hemifacial spasm is a disorder of the seventh cranial nerve , and is characterized by irregular , involuntary and recurrent tonic and clonic contractions of the ipsilateral facial expression muscles .
each spontaneous motor paroxysm starts with eye twitching and progresses to involve the other muscles innervated by the facial nerve .
the episode characteristically begins with a series of twitches that increase in frequency and intensity , followed by a sustained spasm .
the disorder is typical during adulthood and is commonly attributed to vascular compression of the facial nerve emergence at the brain stem .
altogether , posterior fossa or cerebellopontine angle tumors are rare causes of hemifacial spasm , reported in less than 1% of a large series of adult patients . in children ,
the association of hemifacial spasm with tumors is also rare , with very few cases reported .
a 6-year - old girl without any significant past medical history was admitted with intermittent involuntary twitching of the right orbicular region ; the twitching had occurred for 18 months . over time , the spasms became more tonic , and after 4 months , the spasms also involved the right orbicularis oris area .
she was noted to be in good overall condition , showing a normal physical examination without fever or any other signs of infection .
her height was 133 cm , and she weighed 39 kg , with a body mass index of 22.4 .
the neurological examination was noteworthy for dysarthria and right hemifacial spasm [ figure 1 ] .
sustained right hemifacial spasm laboratory evaluations , including a complete blood cell count , electrolytes , blood urea nitrogen and liver enzymes were within the normal range .
cranial magnetic resonance imaging ( mri ) revealed a right - sided heterogeneous lesion from the midbrain to the pons , extending to the cerebellopontine angle , with a slight mass effect on the fourth ventricle [ figure 2 ] .
after the neuroimaging procedures , a cerebral biopsy was performed , which revealed a pilocytic astrocytoma .
the hospital ethic commission approved this case report , and the patient 's parents gave informed consent for publication .
( a ) t2-weighted coronal and ( b ) flair axial mri images showing a right - sided heterogeneous high signal lesion from the midbrain to the pons , extending to the cerebellopontine angle , with a slight mass effect on the fourth ventricle .
( c ) t1-weighted aspect of the lesion , with heterogeneous low signal and ( d ) t1-weighted post - gadolinium sagittal image showing its enhanced pattern
these causes include venous sinus thrombosis , masses of the fourth ventricle , pilocytic astrocytoma , congenital or acquired cholesteatoma , tuberculous meningitis , thickening of the arachnoid membrane , neurosurgical facial nerve injury , accommodative esotropia and mandibular prognathism .
masses may directly impinge on the facial nerve depending on the size and location of the tumor .
some studies described cases in which the facial nerve was compressed against bony structures or tethered to arachnoid adhesions .
this case shows the importance of a thorough neurological evaluation because our patient presented with subtle clinical signs of hemifacial spasm as the initial manifestation of a pilocytic astrocytoma .
children who present with hemifacial spasm , even if very mild , should undergo further investigation .
 hemifacial spasm is a disorder of the seventh cranial nerve , which is characterized by irregular , involuntary and recurrent tonic and clonic contractions of the ipsilateral facial expression muscles . 
 this disorder affects mainly adults , and there are few cases reported in childhood . 
 the main etiologies are vascular problems , although tumors are an important cause of hemifacial spasm via a direct or an indirect mass effect . 
 we report a 6-year - old girl who presented with right hemifacial spasm . 
 magnetic resonance imaging showed a lesion in the cerebellopontine angle , extending from the midbrain to the pons with a slight mass effect on the fourth ventricle . 
 the histological examination revealed a pilocytic astrocytoma . 
Introduction
Case Report
Discussion