on.)]

Cephaloceles have to be diagnosed from dermoid cysts, naevi (Fig. 199),
cephal-hydrocele, and cephal-haematoma. Their recognition is seldom
attended with difficulty. If the margins of the gap in the skull can
be distinctly felt, or the gap in the bone can be shown by the X-rays,
the diagnosis is greatly simplified.

[Illustration: FIG. 199.--Naevus at Root of Nose, simulating
Cephalocele.

(From a photograph lent by Sir George T. Beatson.)]

_Treatment._--Only small cephaloceles are amenable to surgical
treatment; those that are large and contain brain substance are best
left alone, being merely protected from irritation and infection.

While the immediate effects of operation are, on the whole,
satisfactory, the ultimate results are disappointing, as the essential
cause of the intra-cranial pressure persists, and the child develops
hydrocephalus. The method of tapping the sac and injecting iodine has
nothing to recommend it.

#Traumatic Cephal-hydrocele.#--Certain rare cases of simple fracture
of the vault occurring in early childhood have been followed by the
development beneath the scalp of a localised fluid swelling, which
varies in size from time to time and is partly reducible by pressure.
The swelling results from laceration of the membranes, and sometimes
of the brain substance, so that the cerebro-spinal fluid of the
sub-arachnoid space, or even of the lateral ventricle, escapes through
the opening in the skull and bulges beneath the scalp. In a majority
the swelling pulsates synchronously with the heart, and becomes tense
on exertion. A distinct opening in the skull may sometimes be felt.
When associated, as it frequently is, with mental deficiency or the
occurrence of fits, the cyst may be tapped or its neck ligated
(Hogarth Pringle). Otherwise it should be left alone.

HYDROCEPHALUS

An excess of cerebro-spinal fluid may collect in the arachno-pial
space surrounding the brain, or in the interior of the ventricles,
constituting in the former case an _external_, and in the latter an
_internal hydrocephalus_. Hydrocephalus may be acute or chronic.

#Acute hydrocephalus# is practically synonymous with tuberculous
meningitis, although it may result from other forms of meningeal
infection. The excess of fluid is found both in the arachno-pial space
and in the ventricles. This condition only calls for mention here as
attempts have been made to treat it by surgical measures, such as
lumbar punct