The inflammatory pseudotumor presenting periodic acid-Schiff-positive inclusions with acute unilateral facial nerve palsy.

Although most acute peripheral facial palsies can be attributed to Bell's palsy, other factors, such as infection, trauma, and neoplasm, can cause facial palsy as well. Among these, facial nerve tumors are rare but should be considered in the differential diagnosis of facial palsy. Palsies due to facial nerve tumors usually present with slow onset but occasionally present as acute episodes. In such cases, facial nerve decompression is the treatment of choice to allow the tumor room to grow without compressing the nerve or its blood supply. We describe a case of severe, acute facial palsy presenting with a spindle-shaped bone erosion on the mastoid portion of the facial canal. Although facial neuroma was suspected preoperatively, emergency decompression surgery revealed that an unusual inflammatory pseudotumor was responsible for the finding. Postoperative histological analysis revealed extensive destruction of the nerve fibers, with extensive infiltration of foamy macrophages containing characteristic, diastase-resistant, periodic acid-Schiff (PAS)-positive inclusions, which are hallmark of the uncommon bacterial infections. This was a case of facial palsy with an unusual etiology. The case shows the benefit of decompression surgery not only as treatment for the palsy but also as exploratory surgery in cases of facial nerve tumor.