Meninges - Membranes Enveloping Central Nervous System

Meninges - Membranes Enveloping Central Nervous System

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 19 Mar 2014 - 15:40.

Similar to the lungs, which has a covering called pleura and the intestines which have a covering called the peritoneum, the brain and the spinal cord also have a covering called the Meninges.

Both the brain and the spinal cord are wrapped in three layers of tissue called the Meninges. These three layers are called the Pia, Arachnoid and Dura mater from within outwards respectively.

The Pia mater is the innermost layer that adheres to the brain and the spinal cord. The Arachnoid matter is the middle layer, which is very delicate and resembles a spider web like tissue and serves as a channel for the Cerebrospinal fluid. The Dura mater is the outermost layer that is leather like and toughest of the three layers.

The brain and its meninges are protected by a tough bony structure called the skull and the vertebrae. Additional protection is provided by the cerebrospinal fluid, which flows over the surface of the brain in between the meninges. The cerebrospinal fluid also fills the internal spaces within the brain called the ventricles and acts as a cushion, against any minor injuries.

Conditions affecting Meninges: Several conditions affect the meninges. Inflammation of the meninges is the commonest condition affecting the meninges of the brain and the spinal cord. Inflammation of the meninges leads to a condition called Meningitis.

In Meningitis, the membranes covering both the brain and spinal cord are inflamed. Inflammation of meninges may be due to viral or bacterial infections. However, though more common, meningitis due to a virus is not as serious as the one caused due to bacterial infections.

Bacterial meningitis though less common is more dangerous than the viral form of meningitis. Both the forms can occur at any age. However, the bacterial form mostly affects children where as the viral form affects young adults. In very rare cases it may be due to fungal infection which usually presents itself in cases suffering from AIDS.

Though several varieties of the virus can cause viral meningitis, the most common variety is due to a virus called Coxsackie virus.

Bacterial meningitis can occur for no apparent reason and can affect a child or even a teenager. The primary cause can be a streptococcus or meningococus. The secondary cause may be due to some bacterial infection elsewhere in the body most commonly an infection in the lungs.

Bacterial meningitis though commonly affecting a single person can also lead to outbreaks of attacks particularly in institutions like schools and colleges.

Symptoms may appear very slowly over a period of time like in the case of viral form and rapidly over a very short period like in the bacterial form. Usually it starts with a flu like episode and rapidly aggravates to high fever and neck rigidity with lethargy and headache coupled with vomiting and nausea.

The presence of a rash with dark or purple spots that develop into blotches, which don’t fade when pressed, is a certain sign of Meningococcal meningitis. The presence of rash along with fever and other symptoms listed above confirms Meningococcal meningitis without doubt.

In some cases, though not very common the infection may be due to tuberculosis when it causes tuberculous meningitis.

Lumbar puncture and studying the cerebrospinal fluid for values of sugar, chlorides and cells will clinch the type of meningitis whether tubercular, bacterial or viral meningitis depending on the increase or decrease in values of cells, sugar and chlorides.

Treatment depends on the nature of infection. However, early diagnosis and treatment on a war footing may save a precious life.

Though rare, a tumor can also affect the meninges. Meningioma is one such tumor, which can affect the cells of the coverings of the brain and spinal cord. Meningiomas are always benign tumors and usually affect young adults and it is estimated that about 20% of all the brain tumors are Meningiomas.

Subdural and subarachnoid hemorrhages are the commonest condition resulting from severe head injuries or a rupture of a blood vessel within meninges, like in severe hypertension or rupture of an aneurysmal dilatation of a blood vessel and need immediate hospitalization and treatment in Intensive Care Unit.

There are many conditions which can affect the meninges either from birth or acquired after birth, either directly or indirectly, but only the commonest conditions have been covered in brief.

*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.