BRAIN

SPINE

Hemifacial spasm (HFS) is a neuromuscular disorder characterized by frequent involuntary muscle contractions on one side of the face.The first symptom is usually an intermittent twitching of the eyelid muscle that can lead to forced closure of the eye. The spasm may then gradually spread to involve the muscles of the lower face, which may cause the mouth to be pulled to one side. Eventually the spasms involve all of the muscles on one side of the face almost continuously .The disorder occurs in both men and women, although it is more frequent in middle-aged or elderly women. Clonic movements progress to sustained tonic contractions of involved musculature.

Chronic irritation of the facial nerve or nucleus, the near-universal cause of hemifacial spasm, may arise from numerous underlying conditions. Irritation of the facial nerve nucleus is believed to lead to hyperexcitability of the facial nerve nucleus, while irritation of the proximal nerve segment may cause ephaptic transmission within the facial nerve. Either mechanism explains the rhythmic involuntary myoclonic contractions observed in HFS. Compressive lesions (eg, tumor, arteriovenous malformation, Paget disease) and noncompressive lesions (eg, stroke, multiple sclerosis, basilar meningitis) may present as hemifacial spasm. But the majority of cases of hemifacial spasm (previously defined as idiopathic) are caused by aberrant blood vessels (eg, distal branches of the anterior inferior cerebellar artery or vertebral artery) compressing the facial nerve within the cerebellopontine angle.

Imaging Studies

Magnetic resonance imaging is the imaging study of choice, especially if an underlying compressive lesion is suspected. Magnetic resonance angiography aqnd/or angiography prior to a vascular decompression surgical procedure is generally needed.

Non-surgical management

Medications can be used in patients with noncompressive lesions and early idiopathic hemifacial spasm. Response to medication varies but can be satisfactory in early or mild cases. In most patients the treatment of choice is injection of botulinum toxin type A. Side effects of botulinum toxin injection (eg, facial asymmetry, ptosis, facial weakness) usually are transient. Most patients report a highly satisfactory response, but, sometimes, although botulinum toxin ablates the muscular spasm, the sensation of spasm often persists.

Surgical treatment

Starting from the studies of Dr. Peter Jannetta (1977) was noted that HFS is often related to blood vessel pulsating against the facial nerve at his emergency from the brainstem and was also evidenced that moving the vessel and fixing it in another position cure the patient in the majority of cases (approximately 85 - 90% long-term symptom control) . Actually microvascular decompression surgery has become the treatment of choice of HSF and has undergone significant evolution over the past 30 years with the increased ability of surgeons and with to monitor hearing and facial nerve function, thus reducing the incidence of morbidity to less than 5%. The offending arterial loops originate from the posterior inferior cerebellar, anterior inferior cerebellar, or vertebrobasilar artery. In as many as 40% of the patients, neurovascular conflicts are multiple. Because cure of spasms is frequently delayed - by several months to even a few years - early reoperation is not recommended in patients with failure until at least 1 year follow-up. Delayed cure could well be explained by the slow reversal of the plastic changes in the facial nucleus that may have caused the symptoms.

References