=Symptomatology.= As the direct result of the blow the patient is ‘concussed’, remaining in that condition for a variable period of time, a matter of seconds, minutes, or hours, according to the nature of the associated damage to the bone and brain. In the most typical cases, the patient, on regaining consciousness, should recover--again for a variable period of time--complete control over mind and body, returning to work, walking home or visiting hospital or doctor. More usually, however, he remains slightly dazed, though recognizing his surroundings and capable of answering questions. In any case--unless the hæmorrhage is accompanied by grave cerebral lesion--there should be some attempt at recovery, some return to consciousness. The importance of this ‘lucid interval’ cannot be over-estimated. It should be noted, however, that this interval of consciousness is not of itself absolutely diagnostic of middle meningeal hæmorrhage--it ought to be associated with definite localizing symptoms of brain compression (see below). I have encountered several cases in which this lucid interval was present, and in which operative procedures were carried out in the anticipation of finding an extra-dural extravasation, only to find a subdural hæmorrhage. Such subdural hæmorrhages are not infrequently associated with a similar return to the conscious state, but are rarely--if ever--accompanied by the early development of symptoms of localized brain compression. In the event of doubt as to whether the surgeon has to deal with an extra or subdural extravasation lumbar puncture will probably clear up the diagnosis.
The duration of this ‘lucid’ interval is exceedingly variable. It is usually a matter of minutes or hours, though both König and Wiesman narrate cases in which eight days elapsed before the onset of definite localized compression symptoms. I also have recollections of a case in which the patient walked some miles across the moor to see his doctor, and finding him away from home, walked home again, then becoming unconscious and dying shortly afterwards.
All depends on the calibre of the vessel injured and on the existence of a safety-valve, by means of which some of the extravasated blood can escape externally (see p. 97).