Moebius sequence

Moebius sequence is a rare congenital neurological condition. It usually occurs sporadically, without a relevant family history, although rare familial forms have been described. Modern literature has increasingly favoured the term ‘Moebius sequence,’ rather than ‘syndrome,’ reflecting the concept of a pattern of multiple abnormalities arising as a consequence of a single initiating developmental disturbance. A distinctive presentation may include the combination of facial and abducens nerve involvement (the combination of congenital facial paralysis with impaired ocular abduction, resulting in a characteristic mask-like facial appearance and limited ability to smile or move the eyes laterally), particularly when accompanied by Poland anomaly (absence or hypoplasia of the pectoralis major muscle with associated chest-wall or upper-limb abnormalities).

It can present with psychiatric features such as autism spectrum disorder (ASD), behavioural difficulties, anxiety, social communication difficulties and sleep disturbance. ASD and other neurodevelopmental difficulties have been reported, although the strength of the association remains uncertain. Behavioural and psychiatric manifestations may persist into adolescence and adulthood, and difficulties with facial expression and speech can contribute substantially to social and emotional difficulties.

From a morphologic lens perspective, other features include (but are not limited to):

• Ptosis

• Micrognathia

Other characteristic features include congenital, non-progressive facial palsy, which may be unilateral or bilateral and may be asymmetric, together with impaired abduction of one or both eyes. Other cranial nerve involvement may cause dysphagia, dysarthria, impaired tongue movement, hearing impairment and reduced facial or corneal sensation. Feeding and swallowing difficulties are common in infancy and may contribute to aspiration and poor growth. Speech and language impairment is common, while intellectual disability occurs in a minority of affected individuals. Limb abnormalities include clubfoot, syndactyly, brachydactyly and, less commonly, more severe limb reduction defects. Poland anomaly is a recognised association. Ocular complications include strabismus, ptosis, incomplete eyelid closure and exposure-related corneal injury. The condition is non-progressive, although functional, communication and psychosocial difficulties may persist throughout life.

Early diagnosis is important to identify and manage feeding, swallowing, respiratory, ocular, hearing and speech complications; recognise associated neurological, developmental and musculoskeletal abnormalities; provide appropriate developmental, educational and psychiatric assessment and support; and facilitate multidisciplinary management of communication and psychosocial difficulties.