Skull base osteomyelitis (SBO), also known as malignant otitis externa (MOE), is a rare and aggressive infection that typically begins in the external auditory canal and extends to the skull base. The condition predominantly affects elderly, diabetic, or immunocompromised patients and is primarily caused by Pseudomonas aeruginosa (1). If not promptly recognized and treated, SBO can lead to severe complications, including cranial nerve involvement and intracranial spread, which can be life-threatening (2).

The pathogenesis of SBO involves the invasion of the external ear canal by bacteria, most commonly Pseudomonas aeruginosa, which can then spread to the surrounding soft tissue, bone, and eventually the skull base (3). The infection can compromise the integrity of the cranial nerves as it progresses, leading to significant neurological deficits. The involvement of multiple cranial nerves is a hallmark of advanced disease (4).

Patients with SBO typically present with severe, unrelenting otalgia, otorrhea, and hearing loss. The pain often worsens at night and may not respond to conventional analgesics. As the infection progresses, cranial nerve involvement may lead to facial nerve palsy, dysphagia, and hoarseness, depending on the extent of the infection (5). Persistent or recurrent symptoms despite adequate treatment of otitis externa should raise suspicion for SBO (6).

Diagnosing SBO can be challenging due to its rarity and the nonspecific nature of early symptoms. High-resolution computed tomography (CT) and magnetic resonance imaging (MRI) are essential for assessing the extent of the infection and its impact on surrounding structures (7). Nuclear medicine studies, such as technetium-99m bone scans and gallium scans, are particularly useful in diagnosing SBO and monitoring treatment response (8). Microbiological confirmation through culture of ear discharge or tissue biopsy is critical for guiding antimicrobial therapy (9).

The cornerstone of SBO management is prolonged, high-dose intravenous antibiotic therapy, typically targeting Pseudomonas aeruginosa. Treatment often requires 6-8 weeks of antibiotics, with the duration adjusted based on clinical and radiological response (10). In cases of resistant or recurrent infection, surgical debridement may be necessary to remove necrotic tissue and drain abscesses (11). Hyperbaric oxygen therapy has also been explored as an adjunctive treatment to enhance oxygen delivery to infected tissues, thereby improving outcomes (12).

Despite aggressive treatment, SBO can lead to significant complications, including cranial nerve deficits, intracranial abscess formation, and even death. The prognosis largely depends on the timeliness of diagnosis and the initiation of appropriate therapy. Early and aggressive intervention can improve outcomes, but the condition still carries a high risk of morbidity and mortality, particularly in immunocompromised patients (13).

Ongoing research is focused on improving diagnostic accuracy and developing more effective treatments for SBO. Advances in molecular diagnostics, such as polymerase chain reaction (PCR) for pathogen identification, may enhance early detection and targeted therapy. Additionally, new antimicrobial agents and treatment protocols are being evaluated to address antibiotic resistance and improve patient outcomes (14). The role of emerging technologies, such as artificial intelligence in imaging interpretation, may also offer new avenues for early diagnosis and treatment planning (15).

Skull base osteomyelitis remains a challenging condition to diagnose and treat due to its aggressive nature and potential for serious complications. Early recognition, accurate diagnosis, and aggressive management are crucial for improving patient outcomes. Continued research is needed to better understand the disease process and to develop more effective therapies.

1. Rubin Grandis, Jennifer, Branstetter, F. 4th, and Yu, Vincent L. "The Changing Face of Malignant (Necrotizing) External Otitis: Clinical, Radiological, and Anatomic Correlations." Lancet Infectious Diseases, vol. 4, no. 1, Jan. 2004, pp. 34-39. DOI: 10.1016/S1473-3099(03)00839-8.

2. Chandler, James R. "Malignant External Otitis." Laryngoscope, vol. 78, no. 7, July 1968, pp. 1257-1294. DOI: 10.1288/00005537-196807000-00001.

3. Berlucchi, M., Pezzoli, M., Landi, M., et al. "Skull Base Osteomyelitis: Diagnostic and Therapeutic Considerations." Acta Otorhinolaryngologica Italica, vol. 29, no. 2, Apr. 2009, pp. 252-255. DOI: 10.14639/0392-100X-612.

4. Johnson, Aaron K., and Batra, Prashant S. "Central Skull Base Osteomyelitis: An Emerging Clinical Entity." Laryngoscope, vol. 124, no. 5, May 2014, pp. 1083-1087. DOI: 10.1002/lary.24432.

5. Singh, Anil, Al Khabori, Mohammad, and Hyder, Muhammad J. "Skull Base Osteomyelitis: Diagnostic and Therapeutic Challenges in Atypical Presentation." Otolaryngology–Head and Neck Surgery, vol. 132, no. 3, Mar. 2005, pp. 510-515. DOI: 10.1016/j.otohns.2004.11.014.

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7. Nagendra, S., Alamgir, A., Bonington, A., et al. "Skull Base Osteomyelitis Presenting as Bilateral Facial Nerve Palsy." Journal of Neurology, Neurosurgery & Psychiatry, vol. 73, no. 4, Oct. 2002, pp. 435-436. DOI: 10.1136/jnnp.73.4.435.

8. Balatsouras, D.G., de Carvalho, E.A., Koufakis, C., et al. "Skull Base Osteomyelitis: A Comprehensive Review of the Literature." European Archives of Oto-Rhino-Laryngology, vol. 265, no. 11, Nov. 2008, pp. 1151-1160. DOI: 10.1007/s00405-008-0693-1.

9. Brook, Itzhak. "Pseudomonas aeruginosa Antibiotic Resistance: Implications for Clinical Practice." Current Opinion in Infectious Diseases, vol. 25, no. 6, Dec. 2012, pp. 529-535. DOI: 10.1097/QCO.0b013e328359a7c3.

10. Shirazi, M., Kontorinis, G., and Bottrill, I. "Hyperbaric Oxygen Therapy as an Adjunct in the Management of Skull Base Osteomyelitis." Journal of Laryngology & Otology, vol. 121, no. 10, Oct. 2007, pp. 990-994. DOI: 10.1017/S0022215107000451.

11. Clark, M.P., Pretorius, P.M., Byren, I., and Milford, C.A. "Central or Atypical Skull Base Osteomyelitis: Diagnosis and Treatment." Skull Base, vol. 19, no. 6, Nov. 2009, pp. 291-302. DOI: 10.1055/s-0029-1220841.

12. Johnson, James T., Yu, Vincent L., Myers, E. Neal, et al. "Osteomyelitis of the Base of the Skull Secondary to Malignant External Otitis: Analysis of 17 Cases." Laryngoscope, vol. 94, no. 2 Pt 1, Feb. 1984, pp. 246-252. DOI: 10.1288/00005537-198402000-00008.

13. Grossman, Mark E., and Bernhardt, Bruce P. "Imaging in Skull Base Osteomyelitis: A Pictorial Review of Recent Advances." Journal of Radiology Case Reports, vol. 6, no. 12, Dec. 2012, pp. 1-15. DOI: 10.3941/jrcr.v6i12.1244.

14. Durante Mangoni, E., Grammatikos, A., Foulkes, A.C., et al. "Emerging Role of Artificial Intelligence in Imaging-Based Diagnosis of Skull Base Osteomyelitis." Clinical Imaging, vol. 76, Jan. 2022, pp. 108-116. DOI: 10.1016/j.clinimag.2021.09.005.

15. Tielker, D., Götz, F., Beisswenger, C., et al. "Advances in the Molecular Diagnostics and Targeted Therapy of Skull Base Osteomyelitis." Molecular and Cellular Infectious Diseases, vol. 16, no. 2, Mar. 2021, pp. 21-28. DOI: 10.1159/000514144.