THE OTHER BABINSKI SIGN IN HEMIFACIAL SPASM

Joseph Babinski is known for his description of the abnormal plantar reflex bearing his name. Rarely attributed to Babinski is another phenomenon, observed in patients with hemifacial spasm (HFS), which he first described in 1905. This “other Babinski sign”¹ is manifested as follows: “when orbicularis oculi contracts and the eye closes, the internal part of the frontalis contracts at the same time, the eyebrow rises during eye occlusion,” and “this set of occurrences is impossible to reproduce by will.”² In this study we examined the utility of the “other Babinski sign” in differentiating HFS from blepharospasm (BSP).

Methods.

All patients who presented to the Baylor College of Medicine Movement Disorders Clinic between July 1989 and July 2006 and were diagnosed with HFS or BSP by a movement disorders expert were included in this study. As part of our routine evaluation, all patients with HFS or BSP are videotaped before treatment. The diagnosis of HFS was based on the presence of unilateral involuntary facial muscle contractions affecting one or more muscle groups innervated by the ipsilateral facial nerve.³ Patients with BSP had a bilateral contraction of periorbital muscles without other associated facial or oromandibular dystonia.⁴ A patient was considered positive for the presence of the “other Babinski sign” if the videotape showed unilateral contraction of the frontalis muscle, causing eyebrow elevation, with concurrent contraction of the ipsilateral orbicularis oculi muscle, causing eyelid closure (see figure). Patients with unilateral frontalis contraction, but without eye closure, were excluded as such contraction may have been compensatory (voluntary).

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Figure The “other Babinski sign”

Patients with hemifacial spasm (HFS) demonstrating the “other Babinski sign” manifested by elevation of the eyebrow caused by contraction of the frontalis muscle ipsilateral to the facial spasm. BSP = blepharospasm.

Results.

Mean age at the time of initial evaluation for 75 patients with HFS (45 women) was 58.4 ± 12.2 years and for the 73 patients with BSP (50 women) 58.2 ± 12.5 years. The “other Babinski sign” was clearly evident in 19 (25.3%) of the HFS patients (10 women) but in none of the BSP patients. The sensitivity of the “other Babinski sign” as a test of the presence of HFS was 25.3%, specificity 100%, and positive predictive value 100%.

Discussion.

HFS is a peripherally induced movement disorder characterized by irregular, clonic, or tonic contraction of the muscles of the face innervated by the ipsilateral seventh cranial nerve.³ Twitching commonly begins in the orbicularis oculi, but usually spreads to involve muscles of the upper and lower face, including the platysma muscle, and may rarely become bilateral. HFS is typically idiopathic or sporadic, usually attributed to compression of the facial nerve at the root entry zone by an aberrant artery. BSP, a form of focal dystonia of central origin, is a forceful, involuntary, spasmodic contraction of the orbicularis oculi, which may occur in isolation or in combination with other dystonic contractions, including other facial muscles. The combination of BSP and dystonia of other facial or jaw muscles is referred to as craniocervical dystonia (formerly known as Meige syndrome).⁵

The “other Babinski sign” is an underrecognized and useful physical sign that may be present in HFS and is therefore helpful in distinguishing this disorder from BSP, wherein the sign is not reported. Although the origin of “the other Babinski sign” in HFS is not clear, this sign is not seen in BSP, presumably owing to the fact that the motor neuron pools for orbicularis oculi and frontalis muscles have different patterns of suprasegmental innervation. In the case of HFS, however, the co-contraction of these muscles presumably reflects a peripheral co-activation.

This “other Babinski sign” should be differentiated from the compensatory frontalis muscle contraction that may occur in patients with ptosis, such as seen in myasthenia gravis.⁶

Although our patients were referred to us for evaluation of involuntary facial movement and treatment with botulinum toxin, and therefore may not be representative of general population with HFS and BSP, we believe that our finding is valid as the patients were videotaped without the patient or the examiner specifically searching for the “other Babinski sign.” A limitation of our study is that we relied on a review of videotapes to detect the sign, rather than direct examination, and therefore may have missed some cases if the videotape did not capture the sign during the brief video session. Thus, our results probably represent an underestimate of the true frequency of the sign. The yield may have been improved by a longer observation and by employment of electromyography. This is supported by a study involving 35 HFS patients, preselected because of the presence of “other Babinski sign,” all of whom had electromyographic evidence of co-contraction of the frontalis and orbicularis muscles.⁷

Given the lack of uniform terminology regarding this finding, we propose that the “other Babinski sign” be renamed “the brow-lift sign.”

ACKNOWLEDGMENT

The authors thank Cathy Jankovic and Anthony Davidson for their technical assistance.