[Histiocytosis X of the petrous pyramid in adults. X-ray computed tomographic and MRI aspects]

Two cases are reported of histiocytosis X in young adults, both confined to the petrous bone. In one case the clinical signs were those of a progressive facial palsy, developing over 3 years; the other case had pulsatile tinnitus with clear otorrhoea and symptoms of vestibular deficiency. Computed tomography showed extensive bone destruction by a soft-tissue density process which enhanced strongly after iodinated contrast injection. Magnetic resonance imaging (T1 weighted sequences before and after intravenous gadolinium injection) confirmed the presence of a mass lesion in the petrous bone with contrast medium uptake which showed cystic areas within it: it also showed the absence of extension through the dura mater by the intracranial component which remained extradural. It confirmed the patency of arteries and veins, so enabling a differentiation to be made between histiocytosis X and advanced glomus tumours.