Characterization of ocular motor deficits in congenital facial weakness: Moebius and related syndromes.

Congenital facial weakness is present in a heterogeneous group of conditions. Among them is Moebius syndrome, which has been defined as a disorder with congenital, non-progressive facial weakness and limited abduction of one or both eyes. It is typically attributed to agenesis of the abducens and facial cranial nerves. This paper details ocular motor findings of 40 subjects (23 months to 64 years; 24 females, 16 males) with congenital facial weakness: 38 presented at a Moebius Syndrome Conference and two were clinic patients. A new classification scheme of patterns based on ocular motor phenotype is presented. Of 40 subjects, 37 had bilateral and three had unilateral facial weakness. The most common ocular motor pattern (Pattern 1, n=17, 43%) was bilateral horizontal gaze palsy with intact vertical range. Pattern 2 (n=10, 26%) was bilateral horizontal gaze palsy with variable vertical limitations. Pattern 3, which was rare, was isolated abduction deficits (n=2, 5%). Others had full motility range and did not meet minimal criteria for the diagnosis of Moebius syndrome (Pattern 4, n=10, 26%). One subject was too severely affected to characterize. Abnormal vertical smooth pursuit was present in 17 (57%) of 30 subjects: nine with Pattern 1, five with Pattern 2, and three with Pattern 4. Abnormal vertical saccades were present in 10 (34%) of 29 subjects. Vertical saccades appeared slow in nine: six with Pattern 1 and three with Pattern 2. Vertical saccades were absent in one subject with Pattern 2. Abnormal vertical optokinetic nystagmus was present in 19 (68%) of 28 subjects: 10 with Pattern 1, six with Pattern 2, one with Pattern 3, and two with Pattern 4. Reduced convergence was present in 19 (66%) of 29 subjects: nine with Pattern 1, six with Pattern 2, one with Pattern 3, and three with Pattern 4. The most common pattern of ocular motor deficit in Moebius syndrome is bilateral horizontal gaze palsy from pontine abducens nuclear defects, rather than abducens nerve involvement. Defects in the range or dynamic properties of vertical movements in subjects with congenital facial weakness may suggest involvement of ocular motor structures in the midbrain, including oculomotor nerves or nuclei, vertical supranuclear saccadic centres, and convergence neurons. Such deficits were found even in subjects with full vertical motility range. Classification of patterns of ocular motor deficits in congenital facial weakness may assist with further delineation of anatomic localization and identification of genetic deficits underlying these disorders.

Autism spectrum conditions in individuals with Möbius sequence, CHARGE syndrome and oculo-auriculo-vertebral spectrum: diagnostic aspects.

As part of multidisciplinary surveys of three Behavioural Phenotype Conditions (BPCs); Möbius sequence (Möbius), CHARGE syndrome (CHARGE) and oculo-auriculo-vertebral spectrum (OAV), autism spectrum conditions (ASCs) was diagnosed in 45%, 68% and 42% of the individuals, respectively. Diagnostic difficulties due to additional dysfunctions such as mental retardation (MR), impaired vision, reduced hearing and cranial nerve dysfunction, were experienced in all three BPC groups. The applicability of current autism diagnostic instruments, such as the Autism Diagnostic Interview-Revised (ADI-R), the Childhood Autism Rating Scale (CARS) and the Autistic Behaviour Checklist (ABC), in individuals with ASCs and Möbius/CHARGE/OAV was analysed. Use of an extensive battery of diagnostic instruments, including both observational schedules and parent interviews, and, if possible, independent judgements from two clinicians, is essential in the diagnostics of ASCs in these individuals. Further, in individuals who are deaf and blind the applicability of current autism diagnostic instruments is highly questionable.

The localization of facial motor impairment in sporadic Möbius syndrome.

OBJECTIVE: To investigate the neurophysiologic aspects of facial motor control in patients with sporadic Möbius syndrome defined as nonprogressive congenital facial and abducens palsy. METHODS: The authors assessed 24 patients with sporadic Möbius syndrome by performing a complete clinical examination and neurophysiologic tests including facial nerve conduction studies, needle electromyography examination of facial muscles, and recording of the blink reflex and of the trigeminofacial inhibitory reflex. RESULTS: Two distinct groups of patients were identified according to neurophysiologic testing. The first group was characterized by increased facial distal motor latencies (DMLs) and poor recruitment of small and polyphasic motor unit action potentials (MUAPs). The second group was characterized by normal facial DMLs and neuropathic MUAPs. It is hypothesized that in the first group, the disorder is due to a rhombencephalic maldevelopment with selective sparing of small-size MUs, and in the second group, the disorder is related to an acquired nervous injury during intrauterine life, with subsequent neurogenic remodeling of MUs. The trigeminofacial reflexes showed that in most subjects of both groups, the functional impairment of facial movements was caused by a nuclear or peripheral site of lesion, with little evidence of brainstem interneuronal involvement. CONCLUSION: Two different neurophysiologically defined phenotypes can be distinguished in sporadic Möbius syndrome, with different pathogenetic implications.

Möbius syndrome redefined: a syndrome of rhombencephalic maldevelopment.

OBJECTIVE: To investigate the variable clinical picture of Möbius syndrome (MIM no. 157900) and to further understand the pathogenesis of the disorder. METHODS: A standardized questionnaire was submitted to 37 Dutch patients with Möbius syndrome. All underwent standardized neurologic examination with special attention to cranial nerve functions, motor skills, and facial and limb anomalies. RESULTS: Of 37 patients with facial paresis, 97% had bilateral and 3% had unilateral ocular abduction weakness. Further analysis showed isolated abducens nerve palsy in 9%, a conjugated horizontal gaze paresis in 48%, features of Duane retraction syndrome in 34%, and congenital fibrosis of the extraocular muscles in 9%. Other signs included lingual involvement (77%), dysfunction of palate and pharynx (56%), general motor disability (88%), poor coordination (83%), and respiratory abnormalities (19%). CONCLUSION: Möbius syndrome is more than a cranial nerve or nuclear developmental disorder. It is a syndrome of rhombencephalic maldevelopment involving predominantly motor nuclei and axons, as well as traversing long tracts. The authors also noted gaze palsies, Duane retraction syndrome, feeding and respiratory problems, and poor motor development, suggesting a regional developmental disorder.