Brain – Tissue and Systems

The purpose of this article is to describe the basic anatomy and systems involved with brain tumors.  The brain is a part of the central nervous system.  The central nervous system is composed of the brain and spinal cord.  The brain has been studied extensively and is only partially understood by modern science.  The brain can be divided into different components that each helps with a specific role. How these individual parts work together to create a cohesive consciousness, emotion and what we perceive as awareness is a great mystery.  There are numerous diseases that either occur directly in the brain or affect the brain remotely.  An example of a direct disease of the brain would be an astrocytoma occurring in the brain causing headache.  An example of a remote disease affecting the brain would be an insulin secreting tumor of the pancreas that causes low blood sugar and brain dysfunction with loss of consciousness.

The nervous system functions with the basic unit of the nerve.  A nerve is a signal transmission device that sends signals with chemical messengers released from it as well as movement of electrolytes along the nerve itself.  There are several varieties of nerve signaling but they all have a common goal.  The mechanisms that lead to nerve signal creation are quite varied.  As sound waves strike the ear drum they create small oscillations that trigger adjacent nerves to signal to the brain a particular sound pattern.  A light brush of a feather across the finger tips also signals specific nerve types in the skin to transmit signal information.  The brain does the remarkable job of decoding this information and providing an interpretation to us.  Thus, we do not actually feel the feather we feel what our brain tells us what the feather feels like.

All these complex functions are not really considered until there is a problem with the system. Tumors of the brain generally cause some problem with sensation, perception, movement or consciousness.  Fortunately, the brain is quite protected and encased in a protective skull with dural layers surrounding it as well as fluid bathing it to help provide cushioning.  This fluid is known as cerebrospinal fluid.  The brain can also regulate the volume of fluid within the skull by regulating blood flow and blood pressure.  This regulation is also known as cerebral auto-regulation.  Although there is separate division, the entire brain is largely composed of a collection of millions of nerves.  When nerves connect to each other this is referred to as a synapse.

Brain tumors may be either cancer or benign.  Despite the label “benign”, non-cancerous brain tumors can still cause devastating effects because of the effects of pressure near the brain.  The same effects can happen from bleeding around the brain (such as a subdural hematoma) that collects and causes pressure on the brain.  The pressure within the skull is carefully regulated and averages about 5-10 mm Hg.  When this pressure is increased it causes a characteristic set of symptoms referred to as increased intracranial pressure (ICP).

There are many different types of brain tumors.

The most common brain tumors are:

  • Metastatic tumors (tumor that has spread from another primary cancer)
  • Astrocytoma tumors
  • Oligodendroglial tumors
  • Ependymal tumors
  • Choroid plexus tumor
  • Glioblastoma
  • Mixed neuronal-glial tumors
  • Pineal tumor
  • Embryonal tumor
  • Nerve Sheath tumor
  • Meningioma
  • Lymphoma
  • Many others exist

Brain cancer is relatively rare with malignant primary brain tumors accounting for about 1% of all adult cancer.  Brain tumors comprise about 20% of all cancers in children.  Despite the many different types of brain tumors, the symptoms they cause are similar.  The key point of these articles is to emphasize the serious nature of the common symptoms caused by brain tumors.  The best possible outcome will be possible with early recognition and prompt treatment.

The most common symptom of brain cancer is headache.  Headache is the subjective feeling of pain in the head which may be described as an ache, sharp stabbing pain, throbbing, or even change in temperature.  Headache is very common and quite non-specific.  Most people get headaches from time to time and the vast majority of these do not represent cancer.  The headaches caused by brain tumors are usually dull and constant because the tumor provides continuous pressure.  The headache will worsen as the tumor grows usually.  Associated symptoms with the headache that are “red flags” that this is not a typical headache might include nausea, vomiting, dizziness, passing out, or difficulty walking.  More dramatic symptoms such as seizures may occur.  A seizure is a disorganized uncontrollable rhythmic movement of part or all of the body that generally causes loss of consciousness.

When these types of symptoms are noticed the first thing to do is not to ignore it.  These should be brought to the attention of your doctor for investigation.  The investigation of brain tumor symptoms will generally involve an examination followed by some type of brain imaging such as a CAT scan and/or magnetic resonance imaging (MRI).  These tests, particularly the MRI, are extremely sensitive at detecting most brain tumors and occasionally can make a definitive diagnosis based upon characteristic imaging findings.

Some brain tumors will also require a sample of the cells to be taken in order to understand what type of tumor is present.  A sampling of cells for examination under the microscope is known as a biopsy.


  3. Abeloff, M.D. (2008). Abeloff: Abeloff’s Clinical Oncology, 4th ed. Chapter 70.Philadelphia,PA: Churchill Livingstone – Elsevier
  4. Marx JA, Hocberger RS, et al.; Marx: Rosen’s Emergency Medicine, 7th ed. Chapter 101.Los Angeles,CA: Mosby Elsevier
  5. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.