Fractionated Stereotactic Radiotherapy for Acoustic Neuromas: Long-term Outcomes

AimsAcoustic neuromas are rare, benign intracranial tumours. There are a variety of treatment options, with no clear optimal management strategy and wide variation in treated outcomes. We report the outcomes from a 15 year cohort of patients treated at our centre using fractionated stereotactic radiotherapy (52.5 Gy in 25 fractions).Materials and methodsWe analysed a retrospective case series. Patients were identified from patient records and a retrospective review of case notes and imaging reports was undertaken. We assessed tumour response using RECIST criteria and recorded toxicity. Progression-free survival was estimated using the Kaplan–Meier method. The study was conducted according to the STROBE guidelines.ResultsIn total, 93 patients were identified; 83 patients had follow-up data, with a median follow-up period of 5.7 years. The overall control rate using RECIST criteria was 92%. Data on complications were available for 90 patients, with six (7%) experiencing a reduction in hearing, one (1%) developing trigeminal nerve dysfunction and one (1%) a deterioration in facial nerve function. Other toxicities included four (4%) patients who developed hydrocephalus, requiring the placement of a shunt and one (1%) patient who developed radiation brainstem necrosis. After further evaluation this patient was deemed to have been treated within acceptable dose constraints.ConclusionThese data suggest that a good control rate of acoustic neuromas is achievable using fractionated stereotactic radiotherapy to a dose of 52.5 Gy in 25 fractions. Toxicity is considered acceptable but the episode of radiation brainstem necrosis remains of concern and is the subject of further work.     

The modular endoprosthesis for mandibular body replacement. Part 1: Mechanical testing of the reconstruction

IntroductionIn this paper we present the results of the mechanical testing of a new generation modular endoprosthesis, which has been designed to improve the results of mandibular reconstruction.Materials and methodsThe new cementless endoprosthesis consists of a male part, a female part (both with screws on the stems), connected via a dove-tailed connection and secured with a coronal screw.The endoprosthesis was fitted into standardized blocks of synthetic bone (Synbone AG, Malans, Switzerland). The set-up was fixed to an ElectroPuls testing machine at one end and loaded at the other end 25 mm away. Three specimens were loaded continuously until failure to determine the average load to failure of the construct. Five specimens were then loaded cyclically between 10 and 150 N until either failure or 500,000 cycles. A finite element analysis was also performed on the set-up.ResultsOf the five specimens in the fatigue testing, only one survived while the other four either were bent or fractured at the stem of the clamped portion. The specimen that survived had very good bony contact with the prosthesis at the lower border. The connection of the modules via the dove-tailed design did not show any loosening. Finite element analysis showed areas of stress concentration at the superior surface of the stems to 188.8 MPa. This was well below the yield strength of titanium alloy of 897 MPa. Statistical analysis performed for specimens 1 to 4 to calculated lower tolerance bounds on cycles to failure, representing the estimated minimum achievable cycles to failure at 90, 95, and 99% of the population at 90 and 95% confidence levels, showed that the estimated mean cycles to failure was 10,132 cycles at the mean, minimum and maximum loads of 120 N and 18.4 N respectively.ConclusionGood bony contact seems to be essential at the lower border for long-term survival of the reconstruction. Small gaps increase the bending forces and thus shear stresses at the stem. The new design of the modular endoprosthesis is prone to stress concentrations at the superior surface of the stems. This is accentuated by the sharp screw threads of the stems. The loosening of the module connection seemed to have been stopped with the dove-tailed design.     

Postural and Cortical Responses Following Visual Occlusion in Adults With and Without ASD

Autism is associated with differences in sensory processing and motor coordination. Evidence from electroencephalography suggests individual perturbation evoked response (PER) components represent specific aspects of postural disturbance processing; P1 reflects the detection and N1 reflects the evaluation of postural instability. Despite the importance of these cortical responses to postural control, PERs to a perturbation in adults with autism spectrum disorder (ASD) have yet to be reported. The aim was to compare PERs to visual perturbation under varied postural stability conditions in adults with and without ASD. This study is the first to report that while the assessment of postural set is intact, adults with ASD use more cortical resources to integrate and interpret visual perturbations for postural control.     

Can radiological examination of mandibular bone invasion accurately predict the need for mandibular resection in oral squamous cell carcinoma?

Bone invasion by oral squamous cell carcinoma necessitates jaw resection, with preoperative imaging ideally able to guide the resection. A retrospective review of 109 patients with oral squamous cell carcinoma who underwent mandibular resection was performed. Eighty-three had preoperative computed tomography (CT) imaging and 72 underwent magnetic resonance imaging (MRI). The presence of bone invasion on imaging was compared to histopathology. Bone invasion was detected in 44 of 109 resection specimens (40.4%) and was identified on CT in 31 of 83 cases (37.4%) and on MRI in 35 of 72 cases (48.6%). The sensitivity and specificity of CT for detecting bone invasion was 69.0% and 79.6%, respectively, while for MRI was 87.1% and 80.5%, respectively. Histological detection of bone invasion was associated with greater disease-specific mortality (P = 0.002), as was MRI detection of bone invasion (P = 0.027). CT detection was not significant (P = 0.240). Negative prediction of bone invasion was 95% accurate for both modalities in clinically non-invaded mandibles. Survival was reduced in patients who underwent marginal mandibular resection when bone invasion was detected histologically (33.3% vs. 70.5%, P = 0.277) and with CT, although this was not statistically significant. More data are required to determine whether more aggressive resection is warranted when bone invasion is detected preoperatively.