Microvascular Decompression for Trigeminal Neuralgia with Concomitant Persistent Primitive Trigeminal Artery
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.325353
Source of Support: None, Conflict of Interest: None
Keywords: Meckel's cave, microvascular decompression, persistent primitive trigeminal artery, trigeminal neuralgiaKey Message: Trigeminal neuralgia (TN) may be associated with persistent primitive trigeminal artery (PPTA). Surgeons should be aware of its surgical anatomy for effective management of such patients.
TN is a debilitating neuropathic pain condition described as recurrent severe paroxysmal pain restricted to the trigeminal territory, lasting from a fraction of a second up to 2 min, with the pain described as electric shock-like, stabbing, or sharp, and being triggered by innocuous stimuli. Surgical microvascular decompression is considered in patients with medically refractory pain. PPTA is the most common, largest, and most proximally located of the carotid vertebrobasilar communications. Association between TN and PPTA has been described earlier.
A 55-year-old male presented with history of paroxysmal, severe, electric shock-like pain over the right half of the face since 15 years. The patient was tried on several medications and had got some relief earlier in his treatment. At presentation, he was on three medications with inadequate pain control since past 1 year. Magnetic resonance imaging showed neurovascular conflict with compression of the right trigeminal nerve by the superior cerebellar artery. Conspicuously, there was a large vessel connecting the basilar artery to the cavernous segment of the right internal carotid artery passing through the Meckel's cave abutting the trigeminal nerve. The patient was explained about the surgical procedure and the presence of possible dual conflict and consent was taken for the surgical procedure.
Under general anesthesia, the patient was put on park bench position with the head fixed with three point fixation clamps. Retromastoid incision was made and a small craniotomy was done exposing the transverse and sigmoid sinus. After dural opening, CSF was released to make the cerebellum lax. Arachnoid dissection was done to reach the cerebellopontine angle. The superior petrosal vein was coagulated and cut. SCA compressing the TN was readily visible during exposure. Arachnoid dissection, both blunt and sharp, was done to separate the compression. On deeper visualization, a large vessel was seen leading toward the Meckel's cave with close proximity to TN. An endoscope was used to inspect closely, and arachnoid dissection was done to separate PPTA and TN. A finely shredded Teflon piece was placed in between PPTA and TN. Then, another Teflon piece was used to separate the SCA and TN. Close inspection was done to rule out any other vessel near the root entry zone. Endoscopy was again used to visualize and confirm MVD.
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Video timeline with audio transcript
0.01 - In this video, we present microvascular decompression for trigeminal neuralgia (TN) with concomitant persistent primitive trigeminal artery (PPTA).
0.08- A 55-year-old man came with right side trigeminal neuralgia, presently refractory to medications, with increasing pain in the past 1 year despite medical treatment.
0.20- The patient was evaluated with T2 weighted MRI, which showed a loop of the superior cerebellar artery over the trigeminal nerve and compressing it. Concomitant presence of PPTA connecting the basilar artery with the cavernous segment of the ICA was clearly demonstrated in an MRA.
0.41- After the patient gave consent, he was positioned in the left lateral park bench position.
0.48- A retromastoid craniotomy was done, which was small exposing both the transverse sigmoid sinuses.
0.54 - Dura was opened till the transverse sigmoid junction.
0.58- Cerebellopontine angle was dissected by retracting the cerebellum and CSF was released so that the cerebellum was lax and allowed us to further dissect in the cerebellopontine angle.
0.01.11- After dissection, the superior cerebellar artery was seen to compress the trigeminal nerve superiorly. It was dissected away from it and arachnoid dissection was done. We can visualize the cut end of the superior petrosal vein.
0.01.36- After this, we entered deep, and we could see a large vessel deeper into the trigeminal nerve.
0.01.47- Using an endoscope, the relation of the deeper vessel PPTA to the trigeminal nerve was noted, which was medial and deeper to it compressing the trigeminal nerve laterally.
0.02.03- Arachnoid dissection was further carried out to separate the trigeminal nerve from the PPTA. A clear space was created all around the trigeminal nerve through extensive dissection of the arachnoid so that it could be freed away from the PPTA and a Teflon could be placed. This space between the artery and the nerve was created so that we could keep it separate and a Teflon could be placed here.
0.02.42- After this, a Teflon felt that was finely shredded to a Teflon sponge was used to separate the trigeminal nerve from PPTA. The Teflon sponge was pushed between the two structures so that it did not exert pressure on the trigeminal nerve. Because of extensive dissection of the trigeminal nerve, enough space was created between the two so that the Teflon sponge could be freely inserted.
0.03.16- After this, the superior cerebellar artery was taken away from the surface of the trigeminal nerve. You can note that the superior cerebellar artery has fallen back over the trigeminal nerve and the pulsations are felt over the trigeminal nerve. The Teflon sponge was kept over the trigeminal nerve at the root entry zone so that the superior cerebellar artery could be kept away. This ensured that no part of the superior cerebellar artery was in contact with the trigeminal nerve. It was ensured that the Teflon sponge was firmly inserted in that space and was not free to move around.
0.04.33- After this, an endoscope was used to visualize satisfactory microvascular decompression, both from the superior cerebellar artery and persistent primitive trigeminal artery.
0.04.46- Postoperative day one patient had no fresh deficits; the pain had disappeared, and CT scan was essentially normal.
0.04.54- Coming to the discussion, the association of TN with PPTA has been described earlier. In our case, though the superior cerebellar artery was seen compressing the trigeminal nerve, it was closely associated with PPTA as well. So, it was entirely imperative for us to do MVD for that too. This is the first video in the literature that demonstrates PPTA during MVD for TN.
0.05.21- Concluding the video, we state that all neurosurgeons should be accustomed to dealing with such variations in anatomy while dealing with common conditions such as TN.
0.05.30- Thank you
The patient had pain relief immediately after surgery without any neurological deficits. He was discharged 2 days after stopping all his TN medications. Follow-up was done 6 months after surgery, and the patient was without any pain.
Though the association of TN with PPTA has been described earlier, we found only one study that showed an operative view and surgical anatomy of PPTA during surgery. Though a clear demonstration of trigeminal nerve compression by SCA could be done both by imaging and surgical inspection, we could not rule out compression by PPTA on the nerve. Thus, dissection was done and a Teflon piece was placed to separate the PPTA and TN. There are many other cases reported where TN was caused purely due to PPTA. Thus, it was entirely imperative that MVD was done specially when PPTA was seen abutting the TN near the entry to Meckel's cave.
This video demonstrates the surgical anatomy of PPTA associated with TN. Neurosurgeons should be accustomed to dealing with such variations in anatomy while dealing with common conditions like TN.
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