Comparison of MR imaging findings in paediatric and adult patients with acute mastoiditis and incidental intramastoid bright signal on T2-weighted images.

OBJECTIVES: To compare MR imaging features in patients with incidental mastoid T2-hyperintensity with those of clinical acute mastoiditis, to ascertain characteristic differences between them. METHODS: MR images of 35 adult and paediatric patients with clinical acute mastoiditis and 34 consecutive age-matched controls without relevant middle ear pathology and with incidental T2-hyperintensity that covered ≥ 50 % of the mastoid were retrospectively analysed with regard to signal, diffusion, and enhancement characteristics, and presence of complications. RESULTS: Incidental mastoid T2-hyperintensity that covered ≥ 50 % of the mastoid volume was found in 4.6 % of reviewed MR scans (n = 2341), and associated significantly (p < 0.05) less with the involvement of the tympanic cavity (38 % vs. 74 %) and mastoid antrum (56 % vs. 80 %), hypointense-to-CSF signal intensity on T2 FSE (6 % vs. 86 %), intramastoid diffusion restriction (0 % vs. 62 %), intense intramastoid enhancement (0 % vs. 51 %), periosteal enhancement (3 % vs. 69 %), perimastoid dural enhancement 3 % vs. 43 %), bone destruction (0 % vs 49 %), intratemporal abscess or cholesteatoma (0 % vs. 24 %), labyrinth involvement (0 % vs. 14 %), and extracranial abscesses (0 % vs. 20 %). CONCLUSION: Hypointense-to-CSF signal intensity on T2WI, restricted diffusion, intense intramastoid enhancement among other MR imaging characteristics favoured an acute mastoiditis diagnosis over clinically non-relevant incidental mastoid pathology. KEY POINTS: • Intramastoid T2-hyperintensity alone is not a reliable sign for acute mastoiditis. • In acute mastoiditis, intramastoid T2-weighted signal intensity is usually hypointense to CSF. • Diffusion restriction and intense intramastoid enhancement are absent in incidental mastoid effusion. • An ADC value ≥ 1.72 × 10 (-3) mm (2) /s contradicts the AM diagnosis.

Hearing and tinnitus in head and neck cancer patients after chemoradiotherapy.

Head and neck cancer patients treated with high-dose cisplatin and radiotherapy will suffer from hearing deficits. The current low-dose regimen seldom causes hearing threshold decrease. Tinnitus in this patient population has not been investigated earlier. We aimed to evaluate the possible ototoxicity of low-dose (40 mg/m(2)) weekly administered cisplatin with concomitant radiotherapy. Twenty-two patients with locally advanced head and neck cancer were prospectively recruited to participate the study after treatment recommendation for chemoradiotherapy with low-dose cisplatin and intensity-modulated radiotherapy. They filled in a Tinnitus Handicap Inventory and undertook audiologic evaluations before and after treatment. Ototoxicity was determined by >10 dB threshold shift at frequencies 4 and 8 kHz or in pure tone average. A historical cohort of nine patients treated with high-dose (100 mg/m(2)) cisplatin and radiotherapy was used for comparison. After treatment, study patients demonstrated no significant changes in their hearing over frequencies 0.5-4 kHz, and the threshold shifts were minor at 4 and 8 kHz. More than 50 % of patients reported no tinnitus after treatment and the remainder only had slight to moderate tinnitus causing no interference with their daily activities. In contrast, five of the nine patients having received high-dose cisplatin reported disturbing tinnitus. Further, changes in pure tone averages were exhibited in three of these patients and six had significant threshold shifts at 4 and 8 kHz. Head and neck cancer patients treated with concomitant intensity-modulated radiotherapy and low-dose cisplatin seem to experience only minor audiological sequelae and therefore, these patients appear to require no routine audiological monitoring. Such evaluation could be performed only when needed.

Anti-clarin-1 AAV-delivered ribozyme induced apoptosis in the mouse cochlea.

Usher syndrome type 3 is caused by mutations in the USH3A gene, which encodes the protein clarin-1. Clarin-1 is a member of the tetraspanin superfamily (TM4SF) of transmembrane proteins, expressed in the organ of Corti and spiral ganglion cells of the mouse ear. We have examined whether the AAV-mediated anti-clarin ribozyme delivery causes apoptotic cell death in vivo in the organ of Corti. We used an AAV-2 vector delivered hammerhead ribozyme, AAV-CBA-Rz, which specifically recognizes and cleaves wild type mouse clarin-1 mRNA. Cochleae of CD-1 mice were injected either with 1mul of the AAV-CBA-Rz, or control AAV vectors containing the green fluorescent protein (GFP) marker gene (AAV-CBA-GFP). Additional controls were performed with saline only. At one-week and one-month post-injection, the animals were sacrificed and the cochleae were studied by histology and fluorescence imaging. Mice injected with AAV-CBA-GFP displayed GFP reporter expression of varying fluorescence intensity throughout the length of the cochlea in the outer and inner hair cells and stria vascularis, and to a lesser extent, in vestibular epithelial cells. GFP expression was not detectable in the spiral ganglion. The pro-apoptotic effect of AAV-CBA-delivered anti-clarin-1 ribozymes was evaluated by TUNEL-staining. We observed in the AAV-CBA-Rz, AAV-CBA-GFP and saline control groups apoptotic nuclei in the outer and inner hair cells and in the stria vascularis one week after the microinjection. The vestibular epithelium was also observed to contain apoptotic cells. No TUNEL-positive spiral ganglion neurons were detected. After one-month post-injection, the AAV-CBA-Rz-injected group had significantly more apoptotic outer and inner hair cells and cells of the stria vascularis than the AAV-CBA-GFP group. In this study, we demonstrate that AAV-CBA mediated clarin-1 ribozyme may induce apoptosis of the cochlear hair cells and cells of the stria vascularis. Surprisingly, we did not observe apoptosis in spiral ganglion cells, which should also be susceptible to clarin-1 mRNA cleavage. This result may be due to the injection technique, the promoter used, or tropism of the AAV serotype 2 viral vector. These results suggest the role of apoptosis in the progression of USH3A hearing loss warrants further evaluation.

Efficacy of gene transfer through the round window membrane: an in vitro model.

The viral vector-transgene soaked gelatin-sponge method has been shown to be successful in mediating transgene expression across an intact round window membrane (RWM) in mouse in vivo. However, there are many confounding factors which make it difficult to evaluate the role of the RWM in gene transfer. We have created an in vitro model to test the feasibility of gene delivery through an intact RWM. The round window including the bony niche of a CD1 mouse was removed under an operating microscope and fixed with adhesive on the base of a petri dish through which a hole had been drilled. Toluidine blue was injected into the niche containing a hyaluronic acid ester sponge against the round window membrane. The niche was closed with a fascia. A plastic tube containing PBS was fixed on the opposite side, from where the samples were collected at different time points. The concentration of toluidine blue was evaluated spectrophotometrically. An adenoviral vector containing green fluorescent protein (GFP) marker gene was injected into the niche. Samples were collected from the opposite side at different time points. The presence of the vector was studied with GFP PCR. We also modulated the permeability of the RWM by treating it with clinically applicable detergents, histamine or silver nitrate. Silver nitrate and trichloracetic acid caused destruction of the surface epithelium of the RWM as shown by light microscopy. Both toluidine blue and adenoviral vectors passed through the RWM in a time-dependent fashion. RWM cells expressed GFP after Ad-GFP treatment. The permeability of the RWM was decreased after treatment with different detergents, histamine or silver nitrate. RWM offers an atraumatic route to the inner ear. Compared with more invasive gene delivery methods, this technique represents a safer and clinically more viable route of cochlear gene delivery.