Manual of Surgery Volume Second: Extremities—Head—Neck. Sixth Edition.

by Alexis Thomson; Alexander Miles

Fig. 185.—Two Charts of Pyrexia in Head Injuries.

During the progress of the symptoms there is frequently evidence of direct pressure upon definite cortical centres or cranial nerves, giving rise to focal symptoms. Particular groups of muscles on the side opposite to the lesion may first show spasmodic jerkings or spasms (unilateral monospasm), and later the same groups become paralysed (monoplegia). The paralysis frequently affects the whole of one side of the body (hemiplegia) and the oculo-motor nerve is often paralysed at the same time.

The pupils vary so widely in different cases that their condition does not form a reliable diagnostic sign. Perhaps it is most common for the pupil on the same side as the lesion to be contracted at first and later to become fully dilated, while that on the opposite side remains moderately dilated. As a rule, they are irresponsive to light. Ophthalmoscopic examination shows swelling of the disc, and the vessels of the papilla are distended and tortuous.

In cases which go on to a fatal termination, the coma deepens and the muscular and sensory paralyses become general and complete. The vital centres in the medulla oblongata gradually become involved, and death results from paralysis of the respiratory centre. The fatal issue is often hastened by the onset of hypostatic pneumonia. Not infrequently a modified type of Cheyne-Stokes respiration is observed for some time before death ensues.

A similar train of symptoms may ensue in cases of head injury as a result of pyogenic infection having given rise to meningitis or abscess with accumulation of inflammatory exudate.

Pathology.—When any addition is made to the bulk of matter inside the cranial cavity, room is gained in the first instance by the displacement into the vertebral canal of a certain amount of cerebro-spinal fluid. The capacity of the spinal sheath, however, is limited, and as soon as the tension oversteps a certain point, the pressure comes to bear injuriously on the cerebral capillaries, disturbing the circulation, and so interfering with the nutrition of the brain tissue. As the intra-cranial tension still further increases, the pressure gradually comes to affect the cerebral tissue itself, and so the extreme symptoms of compression are produced. The vagus and vaso-motor centres are irritated, and this causes slowing of the pulse, contraction of the small arteries, and increase of the arterial tension which tends to maintain an adequate circulation in the vital centres in the medulla. The Cheyne-Stokes respiration is due to rhythmical variations in the arterial tension: during the period of fall the centres become anæmic and the respiration fails; during the rise the medulla is again supplied with blood, and breathing is resumed (Eyster).

The parts of the brain directly pressed upon become anæmic, while the other parts become congested, and the nutrition of the whole brain is thus seriously interfered with. Different parts of the brain and cord show varying powers of resistance to this circulatory disturbance. The cortex is the least resistant part, and next in order follow the corona radiata, the grey matter of the spinal cord, the pons, and, last, the medulla oblongata. Hence it is that the respiratory and cardiac centres hold out longest.

Depressed Bone as a Cause of Compression.—It is more than doubtful whether a depressed portion of bone is of itself capable of inducing symptoms of compression of the brain. When such symptoms accompany depressed fracture, they are to be attributed either to associated hæmorrhage, or to interference with the circulation and consequent œdema which the displaced bone produces. Fragments of bone may, however, aggravate the symptoms by irritating the cerebral tissue on which they impinge.

Foreign Bodies.—The rôle of foreign bodies, such as bullets, in the production of compression symptoms is similar to that of depressed bone. That foreign bodies of themselves are not a cause of compression seems evident from the fact that it is not uncommon for them to become permanently embedded in the brain substance without inducing any symptoms. Not only have bullets, the points of sharp instruments, and other substances remained embedded in the brain for years without doing harm, but in many cases the patients have continued to occupy important and responsible positions in life.