Gamma Knife Radiosurgery Trigeminal Neuralgia

On the Cutting Edge…… Gamma
knife radiosurgery for the
treatment of Trigeminal Neuralgia
INDIAN DENTAL ACADEMY
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Education
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TRIGEMINAL NEURALGIATRIGEMINAL NEURALGIA
 Def: Trigeminal Neuralgia (TN) is defined as sudden,
usually unilateral, severe, brief, stabbing, lancinating,
recurring pain in the distribution of one or more branches
of fifth cranial nerve.
ETIOLOGYETIOLOGY
 Etiology is largely unknown.
 Possible cause of Trigeminal neuralgia is the vascular
compression of the Trigeminal nerve where it enters the
brain.
 The most common cause of this compression is an
aberrant loop of Superior Cerebellar Artery.

 This compression may cause damage to the myelin sheath
that surrounds the Trigeminal nerve.
 Other causes of compression include:
 Intracranial tumours
 Bony compression from prominent basilar ridge.
 Demyelinating disorders such as ‘Multiple Sclerosis’.
 Viral etiology, chronic granulomatous diseases (e.g.
sarcoidosis), Dental trauma.

TREATMENT MODALITIES
(A) Medicinal Treatment
(B) Surgical Treatment
MEDICINAL TREATMENT:
Carbamazepine 100-200 mg bid, dose can be increased
depending on the severity of pain upto 1200 mg/day in divided
doses.
Gabapentin may be effective. 300 mg per day, titrate up by 300
mg every 2 to 3 days, given QID until relief is achieved.
Baclofen 5-10 mg TID, up to 60 mg / day

SURGICAL TREATMENT
 Percutaneous procedures:
 Percutaneous radiofrequency trigeminal gangliolysis
(PRTG)
 Percutaneous retrogasserian glycerol rhizotomy
(PRGR)
 Percutaneous balloon microcompression (PBM).
 Microvascular decompression
 Gamma Knife Radiosurgery

# INDICATIONS FOR RADIOSURGERY INCLUDE
ONE OR MORE OF THE FOLLOWING:
 A medical condition that places a patient at
unacceptably high risk for anesthesia and open
microsurgery
 Advanced age
 A lesion located within a critical brain region in which
an open operative approach would likely cause a
significant neurological deficit
 A patient who does not wish to undergo traditional
microsurgery

GAMMA KNIFE RADIOSURGERY
 It is a non invasive , scalpeless radiosurgery.
 It is based on the principle that, radiation delivered precisely
to a target will destroy the cells in a particular area while
minimizing injury to surrounding nerves and brain tissue.
 In 1951 Lars Leksell, the inventor of the Gamma knife, was
the first to use radiosurgery for the treatment of functional
disorders such as trigeminal neuralgia .

 The Gamma Knife is not a knife ; it is a complex machine that
uses Cobalt – 60 as the energy source in the radiosurgery
Gamma knife radiosurgery machine

MECHANISM OF ACTION
 In the Gamma Knife Radiosurgery
the patient is fitted with a
collimator helmet with the help of
screws.
 The helmet has 201 separate small
round holes that aim the ionizing
radiation, so that 201 narrow
beams of gamma rays are all
aimed at a single tiny targeted
lesion .
 The tissue thus receives a very
strong dose of radiation without
harming anything along the way .www.indiandentalacademy.com

 All the radiations coming through the
holes are aimed at a single lesion
compressing the trigeminal nerve.
 This 'cross firing' results in destruction
of the lesion with sparing the adjacent
normal brain tissue around it from the
highest doses of radiation .
 Both myelinated and unmyelinated
fibers are affected , exhibiting axonal
degeneration with remnants of some
myelinated axons .

 In case of Intra-cranial tumours, these focused Gamma Rays
distort or destroy the DNA of tumor cells, causing them to
be unable to reproduce and grow. The tumor will shrink in
size over time.
 For blood vessel lesions such as an arteriovenous
malformation (AVM), the blood vessels eventually close off
after treatment.
 Gamma Knife delivers single doses of radiation therapy to
targeted areas of the brain with a precision of less than 1
mm.

PRE – SURGICAL PREPARATIONPRE – SURGICAL PREPARATION
 The Radiosurgery Head Phantom
can be used as a pre surgical
equipment.
 It allows for 3D dose verification
in a large cranial volume.
 Magnetic resonance imaging is the neuro-diagnostic modality
of choice.
 The Trigeminal nerve is identified in coronal, axial, and sagital

RADIOSURGICAL TECHNIQUERADIOSURGICAL TECHNIQUE
 The Gamma knife unit with Cobalt-60 sources is used to
irradiate the target.
 The Trigeminal nerve is targeted at the location of an
imaged vascular compression, or at the site of exit of the
trigeminal nerve from the pons if no compressing vessel is
identified.
 The effectiveness of treatment at this exit zone is probably
because, the proximal nerve is covered by oligodendrocyte
myelin, which is more radiosensitive than the distal
schwann-cell myelin.

STEPS IN GAMMA KNIFE TREATMENTSTEPS IN GAMMA KNIFE TREATMENT
1. HEAD FRAME PLACEMENT
2. TUMOR OR LESION LOCATION IMAGING
3. RADIATION DOSE PLANNING
4. RADIATION TREATMENT

HEAD FRAME PLACEMENTHEAD FRAME PLACEMENT
 In order to keep the head from
moving during treatment, a box-
shaped frame is attached to the
head. Pins designed specifically for
this purpose fasten the head frame
to the skull.
 The head frame also is a guide to
focus the gamma ray beams to the
exact location of the lesion being
treated.

TUMOR OR LESION LOCATION IMAGINGTUMOR OR LESION LOCATION IMAGING
 Once the head frame is in place, the exact location of the
lesion to be treated will be determined using computed
tomography (CT scan) or magnetic resonance imaging
(MRI).

RADIATION DOSE PLANNINGRADIATION DOSE PLANNING
 After the CT or MRI scan has been completed,
the radiation therapy team will determine the
treatment plan

RADIATIONRADIATION TREATMENTTREATMENT
 After being positioned for the treatment, the helmet is placed
over the head frame.

 These holes help to focus the radiation beams on
the target.

DURATION OF THE TREATMENTDURATION OF THE TREATMENT
 The procedure is usually performed under local anesthesia
with mild sedation, takes just 15 to 40 minutes15 to 40 minutes, depending on
the size of the area needing treatment
 The beams can be refocused and the procedure repeated until
the entire diseased area is treated.
 If there are multiple tumors or if the tumor spreads to
another area, radiosurgery can be repeated again and again

OTHEROTHER INDICATIONS OF GAMMA KNIFEINDICATIONS OF GAMMA KNIFE
Apart fromApart from Trigeminal NeuralgiaTrigeminal Neuralgia gamma knife radiosurgery isgamma knife radiosurgery is
also used for:also used for:
 Brain tumorsBrain tumors
Brain metastases from a different primary site
Acoustic neuroma (Schwannoma)
Meningiomas
Pituitary adenoma
Glial tumors
Craniopharyngioma
Chordoma ,Chondrosarcoma

Arteriovenous malformations (AVMs)Arteriovenous malformations (AVMs)
 Angio-occult Vascular Malformations
 Arteriovenous Fistula
Functional disordersFunctional disorders
 Cluster Headaches
 Intractable pain
 Parkinson's disease
 Essential tremors
 Epilepsy
 Obsessive-compulsive disorder

BENEFITSBENEFITS OF GAMMA KNIFEOF GAMMA KNIFE
 The main advantage of the Gamma Knife treatment is that it is
non-invasive , painless, bloodless.
 Patients do not feel pain during the procedure, which is
performed with local anesthesia and mild sedation
 No incision is made in the scalp or skull, complication such as
infection, hemorrhaging and spinal fluid leakage do not occur.
 Lower treatment costs compared to complex surgical
procedures.
 Patients are discharged on the day of treatment and are
usually able to return to their normal activities within 24
hours.

ADVERSE EFFECTS OF THE PROCEDURE
 Headache , Nausea
 Numbness
 Hair loss near treated area (generally temporary)
 Seizures
 Weakness , Loss of balance
 Vision problems
 Radiation exposure should be avoided during pregnancy; may
lead to birth defects.www.indiandentalacademy.com

CONCLUSION
 This cutting edge technology involves no cutting at all.
 Stereotactic Gamma Knife Radiosurgery represents a
novel and effective treatment approach for relieving the
intractable pain of Trigeminal Neuralgia.

Gamma Knife Radiosurgery Trigeminal Neuralgia

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