Section Ii. the Membranes of the Brain.

1. The Dura Mater.

This membrane, serving both as a periosteum to the inner surface of the cranial bones and as a support to a serous membrane—the reflected layer of the arachnoid—is subject to affections of a two-fold character, those peculiar to the fibrous and serous portions.

=Inflammation= of this membrane, may involve either the outer fibrous, or the inner serous layer. In the former case, the membrane appears congested, red and more or less softened. The inflammatory process may result in the formation of pus between the bone and dura mater, and even in gangrene. The disease may also extend to the adjacent portions of the pia mater and brain substance. External injuries, fractures of the bones of the skull, inflammation of the periosteum, otitis, resulting in caries of the temporal bone, may all be causes of inflammation of the outer portion of the dura mater.

Inflammation of the inner surface of this membrane, is marked by the presence of a net-work of delicate red vessels, while the surface is covered by a soft, grayish or yellow semi-purulent matter, and may attend cases of pyæmic poisoning, puerperal peritonitis, or some of the exanthemata.

=Thickening= of the fibrous portion of the dura mater may be found as a result of chronic inflammation, either spontaneous or as the result of external injury. From the identity of structure between this and other fibrous tissues of the body, it is not unlikely that this thickening is often the result of a rheumatic form of inflammation.

External violence is, however, most commonly the cause of the change. In one case, the patient fell down stairs in a state of intoxication, striking the head on the steps. He continued in a state of insensibility for nine days, when he began to show signs of returning consciousness, taking food and drink, but memory, judgment, and all the mental faculties were gone. Death ensued in about two years. The dura mater of the left hemisphere was found greatly thickened. The pia mater infiltrated with a large amount of serous fluid. The convolutions were atrophied, and about four ounces of serous fluid found in the ventricles. The fornix was softened and the septum lucidum entirely destroyed.

=Fibrinous Clots, or Thrombi=, will be occasionally found within the sinuses of the dura mater, where they may have given rise to congestion of the brain, with apoplectic effusions, paralysis, convulsions, coma, etc. They may originate from injuries of the head, inflammation of the dura mater, pulmonary disease, etc.

=Tubercular Deposits= are also sometimes found in this membrane, appearing, however, mainly upon the arachnoid surface. They present the usual character of tubercle, having a whitish or grayish appearance, with the consistence of cheese, and scattered in small particles upon the surface. They are found in tubercular meningitis, (a disease common with children but rare with adults,) and in most of those cases of so-called acute hydrocephalus.

=Tumors= of various kinds are occasionally found in the dura mater, including cystic, fibrous, fatty, osseous and cancerous growths. The latter may cause such absorption of the bones of the skull, as to appear on the exterior of the head.

In one case which came into the dissecting-room some years ago, thin bony formations of the size of a silver quarter dollar were found in the tentorium, and smaller ones in the falx cerebri. Nothing could be learned of the previous history of the case.

2. Arachnoid and Pia Mater.

As morbid conditions of the arachnoid membrane are more common with its visceral layer, and as these conditions usually involve the pia mater, the two membranes are here noticed together. They will be found presenting various degrees of congestion after death, which will not necessarily be a positive indication of the extent of congestion during life.

=Pacchionian Bodies.= Along either side of the great fissure may be noticed within the pia mater of adults, several small white bodies, varying in number and size—the Pacchionian bodies. They may cause absorption and perforation of the dura mater, and even of the bones of the skull. Being looked upon as the result of mere senile changes, they do not indicate the presence of disease, though repeated congestions of the brain appear to favor their more rapid development.

=Inflammation= of these membranes, or meningitis, is a very common affection, and is accompanied with an accumulation within its substance or beneath its layers, of serum, lymph, or fibrine in various proportions. It may be confined to circumscribed portions, or involve a large portion of the membrane, and even extend to the spinal cord. Adhesions between the two surfaces of the arachnoid sometimes result from this form of inflammation.

Insanity in its various forms is most frequently accompanied with some morbid condition of these membranes. In twenty-two cases of insane persons whose brains were inspected by Dr. Marshall, in twenty-one, serous fluid, varying in amount from one to twelve ounces, was found in the ventricles, and in seventeen of these twenty-one cases, similar effusion was found in the sub-arachnoid space, or within the substance of the pia mater. While red injection of the membrane was found only in four cases, yet other conditions—the effusions, &c.—were evidently the result of previous inflammation. In nine cases were the arteries of the brain opaque, thickened, steatomatous, or ossified; conditions highly favorable for deranging the capillary circulation of the membranes or of the brain.

The following statement gives the principal morbid changes of these membranes which have been found in cases of insanity:

1. Injection, more or less intense, of the pia mater, giving a red or scarlet appearance; or, where infiltrated with serous fluid, presenting a pale gray color and increased in thickness.

2. The arachnoid (the visceral layer) becomes opaque and thickened, resembling the dura mater or macerated parchment.

3. The meningeal injection may terminate in serous effusion, either from the free surface of the arachnoid into the sub-arachnoid tissue, (pia mater,) or from the choroid plexus into the ventricles.

4. Albuminous exudations may be found upon the free surface of the arachnoid of the dura mater, covering its whole extent, or confined to definite portions.

5. Adhesions of the two surfaces of the arachnoid may rarely be found. It is most common in the great fissure, and has been found in the ventricles.

6. Blood may be effused upon the surface of the arachnoid or in the substance of the pia mater.

=Serous Effusion.= As has been already intimated, this may be found either in the cavity of the arachnoid—between the reflected and visceral layers—or within the ventricles. In the former position, the quantity is never large, while in the latter, it may amount to twelve or sixteen ounces, and be present for many years. When in such large quantity, there will be great distension of the ventricles and thinning of the corpus callosum and fornix, with destruction of the septum lucidum, as well as more or less separation of the cranial bones. It is only in children and before the bones of the head have become united, that such large accumulations are possible, as at a later period, from the unyielding condition of the walls of the skull, the presence of a single ounce, particularly if suddenly formed, would produce death. In all cases, the danger to life will be in proportion to the rapidity of the formation; a very slow and gradual accumulation permitting either of an expansion of the cranial bones, or a gradual absorption of brain substance, thus preserving an approximation to the normal pressure on the brain tissue.

Serous effusions, like sanguineous, are generally the result of over distension of the cerebral vessels, either from mechanical obstruction, or a weakened condition of the coats of the vessels, with increased force in the action of the heart. It generally attends tubercular meningitis, and may be favored by an anæmic condition of the system. The symptoms during life, attending a rapid effusion of serum, are not so readily distinguished from those of sanguineous effusion, as to enable us to pronounce with certainty in any given case as to the cause of the cerebral pressure.

=Sanguineous Effusion—Apoplexy.= Effusions of blood may be found between the bones and dura mater; between the two layers of the arachnoid; within the substance of the pia mater; within the ventricles, or within the brain substance. Blood clots will seldom be found between the bone and dura mater, except as a result of mechanical injury, and in the majority of cases as an attendant upon fracture. If a fragment of the bone at the same time, be driven through the dura mater, then a clot may be found in the arachnoid cavity. But in another class of cases, where death has resulted from blows upon the head without producing fracture of the bones, the whole surface of the brain in the region of the injury, and not unfrequently in distant parts, after the removal of the dura mater, is found covered with a layer of blood, which at first sight appears to be outside of the membranes; but on close examination, it is found that the blood is effused or infiltrated into the sub-arachnoid tissue, and that it has escaped from the lacerated vessels in the pia mater. The thickness of the layer varies. It is generally in greater quantities at the sides and base of the brain, and the inferior lobes and cerebellum may be covered by it. It is usually thickest over the crura, the pons Varolii and medulla oblongata.

In the same class of cases the blood may be also effused into the ventricles. These appearances are so uniformly the result of violence, as to form a valuable piece of evidence in medico-legal inquiries, to prove that such hæmorrhage and death could not be the result of internal causes.

In the greater number of still-born children, an examination of the head will show a similar condition of things. The surface of the cerebrum generally, with sometimes that of the cerebellum, will be found covered with a layer of coagulated blood effused into the pia mater, while the ventricles will often be filled with clots. Where the history of the case is not known, it might at first be suspected that death was the result of violence inflicted after birth. Violence has, to be sure, been the cause of death, but it is such violence as attends a protracted case of labor, with, perhaps, a large head, and a contracted pelvis of the mother. The wonder is, that from the great pressure to which the head is subjected during labor, that so few children are still-born or do not die soon after birth, from rupture of the cerebral vessels.

Effusions into the ventricles, may also be frequently the result of external violence. The pia mater, the vascular membrane of the brain, we find carried into these cavities by means of the velum interpositum, which forms the roof to the third ventricle, while its borders extend into the lateral, forming the choroid plexuses. The effused blood may, therefore, extend along this membrane into the cavity of the ventricles.

Again, blood may be effused in any portion of the brain substance, constituting true sanguineous apoplexy. Certain parts are much more frequently the seat of these effusions than others. They are more common in the striated bodies or optic thalami—probably from the greater vascularity of those parts—but may be found in the corpora quadrigemina, the pons Varolii, the crura cerebri, or in the cerebral hemispheres, and occasionally in the cerebellum. The symptoms during life will vary according to the location of the effusion; when in the pia mater, or in other words, outside of the brain, paralysis will seldom attend, though the coma may be profound, with relaxation of the muscular system and sometimes convulsions. When the hæmorrhage is in the optic bed or striated body of one side, from the decussation of fibres in the medulla oblongata, paralysis of the opposite side of the body will follow; while if the effusion has taken place in both hemispheres, the palsy will be double-sided, though probably more complete on one side than on the other.

Effusions of blood into the corpora quadrigemina, will most frequently be attended with muscular tremblings or convulsions, and probably impaired sight, with some change in the pupil. When in the medulla oblongata, convulsions, followed by palsy, deep coma, and early death; greater fatality attending effusions at this point, probably, than at any other. When the effusion takes place in the cerebellum, the loss of consciousness will be very temporary; there may be relaxation of muscles without palsy or loss of sensibility, and, it is said, frequent vomiting.

The amount of blood effused is subject to the greatest variation. Clots may be found as large as a hen’s egg, or smaller than a pea. Indeed, violent apoplectic attacks, ending in death, may occur, where the most careful examination will fail to detect any effused blood, death being the result of extreme congestion of the membranes. On the other hand, the presence of a clot is not necessarily fatal, evidence being abundant that they may be so far reabsorbed as to be followed by at least partial recovery.

The following cases will serve to illustrate these several conditions:

CASE I.—Sudden Death from Cerebral Congestion.

Mr. M——, aged thirty-five years, had always enjoyed good health. For some months previous to death, had been working very hard, with a good deal of anxiety, in arranging the affairs of a company of which he was secretary. On the evening previous to his attack, he retired at eleven o’clock, well and in good spirits. At three o’clock A. M., his wife was wakened by his heavy, stertorous breathing, attended with slight convulsive movements of the limbs. In less than a half hour he was dead. The post-mortem showed the heart, lungs, and abdominal organs to be in a perfectly healthy condition, while the most careful examination of every portion of the brain failed to expose the least effusion of blood. The ventricles and sub-arachnoid space contained a moderate amount of serum, while the vessels of the pia mater were strongly engorged with blood.

CASE II.—Apoplectic Attack, followed by Death in Three Days; Clot found in Thalamus.

Mr. J——, aged sixty-one, a butcher, abstemious in his habits but plethoric in temperament, was suddenly stricken down with an attack of apoplexy, which left him with paralysis of the right side of the body, with impaired speech and memory. He gradually and almost entirely recovered. Ten months after, while in the street, he fell with another attack. He partially recovered consciousness, but had complete palsy of the left side, and died in three days. Here, the post-mortem revealed excessive congestion of the pia mater, and a large clot, the size of a hickory nut, in the right optic thalamus. In the left thalamus was a distinct trace of a clot, (nearly absorbed, however,) which had undoubtedly been effused in the attack ten months previously.

CASE III.—Apoplectic attack, followed by Hemiplegia, and Death in Five Years.

Charles E. W——, at the age of forty-seven had a sudden apoplectic stroke, in January, 1867, followed by partial paralysis of right side. In May following, he had a second attack, which greatly increased the hemiplegia, impaired the articulation, and weakened the memory and intellect. His general health and strength gradually failing, he died August, 1872, five years after the original attack.

Post-mortem revealed a greatly thinned and dilated condition of the walls of the arteries of the base of the brain and the remnants of the original clot imbedded in the left optic thalamus, the brain substance around being of a dark color and much softened. From the appearance of the dark, ragged remnant of the clot, it must have been originally of about the size of a robin’s egg.

CASE IV.—Death from Congestion, with Serous Effusion and Softening.

Mr. F. H——, aged thirty, had an attack of brain fever at twenty-three, followed by attacks of severe pain in the head, recurring every few days, weeks or months. These attacks were accompanied with slight convulsive symptoms and delirium, the pain being of a most excruciating character, and lasting from a few hours to two or three days. The attacks were gradually increasing in severity, but without any impairment of the faculties of the mind. On a Saturday night, he was brought home with one of his worst attacks. When I first saw the patient on Sunday evening, I found him in a half-delirious, stupid condition, yet when roused up, giving satisfactory answers to questions, but immediately sinking into his former condition, and every one to five minutes starting suddenly up and, with staring eyes and distorted face, uttering piercing shrieks and screams, and calling to those around to shoot him, split open his head with a hatchet—anything to release him from his sufferings. These paroxysms would sometimes be followed by a convulsive action of the diaphragm and abdominal muscles, ending in his sinking into the same dull, stupid condition as before. In the interval of calm, the respiration was remarkably slow and feeble, with a slow irregular pulse of forty beats to the minute. These symptoms becoming gradually worse, he sank into a comatose condition early Tuesday morning, expiring at daylight, sixty hours after the commencement of the attack.

The post-mortem revealed greatly enlarged Pacchionian glands, with extreme thinning of the skull over the same. The pia mater was considerably congested. Upon turning the brain back for removal from the base of the skull, there was a sudden gush of water from the ventricles, sufficient of which was secured to show that the quantity could not have been less than two ounces. Upon opening the lateral ventricles, these cavities were found unusually large from distension by the fluid, while the septum lucidum and fornix were found in a soft, pulpy condition, the former being completely broken down and detached from the corpus callosum above. The gray portions of the corpora striata were also softer and more easily broken up than was natural.

The appearance presented by a clot, as well as the brain substance immediately around it, will vary according to the time the patient survives the attack. When death follows in a few days, the clot will have a soft, blackish appearance; after a month or six weeks, it becomes firm, and assumes a deep brown color, and at a still later period, it becomes still more firm, and of a pale red tint; lastly, it may become entirely absorbed. Peculiar changes also take place in the brain substance immediately around the clot, which vary according to the time intervening between extravasation and death. The portion immediately in contact with the clot is generally of a dark red or wine color, or, at a later period, of a chocolate brown, and of a soft, pulpy consistency. Exterior to this, the color is paler and of an orange tint, and still further on, of a bluish-white or yellow. The change in structure and consistence of the brain, immediately around the clot, constitutes one form of softening soon to be noticed.