3. The presence of a definite ‘latent’ period.
4. The late development of symptoms pointing to general and local brain compression.
Finally, it may be stated in general that the more indefinite and the more deferred the pressure symptoms, the greater the probability that we have to deal with a localized subdural hæmorrhage. Lumbar puncture may materially aid in the differential diagnosis between extra-dural and subdural hæmorrhages.
The following case affords a typical example of subdural hæmatocele:—
An elderly man fell down, striking the right side of the head against the pavement. He lost his senses for a few minutes and was then brought to the hospital, dazed and complaining of headache (note the absence of any lucid interval). He was sent home in a cab and was assisted to bed by his wife. He kept to his bed during the next week, complaining of constant headache, and was exceedingly irritable (this is the ‘latent’ period). Towards the end of the third week his wife noticed that he seldom used the left upper and lower extremities. This paresis increased steadily, the face was drawn to the right side, and his condition became so serious that the wife brought him again to the hospital (this is the ‘manifest’ period).
When seen by me he was only partly conscious, the mental condition varying, however, during the day. He was exceedingly irritable, muttering to himself in a low tone, words being more or less unintelligible. The left upper extremity was paralysed, the face drawn to the right side, and the left lower extremity was but little used. The pupils were equal, the disks normal. The temperature in the left axilla was two degrees lower than on the opposite side.
The hæmatocele was exposed, cleared out, and the cavity drained. Recovery was rapid and complete. Two years later all was well.
Operation.
The lesion is usually of so gross a nature that little difficulty will be experienced in determining the site for trephining. The protective gauze and scalp-tourniquet are applied as usual (see [p. 14]), and a bradawl introduced through the scalp so as to indent the external table and allow of the subsequent accurate application of the trephine. A scalp-flap, suited to the occasion, is framed, the skull trephined, and the disk of bone elevated and removed. The appearance of the dura mater now allows the operator to verify his diagnosis—the membrane is non-pulsatile, it bulges markedly outwards and presents a blue-purple colour. The bone is then nibbled away in the downward direction towards the lower limit of the clot, the scalp incision being prolonged according to requirements.
In the region of the trephine-hole the dura is incised in a crucial manner, and the four flaps held aside by catgut sutures passed through the apex of each flap. A blunt director is introduced beneath the dura, passing towards the lower limit of the clot, and the membrane slit up to within a short distance of the lower margin of the gap. All meningeal vessels that cross the line proposed for dural section must first be underrun on either side of that line. Retraction of the dura will now allow of adequate exposure of the underlying hæmatoma. Its removal can be carried out with the aid of a spoon, and by means of gentle irrigation (hot saline at a temperature between 110° and 115° Fahrenheit). It is usually impossible to remove the whole of the coagulum, but the greater portion can be got rid of in the manner described.