ABNORMALITIES ASSOCIATED

WITH NERVOUS SYSTEM

BY
EBUOH MARYANN CHIAMAKA
 Diseases of the brain
• Increased intracranial pressure: This is a serious
complication of many conditions that affect the brain.
• The cranium forms a rigid cavity enclosing the brain, the
cerebral blood vessels and cerebrospinal fluid (CSF).
• An increase in volume of any one of these will lead to
raised intracranial pressure (ICP).
• Sometimes its effects are more serious than the
condition causing it, e.g. by disrupting the blood supply
or distorting the shape of the brain, especially if the ICP
rises rapidly.
 Diseases of the brain con’t
• The causes of increased ICP include: cerebral oedema
hydrocephalus i.e the accumulation of excess CSF
expanding lesions inside the skull, also known as
space-occupying lesions – haemorrhage, haematoma
(traumatic or spontaneous) – tumours (primary or
secondary).
• Effects of increased ICP include:
• Displacement of the brain
• Obstruction of the flow of cerebrospinal fluid
• Vascular damage
• Bone changes
 Diseases of the brain con’t
• Head injuries Damage to the brain may be serious even
when there is no outward sign of injury.
• At the site of injury there may be a scalp wound, with
haemorrhage between scalp and skull bones damage to
the underlying meninges and/or brain with local
haemorrhage inside the skull.
• A depressed skull fracture, causing local damage to the
underlying meninges and brain tissue temporal bone
fracture, creating an opening between the middle ear and
the meninges fracture involving the air sinuses of the
sphenoid, ethmoid or frontal bones, making an opening
between the nose and the meninges.
 Diseases of the brain con’t
• Intracerebral haemorrhage and cerebral oedema; These occur
following contusions, lacerations and shearing injuries
associated with acceleration and deceleration, especially
rotational movements.
• Cerebral oedema is a common complication of contusions of
the brain, leading to increased ICP, hypoxia and further brain
damage.
• Cerebral hypoxia: When the mean blood pressure falls below
about 60 mmHg, the autoregulating mechanisms that control
the blood flow to the brain by adjusting the diameter of the
arterioles fail.
• The consequent rapid decrease in the cerebral blood supply
leads to hypoxia and lack of glucose.
 Diseases of the brain con’t
• It leads to Conditions in which autoregulation breaks
down include: cardiorespiratory arrest, sudden severe
hypotension, carbon monoxide poisoning hypercapnia
(excess blood carbon dioxide) etc.
• Alzheimer’s disease/Dementia Dementia is caused by
progressive, irreversible degeneration of the cerebral
cortex and results in mental deterioration, usually over
several years.
• There is gradual impairment of memory (especially short
term), intellect and reasoning but consciousness is not
affected.
• Emotional lability and personality change may also occur.
 Diseases of the spinal cord

• Motor neurone disease: This is a chronic

progressive degeneration of upper and lower
motor neurones, occurring more commonly in
men over 50 years of age.
• The cause is seldom known, although a few cases
are inherited as an autosomal dominant disorder.
• Motor neurones in the cerebral cortex, brain
stem and anterior horns of the spinal cord are
destroyed and replaced by gliosis.
 Diseases of the spinal cord con’t

• Early effects are usually weakness and twitching of the small

muscles of the hand, and muscles of the arm and shoulder
girdle.
• The legs are affected later.
• Death occurs within 3–5 years and is usually due to
respiratory difficulties or complications of immobility.
• Sensory neurons: The sensory functions lost as a result of
disease or injury depend on which neurones have been
damaged.
• Spinal cord damage leads to loss of sensation and cerebellar
function. Peripheral nerve damage leads to loss of reflex
activity, loss of sensation and of cerebellar function.
 Diseases of the spinal cord con’t

• Compression of the spinal cord and nerve roots.

• The causes include; prolapsed intervertebral disc
syringomyelia tumours, metastatic, meningeal or
nerve sheath fractures with displacement of bone
fragments.
• Syringomyelia This dilation (syrinx) of the central
canal of the spinal cord occurs most commonly in
the cervical region and is associated with congenital
abnormality of the distal end of the fourth ventricle.
 Diseases of the spinal cord con’t

• As the central canal dilates, pressure causes

progressive damage to sensory and motor
neurones.
• Early effects include dissociated anaesthesia, i.e.
insensibility to heat and pain, due to compression
of the sensory fibres that cross the cord
immediately they enter.
• In the long term there is destruction of motor and
sensory tracts, leading to spastic paralysis and loss
of sensation and reflexes.
 Diseases of peripheral nerves

• Polyneuropathy; Is Damage to a number of nerves

and their myelin sheaths.
• It occurs in association with other disorders, e.g
nutritional deficiencies, e.g. vitamins B1, B6, B12.
• metabolic disorders, e.g. diabetes mellitus, renal
failure, hepatic failure.
• carcinoma toxic reactions to, e.g., alcohol, lead,
mercury, aniline dyes and
• some drugs, such as phenytoin, isoniazid infections,
e.g. leprosy.
 Diseases of the spinal cord con’t

• Mononeuropathy: Usually only one nerve is damaged and

the most common cause is ischaemia due to pressure.
• The resultant dysfunction depends on the site and extent of
the injury.
• Examples include: pressure applied to cranial nerves in
cranial bone foramina due to distortion of the brain by
increased ICP compression of a nerve in a confined space
caused by surrounding inflammation and oedema, e.g. the
median nerve in carpal tunnel syndrome.
• Bell’s palsy Compression of a facial nerve in the temporal
bone foramen causes paralysis of facial muscles with
drooping and loss of facial expression on the affected side.
 Developmental abnormalities of the nervous system

• Spina bifida: This is a congenital malformation of the

embryonic neural tube and spinal cord.
• The vertebral (neural) arches are absent and the dura mater
is abnormal, most commonly in the lumbosacral region.
• The causes are not known, although the condition is
associated with dietary deficiency of folic acid at the time of
conception.
• These neural tube defects may be of genetic origin or due to
environmental factors, e.g. irradiation, or maternal infection
(rubella) at a critical stage in development of the fetal
vertebrae and spinal cord.
• The effects depend on the extent of the abnormality.
Developmental abnormalities of the nervous system con’t

• Occult spina bifida: In this ‘hidden’ condition the

skin over the defect is intact and excessive growth of
hair over the site may be the only sign of
abnormality.
• This is sometimes associated with minor nerve
defects that commonly affect the bladder.
• Meningocele: The skin over the defect is very thin
and may rupture after birth.
• There is dilation of the subarachnoid space
posteriorly. The spinal cord is correctly positioned.
Developmental abnormalities of the nervous system con’t

• Meningomyelocele: The meninges and spinal

cord are grossly abnormal.
• The skin may be absent or rupture. In either
case there is leakage of CSF, and the meninges
may become infected.
• Serious nerve defects result in paraplegia and
lack of sphincter control causing incontinence
of urine and faeces.
• There may also be mental impairment.
 Tumours of the nervous system
• Primary tumours of the nervous system usually arise from the
neuroglia, meninges or blood vessels.
• Neurones are rarely involved because they do not normally
multiply.
• Metastases of nervous tissue tumours are rare. Because of this,
the rate of growth of a tumour is more important than the
likelihood of spread outside the nervous system.
• In this context, ‘benign’ means slow growing and ‘malignant’
rapid growing.
• Early signs are typically headache, vomiting, visual disturbances
and papilloedema (swelling of the optic disc seen by
ophthalmoscopy).
• Signs of raised ICP appear after the limits of compensation have
been reached.
THE
END