The feasibility of quantitative MRI of extra‐ocular muscles in myasthenia gravis and Graves' orbitopathy

Although quantitative MRI can be instrumental in the diagnosis and assessment of disease progression in orbital diseases involving the extra‐ocular muscles (EOM), acquisition can be challenging as EOM are small and prone to eye‐motion artefacts. We explored the feasibility of assessing fat fractions (FF), muscle volumes and water T2 (T2_water) of EOM in healthy controls (HC), myasthenia gravis (MG) and Graves' orbitopathy (GO) patients. FF, EOM volumes and T2_water values were determined in 12 HC (aged 22‐65 years), 11 MG (aged 28‐71 years) and six GO (aged 28‐64 years) patients at 7 T using Dixon and multi‐echo spin‐echo sequences. The EOM were semi‐automatically 3D‐segmented by two independent observers. MANOVA and t‐tests were used to assess differences in FF, T2_water and volume of EOM between groups (P < .05). Bland–Altman limits of agreement (LoA) were used to assess the reproducibility of segmentations and Dixon scans. The scans were well tolerated by all subjects. The bias in FF between the repeated Dixon scans was ?0.7% (LoA: ±2.1%) for the different observers; the bias in FF was ?0.3% (LoA: ±2.8%) and 0.03 cm³ (LoA: ± 0.36 cm³) for volume. Mean FF of EOM in MG (14.1% ± 1.6%) was higher than in HC (10.4% ± 2.5%). Mean muscle volume was higher in both GO (1.2 ± 0.4 cm³) and MG (0.8 ± 0.2 cm³) compared with HC (0.6 ± 0.2 cm³). The average T2_water for all EOM was 24.6 ± 4.0 ms for HC, 24.0 ± 4.7 ms for MG patients and 27.4 ± 4.2 ms for the GO patient. Quantitative MRI at 7 T is feasible for measuring FF and muscle volumes of EOM in HC, MG and GO patients. The measured T2_water was on average comparable with skeletal muscle, although with higher variation between subjects. The increased FF in the EOM in MG patients suggests that EOM involvement in MG is accompanied by fat replacement. The unexpected EOM volume increase in MG may provide novel insights into underlying pathophysiological processes.     

Retrospective study on the predictive factors in chronic trismus

Trismus is one of the most debilitating and treatment-resistant complications resulting from head and neck oncological treatments. The objective of this study was to assess how primary tumour variables could assist in predicting chronic trismus. From a (retrospective) oncological database (Department of Oral and Maxillofacial Surgery, University Hospitals Leuven), tumour-related, surgical, and oral functional variables were reviewed. Contributing factors for chronic trismus, defined as a mouth opening of less than 35 mm, at least one year after treatment for oral squamous cell cancer, were assessed via logistic regression. A mediational analysis was conducted on the significant predictive variables. Thirteen out of 52 patients were observed to have chronic trismus. A significantly higher prevalence of trismus was found for increasing clinical T classification (p < 0.01), tumours based in the maxilla or the retromolar trigone (p = 0.04), after adjuvant radiotherapy (p = 0.04), and/or with masticatory muscle tumour invasion (p ≤ 0.02). Furthermore, radiotherapy significantly impacted T classification in chronic trismus, while T classification was significantly related to masticatory muscle invasion. Although radiotherapy and clinical T classification are well-established risk factors for postoperative trismus, masticatory muscle invasion should be considered as one of the main predictive factors.     

Age-Related Ultrasound Changes in Muscle Quantity and Quality in Women

This study investigated the age-related changes in muscle quantity and quality in the trunk and limbs of women. A total of 128 females were divided into four age groups: young, middle-aged, young-old and old-old. Muscle thickness (MT) and echo intensity (EI) of the biceps brachii, quadriceps femoris, rectus abdominis, external oblique, internal oblique and transversus abdominis were measured using B-mode ultrasonography. The EIs of the biceps brachii, quadriceps femoris and transversus abdominis were significantly higher in the middle-aged group than in the young group; however, there were no significant differences in MT. Compared with the young group, all other groups had significant changes in both MT and EI of the rectus abdominis, external oblique and internal oblique muscles. Thus, qualitative changes in muscle may occur earlier than quantitative changes, and loss of muscle mass may occur earlier in the superficial abdominal muscles than in the other muscles.     

Jaw-stretch reflex is weaker in patients after orthognathic surgery

ObjectivesThe jaw-stretch reflex (JSR) was studied in both patients and healthy participants in order to investigate the possible long-term impact of orthognathic surgery on the motor function of the masticatory system.DesignJSR was measured in patients before surgery (PC), 1 year after surgery (PS) and in healthy controls (HC) (N = 31 in each group). JSR was evoked by a standardized stretch device and recorded bilaterally from masseter and anterior temporalis muscles using surface electromyography (EMG).ResultsThe peak-to-peak amplitude (which was normalized to pre-stimulus EMG activity) of JSRs in PC and PS were significantly smaller than in HC (P < 0.001; P < 0.001). The onset latency in PS was significantly longer compared with HC (P < 0.05). The duration of JSR in PS was significantly longer than in HC and PC (P < 0.001; P < 0.05).ConclusionPatients with dentofacial deformities are characterized by reduced JSR amplitude. The delayed onset and elongated duration of JSR might be potential indicators of a long-term surgical impact on the motor function of the masticatory system.     

The influence of positioning in urination: An electromyographic and uroflowmetric evaluation

PurposeWe conducted a cross-sectional study to evaluate whether the different positions during urination influence the electrical activity of the abdominal and perineal musculature, as well as the uroflowmetric parameters of children with lower urinary tract dysfunction (LUTD).Materials and methodsNinety-four children between the ages of 3 and 14 years with symptoms of LUTD were evaluated. All underwent uroflowmetry and electromyography tests (abdominal and perineal) in two different positions: oriented position (trunk bent slightly forward and feet flat) and atypical position (standing on toes for boys and buttocks not in contact with the lavatory seat and legs flexed in girls). We excluded nine patients due to suspicions of outside interference or elements complicating the analysis of charts.ResultsAmong patients evaluated 55 (64.7%) were girls and 30 (35.3%) were boys with an average age of 8.5 years. Children urinating in atypical position showed higher levels of perineal electrical activity than when they were in normal position (p = 0.018). However, there was no difference in the pattern of the curve if normal or abnormal when comparing the two groups (p = 0.824). When evaluated separately, the boys demonstrated no difference between positions, in relation to perineal electrical activity (p = 0.412) or abdominal electrical activity (p = 0.202).ConclusionsThe electrical activity of the pelvic floor musculature is decreased in the oriented position when compared to atypical positions in female children. Our data suggest that special attention should be given to adopting an adequate posture during urination for girls with LUTD.     

Replication of ancient Egyptian osteotomies of the facial skeleton: insights into the mummification process

A recent radiographic study of an Egyptian mummified head from the Middle Kingdom revealed methodical mutilations of the facial skeleton that were performed after death and prior to wrapping the corpse for burial. These mutilations consisted of removal of the coronoid processes of the mandible and portions of the zygomas presumably via an intraoral approach. They are unique in the archaeological record. The authors hypothesize that the procedures were carried out to facilitate jaw opening and may be related to a ritual known as the ‘Opening of the Mouth’ ceremony. The purpose of this study was to demonstrate the feasibility of performing these remarkable osteotomies on two human cadavers using instruments similar to those available to the ancient embalmer. Bilateral osteotomies of the zygomas and coronoid processes were carried out transorally and the bones removed. Pre- and postoperative maximal incisal opening measured 25 mm and 53 mm, respectively. Postoperative high-resolution computed tomographic (CT) scans were obtained. Comparison of the postoperative cadaver and mummy CT scans demonstrate remarkable similarity between the resections. Results of this study demonstrate that the ancient skeletal mutilations could have been performed transorally during the mummification process and would have enhanced jaw opening.     

Functional roles of oral reflexes in chewing and biting: phase-, task- and site-dependent reflex sensitivity

Because loading during chewing is not totally predictable and jaw-closing muscles are strong and act over short distances, feedback from oral receptors is important in the control of mastication. Information on such feedback can be obtained by studying reflexes in jaw muscle EMGs. This review will deal with the contribution of reflex mechanisms to modifying motor neuron activity during chewing, and the dependency of reflex sensitivity on motor task, phase of movement, and site of stimulation.