Two Cases of Skull Base Osteomyelitis in Elderly Patients after Mastoidectomy.

Yum,  Gunhwee; Jun,  Hyun Su; Kwon,  Soon Young; Jun,  Hyung Jin; Choi,  June

Case Report

Auditory and vestibular disorders

Korean Journal of Audiology 2011;15(1):37-40.

Two Cases of Skull Base Osteomyelitis in Elderly Patients after Mastoidectomy.

Gunhwee Yum, Hyun Su Jun, Soon Young Kwon, Hyung Jin Jun, June Choi

Department of Otolaryngology-Head and Neck Surgery, Korea University Medical Center, Ansan, Korea. mednlaw@korea.ac.kr

Abstract

Skull base osteomyelitis (SBO) is a rare disease and may develop as a complication of paranasal sinusitis or other regional infectious process. The characteristic symptom of SBO is headache and paralysis of cranial nerve. A potentially life-threatening disease, it requires aggressive antibiotic treatment. We present 2 cases of SBO. One case who were not immunocompromised or diabetics had paralysis of lower cranial nerves. The patient was effectively treated with complete mastoidectomy and antibiotics, so had a complete recovery. But, the other patient who were insulin-dependent diabetes mellitus was died due to meningitis and pons palsy.

Keywords: Osteomyelitis;Skull base;Mastoidectomy;Cranial nerve palsy

Address for correspondence : June Choi, MD, PhD, Department of Otorhinolaryngology-Head and Neck Surgery, Ansan Hospital, Korea University Medical Center, 516 Gojan-dong, Ansan 425-707, Korea
Tel : +82-31-412-5170, Fax : +82-31-412-5174, E-mail : mednlaw@korea.ac.kr

Introduction

Skull base osteomyelitis (SBO) is encountered mostly in elderly patients with diabetes, and pseudomonas aeruginosa is the most common pathogen.¹⁾ The characteristic symptom of SBO is a unilateral deep-seated headache, followed by paralysis of the muscles innervated by the lower cranial nerves. Treatment strategies have changed significantly over time. Surgical debridement, once the mainstay of treatment, has been superseded by systemic antibiotic therapy.²⁾ Recently, the authors encountered two cases of skull base osteomyelitis after mastoidectomy.

Case Report

Case 1
A 66-year-old female visited our clinic for evaluation of chronic otorrhea and hoarseness. Four months prior, she had undergone a right side intact canal wall mastoidectomy and tympanoplasty in another tertiary hospital. After the operation, she complained of a severe right-side headache and dizziness. An ear swab culture confirmed a pseudomonal infection. After six weeks of antibiotic treatment, she developed multiple cranial nerve palsies. A physical examination with a laryngeal and nasopharyngeal endoscope revealed weakness in the muscles innervated by the lower cranial nerves (combination of IX, X, XI, Xll) on the right side. Magnetic resonance imaging (MRI) and Computed tomography (CT) scan showed a lesion on the right skull base (Fig. 1A, B), and gallium scintigraphy revealed increased uptake on the right skull base (Fig. 2B). We attempted to remove the remnant mastoid air cells, vestibule and the cochlear bony lesion because a previous long term (six week) third generation cephalosporin (ceftazidime) antibiotic therapy was not effective. Under general anesthesia, we removed the mastoid air cells and labyrinthine structures. After removal of the pathologic bony lesion, the cavity was filled with muscle via a temporalis rotation flap. We did not close the external auditory canal so that we could monitor the spread of the infection. Additionally, the patient was started on intravenous ceftazidime. However, it had documented on microbiological evidence of whole antibiotics resistant pseudomonas aeruginosa except colistin. A gallium scintigraphy revealed decreased uptake over the right side of the skull base (Fig. 2B), and the right-side headache disappeared during combination therapy with intravenous colistin and vinegar irrigation through external auditory canal. After two years, MRI showed no recurrence and no remnant mastoid air cells (Fig. 1C, D). At the most recent follow-up, the patient showed weak clinical signs of lower cranial nerve function without headache or otorrhea.

Case 2
A 69-year-old insulin-dependent diabetic female visited our clinic for evaluation of chronic otorrhea and right side headache. She underwent a canal wall down mastoidectomy and tympanoplasty. Eight weeks after surgery, she developed severe right-side otalgia and discharge. She complained of right side headache but showed no lower cranial nerve palsies. MRI showed a lesion on the right side of the skull base (Fig. 3). Gallium scintigraphy also revealed increased uptake on the right side of the skull base (Fig. 4). The patient was started on intravenous piperacillin-tazobactam and topical ofloxacin drops. A strict regimen of insulin (for diabetes mellitus) and a combination of intravenous antibiotics was administered for several weeks. Despite continuous antibiotic therapy and blood sugar control, osteomyelitis was aggravated to meningitis which caused pons palsy with uncontrolled diabetes mellitus. The patient expired due to meningitis and pons palsy.

Discussion

Skull base osteomyelitis was first described by Meltzer in 1959 and was thought to be a complication of otitis externa caused by Pseudomonas aeruginosa in elderly diabetic or immunocompromised patients.³⁾ Nine years later, Chandler published a review of his personal experience with 13 patients with a condition he called malignant otitis externa.⁴⁾ However, he argued that radical surgical debridement was the only means of successful treatment. Advances in antibiotic treatment and imaging studies have changed this belief.
Infection spreading to the skull base occurs via the fissures of Santorini and the tympanomastoid suture to involve the stylomastoid foramen and jugular foramen. Middle ear involvements are rare until late in the disease.^4,⁵⁾ Cranial nerve involvement is almost extratemporal; spreading to the stylomastoid foramen and jugular foramen results in palsies of the facial nerve (VII) and glossopharyngeal (IX), vagus (X), and accessory nerves (XI).⁶⁾ Intracranial complications include meningitis and cerebral abscess.⁷⁾
Pseudomonas aeruginosa is the most common Gram-negative, obligate aerobic bacillus.¹⁾ There have also been a significant minority of patients with fungal or mixed bacterial and fungal infections, with Aspergillus fumigatus being the most common pathogen.⁹⁾
CT is used to determine the extent of bony destruction in the ear canal wall or the skull base by delineating normal fat planes and bone cortices. Advanced diseases reveal skull base bone destruction and abscess formation.¹⁰⁾ However, CT is not an appropriate tool for evaluating treatment response.¹¹⁾
MRI is considered to be more sensitive than CT scan in delineating soft tissue planes. Most SOMs exhibit low signals on T1-weighted images and high signals on T2-weighted images.¹²⁾ Dural enhancement and involvement of the medullary space of the bone are the significant findings exclusive to MRI; therefore, MRI is recommended when skull base invasion is observed on CT.¹¹⁾ Changes on MRI do not resolve with the disease, so this imaging is not useful for following the course of antibiotic treatment.¹¹⁾
Gallium-67 citrate accumulates in regions of active inflammation by binding to leukocytes and forming a complex with lactoferrin.¹³⁾ Increased uptake will be present in areas of skull base osteomyelitis, returning to normal once the infection is resolved. This type of scan should be repeated every four weeks to monitor the treatment response.⁷⁾
Treatment with quinolones has been shown to have a high success rate, prompting the performance of much work with ciprofloxacin. Strong bone infiltration, effectiveness against pseudomonas, rapid accumulation in tissues via oral administration, and mild side effects make it an appealing long-term treatment. Unfortunately, resistance is becoming increasingly common.⁷⁾ Recent reports have suggested the use of multiple intravenous antibiotics, including carbapenem as well as oral ciprofloxacin. Carbapenem provides enhanced anaerobic and Gram-negative coverage and has been shown to function synergistically with ciprofloxacin.¹⁴⁾ At least four to eight weeks of antibiotics are recommended.¹⁾ The role of surgery is confined to biopsy and possible drainage in the presence of an associated abscess.²⁾ However, in case 1, we performed an operation to remove remnant mastoid air cells, the vestibule and a cochlear bony lesion because previous long term (six week) third generation cephalosporin (ceftazidime) antibiotic therapy was not effective. Hyperbaric oxygen therapy may play a role in the management of chronic, refractory osteomyelitis of the skull base. The relief of hypoxia in infected tissue and bone allows for leukocyte-induced oxidative death of aerobic bacteria such as pasudomonas aeruginosa.¹⁴⁾ Skull base osteomyelitis (SBO) is an uncommon but severe condition generally secondary to malignant otitis externa that is associated with high morbidity and mortality. The disease typically begins with characteristic symptoms of throbbing otalgia, otorrhea, and the sensation of an ear blockage. It eventually spreads to the skull base via the fissures of Santorini and the tympanomastoid suture. SBO occurs most commonly in elderly diabetics and immunocompromised individuals. Confirmation can be made using MRI or a gallium scan. We reported two cases of SBO with symptoms of atypical headache and otorrhea after mastoidectomy, emphasizing the importance of clinical suspicion in diagnosis.

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