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Blepharospasm (BEB) is characterised by bilateral, and usually symmetrical and synchronous, contractions of the orbicularis oculi muscles, often with involvement of the frontalis and corrugator muscles. There may be associated dystonia of the lower face and jaw and of the neck muscles. In most cases no cause is found although BEB may be associated with lesions of the basal ganglia, brainstem, or thalamus. It is more common in women and may be familial. Eye disease and dental procedures may be precipitating factors. In hemifacial spasm (HFS) there are clonic or tonic contractions of muscles innervated by the facial nerve usually on one side, at least initially. In many cases there is vascular compression of the nerve at its exit from the skull. BEB and HFS appear to be distinct entities but a report from Singapore shows that some patients may suffer from both.
One hundred and sixty four consecutive patients with HFS attending a neurology (botulinum toxin treatment) clinic were compared with 501 non-neurological outpatient, age and sex matched controls. The mean age of HFS patients was 55 years (62% women) and of controls 51 years (61% women). A diagnosis of coexisting BEB was made in 9 patients (5.5%) in the HFS group but in none of the controls. Eight of the nine patients with both conditions were women. The BEB began after the HFS in six patients and before in one. The timing was not known for two patients. Magnetic resonance imaging and angiography in six of the nine patients showed vascular compression of the facial nerve on the same side as the HFS in five and no abnormality in one patient (whose HFS and BEB had followed Bell’s palsy). In three patients HFS, but not BEB, was noted to persist in sleep.
Why some patients with HFS should develop BEB is unclear. It is suggested that facial weakness (spontaneous or induced by botulinum toxin treatment) in patients with HFS might cause a reduction in input to an inhibitory reflex affecting the muscles involved in BEB.