title: Clinico-radiologic correlation in unilateral and bilateral hemifacial spasm.
abstract: BACKGROUND
  Bilateral hemifacial spasm (HFS) is rare. Clinico-radiologic correlates utilizing advanced imaging techniques have not been systematically examined in bilateral HFS. The prevalence of bilateral HFS in an Asian population has not been clarified.
  
  
  OBJECTIVE
  We examined the prevalence and clinico-radiologic correlates of bilateral HFS in a clinic-based cohort and compared the clinical characteristics of unilateral HFS patients with and without contralateral neurovascular contact (NVC) in HFS.
  
  
  METHODS
  Patients clinically diagnosed with HFS were examined for bilateral symptoms. Imaging analysis involved the utilization of reformatted, multi-planar three-dimensional time-of-flight magnetic resonance angiography (3D-TOF MRA), and constructive interference at steady state (CISS-MR) sequences. The clinical and imaging data was compared between HFS with and without NVC.
  
  
  RESULTS
  Amongst 162 consecutive HFS patients, 2 (1.6%) had bilateral symptoms. Both patients had unilateral onset followed by bilateral and asynchronous facial contractions. The contralateral side of the face began to twitch at a mean of 1.5 years later. MRI/A revealed significant NVC of the root exit zone (REZ) of the facial nerve on the ipsilateral side with mild NVC contralaterally. The degree of NVC correlated with the clinical severity of the patients' symptoms. MRI/A analysis of 40 HFS patients with unilateral symptoms demonstrated NVC on the contralateral side in six patients (15%). The mean age and duration of symptoms were not different between HFS patients with and without contralateral NVC.
  
  
  CONCLUSIONS
  We demonstrated clinico-radiologic correlation between the clinical severity and the degree of NVC at the REZ of the facial nerve in bilateral HFS. Amongst unilateral HFS, there was no significant difference clinically between those with and without contralateral NVC. The low 1.6% prevalence of bilateral HFS in our Asian cohort was compatible with the rare prevalence in other ethnic populations.
authors.affiliation: Department of Neurology, Singapore General Hospital, National Neuroscience Institute, Singapore 169608, Singapore. gnrtek@sgh.com.sg
authors.forename: E-K
authors.initials: EK
authors.lastname: Tan
authors.forename: L L
authors.initials: LL
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001488:Basilar Artery / Q000473:pathology / Q000503:physiopathology; D015331:Cohort Studies; D018450:Disease Progression; D005154:Facial Nerve / Q000098:blood supply* / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D019569:Hemifacial Spasm / Q000208:ethnology / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011149:Pons / Q000098:blood supply* / Q000473:pathology* / Q000503:physiopathology; D014711:Vertebral Artery / Q000473:pathology / Q000503:physiopathology