Endoscope assisted microvascular decompression for trigeminal neuralgia [Neurosurgery Wiki]

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====== Endoscope assisted microvascular decompression for trigeminal neuralgia ======

A retrospective study in a single institution of 20 patients with TN who received EVD between April 2018 and October 2019. All patients underwent EVD via the [[suboccipital]] [[retrosigmoid approach]] without microscopy at any stage. [[Abnormal muscle response]] (AMR) and [[brainstem auditory evoked potentials]] (BAEPs) were routinely monitored throughout the procedure. Follow-up was conducted by outpatient and telephone interviews. The degree of facial pain was graded using the [[Barrow Neurological Institute Pain Scale]]; a [[BNI]] of 1 was considered as the best result while a BNI of 2 or 3 was considered as a satisfactory result. Follow-up time ranged from 8 to 24 months, with a mean of 18±4.36 months.

All 20 patients with severe preoperative pain (BNI of 5) achieved immediate relief or complete control of pain after surgery (BNI of 1 to 2). Vascular conflicts were observed during surgery in all of the patients. None of the patients experienced hearing loss, facial paralysis, intracranial infection, Cerebrospinal fluid fistula, cerebral hemorrhage, or death, following the operation.

When carried out by surgeons with endoscopic experience, EVD can provide a clear surgical field of view and reduce the risk of surgical injury. The findings indicate that EVD is a safe and effective surgical method for the treatment of TN
((Sun Z, Wang Y, Cai X, Xie S, Jiang Z. Endoscopic Vascular Decompression for the Treatment of Trigeminal Neuralgia: Clinical Outcomes and Technical Note. J Pain Res. 2020 Sep 3;13:2205-2211. doi: 10.2147/JPR.S268441. PMID: 32943913; PMCID: PMC7478366.)).
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Twenty-five patients with facial pain and five patients with hemifacial spasm constituted this study. FIESTA MRI was the pre-operative neuroimaging modality. Retrosegmoid craniectomy was done for all patients. Microscope was initially used for exploration and arachnoid dissection around the nerve. The endoscope was applied thereafter for exploration and confirmation of the proper insertion of the Teflon.
Results

Using the endoscope, cerebellar retraction was reduced by 0.5 to 0.8 cm in 90% of patients. Root entry zone and entry of the nerve through the corresponding skull base foramen was clearly visualized by the endoscope. Endoscope enabled a wider area of exploration and panoramic view, which could not be obtained by the microscope. Patients with trigeminal neuralgia had a median pre-operative VAS of 9, while it was only 1 in early post-operative and 0 in 6-month post-operatively. Patients with HFS were completely recovered.
Conclusion

The advantages of microvascular decompression are still worthy. Complications are minimal, and the view is much more panoramic. The different viewing angles and ability to directly reach corners is an absolute endoscopic advantage. Therefore, avoidance of missing vascular structures and incomplete recovery can be assured
((https://link.springer.com/article/10.1186/s41984-019-0072-5)).

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[[Microvascular decompression for trigeminal neuralgia]] may fail because a compressing vessel at the [[root entry zone]] may be overlooked during surgery. Alternatively, effective decompression may not always be achieved with the visualization provided by the microscope alone. 

Teo et al. theorized that the addition of an endoscope would improve the efficacy of microvascular decompression.

They retrospectively reviewed microvascular decompression of the trigeminal nerve in 114 patients. Before closure, the endoscope was used to inspect the root entry zone. When visualization with the microscope was poor, the endoscope was used to identify an aberrant vessel and to perform or improve the subsequent decompression.

Of 114 patients who underwent microvascular decompression, 113 successfully underwent endoscopy. In 38 patients (33%), endoscopy revealed arteries that were poorly seen (25%) or not seen at all (8%) with the microscope. At a mean follow-up period of 29 months, the pain was completely relieved in 112 patients (99.1%), all of whom were off medication. Complications included trigeminal dysesthesias in nine patients and a wound infection, partial hearing loss, and complete hearing loss in one patient each. The overall complication rate was 9%.

Endoscopy is a simple and safe adjunct to microscopic exploration of the trigeminal nerve. The markedly improved visualization increases the likelihood of identifying the offending vessel and consequently of achieving satisfactory decompression of the nerve. Thus far, the success rate has been high, and the complication profile is comparable to that of other large series
((Teo C, Nakaji P, Mobbs RJ. Endoscope-assisted microvascular decompression for 
trigeminal neuralgia: technical case report. Neurosurgery. 2006 Oct;59(4 Suppl
2):ONSE489-90; discussion ONSE490. PubMed PMID: 17041524.
)).
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Neuroendoscopy was used as an adjunct to the surgical microscope in the MVD of the trigeminal (17 patients), facial (10 patients), and vestibulocochlear (1 patient) nerves in a series of 28 consecutive patients. After a standard microsurgical approach to CNs V, VII, and VIII, the endoscope was used to inspect all aspects of neural anatomy, to assess vascular compression, and to check the results of the decompression. Endoscope use was graded in four categories: Grade I, used but no definite role; Grade II, visualization assisted; Grade III, procedure assisted; and Grade IV, primary role. The usefulness of the endoscope was evaluated in each case.

Results: The endoscope was useful in visualizing the anatomy in all cases. It was especially useful in establishing trigeminal vein compression of CN V in Meckel's cave; observing multiple sources of vascular compression; ensuring adequate decompression after cauterization of vein, insertion of the Teflon felt, or a pexy procedure; and permitting observation of the compression of CN VII at the root exit zone by small arteries and veins. In six patients with trigeminal neuralgia, the trigeminal vein was cauterized and divided by using endoscopic vision only because the venous compression was not completely visualized with the microscope. During a follow-up period of 6 to 52 months (mean, 29 mo; median, 40 mo), all patients were asymptomatic and receiving no medication.

Conclusion: The endoscope is a useful adjunct to MVD in the treatment of trigeminal neuralgia, hemifacial spasm, and disabling positional vertigo or tinnitus
((Rak R, Sekhar LN, Stimac D, Hechl P. Endoscope-assisted microsurgery for microvascular compression syndromes. Neurosurgery. 2004 Apr;54(4):876-81; discussion 881-3. doi: 10.1227/01.neu.0000115151.52925.37. PMID: 15046653.)).
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Twenty-one patients with classic symptoms of trigeminal neuralgia underwent microvascular decompression of the trigeminal nerve through a retrosigmoid approach to the cerebellopontine angle. Endoscopy was used as an adjunctive imaging modality to microscopy. Specifically, endoscopes were used to confirm nerve-vessel conflicts identified by the microscope and to reveal others that escaped microscopic survey. Endoscopes were also used to assess the adequacy of the decompression performed microscopically. A total of 51 nerve-vessel conflicts were identified and treated, 14 of which were discovered only after endoscopy. Additionally, in 5 patients endoscopic examination of the surgical intervention demonstrated that further maneuvers were required to completely decompress the nerve. These results highlight the value of endoscopy in the diagnosis and therapy of cranial nerve pathology in the posterior fossa
((Jarrahy R, Berci G, Shahinian HK. Endoscope-assisted microvascular decompression of the trigeminal nerve. Otolaryngol Head Neck Surg. 2000 Sep;123(3):218-23. doi: 10.1067/mhn.2000.107451. PMID: 10964294.)).
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Abdeen et al. studied the application of combined microsurgical and endoscopic techniques in 21 cases of HFS and 12 cases of TN. With these techniques the surgeon can explore the ventral aspect of the brainstem and cranial nerves without further retraction, can see the groove caused by compression of the offending artery, and can confirm the proper position of the prosthesis after attachment to the dura by fibrin glue. In HFS the most common offending vessels in 75% of cases were the posterior inferior cerebellar artery (PICA) and anterior inferior cerebellar artery (AICA) and in 25% of cases the vertebral artery (VA). In trigeminal neuralgia the offending vessel in 60% of cases was the superior cerebellar artery (SCA), and in 40% of cases the AICA. The overall success rate was 97% with minimal morbidity 3% (facial palsy) and no mortality. The aim of this work is to study advantages and disadvantages of using endoscopy during microvascular decompression for TN and HFS
((Abdeen K, Kato Y, Kiya N, Yoshida K, Kanno T. Neuroendoscopy in microvascular decompression for trigeminal neuralgia and hemifacial spasm: technical note. Neurol Res. 2000 Jul;22(5):522-6. doi: 10.1080/01616412.2000.11740712. PMID: 10935228.)).

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