CHAPTER XXXI. FRACTURES OF THE SKULL. (Part 2)

size and rarely the cause of hemorrhage. Intracranial Sinuses. — The most common site of meningeal hemorrhage, after the middle meningeal artery, is the lateral sinus. The walls of the sinnses are formed by a splitting of the dura and are lined by an endothelial layer which is continuous with the lining membrane of the veins. Sinuses may be the site of throm- bosis and suppuration and when ruptured result in intracranial hemorrhage ; they should be specially avoided when trephining the skull. The superior longitudinal sinus corresponds to a line drawn from the glabella to the inion. A line drawn from the in ion to a point one and a half inches above the external auditory meatus will correspond to the highest part of the lateral sinus where it crosses the lambdoid suture. The lateral sinus then curves down- ward and forward running on the internal surface of the mastoid portion of the temporal. It is joined by the superior petrosal sinus at the posterior end of the upper border of petrous portion of the temporal and by the inferior petrosal sinus just below the jugular foramen after the two sinuses have passed out of the skull. The two cavernous sinuses situated on either side of the cella Turcica drain the ophthalmic vein, anastomose with each other through the circular and transverse sinuses and are themselves drained into the lateral sinuses by means of the petrosal sinuses. A line drawn perpendicular to the surface of the bone just below the inion, if projected into the skull, would correspond to the course of the straight sinus. The straight sinus drains the veins of Galen and the inferior longitudinal sinus which runs in the lower border of the falx cerebri. The blood from the straight sinus is drained by one of the lateral sinuses after having been emptied into torcular Herophili. The occipital is formed by the two marginal sinuses which connect with the sigmoid portion of the lateral sinus; it passes upward and empties into the lateral sinus, the straight sinus or the torcular Herophili; it establishes connection with the deep veins of the neck through the foramen magnum. The origin, course and exit from the skull of the twelve cranial nerves is of importance in diagnosis but the reader will be referred, for this detail, to text-books on the subject. Lesions of different portions of the brain will give different symptoms according to the function of the region injured. "We may divide local injuries of the brain into injuries of the cortical 400 FRACTURES AXD DISLOCATIONS centers and their tracts, and injuries of the base. For practical purposes we may divide the cortex into motor areas, sensory areas, Fis. 518. Fig. 517. — If., Midpoint of naso-inionic line: L.X., Poirier's line and corresponds to Sylvian fissure; I.X., Kocher's equatorial line from- nasion to inion: A.B., German base-line and passes through inferior edge of orbit and upper border of external auditory meatus. Fig. 518. — If., L.X. and I.X. same as in Fig. 517. A line drawn forward and downward at an angle of 60 from median plane is known as Kocher's anterior meridian and lies over precentral convolution. Kocher's posterior meridian is drawn downward and backward 60 from ihe median plane. Fig. 519. — Dotted areas correspond to the most frequent sites of meningeal hemor- rhage. Fig. 520. — Cortical centers. and a number of so-called silent areas. The cortex of the brain is composed of gray matter which in most regions is disposed in five layers. Axis-cylinders from the cells of this gray matter es- FRACTURES OF THE SKULL 401 tablish eomnuniieation between different portions of the cortex and between the cortex and the lower centers situated in the base of the brain and in the cord. The function of the cortex of the brain is to register memories of past experiences. Under certain conditions these centers are stimulated and have the capacity of reproducing the events which they have registered. Thus stimu- lation of the occipital lobe gives us the memory of sights seen, stimulation of the temporo-sphenoidal lobe gives us the memories of sounds heard, stimulation of the motor area gives us the mem- ories of acts performed. It is therefore necessary to know what part of the cortex registers certain experiences in order that we may be able to tell just what symptoms would be produced by injury of a given part of the brain. Conversely, this knowledge having been obtained we may be able to state what part of the brain has been injured from the observation of certain symptoms. The cortex as has been said is divided into certain so-called cen- ters. The frontal area is concerned with conscious selective action, the Rolandic area with motor memories and the reproduction of these memories which results in voluntary motion, while the spinal level is concerned with reflex and vegetative automatism. Experi- ment on lower animals and observation of diseased and traumatic conditions in the human being have determined the function of many regions of the cortex, but there are still many areas the function of which remains unknown. For obvious reasons the more complex and the higher the function of a given area, the more difficult it becomes to ascertain the nature of that function. The occipital lobe on either side of the calcarine fissure is con- cerned with the memories of sights seen ; the temporo-sphenoidal, especially the left, with the memory of sounds heard and muscular memories; the left angular gyrus with the memory of written speech ; the posterior part of the frontal lobe with the memory of printed speech; and the third frontal convolution on the left side is concerned with the memory of spoken speech. Stereognostic sense is located in the parietal lobe. The centers in the Rolandic sensori-motor area are disposed inversely (i. e., the centers for the head are below those for the upper extremity, etc.). The centers for the lower extremity extend onto the mesial surface of the hemisphere. Fracture of the vault may injure one or more of these areas. If the injury is slight, and the center is not de- stroyed, the lesion is said to be irritative and the center overacts. 402 FRACTURES AND DISLOCATIONS If the lesion is more serious and the center is destroyed the func- tion of that center is lost. Thus if the Rolandic area is irritated, the regions of the body supplied by the corresponding centers are thrown into unwonted activity or spasm; but if the lesion is more severe, function of the center is lost. This results in loss of mem- ory for muscular movements and consequently they cannot be voluntarily reproduced. If Broca's convolution is destroyed, the memory for the acts connected with motor speech is lost and con- sequently the movements of motor speech cannot be reproduced. Of recent years, however, there has been some doubt as to the function of Broca's convolution, and it is not now thought to be so essential to speech as formerly. If the lesion penetrates below the cortex, the fibres which asso- ciate these centers may be lacerated and the normal communica- tion between centers is interfered with. Thus a given center can- not be stimulated, as in the normal person, by the activities of an associated center. If a center concerned with speech is destroyed and the function of that part of the cortex lost the patient is said to suffer from aphasia. If the fibres connecting a given cortical center with some other cortical center are lacerated the patient is said to suffer from intercortical aphasia. If the center destroyed is concerned with motor memories the patient has motor aphasia. If the centers concerned with registering purely sensory ideas are destroyed the patient has sensory aphasia. The base of the brain also has centers distributed through its substance which preside over various important functions of a lower order than those found in the cortex. These centers have running through them fibres from the cortex of the brain, so that, in case of injury, we have not only symptoms of lesions in these lower centers but also symptoms of interruptions of impulses from the cortex. In the anterior fossa we have the center for smell situated in the olfactory lobe. In the middle fossa we have the optic thala- mus, the corpora quadrigemina, and the cms. The optic thalamus is concerned with emotional facial expression and lesions of this body may give rise to athetosis or incoordination of the paralyzed hand and pain in the paralyzed limb. The anterior corpora quad- rigemina are associated with motion of the eyeballs and acuity of vision, the posterior corpora quadrigemina are related to hearing and equilibration. The crus contains the nucleus of the third and FRACTURES OP THE SKULL 403 fourth nerves and longitudinal fibres passing from the cerebral cortex to the spinal cord. Lesions of this body give a character- istic set of symptoms in accordance with the nuclei and fibres contained within it: paralysis of the third and fourth nerves will deprive all the muscles of the eye of their nerve supply except the external rectus; injury to the longitudinal fibres may cause hemi- plegia of the opposite side and hemianopsia may be present if the adjacent optic tract is injured by pressure. If both crura are damaged we have a double hemiplegia with paralysis of the third and fourth nerves on both sides, and in some instances optic neu- ritis. In the pons we have a continuation of the longitudinal fibres of the crura, the thermogenic center, and the nuclei of the fifth, sixth, and seventh cranial nerves. Injury to the fibres of the crura as they pass through the pons may produce hemiplegia, disturbance of the thermogenic center, extremely high tempera- ture, and injury to the three cranial nerve nuclei will be followed by symptoms peculiar to each nerve. Injury to the nucleus with loss of function in each nerve will be as follows: for the fifth, hemifacial anesthesia with paralysis of the muscles of mastication ; for the sixth, paralysis of the external rectus of the eye ; and for the seventh, motor paralysis of the muscles of the face. Bilateral symptoms will be present if the lesion involves both sides of the pons. The usual anatomical division of the bulb into pons and medulla is purely artificial. For practical surgical purposes they should be considered together. The medulla resembles the pons and crura in containing longi- tudinal fibres from the cortex together with cranial nerve nuclei. The characteristic symptoms of lesions of the medulla will depend on the nuclei which it contains. In the upper border of the medulla is the nucleus of the eighth cranial nerve which also pro- jects into the pons ; in the lower half of the floor of the fourth ventricle we have the nuclei of the ninth, tenth, and eleventh cranial nerves and at a slightly lower level is found the nucleus of the twelfth. The vomiting center, the vaso-motor center and numerous other centers governing various functions in the body are situated in the bulb, but as yet too little is accurately known concerning them to be of considerable surgical value. Further back in the posterior fossa we have the cerebellum which is concerned in coordinating the various muscular activities 404 FRACTURES AND DISLOCATIONS of the body and in the complex process of equilibration. Another function of the cerebellum consists in the peculiar power of im- parting the proper degree of force to muscular movements. In- jury to the cerebellum may give rise to cerebellar ataxia, obstinate projectile vomiting, and various forms of paralyses and anes- thesias. The association of the cerebellum with the pons, medulla, basal ganglia and cortex is so complete that it is difficult to deter- mine the source of these varied symptoms. The foregoing enumeration is by no means complete as regards location and function of the cortical centers and basal ganglia : there is still considerable dispute concerning the functions of these centers and there are numerous other centers which as yet remain with functions unknown. There are many symptoms occurring in head injuries which could be properly explained if we knew more of the anatomy and physiology of the brain, but for the present the description given will be found of service in roughly deter- mining the seat of injury in fracture of the skull. Etiology. — Trauma is the cause of fracture of the skull but the nature and the degree of violence are so extremely variable that the resultant conditions show the greatest differences in detail. The trauma may be sustained over a small or large area of the skull; the vulnerant body may travel at a high rate of speed (bul- let) or at a slow rate (club) ; the violence may be direct or it may be transmitted through the spinal column or inferior maxilla. The violence may be circumscribed or the head may be squeezed or crushed between heavy objects. Fracture of the skull constitutes from four to six percent of all fractures and possibly more, since we are learning of recent years that the milder forms of the condition have only too frequently gone unrecognized in the past. Statistics are specially misleading in this particular injury, for the following reasons: in the first place the most severe cases never reach the hospital because of immediate death, and secondly the condition is frequently asso- ciated and confused with other injuries ; thirdly, the milder cases are often successfully treated at home, and in many cases are not classified as fractures because of mistaken diagnoses. For these reasons figures derived from a service such as the police surgeon's will come nearer the truth, since it includes all classes of fractures ranging from the mildest to those immediately fatal. Occupation is an important element in the etiologv. Fracture of the skull is FRACTURES OF THE SKULL 405 most frequently found in the male and in middle life. The skull in the aged is much more easily fractured than that of the person in middle life, but on the other hand those advanced in years are not so exposed to injury. Mechanism and Pathology. — The various ways in which the skull is broken, the manner in which fragments are displaced, and the region of the cranium involved have all been subjects of careful investigation, and terms, to designate the peculiarities of the con- ditions, have been applied. Before considering the mechanism of these fractures, it is necessary to again refer to the anatomy with respect to the peculiar formations of the vault and base. The structure of the skull is peculiar to itself and any attempt to liken the manner in which it breaks to that of other objects can at best be but incomplete. Circumscribed blows upon the vault of the skull commonly produce a local depressed fracture with or without injury to the underlying structures. A more extreme blow or squeezing of the skull will result in fissures (with or without de- pression) which are prone to extend towards and involve the base. A certain degree of trauma can be withstood by the vault without apparent injury, the shock being absorbed by the natural elas- ticity of the bone. If the trauma be a little greater, and the skull bent inward sufficiently, the internal table may give and we then have a fracture of the inner table alone; a condition frequently described in text-books, but rarely seen in practice. A still greater trauma results in dissolution of continuity of the entire thickness of the bone. On the other hand a blow from a sharp cutting in- strument may fracture the outer table while the inner table re- mains intact. The skull may be fractured by ''bending" or by "bursting." When violence is applied to the skull in a circum- scribed region the immediate site of injury is ''bent" inward with resultant local fracture which is said to be "fracture by bending." When the violence is applied over a larger area and more slowly, lines of fracture may be found radiating from the site of impact, often involving the base. The action may be likened to the break- ing of a nut in a nut-cracker. This form of fracture is spoken of as " fracture by bursting ' ' ; the most striking examples of which are seen in instances in which the head has been caught and crushed between two heavy objects. We often have evidences of both the bending and bursting action in a given case. If the skull were of a uniform thickness throughout, the mechanism would be 406 FRACTURES AND DISLOCATIONS much easier to determine. As it is we find the peculiarities in the structure of the skull directly influence the directions Avhich fissures take. When fractures of the vault, between the frontal and parietal eminences, involve the base they are frequently ac- companied by fissures extending into the middle fossa. When fractures posterior to the parietal eminence are accompanied by basal fissures they usually extend into the posterior fossa and in like manner those anterior to the frontal eminence involve the anterior fossa. In gunshot wounds, especially when produced by the modern high-pressure bullet, the skull sometimes presents what would seem to be an explosive effect similar to that produced by shooting through a barrel filled with water. The nature of the vulnerant body is an extremely important element, for example; the completely jacketed high-velocity rifie ball will usually pene- trate cleanly, is not prone to carry in any extraneous materials, and the wound is frequently sterile throughout. On the other hand a blow from a hammer besides driving a portion of the bone into the brain will frequently be found to have carried in hair, dirt, or felt, and the wound is therefore much more liable to infection. Fracture by contrecoup has been the subject of much discussion and although it may