title: Discrete cortical infarction with prominent impairment of thumb flexion.
abstract: BACKGROUND
  Intracortical efferent zones in the primary motor cortex for thumb movements, namely thumb flexion, extension, adduction, and abduction, have been described in Macaca mulatta monkeys but not in humans. Even recent cortical mapping based on intraoperative monitoring does not provide information about intracortical efferent zones as it is not ethically possible to search the human motor cortex extensively by punctate electrodes.
  
  
  METHODS
  A 78-year-old man with discrete cortical embolism over the left central sulcus is described. Only a mild weakness of his right thumb was observed. Thumb flexion was affected to a greater degree than thumb extension, adduction, and abduction. The lesion ran along the bottom of the central sulcus and affected part of the precentral and postcentral gyri on both sides of it. Animal studies in Macaca mulatta monkeys have shown that the intracortical efferent zones for thumb movement, especially for thumb flexion, are located in the part of the motor cortex just adjoining the central sulcus that folds down from the "bank" to the depth of the central sulcus. It was possible to explain the prominent weakness of thumb flexion if we applied the results of the animal studies.
  
  
  CONCLUSIONS
  Our case suggests that the same arrangement of intracortical efferent zones found in monkeys may also exist in human beings.
authors.affiliation: Department of Neurology, Tokyo Metropolitan Neurological Hospital, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Terao
authors.forename: H
authors.initials: H
authors.lastname: Hayashi
authors.forename: T
authors.initials: T
authors.lastname: Kanda
authors.forename: H
authors.initials: H
authors.lastname: Tanabe
mesh_terms: D000368:Aged; D001931:Brain Mapping; D002544:Cerebral Infarction / Q000150:complications / Q000175:diagnosis / Q000473:pathology*; D006429:Hemiplegia / Q000209:etiology; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology; D009069:Movement Disorders / Q000209:etiology; D013933:Thumb; D014057:Tomography, X-Ray Computed