Masako Masuda

Preliminary experience with β-tricalcium phosphate for use in mastoid cavity obliteration after mastoidectomy

Objective: To examine the efficacy and safety of mastoid cavity obliteration using highly purified β-tricalcium phosphate (β-TCP) after mastoidectomy in middle ear surgery. Patients: Thirteen patients with cholesteatoma invading the mastoid cavity or showing severe pathologic changes in the mastoid cavity. Intervention: Twelve patients underwent mastoid obliteration with highly purified β-TCP during the first- and/or second-stage operation of a 2-stage canal-up operation: 5 patients during the first and second stages, and 7 patients during the second stage only. One patient with cholesteatoma underwent mastoid obliteration with highly purified β-TCP during a 1-stage canal-up operation. In total, β-TCP was applied in 18 ear operations. Main Outcome Measures: All patients underwent multislice computed tomography (CT) before and after surgery to assess the condition of the middle ear. The amount of residual β-TCP granules in the mastoid cavity was assessed using the following granular shadow grading scale: Grade 0, no granular shadow in the mastoid cavity; Grade 1, residual granular shadows in part of the mastoid cavity; and Grade 2, granular shadows in most of the mastoid cavity. To assess any harmful effect of β-TCP implanted in the mastoid cavity, continuous postoperative discharge and delayed wound healing were recorded. In addition, the bone conduction threshold was assessed using pure-tone audiometry, and the patients were asked whether they experienced vertigo or dizziness during the postoperative follow-up. Results: All the patients who underwent multislice CT less than 11.4 months after mastoid cavity obliteration with β-TCP were Grade 2 on the granular shadow grading scale, whereas all those who underwent multislice CT more than 53.8 months after mastoid obliteration were Grade 0. No patient had continuous postoperative discharge, delayed wound healing, or extrusion of β-TCP granules. No patient showed deterioration of the bone conduction threshold more than 10 dB after mastoid cavity obliteration with highly purified β-TCP or complained of postoperative vertigo or dizziness. Conclusion: Highly purified β-TCP may be safe and reliable for mastoid obliteration. Highly purified β-TCP may also be useful in other surgical procedures, including posterior wall reconstruction of the external auditory canal and scutum plasty.

Unique T cell proliferation associated with PKCμ activation and impaired ZAP-70 phosphorylation in recognition of overexpressed HLA/partially agonistic peptide complexes

Altered peptide ligands (APL) induce T cell responses different from those induced by the original agonistic peptide. As shown for CD4+ T cells, partial agonists induce partial T cellactivation without proliferation because of lower affinities and higher off rates to TCR than those of agonists. To determine whether overexpression of partially agonistic TCR ligands on antigen‐presenting cells provides high‐avidity TCR ligands, we generated L cell transfectants expressing various numbers of HLA‐DR4 covalently linked with APL derived from a streptococcal peptide and observed responses of the cognate T cells. Some overexpressed HLA‐DR4/partially agonistic APL complexes induced T cell proliferation in a density‐dependent manner. However, tyrosine phosphorylation of zeta‐associated protein‐70 (ZAP‐70) and linker for activation of T cells and kinase activity of ZAP‐70 were not detectable. T cell proliferation stimulated with L cell transfectants was sensitive to thePKC inhibitor Gö6976, but to a lesser extent to Gö6983, suggesting the involvement of μ isotype of PKC (PKCμ). In vitro kinase assays revealed that PKCμ activity was up‐regulated only in T cells stimulated with L cell transfectants that induced T cell proliferation. Our data suggest the presence of a unique signaling pathway coupling TCR ligation with T cell proliferation associated with PKCμ activation and impaired ZAP‐70 activation.

A postmeningitic cochlear implant patient who was postoperatively diagnosed as having X-linked agammaglobulinemia

X-linked agammaglobulinemia (XLA) is caused by a mutation in the Bruton tyrosine kinase, leading to an arrest in B cell development. Consequently, patients with XLA show significant decreases in gammaglobulin. Here, we describe a child with postmeningitic deafness and XLA who underwent a cochlear implantation. His psychomotor development had been normal and his congenital immunodeficiency was noticed only postoperatively. Immunoglobulin replacement treatment was started, but he still suffered repeated infections. Eventually, his cochlear implant was removed. A preoperative check of immunological status might be advisable in postmeningitic patients undergoing cochlear implantation to reduce the risk of postoperative infectious complications.