title: Lhermitte sign after chemo-IMRT of head-and-neck cancer: incidence, doses, and potential mechanisms.
abstract: OBJECTIVE
  We have observed a higher rate of Lhermitte sign (LS) after chemo-intensity-modulated radiotherapy (IMRT) of head-and-neck cancer than the published rates after conventional radiotherapy. We hypothesized that the inhomogeneous spinal cord dose distributions produced by IMRT caused a "bath-and-shower" effect, characterized by low doses in the vicinity of high doses, reducing spinal cord tolerance.
  
  
  METHODS
  Seventy-three patients with squamous cell carcinoma of the oropharynx participated in a prospective study of IMRT concurrent with weekly carboplatin and paclitaxel. Of these, 15 (21%) reported LS during at least 2 consecutive follow-up visits. Mean dose, maximum dose, and partial volume and absolute volume (in milliliters) of spinal cord receiving specified doses (≥10 Gy, ≥20 Gy, ≥30 Gy, and ≥40 Gy), as well as the pattern of dose distributions at the "anatomic" spinal cord (from the base of the skull to the aortic arch) and "plan-related" spinal cord (from the top through the bottom of the planning target volumes), were compared between LS patients and 34 non-LS patients.
  
  
  RESULTS
  LS patients had significantly higher spinal cord mean doses, V(30), V(40), and absolute volumes receiving 30 Gy or more and 40 Gy or more compared with the non-LS patients (p < 0.05). The strongest predictors of LS were higher V(40) and higher cord volumes receiving 40 Gy or more (p ≤ 0.007). There was no evidence of larger spinal cord volumes receiving low doses in the vicinity of higher doses (bath-and-shower effect) in LS compared with non-LS patients.
  
  
  CONCLUSIONS
  Greater mean dose, V(30), V(40), and cord volumes receiving 30 Gy or more and 40 Gy or more characterized LS compared with non-LS patients. Bath-and-shower effects could not be validated in this study as a potential contributor to LS. The higher-than-expected rates of LS may be because of the specific concurrent chemotherapy agents or more accurate identification of LS in the setting of a prospective study.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pak
authors.forename: Karen
authors.initials: K
authors.lastname: Vineberg
authors.forename: Felix
authors.initials: F
authors.lastname: Feng
authors.forename: Randall K
authors.initials: RK
authors.lastname: Ten Haken
authors.forename: Avraham
authors.initials: A
authors.lastname: Eisbruch
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D016190:Carboplatin / Q000008:administration & dosage; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000628:therapy*; D059248:Chemoradiotherapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000628:therapy*; D017239:Paclitaxel / Q000008:administration & dosage; D011446:Prospective Studies; D011832:Radiation Injuries / Q000000981:diagnostic imaging; D011836:Radiation Tolerance; D011859:Radiography; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D013116:Spinal Cord / Q000000981:diagnostic imaging / Q000528:radiation effects*
chemical_list: D016190:Carboplatin; D017239:Paclitaxel