1Department of Anesthesiology, Mackay Memorial Hospital, Taipei, Taiwan
2School of Medicine, Mackay Medical College, Taipei, Taiwan
3Institute of Brain Science, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
4Department of Anesthesiology, National Taiwan University Hospital, Taipei, Taiwan
5Mackay Medicine, Nursing and Management College, Taipei, Taiwan
Trigeminal neuralgia (TN) is a chronic neuropathic pain syndrome that primarily involves the division of the fi fth cranial nerve. The classical type, which is most commonly seen, is caused by evidence of neurovascular contact . Secondary TN, which accounts for approximately 15% of all cases, is attributable to an identifiable neurologic disease such as multiple sclerosis or a tumor in the cerebellopontine angle. In an analysis of data from four studies, the percentage of secondary TN induced by tumor was about eight percent . Idiopathic TN, in which no apparent cause of nerve disturbance can be found, accounts for approximately 10% of all cases .
In Figure 1, we see a magnetic resonance imaging (MRI) image from a patient with intractable TN in the right maxillary (V2) and mandibular (V3) nerve dermatomes. The MRI image revealed a brain tumor compressing the nerve root and brainstem.
In Figures 2 and 3, the extracranial approach radiofrequency thermocoagulation (RFT) was completed by radiofrequency needle tips placed close to the opening of the foramen rotundum (FR) and foramen ovale (FO) for isolated V2 and V3 nerve ablation under fluoroscopic guidance. During the procedure, the needle tips were never advanced into the skull base. In this case, this treatment for secondary V2 and V3 TN offered a 90% resolution for a 9 months’ follow-up.
For the patient with poor response to medication and refuses surgery, percutaneous procedures should be considered. In the classical approach for gasserian ganglion ablation, the needle is advanced through the FO into gasserian ganglion and the test of nerve stimulation to a depth appropriate to the division desired. However, the classical approach is not a good method for patients suffering from secondary TN induced by a brain tumor. The deforming anatomy increases the diffi culty of the procedure and also the risk of tumor rupture or tumor bleeding. Instead, extracranial approach RFT via the FR and the FO is relatively suitable for intracranial tumor-induced V2 and V3 TN. RFT of the maxillary nerve via the FR for the treatment of V2 TN has better efficacy, fewer complications, and a shorter length of operation in comparison with RFT of the gasserian ganglion via the FO .
In summary, neuroimaging is a useful diagnostic tool to identify a structural cause in TN. Extracranial approach RFT via FR and FO for isolated maxillary and mandibular division should be considered for patients suffering from intractable TN caused by an intracranial benign tumor.
Figure 1. The Magnetic Resonance Imaging (MRI) Image From a Patient With Intractable TrigeminalNeuralgia in the Right Maxillary (V2) andMandibular (V3) Nerve Dermatomes
(A) The preoperative 3D FIESTA Transverse MRI image shows an extra-axial dural-attached tumor toward the right Meckel cave ex-tension leaded a mass effect on the adjacent pontomedullary brain-stem. (B) The preoperative T1 sagittal image reveals a brain tumor located close to the skull base. (Arrow, left trigeminal nerve; B [redline], skull base; P, pons; T, tumor.)
Abbreviations: Ant., anterior side; Rt., right side.
Figure 2. The Final Image of Fluoroscope on the Anterior- Poster View Before the Radiofrequency Thermocoagulation
Under fluoroscopic guidance, the radiofrequency needle was ad-vanced toward the foramen rotundum (FR). The maxillary nerve(V2) originates as the second division of the trigeminal ganglion and travels through the FR and enters the pterygopalatine fossa.The FR was located on the sphenoid bone and usually can be found on the anterior-poster view.
Abbreviation: Rt., right side.
Figure 3. The Final Image of Fluoroscope on the Lateral View Before the Radiofrequency Thermocoagulation
Under the ﬂuoroscopic guidance, each of two radiofrequency (RF)
needles was advanced closing the opening of foramen rotundum (FR) and foramen ovale individually on the lateral view. Note that needle tip 1 should not be advanced beyond the skull base (Line B) when there was an intracranial tumor. The FR is located on the most superior posterior wall of the roof of the pterygopalatine fossa (C) which needle 2 is close to it. (Line A [blue], pituitary fossa and clivus; Line B [green], the base of the skull; Line C [red], border of pterygopalatine fossa; Number 1, RF needle toward foramen ovale; Number 2, RF needle toward FR)
Abbreviation: Post., posterior side.
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