There are twelve (12) pairs of Cranial Nerves that reside
within the Cranial Cavity (i.e. 12 nerves on the right side and 12
on the left side.) Any of these nerves can be involved in and
their function impaired by different disease processes such as occurs with
Skull Base Tumors.
Figure 1: Diagram of the Cranial Nerves together with their functions.|
There is a category of Cranial Nerve disorders that is considerably
different than any of the other diseases that affect these or other
(the 5th Cranial Nerve),
(the 7th Cranial Nerve) and
(the 9th Cranial Nerve) are specific afflictions that share a common
underlying pathological etiology (cause).
The most common cause is a compression phenomenon exerted on the
Cranial Nerve at its junction with the Brain Stem. This region is
inside the Skull near its Base. The "compression" actually causes
an injury to the normal insulating material surrounding the nerve,
called MYELIN. This insulating material (which acts like rubber
that insulates electrical wires) is injured in these Cranial
Neuralgias as a result of compression that is exerted on the Cranial
Nerve (usually by a tortuous artery and/or a vein, which has come
to rest upon the nerve) at its junction with the Brain stem. The
offending artery gains this peculiar position consequent to
Atherosclerosis ("hardening of the arteries"). As the
atherosclerosis progresses, arteries become slightly elongated and
"firmer". This "lengthening" of the artery results in the artery actually
moving to a "new" position. In these patients, it is their "bad luck" that
the artery "falls" into this particular position relative to the Cranial
Nerve Root junction with the Brain Stem. Once the Myelin is injured, any
"stimulation" of the Cranial Nerve an result in a "short circuit"
(and thus the symptoms specific to the particular Cranial Nerve's
function) just as would happen in an electrical wire where its rubber
insulation had been eroded.
The same compression-distortion injury to the Nerve's Myelin
has also been seen in patients with Cranial Neuralgias associated
Aneurysm (a dilated
portion of a blood vessel) or a tumor. While it is acknowledged that
Aneurysms or tumors are very unusual as causes of these Neuralgias, it is
imperative to obtain an MRI Scan (with Gadolinium contrast agent) in
any of these patients early after the diagnosis has been made in order to
identify these potentially lethal (Aneurysm or Tumor) conditions.
The majority of these rare tumors are completely
Benign Skull Base Tumors.
Since these three conditions have a similar cause, their treatments are
similar. The information that follows in this Section has been prepared
to attempt to answer, in as specific manner as possible, the many
questions that are frequently asked about them. The operative procedures
used to treat these conditions are quite reliable but are ordinarily
considered only for patients WHO HAVE FAILED TO RESPOND TO MEDICATIONS
OR WHO HAVE HAD TO DISCONTINUE THE MEDICATIONS BECAUSE OF AN INABILITY TO
TOLERATE THEM. Medical therapy is usually effective and can remain so for
extended periods of time, particularly for patients with Trigeminal
Neuralgia and Glossopharyngeal Neuralgia. Unfortunately, medical treatment
for Hemifacial Spasm is not nearly as satisfactory or reliable.
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This page last edited on 2/19