title: Unilateral cortical hyperexcitability in congenital hydrocephalus: a TMS study.
abstract: BACKGROUND
  Changes in cortical excitability are considered to play an important role in promoting brain plasticity both in healthy people and in neurological diseases. Hydrocephalus is a brain development disorder related to an excessive accumulation of cerebrospinal fluid (CSF) in the ventricular system. The functional relevance of cortical structural changes described in this disease is largely unexplored in human. We investigated cortical excitability using multimodal transcranial magnetic stimulation (TMS) in a case of congenital hydrocephalus with almost no neurological signs.
  
  
  METHODS
  A caucasian 40 years old, ambidextrous and multilingual woman affected by occult spina bifida and congenital symmetrical hydrocephalous underwent a TMS study. The intracortical and interhemispheric paired pulse paradigms were used, together with the mapping technique.
  
  
  RESULTS
  No significant differences were found in the resting motor thresholds between the two hemispheres. Instead, the intracortical excitability curves were statistically different between the two hemispheres (with short intracortical inhibition (SICI) being strongly reduced and intracortical facilitation (ICF) enhanced in the right one), and the interhemispheric curves showed a general hyper-excitability on the right hemisphere (when conditioned by the left one) and a general hypo-excitability in the left hemisphere (when conditioned by the right one). It is noteworthy that an asymmetric right hemisphere (RH) change of excitability was observed by means of mapping technique.
  
  
  CONCLUSIONS
  We hypothesize that in this ambidextrous subject, the observed RH hyper-excitability could represent a mechanism of plasticity to preserve functionality of specific brain areas possibly devoted to some special skills, such as multilingualism.
authors.affiliation: a Department of Neurology , University Campus Bio-Medico , Rome , Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Guerra
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Curcio
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pasqualetti
authors.forename: Federica
authors.initials: F
authors.lastname: Bressi
authors.forename: Sara
authors.initials: S
authors.lastname: Petrichella
authors.forename: Federica
authors.initials: F
authors.lastname: Scrascia
authors.forename: David
authors.initials: D
authors.lastname: Ponzo
authors.forename: Michela
authors.initials: M
authors.lastname: Ferilli
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Vernieri
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
authors.forename: Florinda
authors.initials: F
authors.lastname: Ferreri
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D006849:Hydrocephalus / Q000151:congenital* / Q000503:physiopathology*; D016135:Spinal Dysraphism / Q000150:complications / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*