Metabolic and Toxic
Diseases of the CNS
Back to Library
Metabolic and toxic disorders of the nervous
system are common causes of neurological disease.
Several major diseases of the CNS have a metabolic or toxic causation, a
reflection of the vulnerability of the nervous system to injury.
The main causes
are vitamin deficiency states, liver failure, carbon monoxide poisoning, and
Several vitamin deficiency states are associated with damage to the nervous
Vitamin B1 (thiamine) deficiency causes Wernicke's encephalopathy.
Vitamin B12 deficiency is commonly associated with pernicious anaemia. In the
nervous system this causes degeneration of the lateral and posterior columns of
the spinal cord, termed 'sub-acute combined degeneration of the cord, leading to
paraesthesiae, ataxia, and sensory abnormalities.
Hepatic encephalopathy is a clinical state that arises in patients with severe
liver failure. Patients develop impaired consciousness, which may progress to
coma. Disease is thought to be due to the presence of excitatory transmitter
substances in the blood, which have not been detoxified by the liver, e.g. GABA.
Carbon monoxide poisoning is commonly encountered, either as an accident
(usually involving faulty heating equipment) or as a result of attempted
suicide. In patients who survive the acute poisoning and are resuscitated,
delayed damage to the brain may occur, signs usually becoming apparent 24-36
hours after exposure to carbon monoxide. There is necrosis of the globus
pallidus, demyelination of the hemispheric white matter and, frequently, diffuse
cortical laminar necrosis.
The brain and peripheral nerves are frequently damaged in chronic alcoholism
Acute alcohol intoxication causes neuronal depression and may lead to death
through cessation of respiration.
Chronic alcoholism is associated with several diseases of both the central and
the peripheral nervous system. It has been difficult to determine whether this
is due to direct toxicity or whether it is caused by the nutritional and vitamin
deficiencies seen commonly in patients dependent on alcohol.
The brains of alcoholic patients show generalized cerebral cortical atrophy,
which sometimes causes cognitive decline. Cerebellar ataxia in patients with
alcoholism is usually caused by cerebellar degeneration associated with severe
atrophy of the cerebellar cortex.
Wernicke's encephalopathy is caused by thiamine deficiency, commonly seen in
patients dependent on alcohol. It presents clinically as a triad of confusion,
ataxia, and abnormal eye movements with ophthalmoplegia. Pathologically, there
are petechial haemorrhages from small vessels in the mammillary bodies, which
are associated with necrosis and loss of neurons, leading to eventual shrinkage
and gliosis. Acute Wernicke's encephalopathy may prove fatal unless B-complex
vitamins (including thiamine) are administered.
Damage to the limbic system from repeated episodes of Wernicke's encephalopathy
causes a permanent impairment of recent memory, termed Korsakoff's psychosis.
Exposure of the fetus to alcohol, when the mother is dependent, leads to growth
retardation and cerebral malformations (fetal alcohol syndrome).
Interested in translating health topics to somali language!
We give here simplified and accurate information about the disease
DISCLAIMER: This website is provided for
general information and it's run by medical students for medical students only
and is not a substitute for professional medical advice. We are not responsible
or liable for any diagnosis or action made by a user based on the content of
this website. We are not liable for the contents of any external websites
listed, nor do we endorse any commercial product or service mentioned or advised
on any of the sites. Always consult your own doctor if you are in any way
concerned about your health