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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.
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There is a category of Cranial Nerve disorders that is considerably
different than any of the other diseases that affect these or other
Cranial Nerves.
TRIGEMINAL NEURALGIA
(the 5th Cranial Nerve),
HEMIFACIAL SPASM
(the 7th Cranial Nerve) and
GLOSSOPHARYNGEAL NEURALGIA
(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
with an
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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Trigeminal Neuralgia (or Tic Douloureux) is a very severe stabbing
facial pain involving one or more of three divisions (or branches) of the
Trigeminal Nerve (the Fifth Cranial Nerve), which supplies
sensation to the face. Because of some important relatively recent
developments, there is a better understanding concerning the cause of
this painful condition. Different medications have been used with varying
success for many years. Surgical treatments in the past involved either
cutting the nerve or its branches or injecting alcohol to deaden the
nerve. The ideal surgical method of management would offer complete
relief of the pain without producing any numbness.
There are essentially three causes that are now recognized. The
most common cause is a compression phenomenon exerted on the Trigeminal
Nerve as it enters the Brain Stem. This region is inside the
skull near its base. The "compression" actually causes an injury to the
normal insulating material, called MYELIN, which surrounds the
nerve (and acts in a manner similar to rubber that insulates electrical
wires.) Usually this compression is exerted by a tortuous artery (and/or
a vein), which has come to rest upon the nerve in an unusual position.
The same compression-distortion injury to the nerve is seen in 10% of
Trigeminal Neuralgia patients resulting from an
Aneurysm (a dilated
portion of an artery) or a tumor. The majority of these rare tumors are
completely benign.
The other important, although unusual cause of Trigeminal Neuralgia
is Multiple Sclerosis, a disease, which attacks myelin.
The least common cause of Trigeminal Neuralgia is arteriosclerosis
("hardening of the arteries") which may produce a small stroke in
this region resulting in this dreadful pain.
All three of these "causes" have in common the fact that they injure
the critical insulating structure, myelin, at a very precise location, the
Brainstem's nerve root entry zone of the Trigeminal Nerve in order to
produce the pain of Trigeminal Neuralgia. Multiple Sclerosis,
aneurysms, tumors, and atherosclerosis obviously involve other areas of
the brain more frequently. It is only when one of these problems
involves this very special "nerve root entry zone" that the problem of
the Trigeminal Neuralgia is produced.
As a general principle, it is important to understand the cause of
a medical problem in order to design the specific treatment aimed at
relieving the causative agent, if possible. It is only in relatively
recent years that the cause of Trigeminal Neuralgia was identified. As a
result, more effective modern treatments were developed.
The diagnosis of Trigeminal Neuralgia is made, primarily, on the
basis of the characteristic pain experienced by the patient. Sharp,
stabbing, electric shock-like short duration pain is the most common
experience. The pain is usually initiated by touching the face, facial
muscle contraction, brushing the teeth, bending the head or neck in
extreme forward or backward positions or during eating.
It is unusual for there to be any abnormal or objective findings on
physical examination of either the motor or sensory portion of the
Trigeminal Nerve during the neurological examination. A small
percentage of patients may exhibit minor diminished sensation in one of
the three divisions of the Trigeminal Nerve.
MRI (including the newer "Thin Slice" technology) and MRA
(Angiography) are the two neuroimaging tests that are considered to
be imperative prior to any consideration for surgical therapies. It is
vitally important to identify the presence or absence of a tumor or
aneurysm as the cause of compression of the Trigeminal Nerve at
its junction with the Brainstem (up to 10% of Trigeminal Neuralgia
patients have either an aneurysm or tumor as the cause of their
Trigeminal Nerve "compression".) It is our firm policy to
make certain that these studies are done for ANY patient with this
syndrome even if medical (non-surgical) management is contemplated.
Once the Neuroimaging studies (described above) have ruled out the
presence of a potentially life-threatening problem (aneurysm and or
tumor), treatment considerations usually involve a vigorous trial of
Medical (non-surgical) therapy. The use of anti-convulsant
medications has proven to be effective for most patients. There are
several among this drug class that have reliably controlled this pain in
most patients for many years. The most effective has been TEGRETOL. Other
newer agents have also had considerable success. Drug treatment
failure is fairly common for several reasons including the intolerance
of the unpleasant side effects for many patients. Others find the cost of
long term medication to be prohibitive. Still others do not obtain
adequate relief.
Unconventional treatments such as acupuncture, cranio-spinal
manipulation, and chiropractic maneuvers are often tried by these
patients who seek alternative medicine approaches. These
"therapies" are unreliable for those who really do have
Trigeminal Neuralgia.
There are three primary surgical procedures currently being employed to
treat this problem. Previous surgical procedures were "destructive."
Pain was relieved by cutting the nerve, which resulted in dense numbness
in the specific distribution of the Trigeminal Nerve.
The more modern approach to this problem was developed by Dr. Peter
Jannetta. This involves an operation performed under general
anesthesia in which a small (keyhole) opening is made in the back
of the head behind the ear (See Figure 2.) Through this opening
we are able to expose the Trigeminal Nerve as it enters the
BRAINSTEM.
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Figure 3A (Left): Operative Photo. Left Trigeminal Neuralgia. The
5th Cranial Nerve Entry Zone (Broad Arrow) is compressed and
distorted at the Brain Stem (Slender Arrow) by an elongated,
tortuous and atherosclerotic Superior Cerebellar Artery Curved
Arrows).
Figure 3B (Right): Operative Photo (Same Case). The tortuous
Artery (Upper Curved Arrow) has been Transposed to an Inoffensive
Position and Held in Place by an Ivalon Sponge (Lower Curved
Arrow). The 5th Cranial Nerve entry Zone (Broad Straight Arrow) is
well decompressed resulting in the RELIEF OF PAIN. The Brain Stem
(Slender straight Arrow) is undisturbed.
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The abnormality causing Trigeminal Neuralgia at the place where
the nerve enters the Brainstem is usually a compressive loop of
artery. It is known that, as the aging process occurs,
arteries throughout our body become longer. In this tight, confined area
of the skull an elongating arterial loop may come to lie against the
nerve as it enters the brainstem. It is able (by compression) to cause
damage to the MYELIN sheath, which insulates the nerve. This
results in the pain of Trigeminal Neuralgia. (See figure 3A)
At surgery, the arterial loop can be repositioned to a better place
using special Microsurgical (Microvascular) techniques (See Figure 3B). It
is prevented from resuming its previous position by inserting a small,
permanent prosthesis usually made of an inert plastic sponge material.
The operation, called "Microvascular Decompression (MVD)" is
highly reliable in achieving total relief of pain without causing any
numbness to the face. It is also probable that this offers a greater
chance of preventing any further recurrence of the pain.
This procedure, while not new, has been utilized extensively for
over 25 years. In scientific terms this is now a period of time
that is long enough to be sure of some prolonged results.
Microvascular Decompression (MVD) appears to be the most
exciting and promising method for treating this problem and
offers a high probability of complete long term cure.
Follow-up information is becoming available from other countries and
surgical groups for periods up to 25 or more years.
Dr. Lazar has performed over 300 MVD procedures after having been
chosen by Dr. Peter Jannetta, in 1976, as one of ten American surgeons
to validate his theory of the cause and the operation (MVD) used to
definitively treat Trigeminal Neuralgia.
Our personal experience with the long-term results of Microvascular
Decompression (MVD) is similar to those from other centers (over 85%
complete long term relief) and very encouraging while the risks to MVD
have proven to be quite small.
It is our philosophy that no operation should be undertaken
lightly.
As with any operation and the use of general anesthetic, there is a
certain (fortunately extremely small) element of risk to life. The
Neuroanesthesiologist
will review the special anesthetic techniques used for this procedure
and answer any questions, which you might have. In making a decision
about a surgical procedure, a patient must carefully weigh the risks
against the potential benefits of affording relief without producing
facial or corneal (eye) anesthesia (numbness) or other complications
associated with other procedures that involve injury to or destruction of
the Trigeminal Nerve. This procedure is usually reserved for
patients who are otherwise in good health and young enough to undergo an
operative procedure. Under most conditions we restrict this procedure to
patients under the age of 70. However, we cannot draw a hard-and-fast
rule in this regard. There have been patients under the age of 65 who
may not qualify for this procedure. On the other hand, there have been
patients up to the age of 74 who have tolerated the procedure quite well
in my experience.
Patients selected for this procedure are usually hospitalized one to five
days following the performance of the operation. The first one to three
postoperative days are spent in the Neurological Intensive Care Unit.
There are a number of vital blood vessels and nervous system structures
in the operative region, which could conceivably be at risk to injury.
There are several nerves, which control the movement of the muscles of
the eye, which, if damaged, could produce double vision. The nerve which
controls hearing, the 8th Cranial (Auditory) Nerve, is very near
the Trigeminal Nerve as is the 7th Cranial (Facial) Nerve
which controls movement of the face. Injuries to these nerves could result
in deafness on this side and/or paralysis of this side of the face.
In my experience, no Trigeminal Neuralgia patient has had any facial
nerve paralysis. We seem to have been successful in reducing the risk to
impairment of hearing to a very low level, partly due to our ability to
monitor hearing function while surgery is being conducted. In the
event that this monitoring test indicates that hearing function seems to
be at risk during surgery, then the operation may be altered in some way
to reduce the risk to injury. The risk to injury to a vital blood vessel
which could produce a stroke (resulting in paralysis of
face/extremities/bowel/bladder) or hemorrhage is exceptionally small.
The chance to achieve satisfactory pain relief, using this
"Jannetta" (or MVD) procedure is almost 85%. Some patients
do not experience relief of pain for some days (or up to several weeks or
months) postoperatively. More than likely, this is the result of the
already present injury to the MYELIN insulation material of the nerve
root, which may take some time to recover. There is another small group of
patients who experience initial relief of pain and suffer a short-lived
recurrence several days or weeks after surgery. In these cases, pain is
usually relieved using Tegretol and/or Dilantin (or some of the newer
anticonvulsant drugs) in doses which were formerly not as effective (prior
to surgery). These medications are progressively withdrawn once the pain
is well controlled. Fortunately, most patients who undergo this operation
are relieved of the pain and do not take any of these medications again.
There are three (3) other small groups of patients to be mentioned.
One group will not achieve pain relief and will remain on
medication. Most of these patients will experience
satisfactory pain relief from lower doses of medications
that were not effective in higher doses prior to surgery. The
smallest group consists of patients who may experience no pain
relief at all. In this case, another operation (through the same site)
would be indicated. Some surgeons have found, at re-operation that the
sponge had slipped. In the few patients that I have had with
this problem, no sponge has slipped; and I have found it necessary to cut
the nerve in order to achieve pain relief. The last category comprises
those few patients in whom the anatomical problems of nerve root
compression cannot be relieved, either because the risk to moving the
artery or vein or dividing the vein would result in a stroke. In this
case, the nerve must be divided in order to relieve the pain. The
consequence of this surgical division of the nerve is a dense numbness
in the face on the side that is cut. It is a satisfactory alternative for
98% of those patients who require relief of the Trigeminal Neuralgia
pain where the nerve cannot be decompressed (Jannetta procedure). In two
percent (2%) of patients where the nerve is cut, a disagreeable, painful,
anesthetic problem may develop (anesthesia dolorosa) in the face on the
side of operation.
Other potential complications to this operation include postoperative
leaking of Cerebrospinal Fluid (the fluid that bathes the Brain and Spinal
Cord) through the incision or into the ear. Should this occur, it would
require an operation to seal the leak since the problem could result in a
serious infection. Infection and hemorrhage are risks to any operation
but like all of those reviewed above, are exceptionally uncommon.
Similarly, the risks for postoperative Brain swelling, problems with
balance and coordination or paralysis of swallowing or extremities are
exceptionally low. Nevertheless, the reader must recognize that
operations are chosen only after medical treatment fails.
Other therapeutic interventions include Percutaneous Glycerol
Rhizotomy, Percutaneous Gasserian Ganglion Balloon Micro-compression,
Percutaneous Radiofrequency Thermocoagulation and Stereotactic
Radiosurgery.
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Figure 4: Diagram Illustrating the Technique for Needle Insertion
for Retrogasserian Glycerol Rhizotomy/ Thermocoagulation & Balloon
Micro-compression.
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A comprehensive review of
the entire subject of Trigeminal Neuralgia and these therapeutic
alternatives is available on this website.
Video Files: The reader is also invited to review our video files on
MVD Procedures.
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Glossopharyngeal Neuralgia is a very painful condition, similar in
severity to Trigeminal Neuralgia. In this case it is the
Glossopharyngeal (or 9th Cranial) Nerve that is involved with the
excruciatingly sharp stabbing pain being experienced in the back of
the throat and deep in the ear region. It may originate with
the act of swallowing. Once again, the cause is a pressure
injury (usually by a blood vessel) to the Glossopharyngeal
Nerve, as it enters the Brainstem.
A
comprehensive review of
this subject is available in monograph form on this website.
It is as imperative here as it is in patients with Trigeminal Neuralgia to
make certain that an MRI ("Thin Slice Technology") and MRA
(Angiogram) has been done to identify the vital anatomical
relationships of the nerves and blood vessels as well as to rule out a
life-threatening problem such as a Brain Tumor or an Aneurysm.
Treatment with the anticonvulsant medications such as Tegretol and/or
Neurontin is a reasonable first attempt to relieve this severe pain.
Unfortunately these drugs are not nearly as effective for
Glossopharyngeal Neuralgia as they are for Trigeminal Neuralgia.
In those patients where medical treatment (usually with Tegretol
and/or Dilantin) fails, Microvascular Decompression (MVD)
treatment is the recommended treatment since it allows the Neurosurgeon to
"decompress" the Glossopharyngeal Nerve. This operation is
more technically demanding compared with that for
Trigeminal Nerve MVD. There are unusual occasions, usually related
to a peculiar anatomical anomaly of the offending arteries where
microvascular decompression is not possible. In these rare instances, the
fibers of the Glossopharyngeal (9th Cranial) Nerve and
the upper two or three fibers of the adjacent Vagus (10th Cranial)
Nerve are cut. This would result in numbness in the back of the
throat and paralysis of some of the muscles in the back of the interior
of the mouth and throat on the one side. These nerves are cut only
when decompression proves to be impossible since it is imperative to
relieve this excruciating pain. Once again, the surgical
results are quite gratifying and have proven to be reliable over long
periods of time.
There are no effective Percutaneous techniques available for
Glossopharyngeal Neuralgia as there are for Trigeminal Neuralgia since the
Glossopharyngeal Nerve is not accessible using Percutaneous
methods.
Radiosurgery alternatives are generally not available
due to the limitations of that technology and the anatomy of the
Glossopharyngeal Nerve relative to other Cranial Nerves and the
Brainstem.
Please consult our comprehensive monograph on this subject in our
Downloads & Information section.
A video of this operation is available in our
Video Library
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This page last edited on 5/9
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