Cranial nerve palsy prevalence and associated factors in patients with malignant otitis externa

Abstract

Objective: To identify the prevalence of cranial nerve (CN) palsy and its associated factors in malignant otitis externa (MOE).

Methods: In a retrospective study, records of MOE patients from 2011 to 2014 were reviewed. MOE and CN involvement were evaluated based on patient demographics, clinical, and paraclinical data.

Results: Overall, 119 MOE patients with a mean age of 65.9 ± 11.3 were included. 69.7% were male, and 63.0% had a history of diabetes. The most common symptoms and signs were otalgia (97.5%), otorrhea (44.5%), and ear canal erythema/edema (24.4%). Thirty-three patients (27.7%) had CN involvement. The facial nerve was mostly involved (26.1%). Skull base osteomyelitis (SBO) was present in 59 patients. When excluding patients younger than 30 and older than 80, age decade was correlated with CN palsy. 66.9% of patients with CN palsy and 65.6% without CN palsy were male, which was significantly different. The following factors were not significantly different between patients with and without CN palsy: Comorbidities, signs and symptoms, diagnostic delay, erythrocyte sedimentation rate level, fasting blood sugar, hemoglobin A1c level, antifungal therapy, hospitalization duration, and SBO on imaging. Tinnitus was correlated with SBO evidence on imaging (specificity: 96.7%).

Conclusion: CN involvement occurs in about three out of 10 MOE patients. Male gender and advanced age may be related to a higher incidence rate of CN palsy. Tinnitus can be a specific indicator of SBO. These findings could help in better decision-making for early interventions.

Level of evidence: 4.

Keywords: cranial nerve palsy; malignant otitis externa; necrotizing otitis externa; skull base osteomyelitis.

FIGURE 1

In the left plot, there is no correlation between age cohorts and cranial nerve (CN) palsy prevalence (p: 0.53); On the right, the plot demonstrates that when age cohorts 1 (20–29 years old cases), 7 (80–90 years old cases), and 8 (90–100 years old case) were excluded from the analysis there is a strong positive correlation between advanced age and CN palsy prevalence among 30–80 years old MOE patients (p ≤ 0.01, r: 0.98).

FIGURE 2

Cranial nerve (CN) involvement based on patients' gender. In patients with cranial nerve involvement, the M/F ratio was 30/3; in those without cranial nerve involvement, this ratio was 53/33 which was significantly different, indicating that the male gender can be related to a higher incidence rate of cranial nerve palsy (p ≤ 0.01).

FIGURE 3

Comparison of skull base osteomyelitis (SBO) prevalence between patients with and without cranial nerve (CN) involvement. SBO was present in 19 out of 33 patients with cranial nerve palsy and 40 out of 86 patients without cranial nerve palsy (p: 0.31).