Samobathi insights



radiofrequency thermocoagulation of gasserian ganglion





Radiofrequency Thermocoagulation of the Gasserian Ganglion is a minimally invasive treatment for Trigeminal Neuralgia. It is safe and can be done in daycare.



UNDERSTANDING THE ANATOMY RROUND GASSERIAN GANGLION





For performing the Gasserion Ganglion Radiofrequency Ablation it is very important to understand the anatomy around the gasserian ganglion. Gasserian Ganglion is situated within the cranium, in an area called the Meckel's cave at the posteromedial part of middle cranial fossa, which is close to the apex of petrous part of the temporal bone.


Relations of The Gasserian Ganglia - The Cavernous sinus, Internal carotid artery, trochlear and optic nerves lies medial to the ganglia. Superiorly lies the temporal lobe of the brain. Posteriorly it is related to brain stem and anteriorly it divides into it's three branches, Ophthalmic(V1) Maxillary (V2) and Mandibular(V3) branches.


These three branches comes out of the cranium through 3 foramens, they are Superior orbital fissure, Foramen Rotundum and Foramen Ovale respectively. For the gasserian ganglion RF our RF needle should enter from below through foramen ovale.


The structures that pass through foramen ovale are Mandibular nerve, Lesser petrosal nerve (branch of the glossopharyngeal nerve), Accessory meningeal artery Emissary vein (connecting the cavernous sinus with the pterygoid plexus of veins)



IMPORTANT RADIOLOGICAL LANDMARKS



Identification of below radiological landmarks are important for the procedure.



Foramen Ovale



For successfully performing trigeminal ganglion block the most important radiological landmark is foramen oval. Foramen ovale can be seen from the submental view. To see the foramen ovale c arm should be tilted caudally and at an ipsilateral oblique direction. It is seen between maxilla & mandible.



ANGLE OF CLIVUS WITH THE PETROUS TEMPORAL



THE ANGLE OF CLIVUS WITH THE SHADOW OF THE PETROUS PART OF TEMPORAL BONE IN TRUE LATERAL VIEW OF SKULL This angle is our direction at which the RF canula needs to be inserted, The tip of the needle should not cross this junction.



Formation of ANGLE OF CLIVUS WITH PETROUS



Clivus and the petrous part of temporal bone lies in different planes. when seen from laterally the shadows of petrous of both the sides merges with one another to form the angle.



GASSERIAN GANGLION RF PROCEDURE





Indications



The indications for Gasserian ganglion RF are Trigeminal neuralgia and Secondary neuralgia due to cancer or multiple sclerosis, when Conservative Therapy is not having adequate response or the patient is unable to tolerate medications.



Contraindications



Contraindications are local infection, sepsis, coagulopathy, increased intracranial pressure, major psychopathology.



Equipment Required



Equipment that are required for the procedure are 25-gauge needle (for skin infiltration), 5-ml syringe (for local anesthetic solution),RF generator and cables,16-gauge intravenous catheter (for introducing the RF needle) RF needles, 10 cm in length 2-mm or 5-mm RF active tip



Preparation



An informed consent should be taken. Prophylactic Antibiotic injected 1/2 hour before the procedure after proper skin test. The patient is asked to fast for sedation during the procedure.



Patient Positioning



The procedure is done in supine position, with a pillow below the shoulder, so that the neck is extended.





Technique



After positioning the patient ipsilateral portion of the face to be painted with antiseptic solution carefully , as pain may be triggered by painting. The area is draped with surgical drape.

C-arm positioning should start from AP view then the fluoroscope position will me changed to cranio-caudal direction to get the submental-view. The Fluoroscope to be rotated to ipsilateral direction so that the foramen ovale can be seen in between the maxilla and mandible.

The Surface point that corresponds to the foramen ovale should be determined by putting a opaque pointer. The point of entry usually lies 2-3 cm lateral to angle of mouth. Local anesthesia (1% lignocaine) injected at the entry point.

After the area is anesthetized an 16-gauge intravenous catheter is first inserted followed by the RF cannula 10 cm in length 2-mm or 5-mm RF active tip by needle through needle technique. While introducing the needle, care should be taken so that it should not passes through oral cavity.

Needle is progressed towards the foramen ovale under tunnel view. Intermittent checking under lateral fluoroscopic view is to be done to make sure that the needle direction is towards the junction of clivus and the coincided shadow of petrous part of temporal bone of left and right side in true lateral view of the skull. The needle tip is not visible at the lateral view unless the tip has crossed the junction. And it should be remembered the tip should not cross more than 2mm above the junction. and in most cases the desired sensory and motor stimulation is usually find before that. Once close to the ganglion sensory and motor stimulation checked. Sensory stimulation is usually done at 0.5V and 50Hz, but in some patients we can get stimulation in lower voltage. The area of paresthesia should match with the area of pain for the best results. Motor stimulation is usually done at 2Hz and the voltage is the double of that of motor stimulation to up to 2 volt. Ophthalmic and maxillary do not have motor part so on motor stimulation we will get the contraction of masseter muscle.

After stimulation careful aspiration is done to avoid position in blood vessel.

Once the needle position is confirmed by stimulation 0.2 - 0,5ml of local anesthetic in injected, alternatively sedation can be given, to make the lesioning time pain free.

Usually three conventional RF lesions are done successively at 65, 70 and 75 degree centigrade and for 60-90 seconds.

Case should be taken for ophthalmic division, to not to lesion at high temperature, that may lead to corneal anesthesia leading to exposure keratitis. The needle is taken out post lesioning. The patient is shifted to post procedure care unit. And monitored for vitals, corneal reflex is checked and ice is applied in cheek to avoid hematoma formation.



Complications



  1. Hematoma in Cheek - Common after percutaneous procedures at gasserian ganglion.
  2. Loss of corneal reflex - May occur following gasserian ganglion neurolysis. Among the percutaneous procedures chance of loss of corneal reflex is highest with RF procedure 7%,followed by Glycerol Rhizolysis 3.7%, and least with balloon Compression 1.5%.
  3. Motor Deficit - Motor deficit is foung to be highest following balloon compression 66%, followed by RF rhizotomy 24%, and least with glycerol injection - 1.7%
  4. Carotid Artery Puncture. Retrobulbar Hematoma and Meningitis are rare but serious complications