Papilloedema
Papilloedema (Figure 1) is the swelling of the
optic nerve head secondary to a build-up of
pressure within the brain known as Intracranial
hypertension (IH).
The outer sheath of the optic nerve is continuous with the
outer meninges of the brain and so any increased pressure
within brain is transmitted through the cerebrospinal fluid
(CSF) to the optic nerve and results in compression of
the optic nerve. Continued pressure causes stasis of the
axoplasmic flow leading to swelling of the optic nerve
head and eventually a loss of axons and optic atrophy. 15
Papilloedema is relatively easy to diagnose but can also
be confused with other causes of oedematous or swollen-
looking optic discs.
Figure 1 - Papilloedema
Causes
Intracranial hypertension can
be caused by a direct increase
of pressure within the CSF, by
bleeding within the brain or skull,
by lesions that occupy space
within the head or by inflammation
of the brain itself.
The CSF is formed in the lateral
ventricles of the brain and flows via the
fourth ventricle into the subarachnoid
space surrounding the brain. It is
absorbed back into the bloodstream
through blood vessels on the surface
of the brain. Our bodies produce
approximately 500ml of CSF every
day, continuously replacing CSF as it is
absorbed. Hydrocephalus occurs when
this balance is disrupted. Although there
are many factors that can disrupt this
balance, the most common is obstruction
along the circulatory pathway of CSF.
The obstruction may develop from a
variety of causes, such as brain tumours,
cysts, scarring and infection. 16
Bleeding between the brain and
the dura mater is known as subdural
haematoma. It can result from head
injury and is relatively common in
falls in elderly people. Blood collects
between the dura, compressing brain
tissue and increasing intracranial
pressure. Other vascular anomalies such
as arteriovenous fistulas, venous sinus
thrombosis and intracranial aneurysms
can occupy space inside the head or
bleed into the brain tissue. Inflammation
of the brain encephalitis or the
meninges (meningitis) lead to swelling
of the brain tissue, causing a rise in
intracranial pressure. 17
In many cases of chronic IH the cause
is unclear. This is known as idiopathic
IH. Idiopathic IH is associated with a
body mass index greater than 30. It is
thought that the rise in prevalence of
papilloedema in developed countries is
linked directly to the global epidemic
of obesity. 18 Idiopathic IH mainly affects women in their 20s and 30s, though it
is not clear why. Conditions linked with
idiopathic IH include hormone problems
such as under or over active thyroid,
some medications such as antibiotics,
steroids and contraceptives, anaemia,
chronic kidney disease and autoimmune
diseases such as Lupus. 19
Patients may experience a constant,
throbbing headache which may be
worse in the morning or when coughing
or straining. Visual acuity is normally
good except in advanced cases. Patients
sometimes describe a transient loss or
‘greying out’ of vision, often related
to coughing, sneezing or postural
changes and typically lasting only a few seconds. Patients may also report
horizontal diplopia caused by a full or
partial sixth nerve palsy and they may
hear a ‘whooshing’ tinnitus in time with
their own heartbeat when lying down.
Patients may also report feeling or being
sick and may experience changes of
mood such as lethargy or irritability. 20
Symptoms
Many patients do not volunteer
symptoms unless directly asked.
Symptoms usually include
headache though the nature of the
headaches can be variable.
Continued overleaf
November 2016 | etCETera
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