PainExam Show Notes: Mandibular Division of the Trigeminal Nerve Block with Dr. David Rosenblum

Introduction

• Host: Dr. David Rosenblum
• Topic: Mandibular Division of the Trigeminal Nerve Block for Cancer Pain Management
• Techniques: Ultrasound and Fluoroscopic Guidance

Overview

• Purpose: Alleviate chronic facial pain, specifically in cancer patients suffering from trigeminal neuralgia or other related conditions.
• Focus: Detailed discussion on the anatomy, clinical presentation, and procedural techniques for effective nerve block.

Anatomy of the Mandibular Nerve

• Origin: Mandibular nerve is a branch of the trigeminal nerve (cranial nerve V).
• Pathway: Exits the middle cranial fossa through the foramen ovale and descends between the lateral and medial pterygoid muscles.
• Sensory Innervation:
  • Anterior two-thirds of the tongue
  • Teeth and mucosa of the mandible
  • Skin of the chin and lower lip
  • Skin over the mandible (excluding the mandibular angle)
  • Tragus and anterior part of the ear
  • Posterior part of the temporalis muscle up to the scalp

Ultrasound-Guided Technique

1. Patient Positioning:
   • Patient lies on their side with the affected side facing upward.
2. Transducer Selection:
   • Curvilinear transducer preferred for deeper structures.
3. Transducer Placement:
   • Place distal and parallel to the zygomatic arch to bridge the coronoid and condylar processes.
4. Anatomical Landmarks:
   • Identify the lateral pterygoid muscle and plate.
   • Use power Doppler to locate the sphenoid palatine artery.
5. Needle Trajectory:
   • Introduce the needle using an out-of-plane approach to target the pterygopalatine fossa (anterior to the lateral pterygoid plate).
   • For the mandibular nerve block, target the area posterior to the lateral pterygoid plate between the medial and lateral pterygoid muscles.
6. Electrostimulation (Optional):
   • Utilize a 22G, 10 cm insulated short beveled needle connected to a peripheral nerve simulator.
   • Position confirmed by motor response from the temporalis and masseter muscles.

Fluoroscopic-Guided Technique

1. Patient Positioning:
   • Similar to ultrasound guidance, patient lies on their side with the affected side facing upward.
2. C-arm Positioning:
   • Position the C-arm to visualize the foramen ovale.
3. Needle Insertion:
   • Insert the needle under fluoroscopic guidance towards the foramen ovale.
4. Contrast Injection:
   • Confirm needle placement with contrast injection.
5. Anesthetic Administration:
   • Administer local anesthetic and/or neurolytic agents.

Clinical Symptoms and Diagnosis

• Symptoms:
  • Unilateral sharp, stabbing, or burning pain in the mandibular nerve distribution.
  • Pain triggered by activities such as eating, talking, washing the face, or cleaning the teeth.
• Diagnostic Imaging:
  • MRI or CT scans to identify causes like vascular compression, mass lesions, or fractures.

Complications and Considerations

• Potential Complications:
  • Bleeding, hematoma, infection, and hypersensitivity reaction to the injectate.
  • Serious complications from neurolytic agents like permanent sensory deficit and tissue necrosis.
• Alternative Treatments:
  • PNS? Radiofrequency or cryoablation for recalcitrant cases.

Conclusion

• Efficacy: Ultrasound and fluoroscopic guidance provide precise targeting of the affected nerves, minimizing collateral damage.
• Safety: Routine use of power Doppler imaging to avoid injury to surrounding vessels.
• Recommendation: Consider these techniques for patients unresponsive to oral medications or unsuitable for surgery.

These show notes provide a comprehensive overview of the discussion, highlighting key points on the anatomy, technique, and clinical considerations for mandibular nerve blocks in cancer patients.