ide for drainage.

CHAPTER XIV

DISEASES OF THE BRAIN AND MEMBRANES

Pyogenic diseases--Meningitis: _Varieties_--Abscess:
_Varieties_--Sinus phlebitis--Intra-cranial tuberculosis.
Cephaloceles--_Meningocele_--_Encephalocele_--
_Hydrencephalocele_--Traumatic cephal-hydrocele--Hydrocephalus;
_Varieties_--Micrencephaly. Cerebral tumours. Tumours of the
pituitary body. Epilepsy--Hernia cerebri. Surgical affections of
cranial nerves--Cervical sympathetic.

PYOGENIC DISEASES

The most important intra-cranial conditions that result from infection
with pyogenic bacteria are: meningitis, abscess of the brain, and
phlebitis of the venous sinuses.

The organisms most frequently associated with these conditions are the
staphylococcus aureus and the streptococcus, but it is not uncommon
to meet with mixed infections in which other bacteria are
present--particularly the pneumococcus, the bacillus foetidus, the
bacillus coli, the bacillus pyocyaneus, and the diplococcus
intracellularis.

By far the most common source of intra-cranial infection is chronic
suppuration of the middle ear and mastoid antrum, the organisms
passing from these cavities to the interior of the skull directly
through a perforation of the tegmen tympani or of the wall of the
sigmoid groove, or being carried in the blood stream by the emissary
veins. In some cases the infection travels along the sheaths of the
facial and acoustic nerves.

Less frequently infective conditions of the nasal cavity and its
accessory air sinuses, and compound fractures of the skull,
particularly punctured fractures, are followed by intra-cranial
complications; or infection is conveyed to the inside of the skull, by
way of the emissary veins, from wounds of the scalp, or from such
conditions as erysipelas of the face and scalp, malignant pustule,
carbuncles, or boils.

At the bedside there is often difficulty in discriminating between the
various pyogenic intra-cranial complications, because many of the
symptoms are common to all the members of this group, and because
more than one condition is frequently present. Thus a localised
meningitis spreading to the brain may set up a cerebral abscess; a
sinus phlebitis may give rise to a purulent lepto-meningitis; or a
cerebral abscess bursting into the sub-arachnoid space may produce
meningitis.

MENINGITIS

#Pachymeningitis.#--This term is applied when the infection involves
the dura mate