title: MRI findings in patients with a history of failed prior microvascular decompression for hemifacial spasm: how to image and where to look.
abstract: OBJECTIVE
  A minority of patients who undergo microvascular decompression for hemifacial spasm do not improve after the first operation. We sought to determine the most common locations of unaddressed neurovascular contact in patients with persistent or recurrent hemifacial spasm despite prior microvascular decompression.
  
  
  METHODS
  Eighteen patients with a history of a microvascular decompression presented with persistent hemifacial spasm. All patients underwent thin-section steady-state free precession MR imaging. Fourteen patients underwent repeat microvascular decompression at our institution. Images were evaluated for the following: the presence of persistent vascular compression of the facial nerve, type of culprit vessel (artery or vein), name of the culprit artery, segment of the nerve in contact with the vessel, and location of the point of contact relative to the existing surgical pledget. The imaging findings were compared with the operative findings.
  
  
  RESULTS
  In 12 of the 18 patients (67%), persistent vascular compression was identified by imaging. In 11 of these 12 patients, the culprit vessel was an artery. Compression of the attached segment (along the ventral surface of the pons) was identified in most patients (58%, 7/12). The point of contact was proximal to the surgical pledget in most patients (83%, 10/12). The imaging interpretation was concordant with the surgical results regarding artery versus vein in 86% of cases and regarding the segment of the nerve contacted in 92%.
  
  
  CONCLUSIONS
  In patients with persistent hemifacial spasm despite microvascular decompression, the unaddressed vascular compression is typically proximal to the previously placed pledget, usually along the attached segment of the nerve. Re-imaging with high-resolution T2-weighted MR imaging will usually identify the culprit vessel.
authors.affiliation: From the Departments of Radiology (M.A.H., B.F.B., C.T.T., S.F., W.T.D.).
authors.forename: M A
authors.initials: MA
authors.lastname: Hughes
authors.affiliation: From the Departments of Radiology (M.A.H., B.F.B., C.T.T., S.F., W.T.D.) Otolaryngology (B.F.B.), University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: B F
authors.initials: BF
authors.lastname: Branstetter
authors.affiliation: From the Departments of Radiology (M.A.H., B.F.B., C.T.T., S.F., W.T.D.).
authors.forename: C T
authors.initials: CT
authors.lastname: Taylor
authors.affiliation: From the Departments of Radiology (M.A.H., B.F.B., C.T.T., S.F., W.T.D.).
authors.forename: S
authors.initials: S
authors.lastname: Fakhran
authors.affiliation: From the Departments of Radiology (M.A.H., B.F.B., C.T.T., S.F., W.T.D.).
authors.forename: W T
authors.initials: WT
authors.lastname: Delfyett
authors.affiliation: Neurosurgery (A.M.F., R.F.S.).
authors.forename: A M
authors.initials: AM
authors.lastname: Frederickson
authors.affiliation: Neurosurgery (A.M.F., R.F.S.) sekularf@upmc.edu.
authors.forename: R F
authors.initials: RF
authors.lastname: Sekula
mesh_terms: D000328:Adult; D000368:Aged; D005154:Facial Nerve / Q000098:blood supply; D005260:Female; D019569:Hemifacial Spasm / Q000473:pathology* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D061145:Microvascular Decompression Surgery / Q000379:methods*; D008875:Middle Aged; D012086:Reoperation