BRAIN FAILURE
BRAINSTEM
B
disease
is a rare, fatal brain disease
associated with an infective agent called
a prion which, in some cases, has been
linked with BSE
(bovine spongform
encephalopathy),
a disease in cattle.
Multiple sclerosis
is
a
progressive
disease of the brain and spinal cord.
Degenerative brain diseases include
Alz-
heimer's disease
and
Parkinson's disease.
Emotional or behavioural disorders are
generally described as psychiatric ill-
nesses; but the distinction between
neurological and psychiatric disorders
is now much less clear.
b ra in
failu re See
brain
syndrome,
organic
.
b ra in haem o rrh ag e Bleeding within
or around the brain that is caused
either by injury or by spontaneous rup-
ture of a blood vessel. There are 4
possible types of brain haemorrhage:
subdural
,
extradural
,
subarachnoid
, and
intracerebral.
Extradural and subdural
haemorrhages are usually the result of
a blow to the head (see
head injury
).
Subarachnoid and intracerebral haem-
orrhages usually occur spontaneously
due to rupture of
aneurysms
or small
blood vessels in the brain.
b rain im aging Techniques that provide
pictures of the brain; they are used to
detect injury or disease and include
X-rays
,
angiography
,
CT scanning
,
MRI
,
PET
(positron emission tomography)
scanning, and
SPECT
(single photon
emission CT). X-ray films can show
changes in the skull caused by a fracture
or, rarely, by a
brain tumour
or
aneur-
ysm. Angiography shows up the blood
vessels in the brain, and is used to
investigate
subarachnoid haem orrhage
,
aneurysms, abnormalities of the blood
vessels, and other circulatory disorders.
CT scanning gives images of the brain
substance; it gives clear pictures of the
ventricles (fluid-filled cavities) and can
reveal tumours, blood clots, strokes,
aneurysms, and abscesses. MRI is espe-
cially helpful in showing tumours of the
posterior fossa (back of the skull). PET
and SPECT scanning are specialized
forms of
radionuclide scanning
that use
small amounts of radioactive material
to give information about brain func-
tion as well as structure. They enable
blood flow and metabolic activity in the
brain to be measured.
Ultrasound scanning
is used only in
premature or very young babies since
ultrasound waves cannot penetrate the
bones of a mature skull.
brain stem A stalk of nerve tissue that
forms the lowest part of the brain and
links with the spinal cord. The brainstem
acts partly as a highway for messages
travelling between other parts of the
brain and spinal cord. It also connects
with 10 of the 12 pairs of
cranial nerves
(which emerge directly from the under-
side of the brain) and controls basic
functions such as breathing, vomiting,
and eye reflexes. Brainstem activities
are below the level of consciousness,
and they operate mainly on an auto-
matic basis.
The brainstem is composed of 3 main
parts: the midbrain, pons, and medulla.
The midbrain contains the nuclei (nerve-
cell centres) of the 3rd and 4th cranial
nerves. It also contains cell groups invol-
ved in smooth coordination of limb
movements. The pons contains nerve
fibres that connect with the
cerebellum
.
It also houses the nuclei for the 5th-8th
cranial nerves. The medulla contains the
nuclei of the 9th-12th cranial nerves. It
also contains the “vital centres” (groups
of nerve cells that regulate the heart-
beat, breathing, blood pressure, and
digestion (information on which is relay-
ed via the 10th cranial nerve (see
vagus
BRA IN STEM
92
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