title: MRI Findings in Nonlesional Hypertrophic Olivary Degeneration.
abstract: OBJECTIVE
  Investigate the relative frequency of nonlesional versus lesional hypertrophic olivary degeneration (HOD) and potential explanations for nonlesional HOD.
  
  
  METHODS
  Our radiology report database was queried for "HOD" in all head MRI reports between 7/1/2002 and 7/1/2013 and identified 138 patients. Specific absence of HOD or cases with lesions within the dento-rubro-olivary pathway (DROP) or extending into the inferior olivary nuclei (ION) were excluded (22 in total). For included patients, 19 locations with the anatomic potential to connect to the ION or DROP were reviewed and grouped into embryological categories, along with the use of the drug metronidazole.
  
  
  RESULTS
  A total of 51 of 116 (44%) HOD patients did not have a causative lesion in the DROP. The 27/51 (53%) of these patients had progressive ataxia with palatal tremor (PAPT). The 28/51 (55%) patients had one or more lesions outside of the DROP and one of these 28 patients used metronidazole. The remaining 23/51 (45%; 19% of total HOD cohort) patients had no additional lesions in the brain and 6 of these 23 patients did not have a clinical diagnosis of PAPT.
  
  
  CONCLUSIONS
  Forty-four percent of patients with HOD did not demonstrate an MRI-identifiable lesion in the DROP, and 45% of those patients did not have identifiable brain lesions outside of the DROP. Thus, nearly a fifth of HOD cases may be truly idiopathic. A majority of patients without a DROP lesion had bilateral HOD and two-thirds were male.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Chris N
authors.initials: CN
authors.lastname: Gu
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Carrie M
authors.initials: CM
authors.lastname: Carr
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kaufmann
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Kotsenas
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Hunt
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Wood
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000473:pathology*; D009847:Olivary Nucleus / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: Hypertrophic olivary degeneration; dento-rubro-olivary pathway