Hemifacial spasm diagnosis

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Diagnosis of hemifacial spasm is mostly clinical, based on:

Typical symptoms:

Involuntary, irregular, clonic or tonic contractions of muscles on one side of the face.

Starts typically around the orbicularis oculi (eye) and spreads to perioral (mouth) muscles over time.

May worsen with stress, fatigue, or voluntary movements.

Pattern:

Unilateral (affecting only one side).

Persisting during sleep in severe cases (unlike tics).

No other associated neurological signs (except in secondary cases).

MRI of the Brain (high-resolution):

To detect neurovascular compression at the root exit zone of the facial nerve (common cause).

To exclude tumors, cerebellopontine angle masses (e.g., schwannoma, meningioma), vascular malformations, or demyelinating lesions.

Magnetic Resonance Angiography (MRA):

Helps visualize offending vessels (AICA, PICA, vertebral artery) in close contact with the facial nerve.

Special Sequences:

3D constructive interference in steady state (3D-CISS) or FIESTA sequences provide better cranial nerve visualization.

Rarely needed but can help in unclear cases:

Electromyography (EMG):

Shows involuntary bursts in facial muscles.

Lateral spread response is a classic finding: stimulation of one branch of the facial nerve produces a response in muscles innervated by another branch (due to ephaptic transmission across fibers).

Diagnosis often needs prior exclusion of many other movement disorders affecting the face, with frequent phenomenological overlaps with blepharospasm, post-facial palsy, facial motor tics, etc. The clinical diagnosis shall be supported by modern brain imaging techniques, and sometimes electromyography, as some particular aetiologies may require specific treatment. Primary forms are associated with vascular compression of the ipsilateral seventh cranial nerve, whereas secondary forms can be caused by any injury occurring on the facial nerve course ¹⁾.

Neuroradiologists received a file with the description of the novel sign, named Prevedello Sign (PS). In a second moment, the same neuroradiologists were asked to identify the presence of the PS and, if it was present, to report on which side. A total of 35 patients were included, mostly females (65.7%) with a mean age of 59.02 (+0.48). Since the 35 cases were independently evaluated by two neuroradiologists, a total of 70 reports were included in the analysis. The PS was present in 66 patients (sensitivity of 94.2%, specificity of 91.4% and positive predictive value of 90.9%). When both analyses were performed in parallel (standard plus PS), the sensitivity increased to 99.2%. Based on the findings of this study, the authors conclude that PS is helpful in determining the neurovascular conflict location in patients with HFS. Its presence, combined with the standard evaluation, increases the sensitivity of the MRI to over 99%, without increasing risks of harm to patients or resulting in additional costs ²⁾

Jankovic Rating Scale for Hemifacial Spasm

In typical cases of HFS, the diagnostic work-up is negative.

Most patients should have MRI of the posterior fossa (CT scan is less sensitive here) to R/O tumors or AVMs.

Vertebral angiography is usually not performed if imaging is normal. The neurovascular compression responsible for HFS usually cannot be identified on angiography.

Abnormal lateral spread response (LSR) is a typical finding in facial electromyography (EMG) in patients with hemifacial spasm (HFS). Although intraoperative monitoring of LSR has been widely used during microvascular decompression (MVD), the prognostic value of this monitoring is still debated.