Brain phenotyping in Moebius syndrome and other congenital facial weakness disorders by diffusion MRI morphometry

Multidisciplinary Care for Moebius Syndrome and Related Disorders: Building a Management Protocol

Moebius syndrome is a collection of orofacial anomalies with highly variable features affecting many different systems but characterised by bilateral facial palsy and absent eye abduction. We largely regard Moebius syndrome as a diagnosis of exclusion. Lack of awareness and knowledge means that children often fall between services, leading to treatment delays and difficulty interfacing with social care and schools, with long-term impact on physical health and psychosocial development. We developed a multidisciplinary team comprising core clinicians (lead physician, geneticist, speech and language therapist, psychologist and specialist nurse) and an expanded group to encompass the other affected systems. The interactions between our specialties lead to the development of a treatment protocol, which we present. The protocol harnesses the aspects of care of children with a range of other rare diseases at a specialised paediatric centre and synthesises them into a holistic approach for MBS and related conditions. Management is sequenced on an "ABC-style" basis, with airway, feeding, vision and speech taking priority in the early years. We define management priorities as airway stabilisation with swallow assessment, ocular surface protection and maintenance of nutritional support. Management principles for issues such as speech, reflux, drooling and sleep issues are outlined. In later years, psychological support has a prominent role geared towards monitoring and interventions for low mood, self-esteem and bullying.

Prenatal diagnosis of Poland-Möbius syndrome by multimodality fetal imaging

We describe prenatal diagnosis of Poland-Möbius syndrome using a combination of ultrasound and MRI. Poland syndrome was diagnosed based on absence of the pectoralis muscles associated with dextroposition of the fetal heart and elevation of the left diaphragm. Associated brain anomalies that led to the diagnosis of Poland-Möbius syndrome, included ventriculomegaly, hypoplastic cerebellum, tectal beaking, and a peculiar flattening of the posterior aspect of the pons and medulla oblongata, which has been reported by postnatal diffusion tensor imaging studies as a reliable neuroimaging marker for Möbius syndrome. Since abnormalities of cranial nerves VI and VII may be difficult to detect prenatally, careful attention to the appearance of the brain stem as illustrated in the current report may aid in the prenatal diagnosis of Möbius syndrome.

Echoencephalography of Möbius sequence: A congenital cranial dysinnervation disorder with brainstem calcifications

BACKGROUND AND PURPOSE

Möbius sequence (MBS) previously known as Möbius syndrome is a rare nonprogressive developmental defect of the rhombencephalon leading to congenital abducens (VIth) and facial (VIIth) nerve palsy. Echoencephalography is the first, safe, noninvasive, and cost-effective imaging modality available at bedside. No study on the use of echoencephalography in neonates for the diagnosis of MBS has been previously reported.

METHODS

In this single tertiary center study, more than 18,000 neonates underwent echoencephalographic imaging over the span of two decades. Imaging was performed through the anterior, posterior, and lambdoid fontanelles. All neonates found to have calcifications of brainstem tegmental nuclei underwent additional imaging studies. Each neonate with MBS was carefully examined by the same investigator.

RESULTS

Five neonates were shown to have punctate, bilateral, symmetrical tegmental pontine calcifications through all three acoustic windows. These calcifications extended caudally in most patients, and rostrally in 2 patients. Brainstem hypoplasia was best seen through the posterior fontanelle. Three out of five infants were noted to have brainstem hypoplasia with straightening of the floor of the fourth ventricle. In two children, facial collicular bulges and hypoglossal eminences were present. All five infants fulfilled clinical diagnostic criteria of MBS. In addition, a wide array of cerebral defects is identified. Echoencephalographic findings were confirmed by other imaging modalities.

CONCLUSION

Knowledge of echoencephalographic features of MBS should improve its early recognition. A detailed description of the various imaging phenotypes of MBS is necessary to characterize the etiology of this heterogeneous congenital cranial dysinnervation disorder.

Moebius Syndrome: An Updated Review of Literature

Moebius Syndrome, is a rare, non-progressive congenital neuropathological syndrome characterized primarily by the underdevelopment of the facial (CN VII) and abducens nerve (CN VI). Other features of Moebius Syndrome include facial nerve paresis, ophthalmoplegias, orthodontic deficiencies (including crowded dentition, swollen and hyperplastic gingiva, dental calculus, etc.), musculoskeletal abnormalities, and impaired mental function. Due to the rarity of the disorder, very few case studies have been reported in the literature. This article summarizes the significant features of the disease according to commonalities in reported cases, along with several newly recognized features cited in recent literature. We have explored the different diagnostic criteria and the newly recognized imaging modalities that may be used. Understandably, the condition detrimentally affects a patient's quality of life; thus, treatment measures have also been outlined. This study aims to provide updated literature on Moebius Syndrome MBS and improve understanding of the condition.

Facial Expression Time Processing in Typical Development and in Patients with Congenital Facial Palsy

Temporal dynamics of behavior, particularly facial expressions, are fundamental for communication between individuals from very early in development. Facial expression processing has been widely demonstrated to involve embodied simulative processes mediated by the motor system. Such processes may be impaired in patients with congenital facial palsy, including those affected by Moebius syndrome (MBS). The aims of this study were to investigate (a) the role of motor mechanisms in the processing of dynamic facial expression timing by testing patients affected by congenital facial palsy and (b) age-dependent effects on such processing. Accordingly, we recruited 38 typically developing individuals and 15 individuals with MBS, ranging in age from childhood to adulthood. We used a time comparison task where participants were asked to identify which one of two dynamic facial expressions was faster. Results showed that MBS individuals performed worse than controls in correctly estimating the duration of facial expressions. Interestingly, we did not find any performance differences in relation to age. These findings provide further evidence for the involvement of the motor system in processing facial expression duration and suggest that a sensorimotor matching mechanism may contribute to such timing perception from childhood.

Differentiating Moebius syndrome and other congenital facial weakness disorders with electrodiagnostic studies

INTRODUCTION

Congenital facial weakness (CFW) can result from facial nerve paresis with or without other cranial nerve and systemic involvement, or generalized neuropathic and myopathic disorders. Moebius syndrome is one type of CFW. In this study we explored the utility of electrodiagnostic studies (EDx) in the evaluation of individuals with CFW.

METHODS

Forty-three subjects enrolled prospectively into a dedicated clinical protocol and had EDx evaluations, including blink reflex and facial and peripheral nerve conduction studies, with optional needle electromyography.

RESULTS

MBS and hereditary congenital facial paresis (HCFP) subjects had low-amplitude cranial nerve 7 responses without other neuropathic or myopathic findings. Carriers of specific pathogenic variants in TUBB3 had, in addition, a generalized sensorimotor axonal polyneuropathy with demyelinating features. Myopathic findings were detected in individuals with Carey-Fineman-Ziter syndrome, myotonic dystrophy, other undefined myopathies, or CFW with arthrogryposis, ophthalmoplegia, and other system involvement.

DISCUSSION

EDx in CFW subjects can assist in characterizing the underlying pathogenesis, as well as guide diagnosis and genetic counseling.