Human Brain & Behaviour
CAUSES OF BRAIN DAMAGE
Atumor is a mass of new & abnormal tissue that is not physiologically beneficial to its surrounding
Also called neoplasms new tissue
Space-occupying lesions: they are foreign objects that cause damage to the CNS by putting pressure
on it & occupying space that is normally occupied by the CNS.
Different types of tumors damage is not only caused by exerting pressure.
Tumors differ in terms of what type of cell gives rise to the tumor, how rapidly they grow, whether
they infiltrate and destroy surrounding neural tissue or remail relatively encapsulated, and how
likely they are to recur if they are removed.
Benign tumors: not likely to recur
Malignant: more likely to recur
4 major types of brain tumors: originating from
a) glial cells
b) the meninges
c) nervous tissue
d) other parts of the body already infected with a tumor
TumorsArising From Glial Cells
Gliomas = Most common type of tumors
2 main types of gliomas
Astrocytomas: tumors that arise from the growth of astrocytes. Tend to grow slowly and
usually benign. Some are well encapsulated, so the damage that they cause tends to come
from compression of the surrounding tissues. Other astrocytes infiltrate surrounding neural
tissue. If tumor started to grow in a relatively accessible location, surgery can correct proble.
Even if benign, very dangerous if location is inaccessible. Options: Surgery or
Glioblastoma: Opposite of astrocytomas grow quickly, highly malignant, are not
encapsulated, they infiltrate surrounding tissue making it hard to spare surrounding tissue
while removing tumor. Treatment: Chemotherapy.
Medulloblastoma: Less common (2-6% of all glicomas) highly malignant infiltrating
tumor. Tend to form around cerebellum and brainstem early in life. Because of the location
and nature of these tumors, chemotherapy is usually the best treatment option, however
prognosis for these individuals is quite poor since brainstem and cerebellum are responsible
for basic survival functions.
TumorsArising From The Meninges
Meningiomas: Tumors that grow out of (and remain attached to) the meninges. Most of them
grow out of the dura mater, forming an ovoid shape. Tend to be well encapsulated since they
grow out of tissues found outside the CNS. Harmful effects are therefore due to exerted
pressure. Most are relatively benign but there are also some malignant varieties. Treatment:
Surgery due to accessible location.
Mestatic Tumors: Secondary tumors that form from migrated tumor tissue. Primary site can be
located in parts of the body such as the lungs, breasts, uterus, or kidneys. Most commonly,
original site of tumor is outside of the CNS.
Simple metastatic tumors: occur when only one tumor forms at one site. Treated with surgical or radiological treatment quite effective.
Multiple metastatic tumors: More common; usually spreading from the lungs to the CNS.
Treatment of chemotherapy or whole-brain radiotherapy but prognosis is quite poor.
Neuropsychological Effects of Tumors
Behavioural symptoms vary
Slow-growing infiltrating astrocytoma near primary visual cortex = gradual blindness in parts of
a visual field
Tumors in pituitary gland can have similar effects to those of a visual cortex tumor
Rapidly growing meningioma numbness & paresis to the feet and legs.
Mestatic tumors in the left temporal love speech disturbances, receptive language problems
Tumors in left parietal lobe apraxia
Tumors can also cause epileptic seizures and release substances that are toxic to the brain
If tumor is located in ventricles and releases toxins can easily cause defects not confined to a
specific region within which it originates.
Occurs when the blood supply to the brain is interrupted; interruption can be sudden or gradual,
complete or relative, permanent or transient.
They are the leading cause of disabling neurological damage and the 3 most common cause of
death in the developed world.
Cerebrovascular Accident = A.k.a = Stroke
Stroke = Cerebrovascular Accident (CVA) = a class of cerebrovascular disorders, all of which
result in interruptions to the brain's blood supply.
CVAresults in cerebral ischemia
Alack of blood supply to the brain.
If severe, or long-lasting enough to kill neurons, the damaged area is called an infarct.
Infarcts can be very small if CVAis restricted to small, minor arteries.
Large if CVAis in a major vessel.
Interruptions in blood supply can be caused by many things blocked cerebral arteries,
broken cerebral arteries, or interruptions of blood supply outside of the CNS.
If a blood clot forms within a cerebral blood vessel.
Can also form outside of the brain
If it forms in the heart, it can cause a heart attack
Cause: atheroscleosis: fatty deposits build up inside the walls of blood vessels, constricting the
vessel more and more and possibly even completely blocking it.
Buildup of fatty deposits = gradual = the symptoms appear gradually
Constriction of blood flow tends to influence relatively large areas of the brain, and the
neuropsychological symptoms that result from the disorder are usually diffuse and gradual in
Similar in form to a thrombosis = both involve the blocking of an artery by the buildup of a
However, while thrombosis remains at point of origin, embolism is normally a clot that travels
in the bloodstream from 1 part of the body to another.
Typically, substance travels from a spot where arteries are relatively large to a place where the
arteries are smaller than the point of original formation, so even though it may not have blocked
before, it may now block the smaller arteries.
Embolisms can be extremely dangerous if the blockage is not relieved immediately.
Prognosis: Can be treated surgically depending on where they form
Also treated with anticoagulant drugs.
Breakage of a blood vessel
Presence of a thrombosis or embolism can cause blood pressure to build to a point that the
walls of the artery cannot sustain
Artery itself - malformed, having a weak spot called an aneurysm.
Abnormally high blood pressure, hypertension, and the piercing of a blood vessel by a
foreign or displaced object, such a bullet.
Interruption in blood supply
Supply of oxygen and glucose is disrupted
Blood itself is somewhat toxic to the neural tissue.
Bleeding = pressure = compression injuries in other areas = displacement of neural centers
associated with vegetative functions = medulla
Hemorrhage occurs within the brain
Bleeds are usually caused by hypertension
Damage due to interruption of blood flow, toxicity of the uncontained blood, &
pressure buildup at & away from the site of the bleed.
Usually unlikely to recur
Prognosis: Quite Poor