Early Diagnosis of Aseptic Meningitis in Ramsay Hunt Syndrome on 10-Minute Delayed CE 3D FLAIR Image: a Case Report

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Early Diagnosis of Aseptic Meningitis in Ramsay Hunt Syndrome on 10-Minute Delayed CE 3D FLAIR Image: a Case Report

INTRODUCTION

Ramsay Hunt syndrome (RHS) is caused by the reactivation of varicella-zoster virus (VZV) in the geniculate ganglion. RHS presents with a triad of characteristic manifestations: ipsilateral facial paralysis, ear pain, and vesicles on the face. By 2020, a few reports of complication in RHS, such as encephalitis, meningitis, brain stem involvement, and cerebellar involvement, had been published (1-4). Among the published reports, three cases of RHS complicated by meningoencephalitis and meningitis were reported in 2019 and 2020 (1, 3, 4).

Recent advances in MRI techniques have enabled assessment of the internal auditory canal (IAC). Until now, while it is not routine to use three-dimensional fluid- attenuated inversion recovery (3D-FLAIR) sequence, the 3D FLAIR sequence is used, and has the role of evaluating different fluid compositions in the inner ear structure, compared to the standard sequence (5). Contrast-enhanced (CE) delayed 3D FLAIR using low concentrations of gadolinium contrast material can detect blood-labyrinth

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Received: May 26, 2021 Revised: July 14, 2021 Accepted: July 15, 2021 Correspondence to:

Da Mi Kim, M.D.

Department of Radiology, Chungnam National University Hospital, Chungnam National University School of Medicine, 282 Munhwa-ro, Jung-gu, Daejeon 35015, Korea.

Tel. +82-42-280-8087 Fax. +82-42-253-0061 E-mail: damirad@daum.net

iMRI 2021;25:197-200 https://doi.org/10.13104/imri.2021.25.3.197

Case Report

Ramsay Hunt syndrome (RHS) is a disease caused by varicella-zoster virus (VZV) infection that can be diagnosed through clinical symptoms with or without imaging evaluations. The typical features of RHS on imaging evaluation include signal changes and enhancement in the internal auditory canal (IAC) nerves, and the labyrinthine segment of cranial nerve VII (CN VII) and cranial nerve VIII (CN VIII). In some patients, inner ear structure (cochlear and vestibular apparatus) is involved in RHS. Neurologic complications, such as encephalitis and meningitis, are rare in RHS, but are known to occur. Therefore, magnetic resonance imaging (MRI) is necessary to detect both abnormal signal intensity in the IAC, CN VII, CN VIII, inner and ear structure, and CNS complications. We report an RHS patient with CN VII, VIII, and leptomeningeal enhancement within the cerebellar folia on 10-min delayed, contrast-enhanced (CE), three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) imaging.

Keywords: Ramsay Hunt Syndrome; Magnetic resonance imaging;

3D fluid-attenuated inversion recovery; Internal auditory canal;

10-minute delayed 3D fluid-attenuated inversion recovery

pISSN 2384-1095 eISSN 2384-1109

Mi Hyun Kang, Da Mi Kim, In Ho Lee, Chang June Song

Department of Radiology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Korea

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Early Diagnosis of Aseptic Meningitis in Ramsay Hunt Syndrome | Mi Hyun Kang, et al.

barrier breakdown with high sensitivity (6, 7), while 10-min delayed CE 3D-FLAIR images can be useful for diagnosing inner ear abnormalities and related central nervous system (CNS) complications (5).

We report a case of RHS in which the patient was early diagnosed with aseptic meningitis using 10-min delayed CE 3D-FLAIR sequences on IAC MRI.

CASE REPORT

An 18-year-old man with no previous medical history experienced sudden right otalgia, ear fullness, and fever for three days. Upon evaluation four days later, he had developed right facial pain and peripheral facial paralysis.

Physical examination showed that the vesicular rashes were in the right external auditory canal, and the tympanic membrane was displaying erythematous changes. During hospitalization, the patient complained of new-onset dizziness and headache.

IAC MRI was performed for further evaluation using a Philips Achieva 3T 16 Channel MRI System (Philips Healthcare, Best, The Netherlands), including axial T1- weighted images (T1WI), T2-weighted images (T2WI), diffusion-weighted imaging (DWI), 3D FLAIR, CE T1WI, 10-min delayed CE 3D FLAIR, coronal T1WI, T2WI, and CE T1WI. The 10-min delayed CE 3D FLAIR was obtained in the axial plane at 10 minutes after the injection of intravenous contrast material, different from the CE T1WI, which are immediately acquired after IV contrast material injection.

The scanning parameters for 10-min delayed CE 3D FLAIR sequence were TR, 8000 ms; TEeff, 268 ms; inversion time, 2400 ms; FOV, 200 × 200 mm; voxel size, 0.8 × 0.8 × 0.8 mm; acquisition time, 4 minutes 48 seconds; reconstruction matrix, 256 × 256; slice thickness, 1.6 mm; echo-train length, 80; flip angle, 90 degree. On MR imaging (Fig.

1), asymmetric enhancement was observed in the fundal portion and labyrinthine segment of the right cranial nerve VII (CN VII) on CE T1WI. Enhancement in the right CN VII and VIII in the IAC and more subtle enhancement in the ipsilateral cochlea were seen only on the 10-min delayed 3D CE FLAIR images; such enhancement was not clearly detected by T1WI, T2WI, or pre-3D FLAIR. Leptomeningeal enhancement in the right cerebellar folia, suggestive of local meningitis, was seen only on the 10-min delayed 3D CE FLAIR images. Also, soft tissue swelling with enhancement in the right external ear was seen on both the CE T1WI and the 10-min delayed CE FLAIR images.

After the MRI evaluation, the patient underwent cerebrospinal fluid (CSF) studies, which revealed an elevated opening pressure of up to 158 mmHg with a positive Q-test. The CSF analysis showed a slightly elevated white blood cell (WBC) count (20/uL, with 52% lymphocytes and 47% monocytes), suspicious of meningeal non-bacterial inflammation. In the polymerase chain reaction (PCR) results, only VZV was positive. The CSF showed an elevated VZV antibody titer, and a VZV CNS infection was diagnosed by PCR analysis of the CSF.

The patient was treated with methylprednisolone and acyclovir, and at the time of discharge, had partial improvement of his symptoms.

DISCUSSION

RHS, which is caused by latent VZV infection, involves the sensory fibers of CN VII and CN VIII (1). Patients present with peripheral facial nerve palsy associated with sensorineural hearing loss, tinnitus, vertigo, and painful vesicular eruption within the external ear canal, the auricle, and the tympanic membrane. Other symptoms include fever, headache, and rarely, symptoms of meningeal irritation (2, 3). Aseptic meningitis from the viral infection is usually diagnosed clinically, and confirmed by imaging studies.

Many studies on RHS have been published since 2006, and have demonstrated the usefulness of pre-3D FLAIR and CE 3D FLAIR for evaluating pathologic conditions in the inner ear and diagnosing meningoencephalitis (5-8).

3D FLAIR sequences are useful, because they are thinner slices that allow for multi-planar reformation, and can be obtained with high resolution in a reasonable amount of time. Also, they are highly sensitive to T1-weighted changes in fluid without CSF inflow artifacts, and 3D datasets of the images are compatible with computer-assisted analysis (6). Furthermore, inner ear hyperintensity on 3D FLAIR is considered a predictor of the patient’s hearing-related outcomes (6).

Because of the higher sensitivity to subtle changes in fluid composition, the reduced incidence of artifacts from CSF motion, and high sensitivity to low concentrations of Gd, CE 3D-FLAIR is valuable for the evaluation of various inner ear diseases, such as sudden sensorineural hearing loss, RHS, intralabyrinthine hemorrhage (hyperacute to subacute stages), schwannoma, Meniere’s disease (idiopathic endolymphatic hydrops), vestibular neuritis, labyrinthitis, and leptomeningeal disease (6, 7, 9).

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https://doi.org/10.13104/imri.2021.25.3.197

In RHS, abnormal enhancement of the canalicular segment or asymmetric enhancement of the labyrinthine and/or mastoid segment of CN VII compared to the normal side is sometimes observed, and CN VIII and membranous labyrinth structures can also show abnormal enhancement on CE T1WI and 3D FLAIR sequences (10). At this time, the

condition should be distinguishable from normal CN VII enhancement. Our patient showed asymmetric enhancement in the fundal portion and labyrinthine segment of the right CN VII on the CE T1WI sequences, as well as asymmetric enhancement in the intracanalicular segment of CN VII and VIII on the 10-min delayed CE 3D FLAIR sequences.

Fig. 1. Axial T1-weighted image (a) shows no abnormal signal intensity in the intracanalicular segment of CN VII and VIII. Axial 3D FLAIR image (b) shows subtle increased signal intensity in the fundal portion of the right CN VII. Axial contrast- enhanced T1-weighted images (c) show asymmetric enhancement in the fundal portion and labyrinthine segment of the right CN VII (arrow), and mild swelling with enhancement in the right external ear (empty arrow). Axial contrast- enhanced T1-weighted image (d) shows no abnormal enhancement in the right cerebellar folia. Axial contrast-enhanced 10-min delayed CE 3D FLAIR images (e) show asymmetric enhancement in the intracanalicular segment of CN VII and VIII (arrow), and right external ear (empty arrow). Axial contrast enhanced 10-min delayed CE 3D FLAIR images (f) show subtle enhancement in the right cochlea (right internal auditory canal, arrow). Axial contrast-enhanced 10-min delayed CE 3D FLAIR images (g) show leptomeningeal enhancement in the right cerebellar folia (arrow).

a b c

d e f

g

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Early Diagnosis of Aseptic Meningitis in Ramsay Hunt Syndrome | Mi Hyun Kang, et al.

Also, abnormal leptomeningeal enhancement along the right cerebellar folia was only detected on 10-min delayed CE 3D FLAIR. Our case showed that the 10-min delayed CE 3D FLAIR MR sequences were more sensitive than pre-3D-FLAIR and CE T1WI for the diagnosis of inner ear and leptomeningeal abnormalities. A previous study (5) explained the usefulness of delayed CE FLAIR MR images, as in our report. In comparison to CE T1WI or pre-contrast and CE 3D FLAIR MR images, delayed CE FLAIR MR images seem to be of superior diagnostic utility for leptomeningeal infectious or tumoral diseases.

The utility of pathophysiologic analysis using CE 3D FLAIR images for the diagnosis of inner ear disease is attributable to its less invasive nature, and the fact that it enables observation of the inner ear structure, without intratympanic gadolinium injection. The signal intensity ratio is very useful for semiquantitative evaluation of disrupted blood-labyrinthine barriers. A previous study (5) showed that 4-hour delayed CE 3D FLAIR images can be used to identify the vestibular nerve and inner ear structures. That study reported that both 4-hour delayed CE 3D FLAIR and 10-min delayed CE 3D FLAIR images showed increased signal intensity in the cochlea, vestibule, and CN VII and VIII. The 4-hour delayed CE 3D FLAIR was superior to the 10-min delayed CE 3D FLAIR for assessing neural inflammatory conditions, such as neuritis, while the 10-min delayed CE 3D FLAIR was better than the 4-hour delayed CE 3D FLAIR for the diagnosis of neural non-inflammatory conditions, such as sudden sensorineural hearing loss (5).

There is currently no consensus on the acquisition of IAC MRI using delayed CE FLAIR images. Considering the workable scan time, our institution routinely performs only 10-min delayed CE 3D FLAIR in IAC MRI to catch conditions that routine MR examination might overlook. The 10-min delayed 3D CE FLAIR images are very useful not only for the evaluation of inner ear diseases, but also for the early detection and diagnosis of aseptic meningitis in RHS.

In conclusion, the IAC MRI protocol can be modified to include 10-min delayed CE 3D FLAIR sequences; and in RHS patients, radiologists should consider not only the inner ear, but also CNS complications.

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