Neurotoxicity with chloramphenicol--an electron microscopic study.

The peripheral nerve and spinal ganglion of chloramphenicol-administered and normal animals were examined mainly with the electron microscopy. The experimental animals consisted of three dogs and one rabbit. They were highly injected or given orally high doses of chloramphenicol with a duration from 70 to 130 days. Pathological finginds were briefly summarized as follows. In the sural nerve the changes in myelin sheaths and Schwann cells were more prominent than those in axons. The myelin sheaths were swollen and had a tendency to be curled and compress the azon in some fibers. Other fibers showed the degeneration of myelin sheaths, revealing fragmentation, thinning, and honeycomb structure. The changes in axons were mild, showing an increase of neurofilaments and local accumulation of mitochondria. Schwann cells were often hypertrophied and abundant endoplasmic reticula, vacuoles and ribosomes were observed in the cytoplasm. The processes of Schwan cells were not active, but the picture that a myelinated fiber was surrounded by some processes of Schwann cells was seen in some occasions. In the posterior root ganglion at the lumbar cord, some of nerve cells showed changes, such as breakdown of Nissl substance, swollen mitochondria and indentation of nuclear membrane. The satellite cells showed no significant change.