title: Impact of hyponatremia on nerve conduction and muscle strength.
abstract: BACKGROUND
  Hyponatremia is associated with unstable gait and propensity to falls. The potential contribution of peripheral nervous system dysfunction induced by hyponatremia has not yet been addressed by prospective studies.
  
  
  METHODS
  In the first part of this prospective study, we performed two tests evaluating muscle strength (grip test and quadriceps isometric contraction test) together with a timed up and go (TUG) test in 11 patients with chronic mild-to-moderate hyponatremia before and after the normalization of natremia. In the second part, we measured nerve conduction velocities and F-wave latencies in nine patients with profound hyponatremia (< 125 mmol/L) before and after the normalization of natremia.
  
  
  RESULTS
  No significant change in muscle strength was observed when natremia was corrected from 127·7 ± 2·5 to 136·1 ± 1·8 mmol/L, contrary to a significant improvement in TUG from 14·9 ± 5·1 to 12·5 ± 4·7 s (P = 0·006). Nerve conduction velocities and F-wave latencies showed significant improvement in most of the studied nerves when natremia was corrected from 121·9 ± 2·4 to 135·5 ± 3·4 mmol/L (e.g. mean increase of 14·3% for motor nerve conduction and mean decrease of 21·6% for F-wave latency of left peroneal nerve).
  
  
  CONCLUSIONS
  Whereas chronic mild-to-moderate hyponatremia has no impact on muscle strength, we demonstrate for the first time an impact of profound hyponatremia on nerve conduction studies. Further studies are needed to ascertain the contribution of these latter results on gait disturbances, propensity to falls and attention deficits associated with hyponatremia.
authors.affiliation: Internal Medicine, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Vandergheynst
authors.affiliation: Internal Medicine, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Gombeir
authors.affiliation: Neurology, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Flavio
authors.initials: F
authors.lastname: Bellante
authors.affiliation: Neurology, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Perrotta
authors.affiliation: Neurology, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Gauthier
authors.initials: G
authors.lastname: Remiche
authors.affiliation: Emergency Medicine Departments, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Christian
authors.initials: C
authors.lastname: Mélot
authors.affiliation: Neurology, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mavroudakis
authors.affiliation: Internal Medicine, Erasme University Hospital, Université Libre de Bruxelles, Brussel, Belgium.
authors.forename: Guy
authors.initials: G
authors.lastname: Decaux
mesh_terms: D000368:Aged; D002908:Chronic Disease; D005080:Exercise Test; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D007010:Hyponatremia / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D011446:Prospective Studies; D052097:Quadriceps Muscle / Q000502:physiology
keywords: F-wave latencies; hyponatremia; muscle strength; nerve conduction velocity; timed up and go test