Tag: Trigeminal nerve

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Extradural disconnection of the cavernous sinus with preservation of the internal carotid artery: indication and technique

Acta Neurochirurgica (2023) 165:2951–2956

Extradural disconnection of the cavernous sinus (CS) with preservation of the internal carotid artery (ICA) is indicated for aggressive and recurrent tumors, in patients presenting loss of oculomotor function and non-functional circle of Willis.

Method Extradural resection of the anterior clinoid process disconnects the CS anteriorly. The ICA is dissected in the foramen lacerum via extradural subtemporal approach. The intracavernous tumor is split and removed following the ICA. Bleeding control of the inferior and superior petrosal and intercavernous sinuses completes posterior CS disconnection.

Conclusion This technique can be proposed for recurrent CS tumors and need of ICA preservation.

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Anatomical relationship between the foramen ovale and the lateral plate of the pterygoid process: application to percutaneous treatments of trigeminal neuralgia

Neurosurgical Review (2022) 45:2193–2199

Our aim was to clarify the variations in the positional relationship between the base of the lateral plate of the pterygoid process and the foramen ovale (FO), which block inserted needles during percutaneous procedures to the FO usually used for the treatment of trigeminal neuralgia.

Ninety skulls were examined. The horizontal relationship between the FO and the posterior border of the base of the lateral plate of the pterygoid process was observed in an inferior view of the skull base. Skulls that showed injury to either the FO or the lateral plate of the pterygoid process on either side were excluded.

One hundred and sixty sides of eighty skulls were eligible. The relationship between the FO and the posterior border of the base of the lateral plate was classified into four types. Among the 160 sides, type III (direct type) was the most common (35%), followed by type I (lateral type, 29%) and type IV (removed type, 21%); type II (medial type) was the least common (15%). Of the 80 specimens, 53 showed the same type bilaterally.

In type IV, the posterior border of the base of the lateral plate is disconnected from the FO, so percutaneous procedures for treating trigeminal neuralgia could fail in patients with this type.

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Hypertrophic Interstitial Neuropathy of the Trigeminal Nerve

Neurosurgery 87:E41–E47, 2020

Hypertrophic interstitial neuropathy (HIN) is an uncommon, non-neoplastic lesion typically affecting peripheral nerves. Cranial nerve (CN) involvement is exceedingly rare. We present a case of isolated trigeminal nerve HIN manifesting with V3 distribution neuralgia.

CLINICAL PRESENTATION: A 50-yr-old male presented with left sided trigeminal neuralgia refractory to medical management. The patient underwent retromastoid craniectomy for possible microvascular decompression. Intra-operatively, the trigeminal nerve appeared to be focally enlarged with a sausage-like configuration. We selectively resected 1 fascicle which was predominantly involved. Histopathological examination revealed onion bulb formations composed of Schwann cells around centrally placed axons. A diagnosis of HIN was made. Postoperatively, the patient experienced complete resolution of symptoms.

CONCLUSION: This is the third case of isolated trigeminal nerve HIN in the literature. We performed a selective resection in a patient presenting with trigeminal neuralgia, resulting in complete resolution of symptoms. It is reported here with intraoperative microscope images, along with a review and analysis of this topic as it related to CN.

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Endoscopic endonasal approach to primitive Meckel’s cave tumors

Acta Neurochirurgica (2018) 160:2349–2361

Recently, an alternative endoscopic endonasal approach to Meckel’s cave (MC) tumors has been proposed. To date, few studies have evaluated the results of this route. The aim of our study was to evaluate long-term surgical and clinical outcome associated with this technique in a cohort of patients with intrinsic MC tumors.

Methods All patients with MC tumors treated at out institution by endoscopic endonasal approach (EEA) between 2002 and 2016 were included. Patients underwent brain MRI, CT-angiography, and neurological evaluation before surgery. Complications were considered based on the surgical records. All examinations were repeated after 3 and 12 months, then annually. The median follow-up was of 44.1 months (range 16–210).

Results The series included 8 patients (4 F): 5 neuromas, 1 meningioma, 1 chondrosarcoma, and 1 epidermoid cyst. The median age at treatment was 54.5 years (range 21–70). Three tumors presented with a posterior fossa extension. Radical removal of the MC portion of the tumor was achieved in 7 out of 8 cases. Two patients developed a permanent and transitory deficit of the sixth cranial nerve, respectively. No tumor recurrence was observed at follow-up.

Conclusion In this preliminary series, the EEA appeared an effective and safe approach to MC tumors. The technique could be advantageous to treat tumors located in the antero-medial aspects of MC displacing the trigeminal structures posteriorly and laterally. A favorable index of an adequate working space for this approach is represented by the ICA medialization, while tumor extension to the posterior fossa represents the main limitation to radical removal of this route.

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Role of the petrous ridge and angulation of the trigeminal nerve in the pathogenesis of trigeminal neuralgia, with implications for microvascular decompression

Acta Neurochirurgica (2018) 160:971–976

Vascular compression is the main pathogenetic factor in apparently primary trigeminal neuralgia; however some patients may present with clinically classical neuralgia but no vascular conflict on MRI or even at surgery. Several factors have been cited as alternative or supplementary factors that may cause neuralgia. This work focuses on the shape of the petrous ridge at the point of exit from the cavum trigeminus as well as the angulation of the nerve at this point.

Methods Patients with trigeminal neuralgia that had performed a complete imagery workup according to our protocol and had microvascular decompression were included as well as ten controls. In all subjects, the angle of the petrous ridge as well as the angle of the nerve on passing over the ridge were measured. These were compared from between the neuralgic and the nonneuralgic side and with the measures performed in controls.

Results In 42 patients, the bony angle of the petrous ridge was measured to be 86° on the neuralgic side, significantly more acute than that of controls (98°, p = 0.004) and with a trend to be more acute than the non-neuralgic side (90°, p = 0.06). The angle of the nerve on the side of the neuralgia was measured to be on average 141°, not significantly different either from the other side (144°, p=0.2) or from controls (142°, p = 0.4). However, when taking into account the grade of the conflict, the angle was significantly more acute in patients with grade II/III conflict than on the contralateral side, especially when the superior cerebellar artery was the conflicting vessel.

Conclusion This pilot study analyzes factors other than NVC that may contribute to the pathogenesis of the neuralgia. It appears that aggressive bony edges may contribute—at least indirectly—to the neuralgia. This should be considered for surgical indication and conduct of surgery when patients undergo MVD.

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Intraoperative monitoring of sensory part of the trigeminal nerve using blink reflex during microvascular decompression for trigeminal neuralgia

Acta Neurochirurgica (2018) 160:165–169

Intraoperative monitoring during cerebellopontine angle surgery is widely accepted. While techniques which monitor cranial motor nerves are commonly used, monitoring the sensory afferents has been challenging. Considering the reflex arc, blink reflex (BR) might be useful in monitoring the sensory part of the trigeminal nerve, the brainstem connections and the facial nerve.

We describe the case of a patient who developed hemifacial hypoesthesia after microvascular decompression surgery for trigeminal neuralgia. Intraoperative BR showed a severe loss of R1 amplitude.

BR might be a useful intraoperative technique to monitor the sensory part of the trigeminal nerve.

Keywords

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Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography

Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography

Acta Neurochir (2016) 158:429–435

There are no large series studies identifying the locations of cranial nerves (CNs) around trigeminal schwannomas (TSs); however, surgically induced cranial neuropathies are commonly observed after surgeries to remove TSs. In this study, we preoperatively identified the location of CNs near TSs using diffusion tensor tractography (DTT).

Methods An observational study of the DTT results and intraoperative findings was performed. We preoperatively completed tractography from images of patients with TSs who received surgical therapy. The result was later validated during tumorectomy.

Results A total of three consecutive patients were involved in this study. The locations of CNs V-VIII in relation to the tumor was clearly revealed in all cases, except for CN VI in case 3.The predicted fiber tracts were in agreement with intraoperative observations.

Conclusions In this study, preoperative DTT accurately predicted the location of the majority of the nerves of interest. This technique can be applied by surgeons to preoperatively visualize nerve arrangements.

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Classification of the Superior Petrosal Veins and Sinus Based on Drainage Pattern

Classification of the Superior Petrosal Veins and Sinus Based on Drainage Pattern

Operative Neurosurgery 10:357–367, 2014

The increasing number of reports of complications after sacrificing the superior petrosal veins, the largest veins in the posterior fossa, has led to a need for an increased understanding of the anatomy of these veins and the superior petrosal sinus into which they empty.

OBJECTIVE: To examine the anatomy of the superior petrosal veins and their size, draining area, and tributaries, as well as the anatomic variations of the superior petrosal sinus.

METHOD: Injected cadaveric cerebellopontine angles and 3-dimensional multifusion angiography images were examined.

RESULTS: The 4 groups of the superior petrosal veins based on their tributaries, course, and draining areas are the petrosal, posterior mesencephalic, anterior pontomesencephalic, and tentorial groups. The largest group was the petrosal group. Its largest tributary, the vein of the cerebellopontine fissure, was usually identifiable in the suprafloccular cistern located above the flocculus on the lateral surface of the middle cerebellar peduncle. The medial or lateral segment of the superior petrosal sinus was absent in 40% of cerebellopontine angles studied with venography.

CONCLUSION: The superior petrosal veins and their largest tributaries, especially the vein of the cerebellopontine fissure, should be preserved if possible. Obliteration of superior petrosal sinuses in which either the lateral or medial portion is absent may result in loss of the drainage pathway of the superior petrosal veins. Preoperative assessment of the superior petrosal sinus should be considered before transpetrosal surgery in which the superior petrosal sinus may be obliterated.

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The epidural approach to the Meckel’s cave

The epidural approach to the Meckel’s cave- a how I do it

Acta Neurochir (2014) 156:217–220

Meckel’s cave (MC) is a meningeal cleft lying in the middle fossa laterally to the cavernous sinus. Tumours that develop inside the MC may require a surgical resection. The authors describe the surgical technique of the intracranial epidural approach to the MC.

Methods Based upon anatomical dissection showing the relevant surgical anatomy, and illustrated by the video of an operated case, the authors detail the surgical procedure. The key point is to shave the floor of the middle fossa and skeletonize the superior orbital fissure, rotundum and ovale foramen in order to delineate the plane of dural elevation and expose the lateral wall of the MC. The rules of exposure and resection of the tumour are then shown. Variations and limitations of the approach are discussed.

Conclusion Conducted in a stepwise manner and following relevant landmarks, the epidural anterolateral approach offers a safe and reliable exposure to the diseases that develop within the MC.

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Foramen ovale puncture, lesioning accuracy, and avoiding complications

FO puncture

J Neurosurg 119:1176–1193, 2013

Foramen ovale (FO) puncture allows for trigeminal neuralgia treatment, FO electrode placement, and selected biopsy studies. The goals of this study were to demonstrate the anatomical basis of complications related to FO puncture, and provide anatomical landmarks for improvement of safety, selective lesioning of the trigeminal nerve (TN), and optimal placement of electrodes.

Methods. Both sides of 50 dry skulls were studied to obtain the distances from the FO to relevant cranial base references. A total of 36 sides from 18 formalin-fixed specimens were dissected for Meckel cave and TN measurements. The best radiographic projection for FO visualization was assessed in 40 skulls, and the optimal trajectory angles, insertion depths, and topographies of the lesions were evaluated in 17 specimens. In addition, the differences in postoperative pain relief after the radiofrequency procedure among different branches of the TN were statistically assessed in 49 patients to determine if there was any TN branch less efficiently targeted.

Results. Most severe complications during FO puncture are related to incorrect needle placement intracranially or extracranially. The needle should be inserted 25 mm lateral to the oral commissure, forming an approximately 45° angle with the hard palate in the lateral radiographic view, directed 20° medially in the anteroposterior view. Once the needle reaches the FO, it can be advanced by 20 mm, on average, up to the petrous ridge. If the needle/radiofrequency electrode tip remains more than 18 mm away from the midline, injury to the cavernous carotid artery is minimized. Anatomically there is less potential for complications when the needle/radiofrequency electrode is advanced no more than 2 mm away from the clival line in the lateral view, when the needle pierces the medial part of the FO toward the medial part of the trigeminal impression in the petrous ridge, and no more than 4 mm in the lateral part. The 40°/45° inferior transfacial–20° oblique radiographic projection visualized 96.2% of the FOs in dry skulls, and the remainder were not visualized in any other projection of the radiograph. Patients with V1 involvement experienced postoperative pain more frequently than did patients with V2 or V3 involvement. Anatomical targeting of V1 in specimens was more efficiently achieved by inserting the needle in the medial third of the FO; for V2 targeting, in the middle of the FO; and for V3 targeting, in the lateral third of the FO.

Conclusions. Knowledge of the extracranial and intracranial anatomical relationships of the FO is essential to understanding and avoiding complications during FO puncture. These data suggest that better radiographic visualization of the FO can improve lesioning accuracy depending on the part of the FO to be punctured. The angles and safety distances obtained may help the neurosurgeon minimize complications during FO puncture and TN lesioning.

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The role of the cerebellopontine angle cistern area and trigeminal nerve length in the pathogenesis of trigeminal neuralgia

Role of CPA cistern and TN

Acta Neurochir (2013) 155:863–868

The aim of this prospective study was to evaluate whether the cerebellopontine angle (CPA) cistern area and trigeminal nerve cisternal length play a role in the pathogenesis of trigeminal neuralgia (TN).

Methods High-resolution 1.5 T magnetic resonance imaging of the posterior fossa was performed in 26 patients with TN and 18 age-matched healthy controls. Axial T2- weighted, three-dimensional constructive interference in steady-state (3D-CISS) was used to measure bilaterally the cross-sectional area of the CPA cistern and trigeminal nerve cisternal length.

Results In patients, the cross-sectional area of the CPA cistern and trigeminal nerve cisternal length was smaller on the affected side (p=0.04). Healthy controls tended to have larger cisternal areas and longer trigeminal nerve lengths than patients (p=0.059, p=0.071, respectively). Larger CPA cisternal areas tended to be seen in older patients. There was a strong correlation between the crosssectional area of the CPA cistern and the length of the trigeminal nerve (p=0.000).

Conclusions Smaller CPA cisterns and short cisternal trigeminal nerves impact the pathogenesis of essential TN by facilitating the neurovascular conflict, especially in younger patients. Trigeminal nerve cisternal measurement provides an easy and direct estimation of the CPA area. This information can be used for surgical planning and potentially for outcome prediction.

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Patients with idiopathic trigeminal neuralgia have a sharper-than-normal trigeminal-pontine angle and trigeminal nerve atrophy

Acta Neurochir (2012) 154:1627–1633

Trigeminal neuralgia (TN) is primarily diagnosed by symptoms and patient history. Magnetic resonance (MR) imaging can be helpful in visualizing the neurovascular compression of the trigeminal nerve in TN patients, but the current parameters used as diagnostic markers for TN are less than optimal. The aim of this study is to assess whether the angle between the trigeminal nerve and the pons (the trigeminal-pontine angle) on the affected side of patients with idiopathic TN differs from that of the unaffected side and that found in controls without TN.

Methods A case-control study of 30 clinically diagnosed idiopathic TN patients aged 30 to 79 years and 30 age- and sexmatched controls was conducted.We compared the trigeminalpontine angle and trigeminal nerve atrophy via fast-imaging employing steady-state acquisition (FIESTA) MR imaging.

Results A sharp trigeminal-pontine angle was observed in 25 patients (25/30) on the affected side. As such, the mean angle of the trigeminal nerve on the affected side (40.17) was significantly smaller than that on the unaffected side (48.91, p=0.001) and that in the control group (52.02, p<0.001).

Conclusions A sharp trigeminal-pontine angle on the affected side was found in idiopathic TN patients by FIESTA imaging. This suggests that a sharp trigeminal-pontine angle increases the chance of neurovascular compression on the medial side of the trigeminal nerve.

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Trigeminal schwannomas: experience with 57 cases and a review of the literature

Neurosurg Rev (2011) 34:159–171. DOI 10.1007/s10143-010-0289-y

Trigeminal schwannoma is a mostly benign tumor that can be cured by complete resection. Over the last few decades, several pioneers have developed surgical approaches enabling the total removal of such tumors.

We analyzed 57 patients who underwent radical surgery, including 45 patients who underwent skull base surgery as their initial treatment, for removal of trigeminal schwannomas. Here, we report the surgical management of these cases. Since 1990, all such patients have been treated using three main types of middle fossa skull base approaches, which minimize the exposure of the brain: the anterior transpetrosal approach, subtemporal interdural approach (Dolenc), or a combination of these approaches.

Before 1990, total tumor removal was achieved in only three of eight patients (38%). After 1990, the tumors were totally removed in 43 patients (90%) and were nearly completely removed in an additional three patients (6%). Among the patients who underwent skull base surgery as their initial treatment, a complete resection was achieved in 93% (42/45 patients) of the cases. However, total surgical removal after surgery and Gamma knife surgery was very difficult because of dense adhesions to the brain stem and cranial nerves. No surgery-related mortalities occurred in this series, and the individual KPS scores were more than 90% among the patients who underwent skull base surgery. No recurrences requiring additional surgery have occurred after an average follow-up period of 4.9 years.

Most of the trigeminal schwannomas could be removed totally and safely during a single operation after the introduction of skull base surgery. Therefore, radiosurgery should not be applied as the treatment of first choice for younger patients. A correct anatomical knowledge is critical for minimizing brain exposure and avoiding surgical complications.

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Trigeminal schwannomas: experience with 57 cases and a review of the literature

Neurosurg Rev. DOI 10.1007/s10143-010-0289-y

Trigeminal schwannoma is a mostly benign tumor that can be cured by complete resection. Over the last few decades, several pioneers have developed surgical approaches enabling the total removal of such tumors.

We analyzed 57 patients who underwent radical surgery, including 45 patients who underwent skull base surgery as their initial treatment, for removal of trigeminal schwannomas. Here, we report the surgical management of these cases. Since 1990, all such patients have been treated using three main types of middle fossa skull base approaches, which minimize the exposure of the brain: the anterior transpetrosal approach, subtemporal interdural approach (Dolenc), or a combination of these approaches.

Before 1990, total tumor removal was achieved in only three of eight patients (38%). After 1990, the tumors were totally removed in 43 patients (90%) and were nearly completely removed in an additional three patients (6%). Among the patients who underwent skull base surgery as their initial treatment, a complete resection was achieved in 93% (42/45 patients) of the cases. However, total surgical removal after surgery and Gamma knife surgery was very difficult because of dense adhesions to the brain stem and cranial nerves. No surgery-related mortalities occurred in this series, and the individual KPS scores were more than 90% among the patients who underwent skull base surgery. No recurrences requiring additional surgery have occurred after an average follow-up period of 4.9 years.

Most of the trigeminal schwannomas could be removed totally and safely during a single operation after the introduction of skull base surgery. Therefore, radiosurgery should not be applied as the treatment of first choice for younger patients. A correct anatomical knowledge is critical for minimizing brain exposure and avoiding surgical complications.

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Percutaneous approach to the foramen ovale: an anatomical study of the extracranial trajectory with the incorrect trajectories to be avoided

Acta Neurochir (2010) 152:1043–1053. DOI 10.1007/s00701-010-0604-y

Meckel’s Cave may be accessed percutaneously through the foramen ovale (FO). Detailed knowledge of the region’s anatomical surroundings is invaluable in improving target accuracy and preventing complications with this approach. The approach has been used in the treatment of trigeminal neuralgia as well as in performing biopsies of lesions located in the parasellar region, described formerly by the senior author (M.S.). A comprehensive cadaveric study of the region traversed by needle is thus presented.

Materials and methods Three cadaveric heads (six sides) were fixed in formaldehyde and injected with latex. A detailed description of the regional anatomical needle trajectories was performed.

Results An “inverted pyramid” subdivided into three segments is described. The inferior third begins at cutaneous penetration and ends at the parotid duct (PD). The middle third extends from the PD to the lateral pterygoid muscle (LPM). The superior third starts from the LPM and ends at the FO. The main vascular anatomical variation was with regard to the maxillary artery (MA). In half of the cases, the MA traveled though the middle of the pyramid and in the other half through the upper third.

Conclusions Although widely used, the FO approach carries risks. Special attention is warranted when the needle traverses the upper third of the pyramid to avoid the variant course of the MA. Image-guided techniques and detailed anatomical knowledge are necessary to expand the use of this route not just for approach to lesions within the parasellar and upper third of the petroclival region but also to lesions invading the infratemporal fossa.

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