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1
Department of Radiology, Hospital General Universitario de Alicante, C. Pintor Baeza s.n., Alicante 03010, Spain.
2
Department of Pediatric Radiology, Hospital Universitario La Fe, Avda.
Campanar, 21, Valencia 46009, Spain.
Received November 23, 1998;
accepted after revision June 16, 1999.
Address correspondence to F.
Fernández-Latorre.
Abstract
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MATERIALS AND METHODS. We retrospectively studied 14 patients with Langerhans' cell histiocytosis affecting the temporal bone. All patients were examined initially and sequentially with CT. In six patients, MR imaging was also done.
RESULTS. Temporal bone involvement was the initial form of presentation in 12 patients. In eight patients, temporal bone involvement presented as an isolated manifestation, and in four it was associated with multisystemic involvement. In the remaining two patients, temporal bone involvement appeared during the course of the Langerhans' cell histiocytosis. Bilateral involvement was seen in four patients. In two patients, the temporal bone was affected only at the petrous apex. CT showed destruction of bone in all 14 patients and an associated soft-tissue homogeneous mass after injection of IV contrast material in 12 patients. CT showed a heterogeneous appearance of the soft-tissue mass in two patients. The average period of follow-up was 5 years. In seven of the 14 patients, the disease had a satisfactory evolution in which the bony lesions of the temporal bone reossified and remodeled over the course of a year.
CONCLUSION. In Langerhans' cell histiocytosis, involvement of the temporal bone is usually seen on radiographs as extensive lytic lesions associated with soft-tissue masses. The lesions that remit show early disappearance of the soft-tissue mass, followed by reossification and remodeling of the involved bone. Patients with limited initial involvement of the temporal bone have a better prognosis on long-term follow-up than do patients with the multisystemic form.
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In this article we present the initial clinical and radiologic findings and follow-up of 14 pediatric patients with the temporal bone affected by Langerhans' cell histiocytosis.
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All patients included in this study initially underwent CT of the temporal bone before and after administration of IV contrast material. On the unenhanced studies, 1-mm-thick axial sections were obtained with a bone algorithm; on the contrast-enhanced studies, 2.5-mm-thick axial sections were obtained using algorithms for bone and soft tissues. Follow-up CT studies were performed at 3, 6, and 12 months. Subsequent radiologic follow-up varied depending on the clinical course of the condition. Initial and follow-up MR imaging were performed using a 1.5-T unit only on the two patients with involvement limited to the petrous apex. In another four patients, MR imaging was done at follow-up (on three patients with a 1.5-T unit and on one with a 0.5-T unit) to assess the central nervous system, especially the hypothalamic-hypophyseal axis. The behavior of the temporal lesions could not be evaluated in these four patients because the lesions were not present when the MR study was performed. Images were obtained in the transverse plane with a long TR double-echo spin-echo sequence (TR range/TE range, 2200-3000/13-100) and in the coronal plane with a short TR spin-echo sequence (TR/TE, 600/20) before and after gadolinium administration. Average length of follow-up was 5 years (range, 2-14 years).
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Eleven patients (78.6%) had otologic symptoms; in six of these patients, this was the first clinical evidence of the disease. The clinical findings were otorrhea in eight patients, periauricular mass in six patients, and stenosis of the external auditory canal due to a polyp protruding into it and eczematous lesions in the external auditory canal in two patients. One patient died as a consequence of neurologic complications resulting from extensive involvement of the skull base. Of the two patients with disease limited to the petrous apex, one presented with diplopia and the other with diplopia and ophthalmoplegia.
In all patients, CT showed destruction of bone, which was bilateral and relatively symmetric in four patients (Figs. 1A, 1B 2, 3A, 3B). In 12 patients, the mastoid process was involved. Associated lesions in the squamous part of the temporal bone were seen in eight patients and in the middle ear in nine. Destruction of the auditory ossicles was seen in two patients, extension to the bony labyrinth (Fig. 1A), (Fig. 1B) in two, and lesions limited to the petrous apex (Figs. 4A, 4B, 4C, 4D, 4E) in two. All patients had an associated soft-tissue mass, which appeared homogeneous in 12 patients and heterogeneous in two after administration of contrast material. In three patients, extradural extension was seen adjacent to the temporal lobe. In the two patients with involvement of the petrous apex, MR imaging showed with more precision than did CT both the extent of the lesion and its relationship to adjacent structures such as the temporal lobe and cerebellopontine angle. In both of these patients, the soft-tissue mass was hyperintense on T2-weighted images with no evidence of peripheral edema and relatively isointense to hypointense on T1-weighted images, showing marked enhancement after administration of contrast material (Figs. 4A, 4B, 4C, 4D, 4E).
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The therapeutic approach combined surgery with radiotherapy in the earliest cases, but more recently patients have been treated with local or systemic corticosteroids combined with radiotherapy. Two patients were treated percutaneously under sonographic guidance with a single injection of 40 mg of triamcinolone on each mastoid.
After a mean follow-up period of 5 years, five of eight patients with involvement limited to the temporal bone had no recurrence and remained free of symptoms with no signs of this illness; however, in one patient with involvement of the petrous apex, a small mass was still visible on follow-up MR imaging. In the other four patients, regression of the soft-tissue mass occurred during the first 3 months after treatment and the process of reossification occurred about a year later. In contrast, five of the six patients with multisystemic involvement at the time of presentation had recurrences, mainly in the skull and other bones, and the disorder is still present in four patients. All four of these patients developed diabetes insipidus. In all patients with recurrences, the bony lesions were more extensive on recurrence than initially, affecting the sphenoid bone, especially its greater wings. In two of the four patients who developed diabetes insipidus, MR imaging showed an absence of normal bright signal of the neurohypophysis, with thickening and enhancement of the pituitary stalk seen on T1-weighted images.
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of the disease. The etiology and pathogenesis are still unknown. Most studies suggest that it is a reactive disease caused by abnormal immune regulation [2].
Involvement of the temporal bone has been described in 15-61% of all cases of Langerhans' cell histiocytosis [4, 5, 6]. In our series, temporal bone involvement was present in 14 (22.6%) of 62 patients, and involvement was bilateral in four (28.6%) of 14 patients, similar to rates in other studies [4, 5, 6]. Most authors agree that otologic involvement usually occurs during the course of multisystemic disease, although it may be the only symptom present in 5-25% of patients [4, 5, 6, 7]. In our series, eight (12.9%) of the 62 children with Langerhans' cell histiocytosis had only otologic manifestation at the onset of the disorder. Nevertheless, patients with disease limited to the temporal bone should have a full examination to exclude the possibility of multisystemic changes [8].
The most frequent otologic symptom is otorrhea that is resistant to medical treatment. Other findings are mastoid swelling, aural polyps, and periauricular eczema. Erosion of the posterior bony external auditory canal with sagging of the canal wall skin is frequently seen [4, 6, 8].
Because the otologic findings are similar to those of otomastoiditis, diagnosis is often delayed [1, 8]. Therefore, chronic otitis media or cholesteatoma should be diagnosed only after careful consideration in children younger than 3 years, especially when the erythrocyte sedimentation rate is elevated. In these patients, Langerhans' cell histiocytosis should be considered, especially when major radiologic changes are seen that are out of proportion with mild clinical findings [8]. Conductive deafness caused by infiltrative changes in the middle ear, involvement of the auditory ossicle chain, and obstruction of the external auditory canal have been described [4, 9].
Neurosensorial deafness and vertigo resulting from involvement of the bony labyrinth rarely occur. Paralysis of the cranial nerves is also unusual, although paralysis of the seventh and eighth cranial nerves have been described [4]. Involvement of several cranial nerves suggests extension of the disorder to the base of the skull or to the central nervous system [4]. However, because this rarely occurs in Langerhans' cell histiocytosis, other diagnoses, especially rhabdomyosarcoma and metastasis, should be considered in such patients. In our series, only the two patients with involvement of the petrous apex alone had paralysis of cranial nerves.
Usually CT studies show extensive destruction of the temporal bone involving the mastoid, with the squamous part and the middle ear being less affected [1, 9]. The lesions have indistinct margins, and the smaller structures of the bony labyrinth and auditory ossicle chain may show erosion (Fig. 1A), (Fig. 1B). However, involvement of the auditory ossicles and the internal ear is not as frequent as might be expected from the extensive bony damage usually seen [1, 9]. In our series, only two patients had destruction of the auditory ossicle chain, and another two had involvement of the bony labyrinth. In all our patients, CT showed associated enhanced soft-tissue masses that occasionally had extradural extension. On MR imaging, these masses showed a strong signal intensity on T2-weighted imaging and variable signal intensity (low to high) on T1-weighted imaging, often with edema or inflammation around the lesion [5, 10] and with marked enhancement after administration of gadolinium (Fig. 4A), (Fig. 4B), (Fig. 4C), (Fig. 4D), (Fig. 4E). In the two patients studied with MR imaging in our series, the mass showed a low signal intensity on T1-weighted imaging and a strong signal on T2-weighted imaging, with no edema and with marked homogeneous enhancement after administration of contrast material.
The radiologic differential diagnosis includes mastoiditis, rhabdomyosarcoma, and metastasis [1, 5]. Extensive destruction of bone and large soft-tissue masses is not usually seen in mastoiditis, but the other three conditions may have similar clinical and radiologic findings. However, the clinical presentation and radiologic findings can be diagnostic of Langerhans' cell histiocytosis, especially when bilateral involvement is present. A definite diagnosis is established at biopsy.
To our knowledge, only one case of Langerhans' cell histiocytosis limited to the apex of the petrous bone has previously been described in the literature [4]. In our two patients with involvement of the apex of the petrous bone, CT delimited bony destruction of the petrous apex better than MR imaging did; however, MR imaging, because of its multiplanar capacity and higher contrast resolution, provided a clearer delineation of the extension of the soft-tissue mass and its relation to adjacent structures [5].
Classically, local treatment of Langerhans' cell histiocytosis of the temporal bone included mastoidectomy and radiotherapy, although the current tendency is to use local injection of steroids. Treatment of the multisystemic form includes chemotherapy, steroid injections, and immunotherapy [11].
The clinical course of Langerhans' cell histiocytosis is unpredictable. There is no generally accepted prognostic factor, and no completely satisfactory clinical classification has yet been established [3]. However, five of our six patients with associated lesions in other organs had recurrences, with a strikingly high frequency of involvement of the hypothalamic-hypophyseal axis leading to diabetes insipidus.
After an average follow-up period of 5 years, seven (50%) of our 14 patients are free of disease. One patient died as a consequence of neurologic complications resulting from extensive involvement of the base of the skull, and the remaining six patients have partial remissions and are still being treated. Both patients with disease limited to the petrous apex had a striking absence of lesions in other organs and a favorable clinical course.
In conclusion, we reviewed a series of 14 patients with Langerhans' cell histiocytosis involving the temporal bone, including two patients with involvement limited to the petrous apex, which is an unusual form of presentation. Langerhans' cell histiocytosis of the temporal bone usually appears as extensive bony destruction associated with a soft-tissue mass of variable size that usually enhances uniformly after administration of IV contrast material. Langerhans' cell histiocytosis affecting only the temporal bone may recur, but prognosis on long-term follow-up is good, and the lesions tend to reossify and remodel. In the multisystemic form of the disease, recurrences are more frequent.
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