Is there a role for [18F]-FMISO PET to guide dose adaptive radiotherapy in head and neck cancer? A review of the literature.

Purpose: Hypoxia is a major cause of radioresistance in head and neck cancer (HNC), resulting in treatment failure and disease recurrence. 18F-fluoromisonidazole [18F]FMISO PET has been proposed as a means of localising intratumoural hypoxia in HNC so that radiotherapy can be specifically escalated in hypoxic regions. This concept may not be deliverable in routine clinical practice, however, given that [18F]FMISO PET is costly, time consuming and difficult to access. The aim of this review was to summarise clinical studies involving [18F]FMISO PET to ascertain whether it can be used to guide radiotherapy treatment in HNC. Methods: A comprehensive literature search was conducted on PubMed and Web of Science databases. Studies investigating [18F]FMISO PET in newly diagnosed HNC patients were considered eligible for review. Results: We found the following important results from our literature review: 1)Studies have focussed on comparing [18F]FMISO PET to other hypoxia biomarkers, but currently there is no evidence of a strong correlation between [18F]FMISO and these biomarkers.2)The results of [18F]FMISO PET imaging are not necessarily repeatable, and the location of uptake may vary during treatment.3)Tumour recurrences do not always occur within the pretreatment hypoxic volume on [18F]FMISO PET.4)Dose modification studies using [18F]FMISO PET are in a pilot phase and so far, none have demonstrated the efficacy of radiotherapy dose painting according to [18F]FMISO uptake on PET. Conclusions: Our results suggest it is unlikely [18F]FMISO PET will be suitable for radiotherapy dose adaptation in HNC in a routine clinical setting. Part of the problem is that hypoxia is a dynamic phenomenon, and thus difficult to delineate on a single scan. Currently, it is anticipated that [18F]FMISO PET will remain useful within the research setting only.

The association of vascular loops within the internal auditory meatus or contacting the vestibulo-cochlear nerve with audio-vestibular symptoms. A systematic review and meta-analysis.

BACKGROUND: Intrameatal vascular loops (IVL) entering the internal auditory meatus (IAM) and neurovascular contact (NVC) with the vestibulo-cochlear nerve (CN VIII) have been proposed to have a relationship with audio-vestibular symptoms. PURPOSE: This systematic review and meta-analysis aimed to determine whether the presence of IVLs and CN VIII NVC on magnetic resonance imaging (MRI) is associated with tinnitus, sensorineural hearing loss (SNHL) or vertigo and any specific subtypes. DATA SOURCES: All studies comparing the presence of IVL or CN VIII NVC in ears with these audio-vestibular symptoms and controls were identified through MEDLINE, EMBASE, Web of Science Core Collection, Scopus and Cochrane Register of Controlled Trials databases. STUDY SELECTION: 16 studies and 3,455 ears (1526 symptomatic ears and 1929 control ears) were included. DATA ANALYSIS: Meta-analysis was performed using a bivariate random effects model. Pooled odds ratios (ORs) were calculated, and heterogeneity was evaluated with Cochran's Q test with statistical significance defined as p<0.05. DATA SYNTHESIS: There was no significant association between the presence of undefined tinnitus or SNHL and that of IVL (OR 0.90 95% CI 0.47, 1.70; OR 0.67, 95% CI 0.36, 1.25) or CN VIII NVC (OR 1.15, 95% CI 0.68, 1.95; OR 0.89, 95% CI 0.33, 2.40). However, the subgroup of sudden onset SNHL was associated with IVL (OR 1.34, 95% CI 1.04, 1.73) (p=0.02). There was no significant difference in the prevalence of IVL (OR 0.97, 95% CI 0.64, 1.48) or CN VIII NVC (OR 0.99, 95% CI 0.42, 2.32) between ears with undefined vertigo and control ears. However, there was an association between the presence of CN VIII NVC and the specific diagnosis of vestibular paroxysmia (OR 13.19, 95% CI 2.09, 83.16) (p=0.006). LIMITATIONS: Our meta-analysis is limited by selection bias, small number of eligible studies and moderate heterogeneity. CONCLUSIONS: IVL or CN VIII NVC on MRI are unrelated to symptoms of undefined tinnitus, SNHL and vertigo. However, CN VIII NVC is associated with vestibular paroxysmia whilst IVL is associated with sudden onset SNHL. ABBREVIATIONS: AICA = anterior inferior cerebellar artery, CI = confidence interval, CN = cranial nerve, CPA = cerebellopontine angle, IAM = internal auditory meatus, NVC = neurovascular contact, OR = odds ratio, SNHL = sensorineural hearing loss, SoSNHL = sudden onset sensorineural hearing loss.

MRI features to aid the identification of lateral temporal bone cephaloceles.

OBJECTIVES: To evaluate ancillary MRI features which may aid the identification of lateral temporal bone cephaloceles (LTBCs). METHODS: A retrospective cohort study analysed patients with MRI evidence of surgically confirmed spontaneous LTBCs as defined by intracranial contents traversing the tegmen tympani or mastoideum. Cases were identified from radiology and surgical databases. Two observers analysed three-dimensional T 2W temporal bone and whole brain imaging according to a priori criteria by consensus, with emphasis on the relationship of any adjacent cerebrospinal fluid (CSF) cleft to the defect. The contents, location, and clinical features of the LTBCs were recorded. RESULTS: Eighteen patients (11 female, 7 male; mean age 59.3 years, age range 42-86 years) with 20 surgically confirmed spontaneous LTBCs (2 bilateral;16 unilateral) were evaluated. A temporal lobe sulcus or other CSF cleft extending to or traversing the defect was identified in 19/20 (95%) cases. Isointense CSF tympanomastoid signal was present in 41.2% cases, whilst superior semi-circular canal dehiscence was found in 40% of cephaloceles. At least two MRI features of idiopathic intracranial hypertension were seen in 38.9% patients. Cephaloceles were most commonly centred on the tegmen tympani (55%). Meningoencephaloceles were present in 95% cases. CONCLUSION: A temporal lobe sulcus or CSF cleft extending to or traversing the defect may aid the identification of LTBCs. Isointense CSF tympanomastoid signal, superior semi-circular canal dehiscence and MRI features of idiopathic intracranial hypertension are only present in under half of LTBCs. ADVANCES IN KNOWLEDGE: The study details novel ancillary MRI features of LTBCs which may aid their identification.

Active middle ear implantation: imaging in the pre-operative planning and post-operative assessment of the Vibrant SoundbridgeTM.

Active middle ear implants augment sound waves and directly stimulate the middle ear structures. The most frequently utilised active middle ear implant is the Vibrant Soundbridge TM (VSB).CT plays a vital role in appropriate patient selection and surgical planning of active middle ear implant surgery. The VSB TM offers a number of options for implant placement. The ideal location is influenced by the patient's middle ear and mastoid anatomy as well as the type and severity of the hearing loss. CT provides important information on the surgical access to the middle ear and helps determine the most appropriate implant site by assessing the adjacent middle ear anatomy and the continuity of the ossicular chain. Post-operative active middle ear implant imaging may be indicated in the setting of poor auditory outcomes and when revision surgery is being considered so as to assess for suboptimal implant placement or migration.This pictorial review will describe the VSB TM middle ear device and explain the role of imaging in both the pre-operative and post-operative settings.