Operation is always imperative unless the patient is seen too late and it is obvious that the condition is hopeless.
Before operation is decided on the following points must be carefully considered: (1) Is it possible that the symptoms simulating the intracranial lesion are due to suppuration still limited to the temporal bone? (2) What is the character of the lesion? and (3) What is its situation?
As a rule, so long as the suppurative process is limited to the middle ear and to the mastoid region, the symptoms are those of a local septic infection. At the same time it must be remembered that in infants and in young children it is not uncommon for retention of pus within the middle ear to produce a clinical picture closely simulating an intracranial suppurative lesion. The ear, therefore, should always be inspected in every case. Sometimes a bulging membrane is discovered or the existing perforation is found to be insufficient for drainage. In such cases the symptoms may subside on free drainage being obtained by the simple act of paracentesis of the tympanic membrane.
If, however, free drainage already exists, the mastoid operation should be performed at once.
If the intracranial symptoms be still somewhat indefinite, and there is no apparent urgency, the intracranial cavity should not be explored immediately unless this is found to be imperative at the time of operation. This can be done later, if the symptoms do not subside.
Although exploration of the intracranial cavity is always urgent when it is certain that an intracranial suppurative lesion is present, yet to explore with a negative result is a grave misfortune, owing to the possibility of infecting the intracranial cavity.
Although the surgeon may be certain that an intracranial lesion is present, yet it may be very difficult to determine its character or whether several lesions coexist. The surgeon must therefore be prepared to act according to what he finds at the time of operation.
Thus, if exploration of the temporo-sphenoidal lobe be negative, and yet the cardinal symptoms point to an intracranial abscess, the cerebellum must also be explored. Again, if the diagnosis of intracranial abscess be doubtful before operation, and if, during the operation, lateral sinus thrombosis be discovered, it is wiser to limit the operation to tying of the jugular vein and removal of the septic thrombus. The bone, however, should be removed above and behind the sinus so as to expose the dura mater covering the temporo-sphenoidal lobe and the cerebellum.
In such cases, if the symptoms of intracranial suppuration still continue, it is an easy matter to explore the temporo-sphenoidal lobe or cerebellum at a subsequent operation.
Although under exceptional circumstances (see [p. 461]) it may be justifiable to open an intracranial abscess by directly trephining the skull over it, yet free opening of the mastoid process should be the first step in the operation, as the primary focus of the disease exists within the temporal bone. In addition, much information may thus be gained in a doubtful case with regard to the situation of the intracranial lesion.