Cochlear implantation after deafness from Pasteurella multocida meningitis
- Jeffrey Dewitt Warner ,
- Ashwini Milind Tilak ,
- Sudhir Manickavel and
- Erika Walsh
- Otolaryngology-Head and Neck Surgery, University of Alabama at Birmingham, Birmingham, Alabama, USA
- Correspondence to Mr Jeffrey Dewitt Warner; jdwarner@uab.edu
Abstract
A woman in her late 40s who works as a veterinary technician represented to the emergency department with increasing headache, confusion, neck stiffness, subjective fevers and distorted hearing 2 days after diagnosis of viral infection at an outside emergency department.
Diagnosis of Pasteurella multocida was made from blood cultures and lumbar puncture. Intravenous ceftriaxone was administered for 21 days. By the time of resolution of acute meningitis, she had become completely deaf bilaterally. MRI revealed faint early ossification/possible labyrinthitis ossificans of the basal cochlea, which was confirmed on surgical exploration during the placement of cochlear implants bilaterally 42 days later. We discuss how the atypical features of this infection lead to diagnostic delay and high morbidity, the unique imaging/surgical findings resulting from the infection, and the clinical utility of early and bilateral cochlear implantation in this and similar cases.
Background
Meningitis is inflammation of the subarachnoid space and surrounding meninges, often due to infection of the cerebrospinal fluid or brain parenchyma. It can have serious sequelae including altered mental function, seizures, hearing loss, vertigo and focal neurological deficits/gait disturbances. The most common causative organisms are Streptococcus pneumoniae, Neisseria meningitidis, group B streptococci and Listeria monocytogenes, respectively.1 Bacterial meningitis in adults has an incidence of 4–6 cases per 100 000 per year, with the most common neurological abnormalities reported at discharge being hearing loss and hemiparesis, sometimes as common as 14% and 4% of cases, respectively.2 3 It is important to be aware that the classic triad of neck stiffness, altered mental status and fever is often only present in 44% of cases of meningitis. Most cases present with at least two out of four of neck stiffness, altered mental status, headache and fever.3
One mechanism by which meningitis is thought to cause deafness is through the spread of infection or inflammation to the inner ear, also known as labyrinthitis, via flow of cerebrospinal fluid through the cochlear aqueduct into the perilymph.4 Labyrinthitis clinically manifests with vestibular symptoms of vertigo and with symptoms of hearing loss.5 Meningitic hearing loss may be complicated by labyrinthitis ossificans (LO), the inflammation-driven formation of new bone in the lumen of the otic capsule. It has been found that the progression of ossification of the cochlea correlates inversely with open-set speech discrimination outcome on recovery from cochlear implantation, thus highlighting the importance of initiating implantation as soon as possible after the onset of post-meningitic deafness and considering simultaneous bilateral implantation.6 7
Case presentation
A veterinary technician in her late 40s initially presented to an outside emergency department with a headache that started 2 days prior. During the first 24 hours of symptoms, she began to experience worsened headache, subjective fevers and confusion; she thus sought treatment at an urgent care clinic. After being seen there, she was directed to an outside hospital’s emergency department, where workup revealed elevated white bcell count (WCC) (22x106/L). She was diagnosed with a viral infection at that emergency department and discharged home, and later that night she began to develop neck stiffness/pain, nausea, vertigo and a distortion of her hearing that she described as ‘making everything sound like a helium balloon’. By the following morning the distortion had progressed to subjectively complete bilateral deafness, and she was taken to our institution’s emergency department.
On physical examination, she was afebrile with normal vital signs. She had neck stiffness and was mildly confused on initial interview but fully oriented. She was also found to have a scratch on her lower leg and right hand without visible drainage or cellulitis that she said she scraped on surfaces at work.
After admission, treatment and clinical improvement, detailed history revealed that during her work at a veterinary clinic she is often scratched and bitten by dogs and cats. She had no other medical conditions and took no medications consistently prior to this admission and her other medical history was non-contributory.
While in the hospital, multidisciplinary consultation with infectious disease, audiology and otolaryngology was obtained.
Investigations
While in the emergency department, initial bloodwork revealed lactic acidosis (2.8 mMol/L) (normal range 0.5–2.2 mMol/L) consistent with sepsis and a WCC of 19x106/L. This was a mild reduction in WCC from the one performed at the outside hospital despite no reported treatment with antibiotics from the outside hospital. This, combined with her hearing loss, neck stiffness and confusion, raised suspicion for bacterial meningitis. Lumbar puncture was performed, cerebrospinal fluid (CSF) was grossly turbid with high protein, low glucose, and a WCC of 3 376 /cc. Blood and CSF cultures taken at this time eventually grew Pasteurella multocida, with blood cultures positive in 4/4 bottles.
A CT of the head with contrast did not reveal any acute abnormality.
MRI revealed diffuse subarachnoid fluid-attenuated inversion recovery (FLAIR) hyperintense signal with subtle leptomeningeal enhancement along the cerebral sulci, concerning for meningitis. Broad spectrum antibiotic treatment was initiated
Five days after admission, a formal audiology evaluation was performed, revealing no response to pure tones from 250 Hz to 8000 Hz bilaterally. Tympanograms were type A bilaterally with normal middle ear function. Ear, nose and throat consultation was performed, revealing normal otoscopic exam and no response on Rinne and Weber tuning fork exams. A formal CT temporal bone without contrast performed 6 days after presentation again did not reveal any abnormality to explain hearing loss. However, high-dose steroids (1 mg/kg prednisone for 7 days, 90 mg daily in this case) were started at this time due to the hearing loss in an attempt to prevent further cochlear damage/inflammation.
After discharge from the hospital the patient was seen in otology clinic, 18 days after initial presentation. At this time, audiogram again revealed bilateral profound hearing loss and no response on speech recognition threshold testing with normal tympanograms bilaterally. Repeat MRI performed 16 days after initial presentation was reviewed, revealing bilateral labyrinthine enhancement on T1 contrast-enhanced sequences consistent with labyrinthitis, as well as some attenuation of T2 signal in the cochlea and semicircular canals concerning for early LOs (figure 1). CT temporal bone without contrast performed 18 days after initial presentation did not reveal frank ossification but was suspicious for subtle early ossification particularly in the left lateral semicircular canal (figure 2).
T2-weighted MRI performed 16 days after initial presentation revealing subtle attenuation of T2 signal in the left labyrinth (circled on the left) greater than right labyrinth (circled on the right), concerning for early labyrinthitis ossificans.
CT temporal bone without contrast, axial view, performed 18 days after initial presentation. There is some suspicion for subtle early ossification particularly in the left lateral semicircular canal (Indicated by blue arrow).
Differential diagnosis
Initially at the outside hospital, this patient was diagnosed with what was assumed to be a viral upper respiratory infection, although the only symptom she displayed consistent with this diagnosis was fever. However, when she eventually presented to our institution’s emergency department, the constellation of symptoms and lab work including neck stiffness, high WCC and lactic acidosis prompted a lumbar puncture, analysis of which revealed a bacterial source of meningitis, particularly P. multocida.
Treatment
Immediate treatment on presentation with vancomycin, ceftriaxone, acyclovir and dexamethasone was initiated due to sepsis presentation and concern for meningitis in the setting of unknown speciation. Acyclovir was discontinued once CSF gram stain revealed gram negative diplococci. After infectious disease consultation and on speciation of culture revealing P. multocida, vancomycin and dexamethasone were discontinued. Treatment with intravenous ceftriaxone 2 g two times per day for 3 weeks was completed. On otolaryngology consultation for bilateral hearing loss, 1 mg/kg prednisone for 7 days was recommended to minimise further cochlear damage from progression of possible labyrinthitis.
Outcome and follow-up
In the month following discharge from the hospital, she was evaluated for bilateral cochlear implant (CI) placement and was audiologically a candidate in both ears. Given the likelihood of progression of ossification in the setting of meningitis, early bilateral cochlear implant was recommended. The infectious disease team was contacted to ensure she completed her full antibiotic course prior to implantation. About a month after discharge, she successfully underwent bilateral CI612 internal (Cochlear Americas, Sydney, Australia) cochlear implant placement. Intraoperatively, it was found that no standard neurological response threshold readings were detected from the cochlear implant electrodes of: right ear: 1–3; left ear: 1–4 and 14–15. This likely indicates early ossification of the cochlear basal turns bilaterally. Other operative findings included inflammatory and fibrous soft tissue obstructing the round window bilaterally (left worse than right), as well as confirmation of early ossification of the bilateral cochlear basal turns (right worse than left).
A month after implantation her CI was activated, and a month after activation her performance with the implant was tested. At this visit she was able to hear with only mild complaints of overwhelming ambient noise. She was again seen 2 months after implantation and continued to perform well.
Discussion
While P. multocida meningitis is a rare case, this is not the first. However, most cases are described in extremes of age.8–13 P. multocida is a bacteria classically carried and transmitted by animals and domestic pets, and the most common routes of infection reported are from pets licking patients’ pre-existing wounds, having mouth-to-mouth contact with patients, or from bites by these animals.14–17 This makes sense in the context of the case as the patient was working at a veterinarian’s office. Such a workplace hazard contributing to a severe disease state in this case demonstrates the importance of appropriate risk assessment and personal protective equipment for employees of such offices. While no prior cases of hearing loss specifically from P. multocida meningitis were found, hearing loss from meningitis is not uncommon.18–25 The most agreed-on mechanism by which meningitis brings about hearing loss is through spread of infection from the CSF into the perilymph of the cochlear apparatus, with three main mechanisms eventually contributing to hearing loss: inflammation-induced ossification of inner ear structures (LOs), inflammatory damage to the vestibulocochlear nerve (neuritis), and fibrous/inflammatory exudate causing obstruction of fluid/soundwave transmission through the cochlear apparatus.7 26–32 Obstructing exudate was seen surgically, which is unsurprising given that characteristics of the P. multocida toxin include being a strong mitogen for fibroblasts.33–36 The intraoperative neurological stimulation findings and MRI results point towards early ossification of the basal portions of the basilar membrane in this patient as well.37 38
In this case, MRI evidence of ossification did not appear until 14 days after her complaints of hearing loss. As seen in some animal models, postmeningitic hearing loss has a latency period of up to 12 hours, with hearing loss progression beyond this point lasting up to an average of 36 hours postinfection if untreated.39 40 Another animal study demonstrated that labyrinthine mineralisation only begins at least 3 days after infection, therefore, ossification visible by MRI is a late manifestation compared with the rapid-onset hearing loss.26
With meningitis caused by atypical organisms, the typical empiric meningitis treatment guidelines must be adapted based on reports of similar cases. The infectious disease team in this case advised the use of antibiotic therapy (ceftriaxone) that P. multocida is classically susceptible to and which also has effective CSF penetration.12 13 41
While cochlear implantation for post-meningitic deafness is not a common scenario, some studies have been conducted to identify ways to optimise outcomes in these scenarios.28 42–45 It has been found that the progression of ossification of the cochlea correlates inversely with open-set speech discrimination outcome, thus highlighting the importance of initiating cochlear implantation as soon as possible after the onset of postmeningitic deafness.6 This case demonstrates the early and late findings of LO from meningitis on MRI versus CT, and is another example of the superiority of MRI in early detection of LO; thus, CT+MRI focused on the cochlea along with a high index of suspicion for bacterial meningitis should be standard of care for scenarios such as these, especially when planning for cochlear implantation.46 47
Learning points
-
This case of an atypical cause of meningitis by Pasteurella multocida demonstrates why the index of suspicion must remain high in unusual presentations.
-
Imaging evidence of the cochlear inflammation/ossification in this case lagged behind the rapid hearing loss and was not apparent on MRI until 14 days after the onset of hearing loss. Unique imaging methods can be ordered to evaluate these situations including contrast MRI imaging focused on the middle/inner ear anatomy, and spiral CT temporal bone imaging with Stenver-Poschl reformatting to delineate the cochlea/skull base.
-
Meningitis with P. multocida as an infective source is not common enough to have standard treatment recommendations/algorithms, with only anecdotal regiments found in the literature. This presented a situation where the clinician had to lean on experience and extrapolation of treatment methods for other organisms.
-
Cochlear implantation for acquired hearing loss from an episode of meningitis is an uncommon situation. In this case, hearing was effectively recovered with bilateral implantation after a case of meningitis with early but symptomatically severe cochlear ossification.
Ethics statements
Patient consent for publication
Footnotes
-
Contributors JDW drafted, edited and revised the manuscript, wrote response letter to revisions, designed the case layout/reporting of information, contributed to final approval of the publication, and agrees to accountability for accuracy and integrity of the work. JDW is the corresponding and submitting author, as well as guarantor. AMT contributed to the conception of the work, critically edited the work, contributed to revisions, revision responses and letters, critiqued the case layout/reporting of information, contributed to final approval of the publication, and agrees to accountability for accuracy and integrity of the work. AMT also contributed to the care of the patient. SM contributed to edits of the draft paper, as well as the acquisition of data for the work, contributed to final approval of the publication, and agrees to accountability for accuracy and integrity of the work. EW contributed to conception of the work, to revisions and edits of the draft, to final approval of the publication, and agrees to accountability for accuracy and integrity of the work. EW also contributed to the care of the patient. EW is senior author.
-
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
-
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
-
Competing interests None declared.
-
Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.
References
Use of this content is subject to our disclaimer