Quantitative Anatomic Study of the Minipterional Craniotomy in the Paraclinoid Region: Benefits of Extradural Anterior Clinoidectomy

Cranioorbital Pretemporal Skull Base Approach with Anterior Clinoidectomy for Removal of Large Left Clinoid Meningioma: "Unwrapping" Encircled Internal Carotid Artery and Decompressing Optic Nerve: 2-Dimensional Operative Video

Clinoidal meningiomas are meningiomas arising from or in the vicinity of the anterior clinoid process.1 Despite advanced microsurgical techniques, clinoidal meningiomas remain challenging.2 Extradural anterior clinoidectomy with optical unroofing remains an important tool in skull base surgery, which provides a safe operative corridor, facilitating greater extent of resection and enhancing overall outcome, particularly visual function.2-13 A 66-year-old woman presented with history of visual disturbances. Magnetic resonance imaging revealed a dural-based tumor consistent with a large left clinoidal meningioma, with tumor wrapping (encircling) around the left trunk and internal carotid artery (ICA) bifurcation, elevating the left middle cerebral artery M1 segment, and invading the left optic canal. Left cranio-orbital craniotomy with pretemporal exposure was used (Video 1).1,9 A high-speed diamond drill with irrigation completed the extradural anterior clinoidectomy and optical canal unroofing. Use of a 1-mm Kerrison rongeur should be done with utmost care. The tumor was unwrapped via meticulous piecemeal removal. Final dissection and ICA unwrapping was done when the tumor was debulked enough that dissecting it off the artery was safe and under less tension. Due to its obscurity, final decompression of the left optic nerve with incision and opening of the falciform ligament was performed at the end of the procedure.10 Postoperative neuro-ophthalmologic examination showed a grossly unchanged left visual field with some visual acuity improvement. Resection of tumor encircling the ICA has been described previously;14 however, to the best of our knowledge, this is the first video describing removal of a tumor surrounding the ICA (perfomed by senior author K.I.A.), essentially "unwrapping" the left ICA trunk and its bifurcation. The patient consented to publication.

Toward "bigger" data for neurosurgical anatomical research: a single centralized quantitative neurosurgical anatomy platform

Quantitative neurosurgical anatomy research aims to produce surgically applicable knowledge for improving operative decision-making using measurements from anatomical dissection and tools such as stereotaxis. Although such studies attempt to answer similar research questions, there is little standardization between them, offering minimal comparability. Modern technology has been incorporated into the research methodology, but many scientific principles are lacking, and results are not broadly applicable or suitable for evaluating big-data trends. Advances in information technology and the concept of big data permit more accessible and robust means of producing valuable, standardized, reliable research. A technology project, "Inchin," is presented to address these needs for neurosurgical anatomy research. This study applies the concept of big data to neurosurgical anatomy research, specifically in quantifying surgical metrics. A remote-hosted web application was developed for computing standard neurosurgical metrics and storing measurement data. An online portal (Inchin) was developed to produce a database to facilitate and promote neurosurgical anatomical research, applying optimal scientific methodology and big-data principles to this recent and evolving field of research. Individual data sets are not insignificant, but a collective of data sets present advantages. Large data sets allow confidence in data trends that are usually obscured in smaller numbers of samples. Inchin, a single centralized software platform, can act as a global database of results of neurosurgical anatomy studies. A calculation tool ensuring standardized peer-reviewed methodology, Inchin is applied to the analysis of neurosurgical metrics and may promote efficient study collaboration within and among neurosurgical laboratories.

The Minimally Invasive Posterolateral Transcavernous-Transtentorial Approach. Technical Nuances, Proof of Feasibility, and Surgical Outcomes Throughout a Case Series of Sphenopetroclival Meningiomas

OBJECTIVE

Sphenopetroclival (SPC) meningiomas are considered among the most complex skull-base neoplasms to approach surgically. We aim to determine whether some SPC meningiomas can be safely and effectively treated using a modified minimally invasive pterional posterolateral transcavernous-transtentorial approach (MIPLATTA).

METHODS

Fourteen patients harboring SPC meningiomas were surgically treated through a MIPLATTA. MIPLATTA includes a minipterional craniotomy, anterior extradural clinoidectomy, peeling of the temporal fossa, decompression of cranial nerves (CNs) in the cavernous sinus, and sectioning of the tentorium to reach the upper part of the posterior fossa.

RESULTS

Gross total resection was achieved in 11 of 14 patients (78%), whereas near-total resection was accomplished in the other 3 patients (22%), each of whom underwent a further complementary retrosigmoid approach for gross total tumor resection. There were no deaths, and 13 of 14 patients were independent at 6 months follow-up (modified Rankin Scale score ≤2). One patient had pontine infarction after the procedure and experienced moderate disability at follow-up (modified Rankin Scale score 3). All patients had some degree of CN impairment. Of 38 cranial neuropathies, 15 (39%) improved, 20 (53%) remained stable, and 3 (8%) worsened postoperatively. Four new CN deficits were observed postoperatively in 3 patients (fourth CN, 2 patients; third CN, 1; fifth CN, 1).

CONCLUSIONS

MIPLATTA is a useful and safe treatment alternative that allows resection of large SPC tumors with dominant invasion of cavernous sinus and middle fossa, preserves hearing and facial motor function, and provides good chances of recovery of visual and oculomotor deficits.

Morphometric Comparison of the Pterional Trans-Sylvian and the Pretemporal Trans-Clinoidal Approaches to the Posterior Communicating Artery

BACKGROUND

Posterior communicating (Pcom) aneurysms in the modern era have tended toward increased complexity and technical difficulties. The pretemporal approach is a valuable extension to the pterional approach for basilar apex aneurysms, but its advantages for Pcom aneurysms have not been previously elucidated.

OBJECTIVE

To quantify characteristics of the pretemporal approach to the Pcom.

METHODS

We dissected 6 cadaveric heads (12 sides) with a pretemporal transclinoidal approach and measured the following variables: (1) exposed length of internal carotid artery (ICA) proximal to the Pcom artery; (2) exposed circumference of ICA at the origin of Pcom; (3) deep working area between the optic nerve and tentorium/oculomotor nerve; (4) superficial working area; (5) exposure depth; and (6) the frontotemporal (superior posterolateral) and (7) orbito-sphenoidal (inferior anterolateral) angles of exposure.

RESULTS

Compared with pterional craniotomy, the pretemporal transclinoidal approach increased the exposed length of the proximal ICA from 3.3 to 11.7 mm (P = .0001) and its circumference from 5.1 to 7.8 mm (P = .0003), allowing a 210° view of the ICA (vs 137.9°). The deep and superficial working areas also significantly widened from 53.7 to 92.4 mm2 (P = .0048) and 252.8 to 418.2 mm2 (P = .0001), respectively; the depth of the exposure was equivalent. The frontotemporal and spheno-Sylvian angles increased by 17° (P = .0006) and 10° (P = .0037), respectively.

CONCLUSION

The pretemporal approach can be useful for complex Pcom aneurysms by providing easier proximal control, wider working space, improved aneurysm visualization, and more versatile clipping angles. Enhanced exposure results in a potentially higher rate of complete aneurysm obliteration and complication avoidance.

Same viewing angle, minimal craniotomy enlargement, extreme exposure increase: the extended supraorbital eyebrow approach

The supraorbital eyebrow approach (SEa) has been commonly used as a straightforward route to reach lesions located in the anterior cranial fossa. The reduced surgical exposure provided by this approach limits its applicability. A modification of the SEa, the extended supraorbital eyebrow approach (X-SEa), allows use of the transylvian corridor to approach parasellar lesions, while maintaining most of the aesthetic advantages of the SEa. To quantify the surgical exposure and maneuverability provided by the X-SEa using a cadaveric study. Eleven heads were used to obtain all stereotactic measurements. Surgical exposure and maneuverability were measured by means of the area of exposure and the angles of attack along key representative points in the anterior circulation. The horizontal angle of attack at the middle cerebral artery provided by the X-SEa was larger than that provided by the SEa (32.6 vs 18.4°, p = 0.009). The X-SEa afforded broader vertical angles of attack at all targets in the anterior circulation (p < 0.05). The total area of exposure provided by the X-SEa was significantly larger than that provided by the SEa (1272 vs 978 ± 156 mm², p = 0.003). The area of exposure in the ipsilateral trigon and in the midline quadrangle was also significantly larger for the X-SEa (paramedian 195 vs 121 mm², p = 0.01; midline 1310 vs 778 mm², p = 0.002). The X-SEa increases the exposure and surgical maneuverability along the anterior and middle cranial fossa when compared to the standard SEa.