Neurophysiological markers in familial amyloid polyneuropathy patients: early changes.
OBJECTIVE
Familial amyloid polyneuropathy-type I (FAP-I) is a hereditary, axonal, sensory-motor and autonomic polyneuropathy, with early involvement of small fibres. Liver transplantation is the only effective therapy in FAP, but should be performed early in the course of the disease. Reliable quantitative methods that could allow the determination of early changes in the peripheral nerve function are essential. Our aim was to find sensitive neurophysiological markers in FAP-I.


METHODS
Eighty-one FAP-I patients were included in this study. They were divided into two groups (G1, asymptomatic FAP-I mutation carriers; G2, early symptomatic). Seventy-six healthy controls formed a control group (G3). Nerve conduction studies, needle electromyography with motor unit potential analysis of the extensor digitorum brevis, RR interval and sympathetic skin response (SSR) were analyzed.


RESULTS
The amplitudes of the motor response of the peroneus nerve and of the plantar SSR were significantly lower in G1 compared to G3. No other differences were found between those two groups. With a cut-off point of 0.2mV for plantar SSR, its sensitivity and specificity are 0.53 and 0.95, respectively. The positive predictive value and the negative predictive value are 0.82.


CONCLUSIONS
SSR response at foot is a useful measurement to detect early dysfunction of peripheral nerve fibres in FAP-I. Its abnormality should be considered a warning sign and lead to a careful clinical assessment.


CONCLUSIONS
SSR is a useful neurophysiological marker in FAP-I.
Conceição
Isabel M
IM
Department of Neurology, Hospital de Santa Maria and Neuromuscular Unit, Institute of Molecular Medicine, Faculty of Medicine, Av Prof Egas Moniz, 1649-028 Lisbon, Portugal. imconceicao@fm.ul.pt
Castro
José F
JF
Scotto
Manuel
M
de Carvalho
Mamede
M
D000328:Adult; D028227:Amyloid Neuropathies, Familial / Q000175:diagnosis*; D015415:Biomarkers / Q000032:analysis*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005528:Foot / Q000294:innervation; D006225:Hand / Q000294:innervation; D006801:Humans; D008297:Male; D009431:Neural Conduction; D012680:Sensitivity and Specificity; D012867:Skin / Q000294:innervation*; D013564:Sympathetic Nervous System / Q000502:physiology*
D015415:Biomarkers