†††††When medications have
failed to control TN, not all sufferers are good candidates or wish
to undergo microvascular decompression surgery.† An alternative category
of treatment are the destructive procedures (rhizotomies) that injure
some portion of the trigeminal nerve. Rhizotomies are less likely to
"cure" TN compared to MVD, as the neurovascular compression is not alleviated.
However, these procedures are technically simpler and may be repeated
if pain recurs.
††††There are several techniques to achieve trigeminal injury or rhizotomy,
as outlined below. These aim to alter trigeminal nerve function, resulting
in partial or complete alleviation of TN pain. An expected side effect
is some loss of feeling (numbness) in the trigeminal distribution. In
rare cases, the numbness is bothersome or even associated with a new
form of pain (ie. post-traumatic neuralgia/trigeminal neuropathy).
Percutaneous Rhizotomy Techniques
These procedures involve inserting a needle
through the cheek and into an opening at the skull base (foramen
ovale). There, a controlled injury to the trigeminal nerve and Gasserion
ganglion may be produced in one of three ways:
The chemical glycerol is delivered to the
space surrounding the Gasserion ganglion and trigeminal nerve root.
The glycerol produces a relatively mild injury to the nerve, with minimal
risk of permanent facial numbness.†
the majority of patients achieve early relief of TN, pain recurs in
approximately half of sufferers within a couple of years.†The procedure
is performed under local anesthesia, usually on an out-patient basis,
and may be repeated when necessary.
A catheter is advanced to the needle tip and a balloon is inflated to
compress the Gasserion ganglion and
trigeminal nerve root.
The injury from this compression maybe particularly effective
for pain involving the upper face (V1), as sensation of the cornea is
usually preserved. However, many patients develop at least temporary
weakness of the chewing muscles following this balloon compression procedure,
and the degree of facial numbness is often more severe than with glycerol
rhizotomy.†The procedure is performed under general anesthesia, followed
by overnight hospital admission.
rhizotomy:†A small electrode is advanced through
the needle. Its correct position within the Gasserion ganglion is tested
with gentle electrical stimulation that causes tingling in parts of
the face. The electrode is then heated to produce a thermal injury of
the nerve. Effective treatment usually necessitates at least partial
facial numbness in the affected trigeminal area. The procedure is performed
under local anesthesia with intravenous sedation added during electrode
Stereotactic Radiosurgery (Gamma Knife)
new technique allows for focused radiation to be delivered to the trigeminal
nerve root, causing injury similar to the percutaneous rhizotomy procedures.†The
procedure involves the attachment of a frame to the patientís head,
followed by a Magnetic Resonance Imaging (MRI) to localize the trigeminal
nerve root target. The patient is then positioned in a Gamma Knife where
beams of cobalt radiation are precisely focused. The resulting trigeminal
nerve root injury usually reduces TN pain within a few weeks. The higher
the dose of radiation used, the longer the pain control may last, but
this also increases the risk of developing facial numbness and/or new
TN pain may be treated by injuring the
peripheral branches of the trigeminal nerve, which are found just beneath
the skin or mouth lining. Injury may be produced by the injection of
alcohol, cutting (sectioning), or removing (avulsion) of the nerve fibers
exiting the skull. While these techniques are usually effective immediately,
they also cause severe or complete numbness of the affected area, at
least temporarily. TN pain often recurs, and therefore other surgical
interventions are usually chosen for long-term pain management.
cutting the trigeminal nerve root near the brain stem is one of the
most effective and oldest treatments for TN. However, this technique
has been largely replaced by microvascular decompression (MVD) which
uses the same surgical approach, or the simpler percutaneous rhizotomy
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