Anatomy - Subarachnoid Haemorrhage
Haemorrhage is the medical
term for bleeding. The rupture of one of the brain's
blood vessels can cause bleeding into the subarachnoid
space - beneath the arachnoid membrane, on top of the
pia mater - and into brain tissue. The bleeding usually
stops, at least temporarily, when a clot forms over
the ruptured area.
The most frequent cause of spontaneous subarachnoid
haemorrhage (not due to injury) is the rupture of a
small aneurysm, or bulging sac, on one of the blood
vessels that supplies the brain. It is usually impossible
to determine why the aneurysm forms and bursts, but
the condition is common in adults and may be associated
with aging, diabetes, pregnancy, hypertension (high
blood pressure), heredity, or trauma.
Cerebral aneurysms are usually of three
types: saccular with a narrow "neck" (called "berry"
aneurysms because of their shape and their tendency
to occur in clusters); saccular with a broad base; and
fusiform, in which a short section of the artery bulges
all the way around. Each shape determines the degree
of difficulty a surgeon faces in attempting to treat
An aneurysm ruptures spontaneously - even during sleep
- and therefore is not related to the strain of hard
work, sexual intercourse, or other physical activity.
Although it is not always possible to discover the
exact source of bleeding, other causes of spontaneous
subarachnoid haemorrhage include: arteriovenous malformations,
small angiomas, certain types of infections, and bleeding
What symptoms can it cause?
A ruptured cerebral aneurysm
at first causes severe headache, which can be followed
by nausea, vomiting, double vision or sensitivity to
light, neck pain or stiffness, weakness, memory loss,
paralysis, coma, or death. How severe the symptoms are
and how long they last will depend on the amount and
location of the bleeding. Blood in and around the brain
can cause pressure, swelling, and brain irritation,
which can lead to drowsiness, confusion, weakness or
paralysis, memory loss, speech problems, behavior changes,
or coma (complete loss of consciousness).
What complications can occur?
The blood vessels around the aneurysm are irritated
by the blood from the haemorrhage and will at times
go into a state of spasm, tightening and narrowing.
This vasospasm ("vaso" meaning vessel) can occur any
time after the rupture until the haemorrhaged blood
has been absorbed by the body, and it can increase any
or all symptoms. It is the body's own attempt to prevent
a second haemorrhage by restricting the flow of blood
through the vessels around the aneurysm. Vasospasm thus
reduces pressure on the delicate aneurysm but unfortunately
also reduces the normal blood supply to parts of the
Ongoing research is being done to discover a medicine
that will control vasospasm; as yet, none has proven
effective. Other complications from subarachnoid haemorrhage,
such as hydrocephalus, haematoma (blood clot), and brain
swelling, involve the brain; but other body systems
can also be affected because of the severe nature of
the illness. Pulmonary embolus, heart abnormalities,
and bleeding from an ulcer may cause further complications.
How is it diagnosed?
- Several tests are used to confirm the diagnosis
of ruptured cerebral aneurysm. Some are explained
in the other parts of this web site.
- Because cerebrospinal fluid flows within the subarachnoid
space, a sample of CSF taken during a spinal tap at
the base of the spine will show blood from the haemorrhage.
- A CT scan will show blood inside the skull and
indicate how much bleeding has occurred.
- To find the source of the haemorrhage, an angiogram
is performed, which may have to be repeated to try
to pinpoint the aneurysm's exact location.
Because the aneurysm can rupture again, a quiet,
restful atmosphere is important. The patient usually
is placed in the Intensive Care Unit (ICU), a highly
specialised area providing close observation with specialised
nursing care. Complete bed rest without physical strain
is essential while the patient's condition stabilises
- usually in preparation for surgery.
Medications will be given when necessary to
reduce pain, control blood pressure, relieve stress,
and maintain fluid balance.
If necessary, a respirator may be used to help the patient
breathe and to control intracranial pressure (ICP).
Most often, however, oxygen is merely administered to
the patient through nasal prongs or a mask.
Various monitoring devices may be used to assess the
patient's condition during recuperation. Among the most
common are: an ECG (heart) monitor, an ICP (Intracranial
Pressure) monitoring device, a Swan-Ganz catheter to
assess the patient's fluid balance, and an arterial
line to continuously measure blood pressure and aid
in drawing frequent blood samples for laboratory study.
Intravenous (I.V.) fluids may be given until liquids
and food can be taken adequately by mouth. The amount
of fluid given will be closely monitored until the dangers
of brain swelling (edema) and vasospasm lessen.
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