[Late progressive radiation myelopathies. A study of 27 cases].
Several conclusions seem evident from this study : firstly radiation myelopathies exist without any doubt; secondly clinical observation, even very attentive, during irradiation is perfectly blind regarding this subject; lastly, one can only, at this time, attempt to anticipate medullary accidents caused by irradiation. Radiation myelopathies exist incontestably. We report 27 new cases which are added to the more than 500 cases already analysed in the world litterature. The improvement of results of cancerology and in particular of radiotherapy make and will continue to make the number of observations published increase. However, if there is no doubt as to existence of these myelopathies, discussions persist concerning their nature : purely vascular, cytotoxic, probably mixed, perhaps maintained and prolonged by a superimposed immunologic phenomenon. Prevention is the sole method at our disposal to be effective. It must be applied as much to the patient as to the technique of irradiation. With regard to the patient treated in a medullary volume, several factors are probably favorable to the development of myelopathy and must cause one to modify eventually the technique of radiation proposed : the existence of anterior vertebral medullary pathology, whatever its nature; two ages demonstrate increased incidences : the young which have relative immaturity of tissue (we report 4 cases patients less than 25 years old), and the old, whose chances of accumulating associated pathologies are great, especially as systemic hypertension and arteriosclerosis are likely to have played a favorable role; the patients for whom restraint is difficult or who present disrupted regions anatomy are qually much more fragile. With regard to the technical plan, several factors incontestably favor the appearance of radiation myelopathy : large medullary volumes irradiated, especially when they encompass the zones of vascular medullary junction; the overlap of fields involving the spinal cord; the reduction of fields too close to the spinal cord not allowing at least 1 cm margin of relative security; the association of physical agents in the measure to which the global dosimetry is uncertain, i.e. in particular the use of high energy electrons for boost dosage, the intensity of which must be chosen with the greatest prudence; finally and most importantly, it seems desirable to us not to surpass at the level of the spinal cord, treating 5 times per week, a dose of 5 000 rads with fractions of 200 rads of 4 500 rads with fractions of 250 rads, and of 4 000 rads with fractions of 300 rads. Can one reasonable pretend always to foresee all radiation myelopathies? No, for on the one hand there exist authentic cases which have occured after doses which were below the limits of tolerance which we have indicated above, in accordance with others authors, and on the other hand, the necessity of sterilising certain inoperable tumors obliges one sometimes to deliver to region of the spinal cord aggressive doses.