Idiopathic Isolated Abscess in an Extraocular Muscle in a Child

An idiopathic muscle abscess is a rare condition that should be consideredin the differential diagnosis of painful limitations of eye movements anddouble vision in children.

We herein present the case of an idiopathic muscle abscess in an 11-year-oldgirl. Myositis was initially suspected, but the magnetic resonance imaging(MRI) scan showed typical signs of an abscess. Antibiotic therapy led to arapid and complete improvement of all symptoms. To our knowledge, this isthe first report of an idiopathic isolated abscess in an extraocular musclein a child.

An otherwise healthy 11-year-old girl was intially seen because of a4-week history of periorbital and upper eyelid edema (Figure 1A), pain during eye movements of the left eye, and doublevision. Visual acuity was 20/20 OD and 20/40 OS. A maximum of 9° of hypotropiawas found on the left side in upgaze and abduction. Binocular visual fieldwas shifted 10° below primary position. No signs of intraocular or extraocularinflammation were seen. Afferent and efferent pupil reactions were normal.Further examination disclosed a subjective desaturation of red color on theleft side. No proptosis could be found on results of exophthalmometry.

Ocular sonography (standardized echography, A- and B-scan) showed athickening of the left superior rectus. Orbital MRI scan showed an abscess(diameter, 8 mm) with central cavitation and a rim of contrast enhancementof about 3 mm surrounded by a diffuse swelling of the left superior rectusmuscle (Figure 2A and B).

The measured serological variables (including adenovirus, human herpesvirus6, herpes simplex virus, varicella-zoster virus, enterovirus, Borrelia burgdorferi, Epstein-Barr virus, measles virus, human immunodeficiencyvirus, syphilis, and cysticercosis) and cerebrospinal fluid variables (includingsediment, glucose and protein levels, and serological findings for B burgdorferi and Russian spring-summer encephalitis) were within referencerange.

Immediately after the first visit, high-dose intravenous antibiotictherapy was introduced (combination of amoxicillin sodium and potassium clavulanate,8.8 g/d for 10 days). No amelioration of symptoms could be observed after2 days, so metronidazole (1.35 g/d for 5 days) and ceftriaxone disodium (2g/d for 19 days) were added. This led to a rapid and complete improvementof all symptoms (visual acuity of 20/20 OU, free motility in all directionsin both eyes without double vision, and no inflammatory signs, including eyelidedema ([Figure 1 B]). An MRI controlscan, obtained 2 weeks after initiation of therapy, showed only a discreteresidual swelling of the affected muscle (Figure 2 C and D).

Main differential diagnoses in children are other inflammations andinfections (eg, diffuse orbital pseudotumor, orbital cellulitis),¹ structural lesions (eg, dermoid cyst),² vascular neoplastic lesions (eg, capillary hemangioma,lymphangioma),³ lymphoproliferative diseases(eg, lymphocytic granuloma),⁴ neurogenictumors (eg, neuroblastoma, plexiform neurofibroma),⁵ mesenchymaltumors (eg, rhabdomyosarcoma), and metastatic carcinoma.

Although the clinical features are frequently suggestive of myositis,they are nonspecific, and noninvasive investigations such as orbital ultrasonographyand MRI scans are required for precise anatomical tissue localization anddiagnosis.

The role of ocular muscle biopsy is probably limited to atypical cases,or those unresponsive to therapy, particularly to exclude neoplasia.

The authors have no relevant financial interest in this article.

Correspondence: Dr Flammer, University Eye Clinic, Mittlere Strasse91, PO Box, CH-4012 Basel, Switzerland (Josef.Flammer@uhbs.ch).Dr Haufschild may be contacted at THaufschild@uhbs.ch