta Otolaryngol 1987;103:254–261. Article PubMed

Figure & Data

References

Citations

Citations to this article as recorded by

PubReader
ePub Link

Cite

Cite: export Copy Download Format; Close

Download Citation

Download a citation file in RIS format that can be imported by all major citation management software, including EndNote, ProCite, RefWorks, and Reference Manager.

Format:

RIS — For EndNote, ProCite, RefWorks, and most other reference management software
BibTeX — For JabRef, BibDesk, and other BibTeX-specific software

Include:

Citation for the content below
Citation and abstract for the content below

Positional nystagmus in pneumolabyrinth: a case report

Res Vestib Sci. 2025;24(2):107-112. Published online June 15, 2025

DOI: https://doi.org/10.21790/rvs.2025.011

XML Download

Figure

Related articles

Positional nystagmus in pneumolabyrinth: a case report

Fig. 1. Axial (A) and coronal (B) views of temporal bone computed tomography show pneumolabyrinth in the ampulla of the left lateral semicircular canal (red arrows). A small pneumocephalus is demonstrated in the left middle cranial fossa (A, yellow arrow).

Fig. 2. (A) Pure tone audiometry reveals a normal hearing threshold on the right side and mixed hearing loss (HL) on the left side on the day of head trauma. (B) The HL on the left side was alleviated 4 months after head trauma except for high-frequency HL.

Fig. 3. A mechanism explaining the characteristic positional nystagmus in pneumolabyrinth involving the left lateral semicircular canal. (A) In a bowed position, the air bubble, which is located at the canal-side ampulla in the perilymphatic space, is floated by the effect of gravity. The continuous buoyant force is utriculopetally applied to the endolymphatic membrane (arrowheads), causing cupula deflection (arrows), which elicits persistent left-beating positional nystagmus. (B) Upon changing the head position from bowing to leaning, the air bubble moves to the most gravity-dependent location by a buoyant force. The endolymphatic membrane returns to the original position (arrowheads), causing transient right-beating positional nystagmus. (C) In the right head-roll position, the air bubble moves to the canal side by a buoyant force, eliciting no typical horizontal positional nystagmus. (D) In the left head-roll position, the continuous buoyant force is utriculopetally applied to the endolymphatic membrane (arrowheads), causing cupula deflection (arrows) and persistent left-beating positional nystagmus. U, utricle.

Fig. 1.

Fig. 2.

Fig. 3.

Positional nystagmus in pneumolabyrinth: a case report