title: Neurophysiological techniques to detect early small-fiber dysfunction in transthyretin amyloid polyneuropathy.
abstract: BACKGROUND
  Transthyretin familial amyloid polyneuropathy (TTR-FAP) is characterized by early selective involvement of small nerve fibers. Initial clinical diagnosis is complicated by psychosocial factors. We evaluated diagnostic accuracy of sural sensory nerve action potentials, plantar sympathetic skin response (SSR), and cortical laser-evoked potentials (LEP) to dorsal foot stimulation in the early diagnosis of TTR-FAP.
  
  
  METHODS
  Sixty-three subjects with TTR-FAP (Val30Met) mutation were split into 2 groups (asymptomatic carriers and early-symptomatic patients) and compared with 33 healthy controls.
  
  
  RESULTS
  The diagnostic accuracy of plantar SSR amplitude and LEP N2 latency was similar; all had very high specificity (94 to 97%) but low sensitivity (22 to 32%) in distinguishing controls from carriers and early-symptomatic patients. No control had abnormal results on both tests.
  
  
  CONCLUSIONS
  Plantar SSR and LEPs have similar diagnostic performance in detecting small-fiber dysfunction in early TTR-FAP; we propose that both tests should be used to investigate this population. Muscle Nerve 49: 181-186, 2014.
authors.affiliation: Department of Neurosciences, Centro Hospitalar Lisboa Norte- Hospital de Santa Maria, Av Prof Egas Moniz, 1649-028, Lisbon, Portugal; Translational and Clinical Physiology Unit, Instituto de Medicina Molecular, Faculty of Medicine, Lisbon, Portugal.
authors.forename: Isabel
authors.initials: I
authors.lastname: Conceição
authors.forename: João
authors.initials: J
authors.lastname: Costa
authors.forename: José
authors.initials: J
authors.lastname: Castro
authors.forename: Mamede
authors.initials: M
authors.lastname: de Carvalho
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D017772:Amyloid Neuropathies / Q000175:diagnosis* / Q000503:physiopathology*; D028227:Amyloid Neuropathies, Familial / Q000175:diagnosis* / Q000503:physiopathology*; D016022:Case-Control Studies; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005528:Foot; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology*; D011446:Prospective Studies; D011930:Reaction Time / Q000502:physiology; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012867:Skin / Q000294:innervation; D013497:Sural Nerve / Q000503:physiopathology*
keywords: familial amyloid polyneuropathy; laser evoked potentials; nerve conduction studies; sensitivity; specificity; sympathetic skin response