it is characterized by unilateral or bilateral paralysis of the sixth and seventh cranial nerves , manifested clinically as external ophthalmoplegia and weakness of facial muscles . even though von graaefe described a case of congenital facial diplegia in 1880 , it was paul julius mbius , a german neurologist , who drew attention to the association of congenital facial diplegia with other malformations in 1888 and 1892 .
only about 300 cases have been reported in the literature , and very few cases of this syndrome have been reported in the radiology literature .
a 2-year - old girl was referred to our department for plain magnetic resonance imaging ( mri ) scan of the brain .
the child 's parents noticed facial asymmetry in the child with deviation of the angle of mouth to the right side on smiling , watering and incomplete closure of the left eye since birth .
the child 's birth and developmental history were normal . on physical examination , facial asymmetry ,
bilateral convergent squint , prominent everted upper and lower lips were noted . left facial nerve paralysis and bilateral abducent nerve paralysis
mild ptosis on left side is also seen ( b ) picture demonstrating left - sided facial paralysis causing deviation of angle of mouth to right side on smiling mr examination was performed using a 1.5 tesla mri scanner ( avanto ; siemens medical solutions , erlangen , germany ) .
axial and sagittal t1-weighted , axial t2-weighted , fluid - attenuated inversion recovery ( flair ) , and three - dimensional ( 3d ) constructive interference in steady state ( ciss ) sequences ( 0.7-mm slice thickness ) were evaluated .
mri brain showed the following findings : 
 absent cisternal and canalicular segments of left facial nerve [ figures 2 and 3]nonvisualization of cisternal segments of bilateral abducens nerves [ figures 2a and c]flattened floor of fourth ventricle with absence of bilateral facial colliculi [ figure 4 ] . 
 
absent cisternal and canalicular segments of left facial nerve [ figures 2 and 3 ] nonvisualization of cisternal segments of bilateral abducens nerves [ figures 2a and c ] flattened floor of fourth ventricle with absence of bilateral facial colliculi [ figure 4 ] .
four ( a  d ) contiguous 0.7-mm thick axial 3d ciss mr images of brain showing the absence of left facial nerve in cerebellopontine angle cistern ( a and c , bent arrows ) .
right facial nerve ( a , black arrow head ) and bilateral vestibulocochlear nerves ( a and c , black arrows ) are visualized .
in addition , there is absence of bilateral abducens nerves ( a , b , and d , white arrows ) in prepontine cisterns , the expected position of bilateral abducens nerves ( a  d images are cranial to caudal sections ) parasagittal ciss mr image of left internal auditory canal ( iac ) showing absent facial nerve in anterosuperior part of left iac ( black arrow ) .
vestibular ( thick white arrow ) and cochlear nerves ( thin white arrow ) are visualized in posterior and anteroinferior parts of left iac respectively .
( anterior is to the left of image and posterior is to the right ) axial t1w mr image at the level of middle cerebellar peduncles showing flattened floor of fourth ( black arrow ) ventricle secondary to absence of bilateral facial colliculi the left anterior inferior cerebellar artery ( aica ) flow void was absent , and mild prominence of the right aica was noted [ figure 5 ] .
axial ciss mr image showing right aica ( black arrow ) and absent left aica ( white arrow )
mbius syndrome is rare disorder , which is characterized by congenital complete or partial facial nerve paralysis with or without paralysis of other cranial nerves .
the definition and criteria for diagnosis of mbius syndrome vary among authors . based on previously published reviews
, kumar used the following criteria for diagnosis of this syndrome : ( a ) complete or partial facial nerve paralysis is an essential criterion for the diagnosis of mbius syndrome , ( b ) limb malformations ( syndactyly , brachydactyly , absent digits , talipes ) are often present , ( c ) bilateral or unilateral cranial nerve palsies ( commonly vi , xii , also ix , x ) may be seen , ( d ) orofacial malformations , ear deformities , and musculoskeletal deformities may also be seen .
recently , verzijl et al . , suggested facial palsy with impairment of ocular abduction as the primary criterion for mbius syndrome , with or without association of other cranial nerve paralysis , musculoskeletal defects , or orofacial malformations .
mbius syndrome manifests soon after birth with inability to close the eyelids during sleep , drooling of saliva , difficulty in sucking , and mask - like facies .
the hypoglossal nerve is the third most common nerve to be involved , causing paralysis and hypoplasia of the tongue .
although neither the etiology nor the pathogenesis of mbius syndrome has yet been elucidated , verzijl et al . proposed two theories based on previous published reviews : ( a ) a developmental rhombomeric defect including facial cranial nerve nuclei due to a genetic cause , or ( b ) an interruption in the vascular supply of the brainstem secondary to an environmental , mechanical , or genetic cause resulting in ischemia in the region of facial cranial nerve nuclei .
an association of absent aica with mbius syndrome is not described in the literature ; however , an association of the ischemic process resulting from an interruption of vascular supply to the brainstem in early fetal development was proposed .
absent left aica with mildly prominent contralateral aica , observed in our case , may be an incidental finding and an anatomic variant . at times , either the posterior inferior cerebellar artery or the aica is absent and one artery supplies the usual territories of both arteries .
however , mri is useful in demonstrating the abnormalities of the cranial nerves and orbital structures .
other computed tomography ( ct ) and mr imaging findings include brainstem hypoplasia with straightening of floor of the fourth ventricle , indicating absence of the facial colliculus ; calcification in pons in the region of abducens nuclei ; absence of hypoglossal eminence at the medulla ; and cerebellar hypoplasia .
based on history and clinicoradiological examinations ( 3d ciss ) , our case was diagnosed as mbius syndrome .
craniofacial syndrome with asymmetric crying facies , congenital heart disease , and other factors may be confused with mbius syndrome .
other neuromuscular disorders such as melkersson  rosenthal syndrome , muscular dystrophy , congenital facial muscular atrophy , cerebral palsy , and congenital myopathies may overlap with mbius syndrome .
the seventh nerve palsy in mbius syndrome primarily affects the upper face , which is differentiated from other lower motor neuron palsies affecting both upper and lower portions of the face .
additionally , this can also be differentiated from supranuclear lesions , which only affect the lower half of the face .
since the disease is congenital and nonprogressive , no definitive and established treatment has been described .
ocular care and careful monitoring of complications that might set in , patient education , and a multidisciplinary approach by health professionals help to reduce the morbidity .
we herein reported a case of mbius syndrome with absent left facial and bilateral abducens nerves .
it is an irreversible condition that causes not only physical abnormalities but also social and psychological disturbances .
ct and mr imaging may depict abnormalities in the brainstem , extraocular muscle hypoplasia , and other associated abnormalities .
mr imaging , particularly 3d ciss sequence , is very useful in evaluating cisternal and cavernous segments of the cranial nerves .
the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s )
has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal .
the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed .
the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s )
has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal .
the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed .
 mbius syndrome is an extremely rare congenital disorder . 
 we report a case of mbius syndrome in a 2-year - old girl with bilateral convergent squint and left - sided facial weakness . the characteristic magnetic resonance imaging ( mri ) findings of mbius syndrome , which include absent bilateral abducens nerves and absent left facial nerve , were noted . 
 in addition , there was absence of left anterior inferior cerebellar artery ( aica ) and absence of bilateral facial colliculi . 
 clinical features , etiology , and imaging findings are discussed . 
Introduction
Case Report
Discussion
Conclusion
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