Autonomic dysfunction in Chagas disease: lack of participation of the vagus nerve.

To evaluate the possible role of the vagus nerve in the development of the dysautonomia in Chagas disease, we examined 18 nerves from chagasic patients and 8 from non-chagasic patients, autopsied at the Department of Pathology, Ribeirão Preto School of Medicine, Brazil. Histological analysis showed mild inflammatory infiltrate composed predominantly of T lymphocytes, in epi-, peri- and endoneurium. No parasites were observed. Semithin sections showed swollen unmyelinated fibres, occasional thinly myelinated fibres, degenerated and atrophic axons, related to myelinated fibres. These findings were confirmed by electron microscopy, and in teased fibres. The changes were observed both in chagasic and in non-chagasic patients. Statistical analysis of the morphometric findings (myelinated fibre density, axonal and fibre diameters) failed to show significant differences between the 2 groups. The frequency of myelinated fibres of various diameters was also similar in the 2 groups. The morphological and morphometrical findings in chagasic patients are mild, non-specific, and could be related to the age of the patients, or with artefacts, since they have also been observed in non-chagasic patients. Retrograde changes due to the ganglionic lesions in the innervated organs cannot be completely ruled out. Our results do not allow us to implicate the vagus nerve in the dysautonomia in Chagas disease.