Fig. 187.—Extra-Dural Clot resulting from hæmorrhage from the Middle Meningeal Artery.
Clinical Features.—The typical characteristics of middle meningeal hæmorrhage are met with only when the bleeding takes place between the dura and the bone. Under these conditions the symptoms of concussion are usually most prominent at first, and those of compression only ensue after a varying interval, during which the patient as a rule regains consciousness. In some cases, indeed, he is able to continue his work, or to walk home or to hospital, before any evidence of intra-cranial mischief manifests itself. This “lucid interval” helps to distinguish the symptoms due to middle meningeal hæmorrhage from those of laceration of the brain substance, as in the latter the symptoms of concussion merge directly into those of compression. Lumbar puncture may aid in the differential diagnosis between extra-and intra-dural hæmorrhage, as blood is present in the fluid withdrawn in the latter, but not in the former.
A few hours after the accident the patient experiences severe pain in the head, and he usually vomits repeatedly. For a time he is restless and noisy, but gradually becomes drowsy, and the stupor increases more or less rapidly until coma supervenes. The pulse usually becomes slow and full. The respiration is rapid (30 to 50), and becomes greatly embarrassed and stertorous. The temperature progressively rises, and before death may reach 106° F., or even higher. Monoplegia, usually beginning in the face or arm on the side opposite to the lesion, gradually comes on, and is followed by hemiplegia, from pressure on the motor areas, underlying the clot. The condition of the pupils is so variable as to have no diagnostic value; but if both are widely dilated and irresponsive to light, the prognosis is grave. Death usually ensues in from twenty-four to forty-eight hours, unless the pressure within the skull is relieved by operation; even after removal of the clot death may ensue if the brain has been lacerated, or if there is hæmorrhage at the base.
When the hæmorrhage takes place from the anterior branch, the clot tends to spread towards the base, and may press upon the cavernous sinus, causing congestion and protrusion of the eye, with paralysis of the oculo-motor nerve and wide dilatation of the pupil.
In some cases of middle meningeal hæmorrhage there is no gross injury to the brain; the area underlying the clot is merely compressed and emptied of blood, and, on being exposed, the brain is found flattened, or even deeply indented by the blood-clot, and it does not pulsate. If the clot is removed, the brain may regain its normal contour and its pulsation return. The mortality is over 50 per cent.
If the fracture is compound, the blood can escape, and therefore the pressure symptoms are less evident or may be entirely absent.
It is a fact of some medico-legal importance that hæmorrhage from the middle meningeal may not take place till some days, or even weeks, after an injury, which at the time was only attended with symptoms of concussion. This condition is known as traumatic apoplexy.
Treatment.—Immediate operation is imperatively called for, not only to arrest the hæmorrhage and remove the clot, but also to ward off the œdema of the brain, which is often responsible for the fatal issue. When there is no external wound, the point at which the skull is to be opened is determined by the symptoms; for example, paralysis of the arm and face on one side indicates trephining over the centres governing these parts on the side opposite to the paralysis.