Skull base osteomyelitis (SBO) is a rare condition most typically associated with malignant otitis externa in adults (otogenic) with underlying diabetes mellitus or some form of immunosuppression.1 Less frequently, cases of nonotogenic SBO have also been described2 where there is no concurrent otitis and in which infection may arise from the paranasal sinuses, the retropharynx, hematogenous spread or represent a recrudescence of partially treated malignant otitis externa.2 Both conditions are rare in childhood with only 6 cases of nonotogenic SBO previously described and most of these in children without comorbidities. We describe a further 2 cases of nonotogenic SBO in immunocompetent and previously healthy children, both of who had a good outcome with conservative medical management. These cases add to the current literature and emphasize the importance of detailed imaging and interpretation from experienced radiologists to ensure early diagnosis and facilitate prompt investigation and treatment.
An 11-year-old girl presented to our emergency department with a 7-day history of fever and a 4-day history of generalized neck pain exacerbated by movement. Other symptoms included right-sided otalgia and intermittent headache. There was no history of foreign travel and no relevant past medical history. Physical examination including neurological assessment was unremarkable apart from pain on lateral flexion and extension of the neck. She was afebrile with normal observations, and the blood tests showed raised C-reactive protein (CRP > 156 mg/L) and mild neutrophilia (7.8 × 109/L). A lumbar puncture performed at admission was normal with 2 white blood cells/μL (all lymphocytes), normal protein and glucose. Intravenous broad-spectrum antibiotics (ceftriaxone) were started and on the next day fibronasoendoscopy, ultrasound of the neck, and magnetic resonance imaging (MRI) of the cervical spine were undertaken all of which were reported as normal. Over the following 24 hours, her symptoms progressed with further restriction of neck movement resulting in computed tomography (CT) of the head and neck which demonstrated no abnormalities. A blood culture taken before starting antibiotics grew a fully sensitive Streptococcus intermedius (Streptotoccus milleri group), and oral clindamycin was added. On day 4, ongoing symptoms prompted re-review of the original MRI on which a skull base lesion was then suggested (see Fig., Supplemental Digital Content 1, http://links.lww.com/INF/C179). Subsequently, the patient underwent whole-body bone scan in addition to SPECT/CT of the skull base to C4. This showed abnormally increased tracer uptake within the clivus, centered on the growth plate, consistent with osteomyelitis of the clivus and a small subperiostal abscess (see Fig., Supplemental Digital Content 1, http://links.lww.com/INF/C179). Marked clinical improvement in pain and neck mobility was noted from day 5 and subsequently she was able to receive ambulatory care. A 6-week course of IV ceftriaxone and oral clindamycin followed by 6 weeks of oral co-amoxiclav resulted in complete resolution of the symptoms and an MRI performed almost 3 months after disease onset showed substantial improvement in marrow signal of the clivus with no features of edema and a reduction in volume of the subperiostal abscess. There has been no recurrence over a follow-up period of 1.5 years.
An 11-year-old boy of Asian origin with no relevant past medical history and no history of foreign travel presented to our emergency department with a 3-week history of fever, neck pain, neck stiffness and headache together with a dry cough for 1 week. The neck pain was exacerbated by movement. On examination, he was febrile (38.4°C) and had a limited range of movement of his neck in all directions due to pain but physical examination including detailed neurological assessment was otherwise unremarkable. The blood test results showed a CRP of 52 mg/L, mild neutrophilia (10.0 × 109/L) and normal chest X-ray. He was started on intravenous ceftriaxone while further radiological investigations were arranged. An initial MRI had to be abandoned due to distress of the patient and a further attempt on day 2 showed a lesion in the clivus. For further characterization, a gadolinium-enhanced MRI in conjunction with a CT was performed on day 3 demonstrating a lesion extending anteriorly from the clivus into the preclival soft tissue (see Fig., Supplemental Digital Content 2, http://links.lww.com/INF/C180). This was of high signal on T2w and STIR imaging, low signal on T1w imaging and demonstrated peripheral contrast enhancement with central diffusion restriction consistent with hyper-cellular content (see Fig., Supplemental Digital Content 2, http://links.lww.com/INF/C180). Imaging appearances were consistent with an abscess. The CT highlighted focal erosion of the cortex of the clivus anteriorly (see Fig., Supplemental Digital Content 2, http://links.lww.com/INF/C180). It was felt that neurosurgical intervention was not necessary at this stage and so the patient was treated conservatively with intravenous antibiotics for 6 weeks followed by 6 weeks of oral clindamycin. The blood culture taken before starting antibiotics remained negative. An MRI scan after 4 weeks of treatment showed improvement of the abscess but not full resolution. On completion of antibiotic treatment, the patient was asymptomatic. There has been no recurrence over a follow-up period of 1 year.
As part of the initial work-up, the patient underwent screening for tuberculosis (TB) and showed positive results for both the tuberculin skin test and an interferon-gamma release assay consistent with previous exposure to Mycobacterium tuberculosis. Given the clinical improvement on conventional antibiotics TB disease as a cause of the SBO was considered unlikely and chemoprophylaxis to treat TB infection was given after completion of treatment for SBO.
SBO has the potential to cause major sequelae through the proximity within the neck of important vascular and neurological structures. It is a rare diagnosis in childhood and therefore may not be considered early on in the context of the more common presenting features of neck pain and fever. Prior to the cases in this report, there are 6 previous reported cases of nonotogenic SBO3–8 which are summarized in Table 1. Based on the published cases along with our cases it appears that the most consistent clinical features associated with this pathology are fever, neck pain and stiffness and occasionally cranial nerve palsy. These clinical signs and symptoms are nonspecific and may also been seen in other pathologies affecting ear, neck and throat areas, such as retropharyngeal abscess,9,10 Lemierre’s syndrome11 or meningitis.12
Because of the nonspecific nature of clinical signs with SBO a high index of suspicion should be maintained for patients with a combination of fever, headache, neck pain or torticollis with or without cranial nerve palsy and in whom no obvious focus can be established. It is quite possible that due to the nonspecific signs and symptoms, highlighted by the 2 cases described in this report, nonotogenic SBO may be more frequent than previously reported in the literature. Imaging modalities that have a role in the investigation of suspected SBO include MRI, CT and bone scan with or without SPECT/CT. MRI has the highest sensitivity and specificity for the diagnosis of osteomyelitis and it has better soft tissue discrimination than CT.13 MRI is safe as there is no radiation risk but the prolonged imaging time compared with CT means that some children require general anesthesia before it can be carried out. This was necessary for case 2, and led to a delay in image acquisition and establishing of the diagnosis. Changes seen on MRI and CT can be subtle as demonstrated by our first case, where both MRI and CT were initially reported as normal. When this is the case but there is high clinical suspicion of SBO, a SPECT/CT could prove useful, which may also help to further improve exact anatomical localization.14,15
In some patients, management may involve surgery to drain collections if identified and to obtain a microbiological diagnosis although the need for surgical intervention needs to be discussed on a patient-by-patient basis. Five out of 6 of the cases previously described underwent surgery in the setting of progressive neurological signs. In our cases, there was no neurological involvement and marked improvement of symptoms occurred within a small number of days with conservative therapy only. A wide variety of Gram-positive and Gram-negative bacteria have been isolated previously for nonotogenic disease in adults and children with Pseudomonas sp. dominating published adult cases2 whereas in children the microbiology seems to be more variable (Table 1). In cases in which SBO is suspected, it may therefore be prudent to use antibiotic agents with good bone penetration, which cover both Gram-negative and Gram-positive bacteria.
Classically, SBO has been described as a complication of otitis externa, which seems to be more common in older diabetic patients, usually caused by Pseudomonas aeruginosa.2 Less commonly, SBO can be nonotogenic, often affecting the sphenoid and occipital bones, especially the clivus2 and in some cases it may represent a complication of sinusitis.16 Some organisms associated with nonotogenic SBO form part of the normal oral flora and it seems therefore possible that nonotogenic SBO is the result of first sinus disease, which then spreads continuously to the base of the skull. However, only case 2 described in this report showed radiological signs consistent with maxillary sinusitis and opacification of the ethmoid cells whereas paranasal sinuses were patent in case 1 suggesting a different route of infection in this patient.
There are no definitive guidelines for the treatment of SBO in children, given its rarity and a consequent lack of clinical studies. Both of our cases were treated with intravenous antibiotics for 6 weeks, followed by 6 weeks of oral antibiotics. Both cases responded well to medical management negating the need for surgical treatment. Previous cases reported in the literature vary so greatly in terms of presentation, severity and etiology that it is hard to draw any conclusions from them regarding the best mode and duration of treatment other than that the clinician should be guided by the individual patient.
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