Blockade of the gasserian ganglion with local anesthetics and steroids and destruction of this neural structure via freezing, radiofrequency lesioning, neurolytic agents, compression, and other means have many applications in contemporary pain management. Advances in radiographic imaging, electronics, and needle technology have improved the efficacy and reduced the cost and complications.
Indications for gasserian ganglion block are summarized in Table 145.1. In addition to applications for surgical anesthesia, gasserian ganglion block with local anesthetics can be used as a diagnostic tool in performance of differential neural blockade on an anatomic basis for evaluation of head and facial pain. This technique also is useful as a prognostic indicator of the degree of motor and sensory impairment that the patient might experience when destruction of the gasserian ganglion is being considered.
Gasserian ganglion block with local anesthetic may be used to palliate acute pain emergencies, including trigeminal neuralgia and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective. Destruction of the gasserian ganglion is indicated for palliation of cancer pain, including the pain of invasive tumors of the orbit, maxillary sinus, and mandible.
This technique also is useful in the management of the pain of trigeminal neuralgia that has been refractory to medical management or for patients who are not candidates for surgical microvascular decompression. Gasserian ganglion destruction also has been used successfully in the management of intractable cluster headache and in the palliation of ocular pain from persistent glaucoma.
The gasserian ganglion is canoe shaped and has three sensory divisions, the ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves, which exit on the anterior convex aspect.
Gasserian Ganglion Block Technique
The patient lies supine with the cervical spine extended over a rolled towel. Approximately 2.5 cm lateral to the corner of the mouth. The skin and subcutaneous tissues are anesthetized with 1% lidocaine with epinephrine. A 13-cm 20-gauge Hinck needle is advanced through the anesthetized area, traveling perpendicular to the pupil of the eye (when the eye is in mid position).
The needle is advanced until contact is made with the base of the skull. The needle tip is withdrawn slightly and “walked” posteriorly into the foramen ovale. Paresthesia of the mandibular nerve may occur as the needle enters the foramen ovale.
If the procedure is performed with fluoroscopic guidance, submental and oblique views are obtained to aid in identification of the foramen ovale. The operator carefully aspirates for blood. Free flow of CSF is typical. Failure to observe free flow of CSF does not mean that the needle tip does not lie within the central nervous system close to the gasserian ganglion but simply that the needle tip rests, not within the trigeminal cistern, but more anteriorly, within Meckel’s cave.
The needle position should be confirmed with radiography before any local anesthetic or neurolytic substance is injected. After needle position is confirmed.
An average volume of 0.4 mL of neurolytic solution is usually adequate to provide long-lasting pain relief. Because of significant interpatient variability in the size of Meckel’s cave, however, careful titration of the total injected volume is indicated.
If hyperbaric neurolytic agents are used, the patient should assume a sitting position, with the chin on the chest before the injection, to ensure that the solution is placed primarily around the maxillary and mandibular divisions and to avoid the ophthalmic division. The patient should remain in the supine position when absolute alcohol is used. This approach to the gasserian ganglion may be used to place radiofrequency needles, cryoprobes, compression balloons, and stimulating electrodes.