Biomedical Engineering Reference
In-Depth Information
Table 22.1 Classification of hydrocephalus along with some examples within this classification
Obstructive HCP
Communicating HCP
Congenital
Congenital
Stenosis of aqueduct of Sylvius, TV a
&FV b
Chiari malformations
Dandy Walker Syndrome, TV a
&FV b
Venous hypertension
Acquired
Acquired
Midline supratentorial tumors
Subarachnoid haemorrhage
Posterior fossa tumors
Meningeal carcinomatosis
a
Third ventricle, b
Fourth ventricle
the 600-2000 Pa range (Irani, 2009 ). HCP cannot be considered a singular patho-
logical entity, but instead, a consequence of a variety of congenital and acquired dis-
orders present within the CNS (Thompson, 2009 ). What can be said with confidence
is that HCP is classified with regards to whether the point of CSF obstruction lies
within the ventricular system (obstructive) or not (communicating), see Table 22.1 .
HCP can be further sub classified as acute or chronic. The prior is caused by the ob-
struction of CSF flow pathways, whilst the latter is characterized by prolonged time
scales for development. In addition, in most cases, this latter form of HCP possesses
no radiographically identifiable flow obstruction.
Normal pressure HCP (NPH): this form was originally described by Hakim and
Adams ( 1965 ). It aims to correlate a triad of disturbances, namely gait disturbance,
dementia symptoms and urinary incontinence. The key point for NPH is that the
aforementioned symptoms occur under the auspice of radiographic hydrocephalus
with normal CSF pressure (Byrd, 2006 ). NPH can be either idiopathic (no clear
aetiology and effects the elderly) or secondary (possesses an identifiable cause,
e.g., subarachnoid haemorrhage). Some thoughts on the aetiology of NPH include
the quashing of deep white matter ischemia as a cause, and instead focusing on
the diminishing compliance of superficial veins or other progressive impairment of
periventricular blood flow (Bradley, 2008 ). What is clear is that no matter what the
encountered aetiology, the final result of NPH is ventriculomegaly (communicating
HCP), which in turn may proceed in entertaining numerous manifestations of the
disease.
Acute HCP: this form of HCP is unlike its chronic counterpart, since it presents
clearly identifiable radiographical obstructions of the CSF flow pathways. The ven-
tricular system itself is affected by the location of these obstructions, for instance,
of the lateral ventricles and third ventricle, whilst an obstructed subarachnoid space
(due to inflammatory or haemorrhagic fibrosing meningitis) may lead to widespread
dilatation (Tully and Ventikos, 2011 ).
Surgical treatment is the preferred therapeutic option when treating hydro-
cephalus (Hamilton, 2009 ; Schödel et al., 2012 ), however this topic will not be
elaborated here.
 
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