The symptoms in the acute diseases of the encephalon are not generally such as point with any distinctness to the exact site of the action, because, though doubtless commencing in different structures, and occasionally limited to them, inflammation in volves so_much the general functions of the brain, as the centre of innervation and the organ of mind, that we can scarcely assign to each part a distinct share in their production ; it rather con cerns us to find out any really available mode of discriminating the two great practical divisions—the scrofulous and the simple inflammation.
§ 1. Scrofulous or Tubercular Inflammation.—This form of in flammation is so much more common in infancy than at more advanced periods, that until recently it was, hardly recognized as occurring after the age of puberty ; and the name by which it was first known, "acute hydrocephalus," was limited to childhood : the records of St. George's Hospital prove that it is not uncom mon up to the age of twenty-five or thirty. Its symptoms and progress have been much more studied in the earlier periods ; and the description of these, in consequence of the modifications due to vital phenomena during the progress of development, will not always be found applicable to the disease as occurring in the adult. Pathological research seems to prove that the disease is the same, at whatever age it occurs ; it is essentially connected with the strumous diathesis, which exerts some mysterious agency in its development, and hence it is numerically far more common than simple inflammation ; indeed, up to the age of twenty-five, the one is the rule, the other the exception ; so much so that, ex cluding infancy altogether, the number of cases occurring in con nection with the scrofulous diathesis, from eight or ten years of age onwards, is probably double that of cases of simple inflam mation at all periods of life collectively ; this fact is very im portant in diagnosis.
The tendency of the inflammatory action is to the effusion of serum rather than of lymph or of pus ; but both conditions fre quently coexist, as well as varying degrees of softening of the cerebral structures. These different lesions probably correspond to different degrees of arterial action during life, as indicated by heat and pain of head, in opposition to dulness, heaviness, and delirium ; at present no certain rule can be laid down by which they may be discriminated : coma and unconsciousness are pretty certain evidences of effusion, but in prolonged cases the brain seems partly to recover its power and become tolerant of the pressure. The susceptibility of the brain in the earlier periods
of life is so much greater than in later years, that inflammation of the brain is then often the first indication of the tubercular diathesis, while afterwards tubercular deposit will have always been first formed in other organs.
Much as has been written on -the diagnosis of the early stage of this disease in infancy, it is practice alone that can give any readiness in its discrimination. A child belonging to a scrofulous family is attacked by slight febrile disorder, with irregularity of the bowels, especially tending to constipation, with vomiting and occasional fretfulness : in such a case it is necessary to observe very carefully all indications referring to the brain ; the mode of standing, walking, sitting, lying; any aversion to light, or dislike to the erect posture, as shown by nestling its head on the mother's bosom, and turning away peevishly from any attempt to amuse or occppy its attention. These circumstances, again, must be compared with the amount of general disturbance : a child suf fering from infantile fevers shows much more weakness and pros tration in comparison with the signs of cerebral affection : in hydrocephalus the heat of skin is most marked over the head, but is not in proportion to the quickness of the pulse ; the tongue is coated but not dry ; the stools are costive and often deficient in bile ; thirst is not urgent ; the vomiting has no necessary con nection with the period of taking food : in infantile fever, the heat of skin is more general, there is dryness of tongue, thirst, and very often a tendency to diarrhoea; listlessness and indifference mark the expression of the features rather than the anxiety and knitting of the eyebrows so often seen in hydrocephalus.
In simple gastric disorder, on the other hand, there is little or no quickness of pulse, no heat of skin or of head ; the tongue is much more coated ; the vomiting and constipation areless obsti nate, yielding more readily to treatment; the countenance may be dull and inexpressive, but it is not anxious.