Distinguishing features of psychogenic (functional) versus organic hemifacial spasm

Hemifacial spasm (HFS) is one of the most common presentations in patients with cranial psychogenic (functional) movement disorders (PMD). Medical records and videos of patients with PMD and HFS were reviewed to identify those with psychogenic HFS and to compare the phenomenology of psychogenic HFS with organic HFS. We identified 18 (9.8%) patients with psychogenic HFS from a cohort of 184 patients with PMDs. There were 14 (78%) women and 4 men, with a mean age at onset of 33 ± 13.5 years. These were compared with 37 consecutive patients with organic (primary) HFS. Patients with psychogenic HFS were significantly younger and had more frequently tonic muscle contractions, bilateral asynchronous hemifacial involvement, isolated lower facial involvement, downward deviation of the mouth's angle, and lack of the "other Babinski sign" compared to those with organic HFS. Other features such as ipsilateral downward movements of the eyebrow; associated tremor, dystonia and hemi-masticatory spasms were more frequently observed in patients with psychogenic HFS but these differences did not reach statistical significance. Lack of other Babinski sign and tonic muscle contractions showed the highest sensitivity (1.00 and 0.87, respectively), whereas downward mouth's angle deviation showed the highest specificity (1.00) for the diagnosis of psychogenic HFS. Besides other features such as suggestibility, distractibility, periods of unexplained improvements observed in most patients with PMDs, several clinical features, such as tonic muscle contractions, downward mouth's angle deviation, predominant lower facial and bilateral involvement, may be helpful in distinguishing psychogenic from organic HFS.