From the description which has been given of the Idiopathic
Muscular Atrophies, 'it will he seen that there exist several
types, all characterised; by a progressive wasting of a greater
or less number of the voluntary muscles of the body, but which,
at the sane time, present differences in their clinical features.
Three principal types have been selected as being most
pronounced in their characters, and in this way the points of
agreement and difference are more clearly brought out.
These points of difference constitute, according to some,
sufficient ground for regarding the various types as distinct
primary muscular affections, and not as essentially one disease,
as the numerous points of agreement would more readily lead one
to believe them to be.
The differences are, it must be remembered, merely differences
of degree of the morbid process and in the initial localisation, both of which seem to be influenced by the date of onset.
Thus, when the disease shows itself in the early period of
development, it is more apt to be attended by hypertrophy, especially in the legs and face; but when the onset occurs at a late
period, wasting, especially at the roots of the limbs, is the
But it has been mentioned under the pseudo-hypertrophic
form that atrophy is almost as important a feature in the disease
as hypertrophy, and that the latter was due to a fatty infiltration. This fatty infiltration is also marked in the face in
the Orbicularis Oris, which is always first affected, and which
gives to the lips the volume they possess. Thus it may be look upon
as a phase of the pseudo-hypertrophic form.
The infantile form, again, affects more frequently the male
sex, and, as in the pseudo-hypertrophic form, we find transmission occurring more usually through the mother.
Many observers in recording cases of the pseudo-hypertrophic
form, speak of the stupid-expression worn by these patients,
even in cases in which the intelligence was undoubtedly unimpaired, and this, no doubt, was due to the greater or less implication of the muscles of the face, and the imperfect performance
of their functions.