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Neuroradiology Case of the Week

Case 124

Loris F. Cedeno, MD and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: A 14-month-old infant presented with a history of acute right-sided mastoiditis.

Radiological Findings: Axial images demonstrate a soft tissue mass with destruction of the inner and outer tables of the posterior mastoid portion of the temporal bone. There is also opacification of the mastoid air cells and epitympanum which is seen extending to the right ossicular chain. The malleus and incus are not eroded. There is no infiltration of the subcutaneous fat adjacent to the soft tissue mass (Figs. 1-4).

Discussion: Eosinophilic granulomas are predominantly seen in children and young adults. The age range of patients is between 2-30 years. The highest frequency occurs in patients aged 5-10 years, and 75% of patients with this disease are younger than 20 years. The skull is a common site of involvement. In the head and neck region, these lesions commonly involve the jaw or temporal bone. Although otologic involvement usually occurs during the course of multisystemic disease, it may be the only symptom present in 5-25% of patients. Temporal bone lesions can be bilateral in up to 30% of cases. The diploic space of the parietal and temporal bones are usually involved. A soft tissue mass overlying the skull defect may be obvious and, often, clinically palpable. These lesions may manifest with cutaneous ear involvement similar to otitis externa or with polyps extending into the external auditory canal. It is estimated that 15-61% of patients with Langerhans’ cell histiocytosis have otologic involvement. If the mastoid portion of the temporal bone is involved, the disease may mimic a postauricular abscess, phlegmon, or otomastoiditis. Cranial nerves VII and VIII may also be involved, with symptoms of hearing loss and vertigo.
     Radiographically, CT studies show extensive destruction of the temporal bone involving the mastoid, with the squamous part and middle ear being less affected. The lesions have indistinct margins, and the smaller structures of the bony labyrinth and auditory ossicular chain may show erosion. Moreover, involvement of these structures is not as frequent as might be expected in light of the extensive mastoid bony destruction. Post-contrast images show associated soft tissue mass enhancement. On MR, these masses are hyperintense on T2WI and variable signal intensity on T1WI. Edema and inflammation around the lesion can also be seen. Post-gadolinium images show marked enhancement of the soft tissue mass.
     The differential diagnosis should include cholesteatoma, mastoiditis, rhabdomyosarcoma and metastatic lesions, among others. Extensive destruction of bone and large soft-tissue masses are not usually seen in mastoiditis, but the other three conditions may have similar clinical and radiologic findings.
     Pathologically, eosinophilic granulomas are characterized by idiopathic proliferation of histiocytes. Definitive diagnosis of histiocytosis is made by histopathology including immunohistochemical detection of S-100 and CD1a antigens.

References:

1. Prayer D, Grois N, Prosch H, Gadner H, Barkovich AJ: MRI imaging presentation of intracranial disease associated with Langerhans cell histiocytosis. AJNR Am J Neuroradiol. 2004 May;25(5):880-891. [Medline]
2. Koch BL: Langerhans histiocytosis of temporal bone: role of magnetic resonance imaging. Top Magn Reson Imaging 2000Feb; 11(1):66-74. [Medline]
3. Goldsmith AJ, Myssiorek D, Valderrama E, Patel M: Unifocal Langerhans’ cell histiocytosis (eosinophilic granuloma) of the temporal bone. Arch Otolaryngol Head Neck Surg 1993 Jan;119:113-116. [Medline]
4. Hellmann M, Stein H, Ebmeyer J, Sudhoff H: Eosinophilic granuloma of the temporal bone. Laryngorhinootologie. 2003 Apr;82(4):258- 261. [Medline]
5. Fernández-Latorre F, Menor-Serrano F, Alonso-Charterina S, Arenas-Jiménez J: Langerhans’ cell histiocytosis of the temporal bone in pediatric patients imaging and follow-up. AJR Am J Roentgenol. 2000 Jan;174:217-221. [Medline]