More often there is a secondary venous thrombosis here, an extension backward of a like process in the sinus into which the vein empties.
Cretefaction and fatty degeneration of the parietes of these vessels also occurs, though, of course, without clinical sig nificance. And the same applies to the endophlebitis deformans chronica de scribed by Huber.
Sinus-thrombosis.—This is a blocking of any one or more of the several venous sinuses of the brain.
Such obstruction is, of course, never of embolic origin, but always due to thrombosis (or, in rare cases, to trauma or ligature). Neighboring septic trouble is more often a cause than in the case of the arteries, but otherwise disease of the vascular wall plays no such part as with the arteries. The causes are, however, many. In children it occurs in maras mus, cholera infantum, whooping-cough, and other conditions of extreme exhaus tion. In the adult, chlorosis, pregnancy and the puerperium, erysipelas (by exten sion, centrally, of a process starting at the surface), cholera, and like disorders that greatly reduce the body-fluids, sep tic processes in adjacent tissues, and any form of debility that greatly weakens the circulation. Most frequent of all are the cases of phlebitis of the lateral petrous and connecting sinuses, due to extension of inflammation from ear disease; the important features of this form belong to the ear section.
There are other less frequent forms of inflammation, starting, perhaps, in the parasinual spaces and involving the sinuses.
Symptoms.—It should be remembered that one or both jugulars may be tied, one or even both lateral sinuses closed, or almost any single sinus blocked, with out the necessary production of symp toms, as has been many times shown by clinical, operative, and, in animals, ex perimental evidence. The only excep tion to this is the straight and possibly the two cavernous sinuses. In the very young, the feeble, or those otherwise ex hausted, blocking of a sinus may have more effect, and be a factor in a general break-up. Such was, perhaps, the ex planation in Rummer's case (Rev. de Med., '99), where a fatal result followed ligation of one internal jugular, some hypermnia and haemorrhage being found in the brain.
The sinuses that are easy of access sur gically are the longitudinal and the two laterals. Besides these, if it were war rantable, it would be quite possible to tie the end of a straight sinus.
Thrombosis of the brain does not lead to any definite increase of the cerebro spinal fluid, as a rule. The only excep tion is where the outflow through the straight sinus is interfered with, or, pos sibly, the venous discharge from the small fringe of choroid plexus in the an gles of the fourth ventricle.
For the most part, the symptoms at tributed to sinus-thronthosis are really due to the attendant sepsis or an extension of the inflammation to neighboring struct ures. Consequently it is only incumbent here to consider the cases where postive symptoms are due to the blocking as such.
It is claimed by ('99) that a mur mur can be detected in the unobstructed internal jugular vein, or that it can be produced artificially by a slight pressure of the stethoscope on the neck close to the base of the skull. If, however, the murmur is absent despite such reinforce ment, while present on the other side, there must be occlusion of the sinus.
The presence or absence of a sinus pulse has no diagnostic value as regards thrombosis (Preysing, '98).
The untoward effects of closure of the straight sinus have been recently studied by the writer ("Normal and Pathological Circulation in the Central Nervous Sys tem," '97, pp. 68 and 83), and the follow ing conclusions (pp. drawn:— In cases of closure of the sinus meths, Galen's vein, or the velar veins, three pos sible outcomes are to be thought of:— "1. Full physiological compensation. There appears to be no evidence to show that perfect compensation can occur.
"2. An increase of ventricular fluid, leading to hydrocephalus.
"The ample anastomoses described, and the fact that normally this venous current has to turn several sharp angles before leaving the skull, make it, at first, unintelligible why there should ever be any trouble following the closure of the sinus rectos or its practical extension, the single trunk of Galen's vein. And, so far as concerns either the vitality of the tissues or the function of the brain-sub stance and nerve-substance proper, there is nothing to show that compensation is less perfect than where other brain-veins are closed.
"The difference depends entirely on the presence, in the territory of this vein, of a peculiar structure, the choroidal tis sue, occurring only in the brain-ventri cles. This tissue normally produces ven tricular fluid. Its activity is easily in fluenced by many conditions, and it re sponds quite naturally to any interfer once with the venous discharge by an in creased production of fluid.
"It is, then, not primarily any venous stasis that causes symptoms, but only the secondary hydrocephalus. And the facts show that this is always bound to occur. This causes death, if at all, only after a lengthy period and in this indirect man ner.
"3. Early death.
"If, however, the velars be closed (i.e., the vena: intimse be cut off from both their regular and collateral outlets), then, so far as present evidence goes, a speedy fatal ending is inevitable. This takes place before there is time for the 1 development of much hydrocephalus, a small quantity of blood-tinged fluid be ing all that has accumulated.
"Up to 1884 the writer was able to col lect three such American cases, and those from foreign sources were merely cor roborative.
"It is still possible that if only the main trunk of one or both velars was ob structed, and the thrombus did not ex tend into any of their branches, the fatal ending might be delayed, but hardly for long."