ETIOLOGY.—Concerning the etiology proper of infantile paralysis little definite is known. It is probable, as has been already noticed, that traumatisms have a much more decided influence than is generally assigned to them. Leyden particularly insists on this influence, and on the facility with which a traumatism relatively severe for a young child may be overlooked, because it would not be recognized as such for an adult. It must be noticed, however, that children are much more liable to have the arms wrenched and pulled violently than the lower extremities; yet in a great majority of cases the lesion is situated in the lumbar cord.
It has been shown that the myelitis, though so limited transversely, is often far more diffused in the longitudinal axis of the cord than might be supposed from the permanent paralyses. This fact corresponds to the initial generalization of the motor disturbance. It seems possible that the traumatic irritation, starting from the central extremity of the insulted nerve, diffuses itself through the cord until it meets with its point of least resistance, and here excites a focal myelitis. That this point should most frequently be found in the lumbar cord would be explained by its relatively less elaborate development, corresponding to the imperfect growth and function of the lower extremities.
A second cause of anterior poliomyelitis is, almost certainly, the presence of some poison circulating in the blood. The frequent occurrence of the accident in the course of one of the exanthemata is one indication of this; other indications are found in such cases as that related by Simon, where three children in one family were suddenly attacked—two on one day, one, twenty-four hours later.151 The same author relates a case of motor paralysis in an adult, followed by atrophy of left lower extremity, and which occurred during a fit of indigestion caused by eating mussels.152 The acute ascending paralysis of Landry, with its absence of visible lesion, has been said to strikingly resemble the effects of poison. Hydrophobia and tetanus are again examples of the predilection exhibited by certain poisons for the motor regions of the cord.
151 Journal de Thérap., 7, vii., 1880, p. 16. These children belonged to an American family, but were seen by several distinguished French physicians.
152 P. 357.
The evidence that infectious diseases may constitute the immediate (apparent) causal antecedent of acute poliomyelitis has led, not unnaturally, to the theory that all cases of acute infantile paralysis are due to a specific infecting agent, some as yet unknown member of the great class of pathogenic bacteria. It may be noticed, however, that the occurrence of the spinal accidents after the ordinary infectious diseases, as scarlatina and measles, should as well indicate that a specific agent proper to itself was at least not essential to its development.153
153 Perhaps the occurrence of diphtheria in the course of scarlatina and typhoid should indicate a similar lack of real specificity in the morbid agent of the former disease.
The influence of exposure to cold, which seems to have been sometimes demonstrated, must probably be interpreted, as in the case of rheumatism and pneumonia, as effective by means of some poison generated in the organism when cutaneous secretion, exhalation, or circulation has been suddenly checked.
DIAGNOSIS.—The diagnosis of the acute anterior poliomyelitis of childhood is usually easy, but unexpected difficulties occasionally arise.
Typical cases are markedly different from typical cases of cerebral paralysis, but in exceptional cases these differences disappear. This is shown in the following table: