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Rare developmental disorder characterized by facial
paralysis (mask-like face) present at birth. Facial nerve development is
absent, and the sixth (abducens) and seventh (facialis) cranial nerves are
most often affected. Other features include numerous abnormalities of the
orofacial region and malformations of limbs. Mental retardation occurs in
approximately 10% of cases.
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Congenital Oculofacial Paralysis; Congenital Facial
Diplegia, Moebius Sequence.
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First described by Henri M. Thomas, an American neurologist, in 1898.
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Rare. Affects males and females equally. Most cases of
Moebius syndrome occur randomly for no apparent reason (sporadic cases).
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Usually sporadic. Cases of autosomal dominant
inheritance described (1898). Gene map locus is 13q12.2-q13. Recurrence risk
is low at less than 1 in 50. Clinically they can often be differentiated by
lack of limb involvement. A Moebius syndrome type II has been described in a
large Dutch family with strong autosomal dominant transmission. Gene map
locus is 3q21-q22. It is associated with multiple vascular abnormalities and
poor prognosis.
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Etiology is unknown. Four possible pathologic
causes have been suggested: (a) hypoplasia to absence of central brain nuclei; (b) destructive
degeneration of the central brain nuclei (this is the most common form; it
is likely caused by a transient brainstem hypoxic event occurring at a
critical time in utero and affecting the structures supplied by the
developing subclavian artery); (c) peripheral nerve involvement; and (d) a
myopathy. Moebius syndrome is thus considered as a nonspecific sign.
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Based on clinical findings. Usually manifests soon after
birth with sixth and seventh nerve palsies, which are either partial or
complete and may be bilateral. Patients present with mask-like facies,
incomplete closure of the eyelids during sleep, drooling of saliva, and
difficulty sucking. Aspiration is common. On examination, multiple other
abnormalities are usually detected. Important to differentiate from
neuromuscular disorders occurring in early childhood.
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Multiple cranial nerves may be involved (nerves
V, VI, VII, IX, X, and XII can all be affected) and lead to orofacial
malformations, abnormalities of tongue coordination, swallowing (bulbar
muscle weakness), and drooling. Speech abnormalities are common. High risk
for corneal abrasions. Usually the affected individuals are mentally normal. However, there is a 10%
incidence of mild mental retardation. Occasionally peripheral neuropathy and
pectoral muscle deficiency. Abnormalities of ventilation (central
hypoventilation and idiopathic tachypnea) presumably result from brainstem
abnormalities. Craniofacial features include micrognathia, ...