Hemifacial spasm as a manifestation of pilocytic astrocytoma in a pediatric patient.

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

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.[1] 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.[2]

The disorder is typical during adulthood and is commonly attributed to vascular compression of the facial nerve emergence at the brain stem. Nevertheless, some rare associations with brain tumors have been described.[34] 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.[4] In children, the association of hemifacial spasm with tumors is also rare, with very few cases reported.[35]

Case Report

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. The spasms could not be suppressed and were not associated with tension or anxiety. No other involuntary movements were observed. The patient had no hearing difficulties, dysphagia or hoarseness. Her early development and her neuropsychomotor acquisitions were normal. There was no family history of neurological diseases.

Upon physical examination, 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]. Fundoscopy examination was normal.

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.

Figure 2

(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

Discussion

A variety of rare causes for hemifacial spasm occurring in childhood have been described. 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.[5] The present case describes a pilocytic astrocytoma located at the cerebellopontine angle.

Tumors can cause hemifacial spasms via a direct or indirect mass effect. 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. A tumor may also kink the brain stem and indirectly stretch the facial nerve.[4]

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.