evaluation of labyrinthine fistula by mr cisternography
TRANSCRIPT
CASE REPORT
Evaluation of labyrinthine fistula by MR cisternography
Oktay Algin & Sami Berçin & Gokce Akgunduz &
Baris Turkbey & Huseyin Cetin
Received: 12 April 2012 /Accepted: 4 May 2012 /Published online: 26 May 2012# Am Soc Emergency Radiol 2012
Abstract Sensorineural hearing loss (SNHL) can developafter trauma and determination of its etiology is crucial fortreatment planning. Computed tomography (CT) is the first-line imaging method in evaluation of trauma victims; how-ever, its value is limited in visualization of perilymphaticfistula or in assessment of cochlear implant candidates.Herein, we present imaging findings of a patient with trau-matic bilateral transverse fractures of temporal bones andresultant SNHL. This patient had a fistula between inner earand subarachnoid space which was detected at non-contrast-enhanced MR cisternography (NCE-MRC) and contrast-enhanced MR cisternography (CE-MRC) scans. To the bestof our knowledge, this is the first case in the literature. Inconclusion, in patients with transverse fractures of temporal
bone, in presence of otic capsule involvement at CT images,the inner ear structures and surrounding organs should becarefully evaluated via NCE-MRC. In case of a suspicion ofa fistula, CE-MRC can help in early diagnosis and can alsohelp to visualize the leakage location, which is of paramountimportance for correct treatment and management of suchcases.
Keywords Perilymph . Trauma .MR cisternography . Innerear . Fistula . MDCT .MRI . Cochlear implantation
Introduction
Cross-sectional imaging methods have an important role inevaluation of inner ear structures, cochlear nerve, centralauditory pathway, and associated intracranial abnormalitiesin patients with sensorineural hearing loss (SNHL) [1, 2].SNHL has several etiologies such as congenital–hereditarycauses, infectious–autoimmune labyrinthitis, trauma, andtumors [3]. Among the etiology of traumatic SNHL, cochlearconcussion, neuronal damage, and/or perilymphatic fistulas(PF) can be accounted [4, 5].
PF is a leakage into the middle ear secondary to a con-nection between middle ear and inner ear [1]. This rarecondition usually develops secondary transverse temporalbone fractures involving otic capsule, middle ear, and themost common manifestations are posttraumatic ear effusionand pneumolabyrinth [6–10]. Additionally, fistula betweenthe subarachnoid space (SAS) and perilymphatic duct candevelop after a transverse fracture. Such fistula has not beenreported previously; however, they may result in SNHL.Herein, we report a case of SNHL following posttraumaticbilateral temporal bone fractures and contrast material-
O. Algin (*) :G. Akgunduz :H. CetinRadiology Department,Ataturk Training and Research Hospital,Bilkent,Ankara, Turkeye-mail: [email protected]
G. Akgunduze-mail: [email protected]
H. Cetine-mail: [email protected]
S. BerçinOtolaryngology Department,Ataturk Training and Research Hospital,Bilkent,Ankara, Turkeye-mail: [email protected]
B. TurkbeyNIH,Bethesda, MD, USAe-mail: [email protected]
Emerg Radiol (2012) 19:557–560DOI 10.1007/s10140-012-1050-3
enhanced MR cisternography (CE-MRC) findings of a fistulabetween SAS and labyrinthine.
Case report
A 20-year-old young man with cochlear implantation pro-cedure plan for bilateral profound SNHL was referred to ourclinic for evaluation of cochlear nerve and inner ear struc-tures. Past medical history revealed a motorcycle accidentwhich happened 6 months ago and his hearing level wasnormal prior to that trauma.
Multidetector computed tomography (MDCT) revealedbilateral transverse temporal bone fractures also involvingthe otic capsule (Fig. 1), whereas middle and external earstructures were normal bilaterally. Non-contrast-enhancedMR cisternography (NCE-MRC) was performed for furtherevaluation, which demonstrated volumetric decrement of thebilateral inner ear structures and bilateral free fluid surround-ing the otic capsule that is more prominently appreciated onthe right side (Fig. 2). A CE-MRC was planned to rule out PF.CE-MRC showed leakage of the intrathecally administeredcontrast into the bilateral otic capsules and their surrounding(Fig. 3). On CE-MRC images, bilateral inner ear structureshad contrast enhancement. The techniques of NCE-MRC and
Fig. 1 Axial MDCT images of obtained right after (a) and 6 months after(b) the trauma demonstrate bilateral transverse temporal bone fractures(white arrows in a, b) and a left occipital bone fracture (black arrow in a)
Fig. 2 Axial NCE-MRC(heavily T2W) images of the pa-tient (a–c) and a 28-year-oldnormal control case (d). Thinsection (voxel size, 0.5×0.5×0.5 mm) T2W MR image showssignificant decrement of theamount of the endo- and peri-lymph within the inner ear bilat-erally (a). A more superior T2WMR image (b) shows punctatehyperintense areas (the fistula)around the otic capsule (whitearrow) (b). MIP images from thepatient (c) and a healthy controlindividual (d) demonstrates theprominent difference betweenimaging findings of the inner earstructures as the MIP image ofthe patient reveals slight visuali-zation of the bilateral semicircu-lar canals due to volumeloss (arrows) (c)
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CE-MRC were described in detail in our previous articles [11,12]. Intrathecally administered contrast material did not leakinto the middle or outer ear structures, hence the leak wasconfined to inner ear structures. Regarding these imagingfindings, the cochlear implantation procedure was postponedand the patient was advised to have strict bed rest followinglumbar drainage. Cochlear implant surgery was planned incase of a spontaneous obliteration of the fistula at follow-up.
Discussion
SNHL can develop secondary to injuries of inner ear structures(sensory hearing loss) or cochlear nerve/brainstem–thalamus(neural–retrocochlear hearing loss) [4, 6, 7]. Determination ofthe etiology of SNHL and condition of inner ear structures areof paramount importance for proper treatment planning [5].Patients with SNHL can benefit from cochlear implantation;however, selection of the appropriate implant can vary accord-ing to the underlying etiology [2, 6]. Moreover, contraindica-tions for cochlear implantation such as active middle eardisease, Michel deformity, labyrinthitis ossificans, and ad-vanced otosclerosis should be further investigated in all patientswith SNHL [4, 5]. Therefore, imaging plays an important rolein management of patients with SNHL; with regard to this,MDCT and MRI of the temporal bones are the two mostfrequently used imaging techniques in SNHL [2, 3].
In patients with SNHL, bony labyrinth pathologies canusually be visualized via MDCT [2, 3], whereas membranouslabyrinth pathologies and cochlear nerve integrity are com-monly evaluated by temporal bone or acoustic canal MRI[4, 5]. In patients with SNHL, imaging techniques cannotalways determine the etiologic factor [3]. The underlyingreason for this can be explained by location of the etiopathol-ogy only at the level of the hair cells of the Corti organ or non-visualization of small fistula [4, 5, 8]. However, current imag-ing equipments–techniques can be inadequate in determinationof such conditions.
Temporal bone fractures are classically grouped in two aslongitudinal and transverse, although several classificationsystems are present [6, 7, 10]. Longitudinal fractures consti-tute approximately 80 % of all fractures and commonly result
in conductive hearing loss [3–5]. Transverse fractures caneffect otic capsule and result in SNHL as well [6, 7]. MDCTis the most useful modality in diagnosis [2–5]. Otic capsuleviolating transverse fractures related secondary bilateralSNHL is an extremely rare condition [1, 5–7].
PF is the presence of an abnormal communication betweenperilymphatic space of the inner ear and middle ear [4]. Thebest diagnostic hint of this rare condition is pneumolabyrinth[4, 6]. PF is an uncommon cause of SNHL and can develop intransverse fractures of temporal bone [6]. Another additionalimmediate complication of transverse temporal bone fracturesis cerebrospinal fluid (CSF) leakage or fistula [6]. In thiscondition, there is an abnormal communication betweenSAS and extradural space. In such cases, abnormal commu-nication most commonly present with otorrhea [9]. Clinicaldiagnosis of patients with otorrhea is challenging since thetympanic membrane remains intact, hence diagnosis isdelayed usually [6, 9]. CSF fistulas can sometimes presentwith rhinorrhea or isolated mastoid effusion and they requireprompt diagnosis, otherwise serious and mortal complicationssuch as meningitis can be seen in 50 % of cases [7, 9].
CSF fistula can develop as a complication of posttraumatictransverse fractures of temporal bones; however, they may notalways manifest with otorrhea but can be isolated within theinner ear structures (otic capsule) as it happened in our case.
Fig. 3 Axial CE-MRC imagesof the patient (a, b) show passageof the intrathecally administeredcontrast material (Gd-DTPA) in-to perilymphatic systems bilater-ally as well as the contrast leakoutside the otic capsulebilaterally (arrows) (a, b)
Fig. 4 Illustration of a fistula between inner ear and subarachnoidspace. CSF (turquoise) cerebrospinal fluid, SCs (dark blue) semicircu-lar canals, CN cochlear nerve, VN vestibular nerve, ES (blue) endo-lymphatic sac, TM tympanic membrane, ET eustachian tube
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The early diagnosis of this urgent condition by clinical andradiologic approaches is difficult [1, 5]. Similar to other peril-ymphatic ones, such fistula can result in permanent hearingloss and/or persistent vertigo if remains untreated [2–5]. Dem-onstration of correct localization of the fistula is an importantrole in presurgical planning. Imaging findings of such type offistula are not detailed presented in the literature and this canbe attributed to limited spatial resolution of the routine imag-ing techniques used in the daily practice.
Cisternographic studies are the most useful methods indiagnosis of otorrhea and rhinorrhea [9]. Radionuclide orCT cisternography has been commonly in use in the past [9].Both methods involve radiation exposure and have limitedspatial resolution [9, 11, 12]. MR cisternography, which hasa decent soft tissue resolution without radiation exposure,has been in use for diagnosis of otorrhea and rhinorrhea andthis may overcome the limitation of the conventional imag-ing methods [9, 12]. Our case and imaging findings supportthis hypothesis. Decrement of the perilymph on NCE-MRCshould be accounted as a sign of such fistula especially inpatients with trauma history. In the presence of suspiciousfindings for fistula at NCE-MRC, CE-MRC can be helpfulfor diagnosis. Additionally, CE-MRC can also be useful inlocalization of the fistula.
The etiology of SNHL both in our patient and in previouslydefined PF cases can be the increased pressure within innerstructures secondary to a communication between the innerear and SAS. Yet, the SAS pressure is much higher than thepressure in the endolymphatic and perilymphatic canals[13, 14]. In the presence of a fistula, the perilymphatic ductis continuously washed by and the perilymph pressureincreases resultantly. Then, the perilymph leaves the oticcapsule through the perforated bony capsule of the inner earand the endolymph, perilymph volumes increase, and theirchemical composition changes as well [13, 14]. The leakedperilymph is replaced by the CSF through the cochlear aque-duct or the fistula and this vicious circle continues constantly(Fig. 4). Such pressure, volume, and chemical compositionchanges also affect the endolymph and lead to damage of haircells of the organ of Corti [1, 13, 14]. Additionally, thecochlear concussion secondary to trauma leads to changes inthe pressure in the inner ear regardless of the otic capsule andresults in microhemorrhage or disturbs the microcirculationand causes SNHL eventually [1].
In conclusion, in patients with transverse fractures of tem-poral bone, in presence of otic capsule involvement at CTimages, the inner ear structures and surrounding organs should
be carefully evaluated via NCE-MRC. MR cisternographymight be helpful in limited cases that CT is inconclusive suchas a symptomatic patient with apparent negative CT examina-tion. In case of a suspicion of a fistula, CE-MRC can help inearly diagnosis and can also help to visualize the leakagelocation, which is of paramount importance for correct treat-ment and management of such cases.
Acknowledgments We gratefully acknowledge Dr. Mehmet Gumusand Prof. Dr. Ergin Atalar for their contributions.
Conflict of interest We declare that we have no conflict of interest.
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