title: Middle interhemispheric variant of holoprosencephaly: a distinct cliniconeuroradiologic subtype.
abstract: BACKGROUND
  The middle interhemispheric variant (MIH) is a subtype of holoprosencephaly (HPE) in which the posterior frontal and parietal areas lack midline separation, whereas more polar areas of the cerebrum are fully cleaved. While the neuroradiologic features of this subtype have been recently detailed, the clinical features are largely unknown.
  
  
  OBJECTIVE
  To present the clinical manifestations of MIH and to compare them with classic subtypes (alobar, semilobar, and lobar) of HPE.
  
  
  METHODS
  The authors evaluated 15 patients with MIH in a multicenter study. Neuroimaging and clinical data were collected and correlated. They compared the data with those of 68 patients who had classic HPE.
  
  
  RESULTS
  The frequency of endocrinopathy in MIH (0%) was lower compared with the classic subtypes (72%) (p < 0.0001). This correlated with the lack of hypothalamic abnormalities. The percentage of patients with seizures (40%) did not significantly differ from classic HPE. Spasticity was the most common motor abnormality, seen in 86% of MIH patients, similar to other subtypes. The frequency of choreoathetosis in MIH (0%) was lower than that for semilobar HPE (41%) (p < 0.0039). This correlated with the lack of caudate and lentiform nuclei abnormalities. Developmental functions, including mobility, upper-extremity function, and language, of the MIH group were similar to the least severe classic type, lobar HPE.
  
  
  CONCLUSIONS
  MIH is a recognizable variant of HPE with differing clinical prognosis. Similar to the lobar subtype by functional measures, MIH differs from classic HPE by the absence of endocrine dysfunction and choreoathetosis.
authors.affiliation: Stanford University School of Medicine and Lucile Packard Children's Hospital, CA, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Lewis
authors.forename: E M
authors.initials: EM
authors.lastname: Simon
authors.forename: A J
authors.initials: AJ
authors.lastname: Barkovich
authors.forename: N J
authors.initials: NJ
authors.lastname: Clegg
authors.forename: M R
authors.initials: MR
authors.lastname: Delgado
authors.forename: E
authors.initials: E
authors.lastname: Levey
authors.forename: J S
authors.initials: JS
authors.lastname: Hahn
mesh_terms: D000293:Adolescent; D001833:Body Temperature Regulation / Q000502:physiology; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology; D002557:Cerebrospinal Fluid Shunts; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003560:Cysts / Q000150:complications; D002658:Developmental Disabilities / Q000209:etiology; D004700:Endocrine System Diseases / Q000150:complications; D004827:Epilepsy / Q000150:complications; D005145:Face / Q000002:abnormalities; D005260:Female; D016142:Holoprosencephaly / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D006849:Hydrocephalus / Q000150:complications; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D009069:Movement Disorders / Q000150:complications; D009460:Neurologic Examination; D012640:Seizures / Q000150:complications; D012886:Skull / Q000002:abnormalities; D014057:Tomography, X-Ray Computed