Enlargement Of The Skull, as a consequence of hypertrophy, takes place only in the child; but it occurs, whether the bones be held together by interstitial membranes still, or by sutures. The enlargement of the skull, and the hypertrophy of the brain, vary together. In its general form, the skull resembles the hydrocephalic skull.

r. In some rare cases, among children in whom the disease has rapidly advanced to a considerable extent, the sutures of the skull become loose and separate, especially at the upper part of the head, and the sutural cartilages become suffused, and are of a reddish color.

Hypertrophy of the brain is sometimes congenital, and is then often combined with hydrocephalus; it more usually comes on during extrauterine life, but is almost exclusively confined to the period of childhood. It is occasionally met with about the time of puberty, and sometimes even in manhood; but at the latter period it is extremely rare.

Congenital hypertrophy is accompanied by very various degrees of arrested development of the vault of the skull, and sometimes, indeed, that part is entirely wanting (acrania), it is attended, also, by general dwarfish growth, and by various faults in the development of the brain, as well as of other organs. When it comes on in childhood and at puberty, it is combined with general enlargement of the lymphatic glands, and but partial obliteration (involution) of the thymus gland: in childhood it is also combined with rickets and a feeble muscular development. And it supervenes upon hydrocephalus, both the congenital and the acquired.

Hypertrophy of the brain usually destroys life with symptoms of pressure on the organ; especially when that condition exists on which I have laid so much stress, viz., closure of the skull. Its course is generally chronic, but not unfrequently it is somewhat acute: the cause of the acute symptoms is found in the fact, that the process, having for some time progressively increased in intensity, at last occasions a rapid and tumultuous addition to the bulk of the brain; but the acuteness is only apparent, for the disease passes unobserved through its first stages, and at length gives rise to severe and rapidly accumulating symptoms, when it has gone on to a considerable extent.

Children will tolerate this disease, even though it advance to a considerable degree; and after having occasioned a corresponding enlargement of the skull, it may continue throughout life unaltered. This, no doubt, is the explanation of those cases of unusually heavy brain and large-sized skull, which are occasionally met with in adults: they are cases in which the size and hydrocephalic form of the skull have given rise to the idea that a foregone hydrocephalus has been cured by hypertrophy of the brain. (Comp. 273).

Hypertrophy is usually a primary and idiopathic disease; frequently, however, it is secondary, and occasioned by some other disease, more especially by morbid growths; and of these tubercle and cancer are its most frequent cause. Its existence, as a secondary disease, has been hitherto almost unnoticed. But the increase in the volume of the brain, in these cases, is so clearly stamped with all the characters of hypertrophy which I have delineated above, and the frequently inconsiderable bulk of the morbid growth so entirely precludes our accounting for these characters by any compression it could exercise, that there can be no doubt such a form of hypertrophy does occur. The brain is subject to a swelling, which, no doubt, belongs to this class, in consequence of the pressure exerted on the medulla oblongata when the first two cervical vertebrae are carious and dislocated. This form of increase of volume must, of course, be accurately distinguished from the swelling produced by congestion and oedema.

Lastly, the hypertrophy which has been the subject of the foregoing remarks, is a disease affecting the cerebrum, and especially its white substance. It is rather a frequent disease; not so, however, with hypertrophy of smaller portions of the brain.

Although the latter be an extremely rare occurrence, there can be no question that smaller portions of the brain really are separately hyper-trophied. Many of the observations brought forward as instances of this occurrence, are undoubtedly erroneous; adventitious formations infiltrated through the cerebral tissue, may have occasioned at once the enlargement and the error. There are, however, some instances which may be relied on, in which the optic thalamus and the pons were hyper-trophied; and I have myself met with a most remarkable case of hypertrophy of the medulla oblongata.

With regard to the question, to be decided by theory and microscopic examination, as to the nature of the added material upon which the increase of volume depends, I have formed the following opinion from repeated investigations:

(1.) The disease is genuine hypertrophy.

(2.) It consists as such, not in an increase in the number of nerve-tubes in the brain from new ones being formed, nor in an increase in the dimensions of those which already exist, either as thickening of their sheaths or as augmentation of their contents, by either of which the nerve-tubes would become more bulky; - but:

(3.) It is an excessive accumulation of the intervening and connecting nucleated substance.

The immediate cause of hypertrophy of the brain may certainly be congestion; but this is by no means sufficient to explain its occurrence. Regarding it from a higher point of view, I am led rather to believe that the hypertrophy of the brain, and the diseases combined with it, especially the excessive development of the lymphatic system, constitute one disease which is based upon some peculiar state of constitution and mode of growth prevailing chiefly in childhood; a belief which is entertained by others also, especially by Munchmeyer.