Trigeminal Neuralgia Radiofrequency Ablation

TRIGEMINAL GANGLION RADIOFREQUENCY ABLATION

RELEVANT ANATOMY

Overview

The Gasserian ganglion, also referred to as the trigeminal ganglion, is a pivotal sensory structure within the trigeminal nerve system. It serves as a central hub for transmitting sensory signals from the face to the brain. Understanding its anatomy is critical for precise interventional procedures.

Location

  • Meckel’s Cavity: This ganglion resides within Meckel’s cavity, a dural recess located in the middle cranial fossa. Meckel’s cavity is filled with cerebrospinal fluid (CSF), which cushions and stabilizes the ganglion, protecting it from external pressures and injuries.
  • Proximity to Bone: Positioned near the apex of the petrous portion of the temporal bone, the ganglion’s proximity to this bony structure makes it a crucial landmark during interventions.

Surrounding Structures

  • Superiorly: The basal surface of the temporal lobe lies directly above the ganglion, making the ganglion vulnerable to pressure or lesions arising from the temporal lobe.
  • Medially: The cavernous sinus is located medial to the ganglion. This venous plexus is anatomically significant as it contains:
    • The internal carotid artery.
    • Cranial nerves III (oculomotor), IV (trochlear), and VI (abducens).
  • Posteriorly: The brainstem, a critical structure for essential neurological functions and pathways, is positioned immediately posterior to the ganglion.

Somatotopic Organization

The Gasserian ganglion is intricately organized into three divisions, each responsible for sensory innervation of distinct regions of the face.

  1. Ophthalmic Division (V1):
    • Occupies the most superior and medial portion of the ganglion.
    • Provides sensory input from the:
      • Forehead.
      • Scalp.
      • Upper eyelid.
    • Exits the skull through the superior orbital fissure.
  2. Maxillary Division (V2):
    • Positioned between the ophthalmic (V1) and mandibular (V3) divisions.
    • Supplies sensory input to the:
      • Lower eyelid.
      • Cheek.
      • Nostril.
      • Upper lip.
      • Upper gum.
    • Passes through the foramen rotundum.
  3. Mandibular Division (V3):
    • Occupies the most lateral aspect of the ganglion.
    • Responsible for sensory input from the:
      • Lower jaw.
      • Lower lip.
      • Chin.
      • Portions of the ear.
    • Additionally, it carries motor fibers to the muscles of mastication, making it unique among the three divisions.
    • Exits the skull via the foramen ovale.

FLUOROANATOMY

Key Structures and Their Significance

  1. Foramen Ovale:
    • Definition: A bony opening in the greater wing of the sphenoid bone.
    • Significance: Serves as the primary entry point for needle placement to access the mandibular branch (V3) and the Gasserian ganglion.
    • Fluoroscopic Views:
      • Lateral View: Shows the foramen as an opening at the base of the sphenoid bone.
      • Submental-Oblique View: Provides a detailed visualization of the foramen’s depth and position, aiding in precise needle trajectory.
  2. Clivus:
    • Definition: A sloped region of the skull base located anterior to the brainstem.
    • Fluoroscopic View: The lateral view highlights its proximity to the foramen ovale, ensuring safe advancement of the needle.
  3. Petrous Ridge of the Temporal Bone:
    • Definition: A dense bony structure located near the middle cranial fossa.
    • Significance: Acts as a medial boundary for the approach to the ganglion, offering a reference point for safe navigation.
  4. Cavernous Sinus:
    • Definition: A venous plexus located medial to the trigeminal ganglion.
    • Risk: Improper needle placement or trajectory can damage this structure, leading to hemorrhage or cranial nerve deficits.
  5. Pterygoid Plates:
    • Definition: Thin bony projections of the sphenoid bone.
    • Fluoroscopic View: Seen as lateral landmarks in submental-oblique imaging, they assist in guiding the needle’s trajectory.
  6. Mandibular Notch:
    • Definition: A depression between the coronoid and condylar processes of the mandible.
    • Significance: Acts as a soft tissue entry point for the needle in percutaneous approaches.

Fluoroscopic Views for Guidance

  1. Lateral View:
    • Offers a clear assessment of the depth and alignment of the needle trajectory relative to the foramen ovale.
    • Helps confirm advancement depth and prevents over-penetration into critical structures like the cavernous sinus or brainstem.
  2. Submental-Oblique View:
    • Provides a three-dimensional perspective of the foramen ovale.
    • Facilitates alignment of the needle path with the plane of the foramen, ensuring precise targeting of the ganglion.
  3. Anteroposterior (AP) View:
    • Visualizes the midline and lateral relationships of key anatomical structures.
    • Ensures accurate needle alignment during advancement and assists in confirming proper placement.

This detailed fluoroscopic guidance ensures procedural accuracy, reducing risks and improving outcomes in interventions targeting the Gasserian ganglion.

INDICATIONS

Indications for Gasserian Ganglion Procedures

  1. Trigeminal Neuralgia:
    • Particularly indicated when patients fail to respond adequately to first-line pharmacological treatments such as carbamazepine or oxcarbazepine, or when side effects from these medications are intolerable.
  2. Atypical Facial Pain:
    • For chronic, poorly localized pain involving the trigeminal nerve distribution that does not meet classical neuralgia criteria.
  3. Cluster Headaches and Migraines:
    • Utilized as an abortive therapy for intractable cases, especially when conventional treatments fail to provide adequate relief.
  4. Postherpetic Neuralgia:
    • Effective in managing persistent pain in the mandibular or maxillary divisions following shingles.
  5. Diagnostic Applications:
    • To confirm trigeminal nerve involvement in facial pain syndromes or as a preparatory step for advanced interventions.

CONTRAINDICATIONS

Absolute and Relative Contraindications

  1. Coagulopathy:
    • Increased risk of hemorrhage necessitates avoidance in patients with bleeding disorders or those on anticoagulant therapy without proper management.
  2. Infections:
    • Localized or systemic infections significantly increase the risk of complications such as meningitis or abscess formation, warranting procedural delays until infection resolution.
  3. Pregnancy:
    • Fluoroscopic radiation exposure is generally contraindicated unless the benefits far outweigh the risks.
  4. Psychiatric Conditions:
    • Severe psychiatric disorders, particularly those impairing cooperation or comprehension, may contraindicate the procedure.
  5. Allergies:
    • Hypersensitivity to local anesthetics or iodinated contrast agents requires identification of alternative medications or avoidance of the procedure.
  6. Cardiovascular Instability:
    • Severe cardiac conditions such as unstable angina or heart failure can pose significant risks during the procedure.
  7. Limited Resources:
    • Avoid performing the procedure in settings lacking the capability to manage potential complications effectively.

EQUIPMENT AND MONITORING

Equipment Checklist

  • Standard ASA Monitoring:
    • Includes ECG, pulse oximeter, and non-invasive blood pressure monitoring.
  • Emergency Equipment:
    • CPR supplies and emergency medications must be readily accessible.
  • Fluoroscopic Imaging:
    • Required for real-time guidance to ensure precise needle placement.
  • Sterile Setup:
    • Includes sterile preparation and draping materials to maintain asepsis.
  • Needles and Tubing:
    • 22–25G, 3.5-inch (90 mm) curved-tip needle for steering.
    • Extension tubing for accurate and controlled injection.
  • Imaging Agents:
    • Nonionic contrast medium for visualization and confirmation of placement.
  • Local Anesthetic:
    • Preservative-free agents are preferred for injection.

Radiofrequency Ablation (RFA) Equipment

  1. RF Cannula:
    • 22G, 100–145 mm with a 2–5 mm active tip.
  2. RF Generator and Accessories:
    • Includes a grounding pad and generator capable of unipolar and bipolar lesioning.

Percutaneous Balloon Compression Equipment

  1. Needle and Catheter:
    • 14G, 100 mm needle and a Fogarty catheter (4 French).

PRE-PROCEDURE STEPS:

  1. Patient Assessment and Preparation:

•             Perform a detailed medical history and physical examination, focusing on the patient’s pain characteristics, trigeminal nerve distribution, and any previous interventions.

•             Obtain informed consent, explaining the procedure, risks (e.g., bleeding, infection, or sensory changes), benefits, and alternatives.

•             Evaluate contraindications, such as coagulopathy, infection, or severe comorbidities.

  • Preoperative Imaging and Planning:

•             Review imaging studies (MRI or CT) to assess the anatomy of the skull base and the location of the foramen ovale.

•             Confirm the target side and plan the needle trajectory using anatomical landmarks.

3. Equipment Preparation:

4. Patient Positioning:

•             Position the patient supine on the fluoroscopy table.

•             Slightly extend the neck and rotate the head contralaterally to the side being treated to optimize access to the target area.

5. Sedation and Monitoring:

•             Administer mild sedation (e.g., midazolam or fentanyl) if required, ensuring the patient can respond to sensory stimulation.

•             Attach standard monitors (ECG, blood pressure, pulse oximeter) and establish IV access for medications.

PROCEDURE STEPS:

  1. Fluoroscopy Setup: Position the C-arm fluoroscope for three essential views:

•             Posteroanterior View: Identify bony landmarks such as the zygomatic arch and greater wing of the sphenoid for initial alignment.

•             Submental-Oblique View: Achieved by tilting the fluoroscope caudally (~20–30°) and rotating it ipsilaterally oblique to visualize the foramen ovale.

•             Lateral View: Used to confirm the depth of the needle tip relative to the skull base and anterior-posterior position.

  • Identification of the Foramen Ovale:

•             Begin with the PA view to locate landmarks like the zygomatic arch and the mandibular notch.

•             Adjust the fluoroscope to the submental-oblique view to identify the foramen ovale, seen as a radiolucent oval opening near the skull base.

  • Marking the Skin Entry Point:

•             Identify the skin entry point approximately 2–3 cm lateral to the corner of the mouth, in alignment with the foramen ovale.

•             Mark this site as the needle insertion point.

  • Skin Preparation and Local Anesthetic Infiltration:

•             Clean the procedural area with an antiseptic solution and drape the site.

•             Infiltrate the skin and subcutaneous tissue at the marked entry point with 1–2 mL of lidocaine to numb the area.

  • Needle Insertion:

•             Use the submental-oblique view to insert the 22G needle in coaxial view technique targeting towards the foramen ovale shadow. 

  • Needle Placement Confirmation:

•             Switch to the lateral view to confirm needle depth, ensuring the tip is positioned at the base of the skull and remains anterior to the clivus.

TRIGEMINAL GANGLION RADIOFREQUENCY ABLATION (RFA)

  1. Needle Placement:

•             Insert the radiofrequency cannula following the same steps for needle entry, mucosal check, and advancement.

2. Ganglion Engagement:

•             Advance the needle beyond the base of the foramen ovale to engage the ganglion.

•             Fluoroscopic View: Use lateral and oblique views to confirm needle placement.

•             Test for motor responses (e.g., masseter muscle twitches) using 2 Hz stimulation.

3. Branch-Specific Targeting:

•             Adjust the needle to elicit paresthesia in the desired trigeminal nerve branch.

•             Fluoroscopic View: Continue monitoring with lateral and submental oblique views to guide positioning.

4. Lesioning Protocol: Apply lesions in sequence

               60°C for 60 seconds.

               65°C for 60 seconds.

               70°C for 60 seconds (do not exceed 70°C).

5. Post-Lesion Stimulation: Test for motor and sensory responses to confirm therapeutic success.

6. Corneal Reflex Testing: If the ophthalmic nerve (V1) is targeted, test the corneal reflex after each lesion.

TRIGEMINAL GANGLION PERCUTANEOUS BALLOON COMPRESSION:

  1. Needle Placement:

•             Insert a 14G needle as described for the block but stop advancing once it reaches the foramen ovale.

•             Fluoroscopic View: Use a submental oblique view for initial placement.

2. Catheter Placement:

•             Pass a 4 French Fogarty catheter through the needle into the foramen ovale.

•             Fluoroscopic View: Confirm catheter position with a lateral view.

3. Balloon Inflation:

•             Inflate the catheter balloon with 1 ml of nonionic contrast.

•             Fluoroscopic Views: Use lateral and posteroanterior (PA) views to confirm the characteristic pear-shaped balloon appearance.

4. Compression: Maintain balloon inflation for 60 seconds to compress the ganglion.

5. Deflation and Removal:

•             Deflate the balloon completely under fluoroscopic guidance.

•             Remove the catheter and needle as a single unit.

POST-PROCEDURE PROTOCOL:

1.            Sterile Dressing Application: Clean the puncture site with antiseptic solution and apply a sterile dressing.

2.            2. Patient Monitoring: Monitor the vitals of patient  and any complications in the recovery area for 1–2 hours to observe for immediate complications.

3.            Complication Assessment:

•             Check for potential complications, such as:

•             Sensory changes: Persistent numbness or hyperesthesia in the trigeminal distribution.

•             Motor weakness: Jaw muscle involvement or mandibular nerve damage.

•             Hematoma or infection: Swelling, redness, or pain at the puncture site.  Post-Procedure Instructions:

•             Advise the patient to rest for 24–48 hours and avoid strenuous activities.

•             Instruct the patient to report any of the following immediately: Severe facial pain or persistent numbness, Signs of infection (fever, chills, or redness at the puncture site), Swelling or difficulty chewing.

4. Documentation

5. Follow-Up Plan: Schedule a follow-up visit in 1–2 weeks to assess the patient’s pain relief and neurological status.

COMPLICATIONS:

  1. Brainstem Compromise

Risk: Anesthetic spread to the brainstem.

Signs: Nausea, vomiting, profuse sweating, horizontal nystagmus, vertigo, ataxia, and respiratory arrest.

2. Vascular Injuries: At-Risk Structures: Carotid artery, accessory meningeal artery.

Potential Complications: Intracerebral hematoma, Hemorrhage in vascular regions, Rare dural arteriovenous fistulae.

9.            Bony Landmarks Injury

               At-Risk Structures: Clivus, petrous ridge of the temporal bone.

               Complication: Cerebral cortex injury from improper needle placement.

9.            Nerve Damage

Lesser Petrosal Nerve: May lead to Crocodile Tears Syndrome (abnormal lacrimation while eating).

Adjacent Cranial Nerves: Damage to oculomotor (III), trochlear (IV), abducens (VI), or trigeminal branches (V1, V2, V3) can result in cranial nerve palsies, anesthesia dolorosa, or masseter weakness.

5. Retrobulbar Hematoma.

6. Corneal Complications Keratitis or corneal anesthesia due to ophthalmic branch (V1) involvement.

7. Nasal and Oral Trauma: Infection or epistaxis from mucosal injury during the procedure.

8. Post-Procedure Reactions

Pain: Local puncture site discomfort or cheek hematoma.

Vasovagal Reaction: Transient hypotension or syncope due to pain or anxiety.

Anesthetic Spread: Unintended effects if anesthesia diffuses to unintended regions.

9. Allergic Reactions

               Risk: Sensitivity to anesthetics or contrast media, potentially causing severe reactions.