Rep. Sica et al., PERIPHERAL NERVOUS-SYSTEM INVOLVEMENT IN HUMAN AND EXPERIMENTAL CHRONIC AMERICAN TRYPANOSOMIASIS, Bulletin de la Societe de pathologie exotique et de ses filiales, 88(4), 1995, pp. 156-163
An electrophysiological and histological study of the muscle and the p
eripheral nervous system (PNS) was carried out in chronic human Americ
an trypanosomiasis (Chagas' disease) and in an experimental Chagas' di
sease (Chd) mouse model. Altogether 995 patients with chronic Chd and
261 mice, experimentally infected with RA and CA-I parasite strains, w
ere investigated. Results were compared with matched controls. Techniq
ues employed in humans were: clinical assessment, conventional electro
myography (EMG), estimated number of motor units, motor and sensory ne
rve conduction velocities, repetitive nerve stimulation and muscle and
sural nerve biopsies. In mice conventional EMG, sciatic nerve conduct
ion time, sciatic nerve action potential amplitude, in vitro miniature
end-plate potentials (MEPPs) and end-plate potentials (EPPs) recordin
gs, muscle, nerve and spinal cord histology and identification of cell
phenotypes within the inflammatory infiltrates were the employed proc
edures. Out of 511 patients submitted to clinical examination, 52 disc
losed signs and symptoms of mixed peripheral neuropathy. By employing
electrophysiological techniques, it could be shown that about 30 % of
the investigated patients had one or more of the following features. d
iminished interference pattern, most of the remainder motor unit poten
tials being (MUPs) polyphasic; reduced number of functional motor unit
s in the thenar, hypothenar, soleus and/or edb muscles, slow sensory a
nd motor nerve conduction velocities; low sensory action potential amp
litude and impairement of neuromuscular transmission. In mice, MUPs du
ration and amplitude were increased at later stages of the infection,
nerve conduction was slow, nerve action potentials were of low amplitu
de, mepps were of low amplitude and double epps were frequently found.
Muscle histology in humans with chronic Chd showed type I and type II
grouping, atrophic angular fibers and targetoid muscle fibers. In mic
e perivascular mononuclear cells infiltrates, small round fibers, musc
le fibers necrosis, atrophic angular fibers, type II muscle fibers gro
uping and grouped muscle fibers atrophy were found. Sural nerve sample
s showed segmental and paranodal demyelination and axonal loss. The sa
me features were observed in mice nerves, also in this model mononucle
ar cells infiltrates at the nerve, dorsal root ganglia and meninges su
rrounding the spinal cord were observed. Muscle and nervous tissues in
filtrates were mainly composed of T lymphocytes with predominance of C
D8 or CD4 subsets according to the parasites strain employed for infec
ting the animals. These findings suggest that the skeletal muscle and
the PNS may be involved in chronic american trypanosomiasis.