"ACOUSTIC NEUROMA" (VESTIBULAR SCHWANNOMA) and FACIAL NERVE Tumors
are an area of specific interest for the Neurosurgeons and staff of
Neurosurgical Consultants. Their successful treatment in most cases
involves the use, where applicable, of highly advanced
Minimally Invasive Microsurgical Techniques.
This revolutionary concept in Neurosurgery greatly limits the amount
of surgical exposure required and therefore, limits the amount of
tissue that is touched and retracted during the operation. Some
procedures incorporate Endoscopic Techniques, which are conducted
through very small holes in the skull. This results in less
post-operative pain, earlier mobilization, diminished hospital stay,
less risk for complications, an earlier return to activities as well
as lower overall costs.
Among our team's particular focus is the PRESERVATION OF HEARING in
patients with these tumors.
ACOUSTIC NEUROMA (VESTIBULAR SCHWANNOMA) is a benign
(non-malignant) tumor that arises from Schwann
cells that surround the Vestibular Nerve (which is a part of
the Eighth Cranial Nerve complex). Schwann cells serve a particular
function to form Myelin, the insulating portion of
nerves that are outside the Brain and Spinal Cord.
Therefore, the term Vestibular Schwannoma may be preferred as
being the more accurate term. Most of these tumors are
not "Neuromas" and most arise from the superior
(upper) division of the Vestibular Nerve, not from the
Cochlear (also known as the Acoustic) Nerve.
FACIAL NERVE NEUROMA is a rare benign tumor of the
Seventh (7th) Cranial Nerve, which shares the
Internal Auditory Canal with the Eighth (8th) Cranial
Nerve complex. The Neurosurgeons of Neurosurgical
Consultants have an exceptional experience with
successful, complete resection of this tumor with preservation of
hearing and Facial Nerve function. Facial Nerve Neuromas
are unusual, almost always completely benign tumors of Schwann
Cells that account for a very small number of the Brain and
Cranial Nerve Tumors while comprising only 0.8% of all "mass lesions"
that involve a critical part of the
called the "Petrous Ridge".
Facial Nerve Neuromas can arise from any segment of the
7th Cranial Nerve from the Cerebellopontine Angle to the
"extra-temporal" peripheral portion which can create a variety of
clinical situations depending on their location, size and relationship
to the Auditory Apparatus. (Please see Figures 9-13 and the
explanations below for a more complete discussion of Facial Nerve
"ACOUSTIC NEUROMAS" (VESTIBULAR SCHWANNOMA) are one of
the most common intracranial tumors, comprising
8-10% of tumors. The annual incidence is 0.78-1.15
cases per 100,000 individuals, resulting in
approximately 2300 new cases per year in the United
As with most other intracranial tumors the exact cause of these
tumors is unknown. However, the association of
Vestibular Schwannoma tumors with
Neurofibromatosis Type 2 (NF-2)
may lead to some insight into the cause. The incidence of
"Acoustic Neuromas" in patients with NF-2 is increased,
with many patients having these tumors bilaterally.
NF-2 is caused by a genetic abnormality on chromosome 22.
Therefore, "Acoustic Neuromas" that arise in other patients
may have a similar abnormality.
Tumor size is closely correlated to the types of symptoms
experienced by these patients. One-sided hearing loss, ringing
in the ears and problems with equilibrium
(dysequilibrium) are related to pressure on the
8th Cranial Nerve. The hearing loss is slowly
progressive in most patients, and is often first noticed as
difficulty in hearing conversation while on the telephone. The
ringing in the ears is high pitched. By the time of
diagnosis of an "Acoustic Neuroma" is made, most patients have
these two symptoms.
Facial numbness, facial weakness, and changes in taste
occur as the tumor causes pressure on the 5th and 7th Cranial
Nerves. These symptoms do not usually occur until the
tumor is a large size. Larger tumors cause pressure on
the Brain Stem, which can cause the following symptoms:
difficulty with balance, headache, nausea/vomiting, double vision,
coma, difficulty breathing, and death. These large tumors can
also cause pressure on the lower cranial nerves causing
difficulty swallowing and hoarseness of the voice.
Symptom frequency varies as follows:
Audiometric and Audiologic Studies are done as baseline
studies to determine the function of hearing on both
sides, with particular attention to the affected ear.
Pure tone audiograms are useful as an initial screening
test, since they identify high tone hearing loss. In addition, a
speech discrimination test is performed to determine the
functional usability of the hearing.
Thin Slice Contrast MRI is the most accurate and useful
diagnostic test for this tumor. The MRI reliably
identifies 98% of tumors, and has almost no false positive
risk. The characteristic finding is a round or oval-shaped
"enhancing" (meaning that it takes up the "contrast" material,
Gadolinium, that is injected into the patient's vein during the MRI
examination) tumor, centered on the Internal Auditory Canal.
Large tumors may show cystic appearing areas. CT scan with
contrast is the second procedure of choice. The CT scan
gives good information about the bony landmarks surrounding the
tumor; however, its soft tissue imaging is less well defined
compared with MRI scans.
- Hearing loss - 98%
- Ringing in the ears (tinnitus) - 70%
- Dysequilibrium - 67%
- Headache - 32%
- Facial numbness - 29%
- Facial weakness - 10%
- Double vision - 10%
- Nausea/vomiting - 9%
- Change of taste - 6%
Masterful Inactivity and Cat-like Observation (otherwise known as
Some "Acoustic Neuromas" grow slowly or not at all,
and 6% actually decrease in size. This option is
typically reserved for patients who: refuse any treatment, have
a very small tumor and are without many symptoms, or are elderly with
many medical complications, and have a small or medium sized
tumor. These patients need to understand that, with
time, the tumor will probably cause complete hearing loss in the
affected ear. Periodic MRI scans are performed to follow the
size of the tumor.
The controversy regarding the treatment of a patient with an
"Intracanalicular Acoustic Neuroma" relates to the "projected natural
history" (what will happen if no treatment is given) of this tumor.
In the absence of sequential MRI Scans over a period of time
THERE IS NO WAY TO DETERMINE THE RATE OF GROWTH OF THESE TUMORS,
particularly in patients who have NO SYMPTOMS. There is
minimal risk to these patients, if they choose to avoid any form of
treatment. However, follow-up scans should be done.
In the event that such a patient subsequently develops symptoms
including Hearing Impairment, it becomes clear that this tumor is
growing and that the ability of the Nerve to accommodate to and
sustain the pressure being exerted upon it is now compromised. At this
point treatment options should be reviewed. IF THE PATIENT WISHES
TO PRESERVE USEFUL HEARING, then a RERTOMASTOID CRANIECTOMY APPROACH
In our opinion, an ASYMPTOMATIC patient with an Intracanalicular
Acoustic tumor should NOT feel compelled to undergo ANY FORM of
treatment UNLESS THEY WISH TO PRESERVE HEARING in the affected ear.
THE RISK TO LIFE and/or MAJOR NEUROLOGICAL DETERIORATION, from an
Intracanalicular Acoustic Neuroma, IS MINIMAL. In a patient who WISHES
TO PRESERVE HEARING then ONLY a RETROMASTOID APPROACH IS APPROPRIATE
(See Figures 7A & 7B below.)
This is rapidly becoming a preferential treatment option
for many patients with small or medium sized tumors.
Previously (and still in many institutions) this treatment option has
been reserved for patients who have residual tumor after
surgery, are elderly, or have multiple medical problems making
surgery too risky. Radiosurgery is more effective for
smaller tumors and certainly should be avoided for
tumors over 3 centimeters in size.
The goals of radiosurgery are, to hopefully,
prevent the tumor from getting any larger. This
occurs in 85% of the patients. The tumor may
shrink in size, but usually does not disappear.
The advantages of this form of Radiation Therapy are that it
is non-invasive, easily tolerated and can be
effective in controlling tumors of limited size.
The disadvantages are primarily related to the swelling
of the tumor as it is being subjected to and damaged by the radiation.
Any injury to Brain, Spinal Cord or Nerves, results in
"swelling". This is a problem for cases of Vestibular
Schwannoma/Acoustic Neuroma since all of them have a major
portion lying in the narrow bone passage within the Skull Base called
the Internal Auditory Canal (IAC). Swelling of the irradiated tumor
puts considerable pressure on the Facial, Vestibular and Cochlear
Nerves, which live within that Canal. Therefore the
real risks to Radiosurgery include:
This is generally the best treatment option for most patients
because it has the best chance of curing the patient.
In addition, a surgical option offers the only opportunity to
conserve hearing in those patients who still have useful hearing. The
Neurosurgeons of Neurosurgical Consultants have a long history of
hearing preservation in selected cases of Acoustic Neuroma.
The choice of what approach to use depends on the size and
location of the tumor, the symptoms of the patient, and the surgeon's
operating preference. It is possible to save the hearing in a
selected minority of cases. As a general rule, one should
acknowledge that the larger the tumor the lower the chance for
hearing preservation. The state of hearing prior to
surgical intervention is an important predetermining factor regarding
hearing preservation. While not impossible, it is most
unlikely to improve hearing by removing the tumor. In some
cases with minimal or poor hearing it is better to sacrifice the
hearing in order to remove the entire tumor.
This approach is used for larger tumors and/or where hearing
preservation may be possible. This involves performing a small
Craniotomy (opening the skull immediately behind the ear on the
affected side), to gain access to the tumor. This is usually
the best approach for larger tumors that cause compression of
adjacent structures such as the Brain Stem. Reconstructive
Cranioplasty (repairing the skull defect with a thin perforated
titanium plate), at the time of surgery generally diminishes
post-operative headaches that many patients experience in the absence
- Delayed, temporary, or permanent facial weakness.
- Delayed, temporary, or permanent hearing loss in the affected ear.
- Possibility for Brain damage in the area surrounding the radiation target.
- The tumor does not "disappear" for a long time (actually measured in years, if ever), making long term follow-up mandatory.
With this approach, the hearing and balance mechanism of the
inner ear are sacrificed. Therefore, the affected ear
is made permanently deaf, and the patient's balance may
be impaired for a variable period of time. The benefits
of this approach are a diminished risk to injury of and
preservation of the Facial Nerve (the 7th Cranial
Nerve). The significant negative aspects of this
approach are permanent hearing loss in the affected ear,
imbalance, higher risk to Brain Stem injury for large tumors and
higher rate of Cerebrospinal Fluid (CSF) leak.
This approach is typically reserved for patients who have a
small tumor and who have good hearing in their affected ear since it
may permit preservation of hearing and still remove the tumor.
This technique has significant limitations in that it may
not be able to remove the whole tumor and in half of all patients (who
have useful hearing to begin with); the surgeon will not be able to
preserve hearing. Additionally there is greater chance
of harming the Facial Nerve. While there are surgeons who
express a preference for this approach, the Neurosurgeons of
Neurosurgical Consultants do not favor it.
The goal of the management, in most cases of Acoustic Neuromas,
is total removal of the tumor without complications.
Nevertheless, there are clinical instances where the surgeon
exercises his judgment, in the patient's best interest, to leave tumor
behind rather than risk the chance of serious additional neurological
injury. The options for the management of patients with
residual tumors include repeat operation at a later date,
Stereotactic Radiosurgery, or to follow the tumor size with serially
conducted MRI scans. On rare occasion, particularly for Giant Tumors,
staged sequential operations may be required.
Acoustic Neuroma (Vestibular Schwannoma) Tumors are an area of
specific interest for the Neurosurgeons and staff of Neurosurgical
Consultants. Among our team's particular focus is the PRESERVATION OF
HEARING in "Acoustic Neuroma" patients. Their successful treatment
in most cases involves the use, where applicable, of highly
Minimally Invasive Microsurgical Techniques.
Some procedures incorporate
- Hearing loss - In small and medium sized tumors it is
sometimes possible to preserve useful hearing by removing the
tumor. If not, then hearing is lost ON THE SIDE OF THE TUMOR.
- Tinnitus (ringing in the ear) - Tinnitus in the affected
ear may be the same or worse postoperatively. Very rarely is
it improved after surgery.
- Dizziness and balance disturbance - During surgery it is
necessary to remove the Vestibular (balance) Nerve from which
the tumor arises. Dizziness is common immediately following
surgery and may be severe for a few days. Imbalance, or
unsteadiness on head motion, is prolonged until the normal
balance mechanism in the opposite ear compensates for the
loss in the operated ear. While recovery is usually quite
swift, it can take several months in some patients.
- Cerebrospinal (CSF) Fluid Leak. If there is leakage of
Cerebrospinal Fluid (CSF) following the operation, a lumbar
drainage catheter may need to be placed in order to allow the
leakage to seal off. Delayed CSF leak is a problem that
impedes wound healing and can lead to infection. If a trial
of drainage fails to resolve the leak, then surgical
correction is required.
- Facial paralysis - Acoustic Neuromas are in intimate
contact with the Facial Nerve, which closes the eye, and
controls the muscles of facial expression. Temporary paralysis
of the face is common, but not universal, following removal of
an Acoustic Tumor and usually results from nerve swelling.
Meticulous microneurosurgical tumor removal, with the
operating microscope and Facial Nerve monitoring, usually
results in the preservation of the nerve. However, even the
most careful technique can result in stretching of the nerve's
delicate blood supply. This may result in swelling of the
nerve, which may cause temporary facial paralysis. In these
cases facial weakness may persist for 6 to 12 months. A few
patients exhibit permanent residual weakness, or complete
- All the general risks of any surgical procedure apply
here as well. Nevertheless, the risks to life, infection,
Brain swelling, haemorrhage, blood clot, air embolus (in the
instance where surgery is done in a semi-sitting position),
paralysis of extremities/swallowing, etc. are generally
minimal in the hands of an experienced team of surgeons and
health care professionals, who work together on a frequent
and regular basis.
While preservation of hearing is possible for patients in whom
there is reasonably functional hearing pre-operatively, it is an
extremely difficult goal to attain from a surgical technical
standpoint. There is no way to predict beforehand whether or not this
effort will prove successful. Intra-operative Neurophysiological
monitoring of hearing is conducted on all of these cases along with
the monitoring of other Cranial Nerves.
Additional information is available on this website at our
Downloads & Information Library
and from our
Acoustic Neuroma Association at Anausa.org
Facial Nerve Neuromas (which can occur at any age and have
no significant gender predilection) are relatively rare,
with approximately 500 cases having been reported in the medical
literature. These tumors are generally regarded to be
slow-growing. They arise from the Schwann cell
sheath of the Facial (7th Cranial) Nerve.
The Facial Nerve takes a fairly long course from its
origin in the Brain Stem, through the Internal Auditory canal and
then twisting and turning through the Skull Base as it makes its way
to exit the skull and enter the muscles of the face. Although any
segment of the Facial Nerve may be involved with a neuroma, it is quite
common for these tumors to involve more than one segment of the
Facial Nerve. The majority of Facial Nerve Neuromas
originate from the "intra-temporal" portion of the Facial
Facial weakness and hearing impairment (sensorineural-type)
are the usual symptoms that bring a patient with a Facial Nerve Neuroma
to their doctor for evaluation. The clinical presentations of
Facial Nerve Neuromas depend on the location of the tumor.
Facial Nerve Tumors that arise within the Internal Auditory Canal
(IAC) usually cause hearing impairment and "dizziness" first.
Tumors of the Geniculate Ganglion, Tympanic and Mastoid segments
produce Facial Nerve "dysfunction" which ranges from facial muscle
spasm to paralysis. Facial Nerve Neuromas that involve the
Tympanic portion of the nerve can cause "conductive-type" hearing
loss. Facial Nerve tumors that lie outside the skull
(extra-temporal) will present as a palpable mass within the Parotid
Modern, high-resolution MRI and CT scanning are imperative
in order to obtain an accurate diagnosis, to define the precise
dimensions of the tumor, and to choose the most appropriate treatment
This is one clinical situation that really demands the
involvement of the patient in making the important treatment
decisions that potentially result in altering their quality
For tumors confined to the Internal Auditory Canal (IAC)
and in whom useful hearing persists, then a HEARING
CONSERVATION procedure using a Retromastoid approach is recommended. If
hearing has already been lost and the tumor is confined to the IAC,
then a Translabyrinthine technique may be appropriate.
Nevertheless, most Facial Nerve Neuromas exhibit a more diffuse
or extensive involvement of the Facial Nerve including the Geniculate
Ganglion and "labyrinthine" portion (see Figure 9 above) of the Facial
Nerve, which most usually requires a middle cranial
fossa or translabyrinthine approach. Rarely is it possible to "separate"
the tumor, in this location, from the Nerve. In order to surgically
excise this subtype of tumor, one must remove the involved portion of
the Facial Nerve which will result in complete Facial Nerve
paralysis. The surgeon will plan to insert a reconstruction
nerve graft as part of the definitive operation. The result of removal
of the tumor and this portion of the nerve is the complete paralysis of
that side of the face until the "new" nerve regenerates which can
take 1 year or longer. Once "re-growth of the Nerve" has occurred
and facial "animation" has returned, movement is likely to be somewhat
disorganized since the "fascicle to fascicle" line-up will be altered.
This is called "aberrant regeneration". It is for this reason that
early diagnosis may improve the outcome of Facial Nerve function,
since the likelihood of a successful graft is partially dependent upon
the duration of the pre-operative paralysis.
For patients with a Facial Nerve Neuroma who have normal
or near normal Facial Nerve function, a reasonable alternative is "careful
observation" coupled with serially performed high quality neuroimaging
(usually MRI Scan) imaging. This will give a more accurate
estimate of the biological behavior in that patient. Once this patient
demonstrates significant progression in the extent of neurological
impairment and/or intracranial extension, surgical treatment becomes
a serious consideration.
Stereotactic Radiosurgery (or "Focused Beam" Radiation) is an
alternative treatment consideration for some patients with
small or medium sized tumors. This is still a relatively
new field with very limited experience with long term follow-up in
this unusual sub-group of patients. This treatment option is certainly
appropriate for patients who have residual tumor after surgery,
are elderly, or have multiple medical problems making surgery too
risky. However, it may also be a preferential method to attempt
to control tumor growth in patients who have no tolerance for the
temporary neurological deficit of Facial Nerve paralysis which is
associated with complete removal of the tumor. Radiosurgery is
more effective for smaller tumors and certainly
should be avoided for tumors over 3 centimeters in size.
The goals of Radiosurgery are, to hopefully, prevent
the tumor from getting any larger. This occurs in 85% of the patients.
The tumor may shrink in size, but usually does not disappear.
The advantages of this form of Radiation Therapy are that it is
non-invasive, easily tolerated and can be effective in controlling
tumors of limited size.
The disadvantages are primarily related to the swelling of
the tumor as it is being subjected to and damaged by the radiation.
Since this type of radiation is targeting a relatively discrete area
within the bone of the skull, injury to Brain, Spinal Cord or Nerves,
is unlikely unless the tumor is directly adjacent to those structures.
This may cause a hearing deficit for cases of Facial Nerve Neuroma
involving the portion of the Nerve that lies directly adjacent to
the lateral (or outside) portion of the Internal Auditory Canal
(IAC). Considerable care must also be exercised if the tumor
has extended to involve the Internal Carotid Artery as it
negotiates it way through the Skull Base to enter the
The real risks to Radiosurgery include:
- Delayed, temporary, or permanent Facial paralysis or weakness.
- Delayed, temporary, or permanent hearing loss in the affected ear.
- Possibility for Brain damage in the area surrounding the radiation target.
- The tumor does not "disappear" for a long time (actually
measured in years, if ever), making long term follow-up mandatory.
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This page last edited on 2/19