Extreme lateral supracerebellar infratentorial approach

Extreme lateral supracerebellar infratentorial approach

Since the first report of application of the extreme lateral supracerebellar infratentorial (ELSI) approach in resecting the posterolateral pontomesencephalic junction (PMJ) region lesions in 2000, few articles concerning the ELSI approach have been published. A review of Chen et al., provided an intimate introduction of the ELSI approach, and evaluated it in facets of patient position, skin incision, craniectomy, draining veins, retraction against the cerebellum, exposure limits, patient healing, as well as advantages and limitations compared with other approaches. The ELSI approach is proposed to be a very young and promising approach to access the lesions of posterolateral PMJ region and the posterolateral tentorial gap. Besides, it has several advantages such as having a shorter surgical pathway, causing less surgical complications, labor-saving, etc. 1).

The extreme lateral supracerebellar infratentorial approach differs from the midline and paramedian supracerebellar infratentorial variants in the area of exposure, patient positioning, and location of the craniotomy. The technique is effective for approaching the posterolateral mesencephalon2).

The extreme-lateral corridor widens the exposure of the paramedian approach to include the anterolateral brainstem surface, offering a complete view of the cisternal space surrounding the middle incisural space 3). It provided visualization of the ambient and tentorial segments of the trochlear nerve 4).

It was initially proposed to treat lesions of the posterolateral surface of the pons principally cavernomas. The versatility of the approach allowed its use for other pathologies like gliomas, aneurysms, epidermoids, and meningiomas 5).

All the extreme-lateral supracerebellar infratentorial (SCIT) approaches warrant a safe route to the quadrigeminal plate. Among the different variants, the median approach had the smallest median surgical area exposure but presented superior results to access the intercollicular safe entry zone 6).

Lesions located at the lateral midbrain surface are better approached through the lateral mesencephalic sulcus (LMS). The goal of a study was to compare the surgical exposure to the LMS provided by the subtemporal approach and the paramedian and extreme-lateral variants of the supracerebellar infratentorial approach.

These 3 approaches were used in 10 cadaveric heads.

Cavalcanti et al., performed measurements of predetermined points by using a neuronavigation system. Areas of microsurgical exposure and angles of the approaches were determined. Statistical analysis was performed to identify significant differences in the respective exposures.

The surgical exposure was similar for the different approaches-369.8 ± 70.1 mm2 for the ST; 341.2 ± 71.2 mm2 for the SCIT paramedian variant; and 312.0 ± 79.3 mm2 for the SCIT extreme-lateral variant (p = 0.13). However, the vertical angular exposure was 16.3° ± 3.6° for the ST, 19.4° ± 3.4° for the SCIT paramedian variant, and 25.1° ± 3.3° for the SCIT extreme-lateral variant craniotomy (p < 0.001). The horizontal angular exposure was 45.2° ± 6.3° for the ST, 35.6° ± 2.9° for the SCIT paramedian variant, and 45.5° ± 6.6° for the SCIT extreme-lateral variant opening, presenting no difference between the ST and extreme-lateral variant (p = 0.92), but both were superior to the paramedian variant (p < 0.001). Data are expressed as the mean ± SD.

The extreme-lateral SCIT approach had the smaller area of surgical exposure; however, these differences were not statistically significant. The extreme-lateral SCIT approach presented a wider vertical and horizontal angle to the LMS compared to the other craniotomies. Also, it provides a 90° trajectory to the sulcus that facilitates the intraoperative microsurgical technique 7).


Five cavernous malformations, two juvenile pilocytic astrocytomas, and one peripheral superior cerebellar artery aneurysm located in this region were approached in eight patients. In this extreme lateral approach, the sigmoid sinus is unroofed more superiorly and the bone flap includes not only a posterior fossa craniotomy but also a portion that extends just above the transverse sinus. The dural opening is based along the transverse and sigmoid sinuses. After the cerebrospinal fluid has been drained, the lateral aspect of the brainstem is approached via the cerebellar surface. A proximal tentorial incision offers additional rostral exposure where needed.

Seven patients in this series underwent successful resection of their lesion. The remaining patient’s aneurysm was clipped successfully with no major complications.

The extreme lateral supracerebellar infratentorial approach differs from the midline and paramedian supracerebellar infratentorial variants in the area of exposure, patient positioning, and location of the craniotomy. The technique is effective for approaching the posterolateral mesencephalon8).


The extreme lateral infratentorial supracerebellar approach to treat pathologies located in the ambient cistern and posterior incisural space is a technically feasible route in selected cases. In this cadaveric study, we demonstrate the benefits of endoscope-assisted microsurgical maneuvers using the extreme lateral supracerebellar infratentorial approach.

An endoscope-assisted infratentorial supracerebellar approach was performed in six formalin-fixed cadaveric heads using standard microneurosurgical methods. Dissections were performed in a stepwise fashion, comparing the exposure afforded by the microsurgical route alone to the endoscope-assisted route, using 0- and 30-degree angled lenses. Relationships among the target and the surroundings neurovascular structures were described.

Endoscope-assisted maneuvers for the extreme lateral supracerebellar approach provide an improved operative view and have the potential to reduce parenchymal trauma and neurovascular injuries. The endoscopic techniques bring the surgeon to the anatomy, enhancing illumination and surgical visualization.

Direct visualization of the posterior and posterolateral incisural space avoids retraction of the occipital lobe and damage to the deep venous complex. The extreme lateral infratentorial supracerebellar corridor is effective for approaching the posterolateral mesencephalic junction and the posterior incisural space in selected cases. Endoscope-assisted microsurgery can improve visualization and minimize parenchymal retraction, which should enhance surgical control 9).


For endoscopic-controlled approaches, the extreme lateral approach provides the largest surgical freedom when accessing the ipsilateral superior colliculus (P < 0.0001), the lateral approach provides the largest surgical freedom to the pineal gland (P < 0.0001), and the paramedian craniotomy provides the largest surgical freedom when accessing the splenium (P < 0.0001). The extreme lateral approach to the pineal gland provided the largest horizontal angle of attack (P < 0.0001), and the extreme lateral approach to the ipsilateral superior colliculus provided the largest vertical angle of attack (P < 0.001). The microscope provides marginally increased surgical freedom and a better angle of attack to specific anatomical targets in the paramedian and extreme lateral approach compared with those provided by the endoscope, but these differences are negligible during intraoperative application.

Presurgical planning and a detailed understanding of the important neurovascular structures in the pineal region are paramount to safe and successful surgical execution. Our current cadaveric study indicates that the medial-to-lateral location of craniotomy can maximize access to pineal region targets. Furthermore, the endoscope is a viable alternative to the microscope for identifying pathology of the posterior incisura. These differences in surgical freedom and angle of attack to the pineal region may be useful to consider when planning minimal-access approaches 10).

Videos

A video illustrates the case of a 52-year-old man with a history of multiple bleeds from a lateral midbrain cerebral cavernous malformation, who presented with sudden-onset headache, gait instability, and left-sided motor and sensory disturbances. This lesion was eccentric to the right side and was located in the dorsolateral brainstem. Therefore, the lesion was approached via a right-sided extreme lateral supracerebellar infratentorial (exSCIT) craniotomy with monitoring of the cranial nerves. This video demonstrates the utility of the exSCIT for resection of dorsolateral brainstem lesions and how this approach gives the surgeon ready access to the supracerebellar space, and cerebellopontine angle cistern. The lateral mesencephalic safe entry zone can be accessed from this approach; it is identified by the intersection of branches of the superior cerebellar artery and the fourth cranial nerve with the vein of the lateral mesencephalic sulcus. The technique of piecemeal resection of the lesion from the brainstem is presented. Careful patient selection and respect for normal anatomy are of paramount importance in obtaining excellent outcomes in operations within or adjacent to the brainstem. The link to the video can be found at: https://youtu.be/aIw-O2Ryleg 11).

Case series

Five cavernous malformations, two juvenile pilocytic astrocytomas, and one peripheral superior cerebellar artery aneurysm located in this region were approached in eight patients. In this extreme lateral approach, the sigmoid sinus is unroofed more superiorly and the bone flap includes not only a posterior fossa craniotomy but also a portion that extends just above the transverse sinus. The dural opening is based along the transverse and sigmoid sinuses. After the cerebrospinal fluid has been drained, the lateral aspect of the brainstem is approached via the cerebellar surface. A proximal tentorial incision offers additional rostral exposure where needed.

Seven patients in this series underwent successful resection of their lesion. The remaining patient’s aneurysm was clipped successfully with no major complications 12).

References

1)

Chen X, Feng YG, Tang WZ, Li HT, Li ZJ. A young and booming approach: the extreme lateral supracerebellar infratentorial approach. Neurosci Bull. 2010 Dec;26(6):479-85. doi: 10.1007/s12264-010-1036-7. Review. PubMed PMID: 21113199; PubMed Central PMCID: PMC5560335.
2) , 8)

Vishteh AG, David CA, Marciano FF, Coscarella E, Spetzler RF. Extreme lateral supracerebellar infratentorial approach to the posterolateral mesencephalon: technique and clinical experience. Neurosurgery. 2000 Feb;46(2):384-8; discussion 388-9. PubMed PMID: 10690727.
3)

Ammirati M, Bernardo A, Musumeci A, Bricolo A. Comparison of different infratentorial-supracerebellar approaches to the posterior and middle incisural space: a cadaveric study. J Neurosurg. 2002 Oct;97(4):922-8. PubMed PMID: 12405382.
4)

Ammirati M, Musumeci A, Bernardo A, Bricolo A. The microsurgical anatomy of the cisternal segment of the trochlear nerve, as seen through different neurosurgical operative windows. Acta Neurochir (Wien). 2002 Dec;144(12):1323-7. PubMed PMID: 12478346.
5)

Giammattei L, Borsotti F, Daniel RT. Extreme lateral supracerebellar infratentorial approach: how I do it. Acta Neurochir (Wien). 2019 Apr 1. doi: 10.1007/s00701-019-03886-5. [Epub ahead of print] PubMed PMID: 30937609.
6)

Cavalcanti DD, Morais BA, Figueiredo EG, Spetzler RF, Preul MC. Supracerebellar Infratentorial Variant Approaches to the Intercollicular Safe Entry Zone. World Neurosurg. 2019 Feb;122:e1285-e1290. doi: 10.1016/j.wneu.2018.11.033. Epub 2018 Nov 14. PubMed PMID: 30447444.
7)

Cavalcanti DD, Morais BA, Figueiredo EG, Spetzler RF, Preul MC. Surgical approaches for the lateral mesencephalic sulcus. J Neurosurg. 2019 Apr 12:1-6. doi: 10.3171/2019.1.JNS182036. [Epub ahead of print] PubMed PMID: 30978690.
9)

Rehder R, Luiz da Costa MP, Al-Mefty O, Cohen AR. Endoscope-Assisted Microsurgical Approach to the Posterior and Posterolateral Incisural Space. World Neurosurg. 2016 Jul;91:210-7. doi: 10.1016/j.wneu.2016.04.017. Epub 2016 Apr 16. PubMed PMID: 27090972.
10)

Zaidi HA, Elhadi AM, Lei T, Preul MC, Little AS, Nakaji P. Minimally Invasive Endoscopic Supracerebellar-Infratentorial Surgery of the Pineal Region: Anatomical Comparison of Four Variant Approaches. World Neurosurg. 2015 Aug;84(2):257-66. doi: 10.1016/j.wneu.2015.03.009. Epub 2015 Mar 28. PubMed PMID: 25827042.
11)

Kalani MYS, Couldwell WT. Extreme Lateral Supracerebellar Infratentorial Approach to the Lateral Midbrain. J Neurol Surg B Skull Base. 2018 Dec;79(Suppl 5):S415-S417. doi: 10.1055/s-0038-1669981. Epub 2018 Sep 25. PubMed PMID: 30456047; PubMed Central PMCID: PMC6240419.
12)

Vishteh AG, David CA, Marciano FF, Coscarella E, Spetzler RF. Extreme lateral supracerebellar infratentorial approach to the posterolateral mesencephalon: technique and clinical experience. Neurosurgery. 2000 Feb;46(2):384-8; discussion 388-9. PubMed PMID: 10690727.

Retrosigmoid transmeatal approach for vestibular schwannoma videos

Retrosigmoid transmeatal approach for vestibular schwannoma videos

Dorsal displacement of the facial nerve is relatively rare in patients with vestibular schwannoma. Its prediction remains difficult in patients with large tumors, even with the recent advances in preoperative radiologic assessments. Anatomic and functional preservation of the facial nerves combined with maximal tumor removal is particularly challenging in this rare anatomic variant, and surgery may lead to postoperative facial nerve paralysis, inadequate tumor removal, and/or a high retreatment rate.

The 3-dimensional video (Video 1) demonstrates a vestibular schwannoma with dorsally displaced facial nerve, which was surgically treated by the retrosigmoid transmeatal approach under continuous facial nerve monitoring. The video was reproduced after informed consent of the patient. A 46-year-old man presented with transient hearing impairmentNeuroimaging displayed a left vestibular schwannoma extending into the internal acoustic meatus. The retrosigmoid transmeatal approach was performed, and a dorsally displaced facial nerve was predicted by preoperative magnetic resonance images and confirmed during surgery. The facial nerve was accurately dissected under continuous facial nerve monitoring, and gross total resection of the tumor was achieved without postoperative facial dysfunction 1).


A case of a mid-sized vestibular schwannoma (T3b according to the Hannover Grading Scale) that was resected through a Endoscopic assisted retrosigmoid approach in semisitting position

A 52-year-old male with acute loss of functional hearing on the right side. Audiometry confirmed a loss of up to 60 dB and lost speech discrimination, there were no associated symptoms such as tinnitus or vertigo. This 2D video demonstrates positioning, OR set-up, anatomical and surgical nuances of the skull base approach and the operative technique for microdissection of the tumor from the critical neurovascular structures, especially the facial and cochlear nerves. A gross total resection was achieved and the patient discharged home after four days with unaltered function of the facial nerve (HB I). At one year follow up there was no indication of residual or recurrence. In summary, the retrosigmoid transmeatal approach is an important and powerful tool in the armamentarium for the microsurgical management of all kinds of vestibular schwannomas. Provided the necessary anesthesiological precautions and intraoperative procedures the semi-sitting position is safe and effective. If needed, the approach can be complemented by the use of an endoscope for visualization of the distal internal auditory canal. The link to the video can be found at: https://youtu.be/pPKT4_5nIn0 2).


The anterior inferior cerebellar artery (AICA) usually runs loosely within the cerebellopontine cistern; in rare cases, however, it is firmly adherent to the petrous dura mater. Recognizing this variation is particularly important in vestibular schwannoma surgery via the retrosigmoid transmeatal approach to prevent the high morbidity associated with vascular injury. This video demonstrates a surgical technique to effectively mobilize the AICA when firmly adherent to the petrous dura mater.

A 39-year-old man presented with a history of progressive right-sided hearing loss without facial weakness or other associated symptoms. Magnetic resonance imaging (MRI) demonstrated an intracanalicular lesion, suggestive of vestibular schwannoma. During follow-up, audiometryconfirmed a further slight deterioration of hearing and repeated MRI demonstrated tumor growth (T2 according to Hannover Grading Scale). Since the patient opted against radiosurgery, a retrosigmoid transmeatal approach under continuous intraoperative monitoring was performed in supine position. Following drainage of cerebrospinal fluid and exposure of the cerebellopontine cistern, the AICA was found to be firmly adherent to the petrous dura mater. Both structures were elevated conjointly and displaced medially for safe drilling of the inner auditory canal, sufficient exposure, and complete excision of the vestibular schwannoma. The patient had an excellent recovery, hearing and facial function were preserved, and no secondary neurological deficits noted.The patient consented to publication of this anonymized video 3).


Skull Base Neurosurgery – University of Colorado


George Kaptain


Paolo Regolo


Sameer A. Sheth

References

1)

Matsushima K, Kohno M, Nakajima N, Ichimasu N. Dorsally Displaced Facial Nerve in Retrosigmoid Transmeatal Approach for Vestibular Schwannoma: 3-Dimensional Operative Video. World Neurosurg. 2019 Mar;123:300. doi: 10.1016/j.wneu.2018.11.261. Epub 2018 Dec 21. PubMed PMID: 30580063.
2)

Evangelista-Zamora R, Lieber S, Ebner FH, Tatagiba M. Retrosigmoid Transmeatal Endoscope-Assisted Approach in Semi-Sitting Position for Resection of Vestibular Schwannoma: 2-D operative Video. J Neurol Surg B Skull Base. 2018 Dec;79(Suppl 5):S385-S386. doi: 10.1055/s-0038-1669985. Epub 2018 Oct 9. PubMed PMID: 30473983; PubMed Central PMCID: PMC6240135.
3)

Tatagiba MS, Evangelista-Zamora R, Lieber S. Mobilization of the Anterior Inferior Cerebellar Artery When Firmly Adherent to the Petrous Dura Mater-A Technical Nuance in Retromastoid Transmeatal Vestibular Schwannoma Surgery: 3-Dimensional Operative Video. Oper Neurosurg (Hagerstown). 2018 Nov 1;15(5):E58-E59. doi: 10.1093/ons/opy052. PubMed PMID: 29617908.

Retrosigmoid approach for glycerin rhizotomy

Retrosigmoid approach for glycerin rhizotomy

In 2013 Goodwin et al., performed a retrospective analysis of patients who received standard microvascular decompression and injection of glycerin to the inferior third of the Trigeminal nerve cisternal portion anterior to the root entry zone with lack of a compressive vessel on MRI as the primary indication. Fourteen patients were identified and demographic information, post-operative course and complications were recorded.

There were eleven females and three males with an average age at time of surgery of 54.8 years. 100% of patients reported that their trigeminal pain was significantly improved following surgical intervention. Four out of fourteen patients reported a 50-80% decrease from the pre-surgery baseline pain at one month and three month follow up. One patient developed a CSF leak, and no surgical site infections or motor deficits were observed.

Intra-operative glycerin rhizotomy in conjunction with microvascular decompression can be used to safely treat patients suffering from trigeminal neuralgia 1).

In 2019 their updated experience with this technique to further validate this novel approach by a retrospectiveanalysis of data obtained in patients in whom glycerin was directly injected into the inferior third of the cisternal portion of the trigeminal nerve.

Seventy-four patients, including 14 patients from the authors’ prior study, were identified, and demographic information, intraoperative findings, postoperative course, and complications were recorded. Fisher’s exact test, unpaired t-tests, and Kaplan-Meier survival curves using Mantel logrank test were used to compare the 74 patients with a cohort of 476 patients who received standard MVD by the same surgeon.

The 74 patients who underwent MVD and glycerin injection had an average follow-up of 19.1 ± 18.0 months, and the male/female ratio was 1:2.9. In 33 patients (44.6%), a previous intervention for TN had failed. On average, patients had an improvement in the Barrow Neurological Institute Pain Intensity score from 4.1 ± 0.4 before surgery to 2.1 ± 1.2 after surgery. Pain improvement after the surgery was documented in 95.9% of patients. Thirteen patients (17.6%) developed burning pain following surgery. Five patients developed complications (6.7%), including incisional infectionfacial palsyCSF leakage, and hearing deficit, all of which were minor.

Intraoperative injection of glycerin into the trigeminal nerve is a generally safe and potentially effective treatment for TN when no distinct site of arterial compression is identified during surgery or when decompression of the nerve is deemed to be inadequate 2).

References

1)

Goodwin CR, Yang JX, Bettegowda C, Hwang B, James C, Biser A, Raza S, Bender M, Carson B, Lee JY, Lim M. Glycerol rhizotomy via a retrosigmoid approach as an alternative treatment for trigeminal neuralgia. Clin Neurol Neurosurg. 2013 Dec;115(12):2454-6. doi: 10.1016/j.clineuro.2013.09.009. Epub 2013 Sep 25. PubMed PMID: 24161889.
2)

Kim TY, Jackson CM, Xia Y, Mashouf LA, Patel KK, Kim ES, Hung AL, Wu A, Garzon-Muvdi T, Bender MT, Bettegowda C, Lee JYK, Lim M. Retrosigmoid approach for glycerin rhizotomy in the treatment of trigeminal neuralgia without overt arterial compression: updated case series. J Neurosurg. 2019 Mar 8:1-7. doi: 10.3171/2018.12.JNS182572. [Epub ahead of print] PubMed PMID: 30849763.
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