Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Steven Doerr, MD, is a U.S. board-certified Emergency Medicine Physician. Dr. Doerr received his undergraduate degree in Spanish from the University of Colorado at Boulder. He graduated with his Medical Degree from the University Of Colorado Health Sciences Center in Denver, Colorado in 1998 and completed his residency training in Emergency Medicine from Denver Health Medical Center in Denver, Colorado in 2002, where he also served as Chief Resident.
From the above description of brain lesion types, it is evident that the
different types are arranged, in general, according to different mechanisms that
lead to brain cell changes which produce various brain lesions. The causes,
however, can be further categorized. The following is a list of causes
containing more specific subsets and descriptions:
Trauma: penetrating or blunt. Blunt trauma may be further subdivided to
include with or without skull fracture. Trauma results in damaged or destroyed
brain tissue with immediate and/or delayed (hours to days, usually) symptoms.
Infectious: Brain lesions caused by a wide variety of pathogenic agents ranging from viruses,
bacteria, fungi, and parasites. Some may develop symptoms quickly over hours to
days (such as in viral and bacterial meningitis) or over many years (such as in
the parasitic infection Cysticercosis).
Malignant: Malignant brain lesions subtypes are termed "primary" if they arise from the brain
tissue cells (such as gliomas and medulloblastomas) and "secondary" if they
originate in other body organs and spread (metastasis) to the brain (such as
colon cancers). Secondary brain lesions are more common than
primary brain lesions. Some lesions develop fairly fast (weeks to months), while
others may develop more slowly. In addition, malignant lesions are often graded,
which means they are assigned a number (I, II, II or IV) based on their
appearance under a microscope. Grade I tumors are less aggressive and tend to
grow and spread more slowly, while grade IV tumors are the highly aggressive and
tend to grow and spread more rapidly.
Benign (non-cancerous): Brain lesions composed of abnormally growing cells which
are non-cancerous (though a rare few may contain some
cancer cells, mainly grade
I). They may cause symptoms if they become large and compress other normal brain
tissue or interfere with the blood supply to the brain. They usually develop
slowly (for example, meningiomas).
Vascular: Three subtypes of vascular brain lesions exist; 1) arteriovenous malformations (weak vascular
areas that may leak or burst, causing blood to leak into brain tissue), 2) abnormal
growth of vessels in the brain (hemangioblastomas associated with von
Hippel-Lindau disease), and 3) the most frequently encountered vascular problem,
strokes (also termed cerebral vascular accidents or CVA's). Most strokes are
caused by clots (about 85%) which cause brain cell damage or death by reducing
or cutting off the blood supply to areas of the brain. Except for the long-term
development of diseases like von Hippel-Lindau, vascular brain lesions generally
produce symptoms within minutes to hours.
Genetic: Errors in human DNA or certain DNA sequences in the genetic
makeup of some individuals can lead to brain lesions, such as neurofibromatosis
or familial British dementia. Most of these lesions develop over years.
Immune: The individual's immune system mistakenly attacks and attempts to
destroy brain tissue components, such as myelin (a sheath surrounding nerve
cells). The resulting scar tissue can be seen in
multiple sclerosis, for
example. These types of lesions usually progress in development over years.
Brain cell death or malfunction: The cause of certain brain lesions, like
those seen with Parkinson's disease, are due in part to the malfunction and
death of brain cells that produce dopamine. However, the underlying cause may be
related to genetics, toxic exposures, or various other combinations of potential
causes. Development usually progresses over years.
Plaques (deposits of substances in brain tissue): Deposits of materials
such as Lewy bodies, amyloid plaques, and neurofibrillary tangles or bundles in
brain tissue are associated with several diseases, most notably Alzheimer's
disease. However, it is not clear whether the deposits are the primary cause or
if they are the secondary results of an underlying (and as of yet) unidentified
cause. Development usually progresses over years.
Ionizing radiation:X-rays, gamma rays and other types of radiation, when
intense enough or if acquired sequentially in high levels, can disable and
destroy brain cells, as well as other cell types.
Many brain lesions may have more than a single cause and are often associated
with multiple risk factors, which some researchers believe may be the cause,
although a direct link to the risk factor(s) is often difficult or unlikely to
be proven by researchers.