Category Archives: Operative Neurosurgery

Update: Midline suboccipital subtonsillar approach

Marcos Tatagiba et al. described the surgical anatomy of the midline suboccipital subtonsillar approach to the hypoglossal canal. This approach includes a midline suboccipital craniotomy, dorsal opening of the foramen magnum and elevation of ipsilateral cerebellar tonsil to expose the hypoglossal nerve and its canal. The midline subtonsillar approach permits a straight primary intradural view to the hypoglossal canal. There is no necessity of condylar resections 1) 2).

It offers excellent access with a panoramic view of the cerebellomedullary cistern and its structures and therefore can be useful for a number of different pathologies in the lower petroclival region 3).


A study was performed on three alcohol (ETOH)-fixed specimens (6 sides), and the technique of the approach was highlighted. The tonsillar retraction needed to view the important structures was measured. Additionally, the records of 31 patients who underwent the STA procedure were evaluated and provide three clinical cases as examples.

Tonsillar retraction of 0.3cm (SD±0.1cm) exposed the PICA with its telo-velo-tonsillar and cortical branches. Retraction of 0.4cm (SD±0.2cm) exposed the spinal root of CN XI. Retraction of 0.9cm (SD±0.01cm) exposed the hypoglossal canal. Retraction of 1.3cm (SD±0.2cm) exposed the root exit zone of the glossopharyngeal nerve. Retraction of 1.6cm (SD±0.3cm) exposed the jugular foramen (JF), and retraction of 2.4cm (SD±0.2cm) exposed the inner auditory canal (IAC). In all of the selected cases, the pathology could be reached and exposed using the STA.

They recommend STA as a straightforward, easy-to-learn and therefore time-saving and safe procedure compared with other standard approaches to the cerebellomedullary cistern and its pathologies 4).

Indications

Glossopharyngeal neuralgia5).

Anterior, anterolateral, and posterior Foramen magnum meningioma6).

There was no significant postoperative complication in the remainder of the patientes, and their conditions improved after surgery 7).

Hypoglossal canal meningioma.

Case reports

2015

Two patients with exophytic or focal lesions in the inferior half of the medulla, who underwent surgery by suboccipital midline subtonsillar approach. This approach was not specifically described to reach MO before, and they found that the lesions produced a mild elevation of the tonsils providing a wide surgical view from the medulla to the foramen of Luchska laterally, and up to the middle cerebellar peduncle, offering a wide and safe access 8).

2010

A 36-year-old woman presented with increased intracranial pressure and cerebellar signs without hypoglossal nerve palsy. Magnetic resonance imaging showed a predominantly cystic mass with a fluid-fluid level in the foramen magnum region extending into the hypoglossal canal. The intracranial tumor was largely removed via a midline suboccipital subtonsillar approach, leaving only a tiny residue in the hypoglossal canal. Histology confirmed a schwannoma with relative hypervascularity. Twenty months later, the tumor recurred and presented as a multicystic dumbbell-shaped lesion, extending intra- and extracranially through the enlarged hypoglossal canal. A complete resection of the intracranial and intracanalicular parts of the tumor was achieved with a small extracranial remnant treated by radiosurgery. Histology revealed a focal increased K(i)67 proliferative index. In this report, we discuss the possible reasons for the absence of hypoglossal nerve palsy and the potential mechanism of the formation of the fluid-fluid level, and we consider the treatment of this lesion 9).

1)

Tatagiba M, Koerbel A, Roser F. The midline suboccipital subtonsillar approach to the hypoglossal canal: surgical anatomy and clinical application. Acta Neurochir (Wien). 2006 Sep;148(9):965-9. Epub 2006 Jul 5. Review. PubMed PMID: 16817032.
2)

Herlan S, Roser F, Ebner FH, Tatagiba M. The midline suboccipital subtonsillar approach to the cerebellomedullary cistern: how I do it. Acta Neurochir (Wien). 2017 Jul 22. doi: 10.1007/s00701-017-3270-5. [Epub ahead of print] PubMed PMID: 28735380.
3) , 4)

Herlan S, Ebner FH, Nitz A, Hirt B, Tatagiba M, Roser F. The midline suboccipital subtonsillar approach to the cerebellomedullary cistern and its structures: anatomical considerations, surgical technique and clinical application. Clin Neurol Neurosurg. 2014 Oct;125:98-105. doi: 10.1016/j.clineuro.2014.07.029. Epub 2014 Jul 27. PubMed PMID: 25113380.
5)

Roser F, Ebner FH, Schuhmann MU, Tatagiba M. Glossopharyngeal neuralgia treated with an endoscopic assisted midline suboccipital subtonsillar approach: technical note. J Neurol Surg A Cent Eur Neurosurg. 2013 Sep;74(5):318-20. doi: 10.1055/s-0032-1327447. Epub 2012 Oct 5. PubMed PMID: 23042141.
6)

Dogan M, Dogan DG. Foramen magnum meningioma: The midline suboccipital subtonsillar approach. Clin Neurol Neurosurg. 2016 Aug;147:116. doi: 10.1016/j.clineuro.2016.05.025. Epub 2016 Jun 6. PubMed PMID: 27321572.
7)

Dobrowolski S, Ebner F, Lepski G, Tatagiba M. Foramen magnum meningioma: The midline suboccipital subtonsillar approach. Clin Neurol Neurosurg. 2016 Jun;145:28-34. doi: 10.1016/j.clineuro.2016.02.027. Epub 2016 Apr 2. PubMed PMID: 27064859.
8)

Rabadán AT, Campero A, Hernández D. Surgical Application of the Suboccipital Subtonsillar Approach to Reach the Inferior Half of Medulla Oblongata Tumors in Adult Patients. Front Surg. 2016 Jan 13;2:72. doi: 10.3389/fsurg.2015.00072. eCollection 2015. PubMed PMID: 26793713; PubMed Central PMCID: PMC4710703.
9)

Li WC, Hong XY, Wang LP, Ge PF, Fu SL, Luo YN. Large cystic hypoglossal schwannoma with fluid-fluid level: a case report. Skull Base. 2010 May;20(3):193-7. doi: 10.1055/s-0029-1246219. PubMed PMID: 21318038; PubMed Central PMCID: PMC3037104.

11TH Hands-on Course on Neurosurgical Approaches

VALENCIA 2017
OCTOBER, 24th-27th
Inscripción on-line:
www.neurosurgeryvalencia.com

DIRECTOR DEL CURSO
José M. González Darder

GUEST FACULTY
Radim Lipina

FACULTY
José Hinojosa Mena-Bernal
Tomáš Hrbáč
Vicent Quilis-Quesada
Luis Real Peña
Javier Sendra Tello
Fernando Talamantes

Esteban Vega Torres

DESCARGAR PROGRAMA

Curso auspiciado por la Sociedad Española de Neurocirugía (SENEC)

Solicitado reconocimiento como “Actividad de Interés Sanitario” por la Consellería de Sanitat Universal y Salut Pública

ORGANIZA

Departamento de Neurocirugía
Hospital Clínico de Valencia

SEDE

PATROCINA

Update: Subtemporal approach

It is one of the surgical routes used to reach the interpeduncular fossa, offers a good access to the medial temporal region.

The subtemporal approach avoids neocortical transgression and injury to the optic radiations. 1) 2)

Indications

The subtemporal approach is historically known as the standard approach for the treatment of tumoral, vascular and inflammatory lesions of the middle cranial fossa, the tentorium, the anterior and middle tentorial incisura, the upper-third of the clivus and the petroclival region. This approach had been recognized universally for many years as the best way to treat basilar artery (BA) apex, P1 and P2 posterior cerebral artery (PCA) and superior cerebellar artery aneurysms until the introduction of the pterional approach in 1976 by Yasargil et al. 3).

Drawbacks

Access to the posteromedial temporal region needs the retraction of the temporal lobe 4) , with a risk of vein of Labbé sacrifice.

Because of the inclination of the tentorium, temporal lobe retraction increases with a more posterior location of the lesion 5).

A more posterior-oriented supratentorial-infra- occipital variation of the subtemporal approach has been described, which is performed to effectively approach and resect epileptogenic lesions in PMT regions 6) 7).

Keyhole subtemporal approaches and zygomatic arch osteotomy have been proposed in an effort to decrease the amount of temporal lobe retraction.

A keyhole and a classic subtemporal craniotomy were executed in 4 fresh-frozen silicone-injected cadaver heads. The target was defined as the area bordered by the superior cerebellar artery, the anterior clinoid process, supraclinoid internal carotid artery, and the posterior cerebral artery. Once the target was fully visualized, Ercan et al. evaluated the amount of temporal lobe retraction by measuring the distance between the base of the middle fossa and the temporal lobe. In addition, the volume of the surgical and anatomical corridors was assessed as well as the surgical maneuverability using navigation and 3D moldings. The same evaluation was conducted after a zygomatic osteotomy was added to the two approaches.

Temporal lobe retraction was the same in the two approaches evaluated while the surgical corridor and the maneuverability were all greater in the classic subtemporal approach.

The zygomatic arch osteotomy facilitates the maneuverability and the surgical volume in both approaches, but the temporal lobe retraction benefit is confined to the lateral part of the middle fossa skull base and does not result in the retraction necessary to expose the selected target 8).


With the help of an endoscope, Sun et al exposed the internal auditory canal and cerebellopontine through a translabyrinthine approach and the inferior colliculus through a keyhole subtemporal approach. This double approach can be combined to expose the internal auditory canal and cerebellopontine angle and inferior colliculus satisfactorily in the same surgical setting. This combined approach can avoid retraction of the cerebellum and reduce serious adverse events and complications 9).

As a minimally invasive approach, this can be considered an effective method for removal of vestibular schwannoma and auditory midbrain implantation in the same surgical setting, while avoiding retraction of the cerebellum and serious adverse events and complications.

see Subtemporal medial transpetrous approach.

see Subtemporal transtentorial approach.

Subtemporal Approach for AICA Aneurysm Clipping

The subtemporal approach represents a feasible approach for retrochiasmatic craniopharyngiomas when gross total resection is not mandatory. It provides rapid access to the tumor and a caudal-to-cranial visualization that promotes minimal manipulation of critical neurovascular structures, particularly the optic apparatus 10).

Subtemporal approach for distal basilar occlusion for giant aneurysm

1) , 7)

Smith KA, Spetzler RF: Supratentorial-infraoccipital approach for posteromedial temporal lobe lesions. J Neurosurg 82:940–944, 1995
2)

Tubbs RS, Oakes WJ: Relationships of the cisternal segment of the trochlear nerve. J Neurosurg 89:1015–1019, 1998
3)

Yasargil MG, Antic J, Laciga R, Jain KK, Hodosh RM, Smith RD. Microsurgical pterional approach to aneurysms of the basilar bifurcation. Surg Neurol. 1976 Aug;6(2):83-91. PubMed PMID: 951657.
4)

Olivier A: Temporal resections in the surgical treatment of epilepsy. Epilepsy Res Suppl 5:175–188, 1992
5)

Campero A, Tróccoli G, Martins C, Fernandez-Miranda JC, Yasuda A, Rhoton AL Jr: Microsurgical approaches to the medial temporal region: an anatomical study. Neurosurgery 59 (4 Suppl 2):ONS279–ONS308, 2006
6)

Russell SM, Kelly PJ: Volumetric stereotaxy and the supra- tentorial occipitosubtemporal approach in the resection of posterior hippocampus and parahippocampal gyrus lesions. Neurosurgery 50:978–988, 2002
8)

Ercan S, Scerrati A, Wu P, Zhang J, Ammirati M. Is less always better? Keyhole and standard subtemporal approaches: evaluation of temporal lobe retraction and surgical volume with and without zygomatic osteotomy in a cadaveric model. J Neurosurg. 2017 Jul;127(1):157-164. doi: 10.3171/2016.6.JNS16663. Epub 2016 Sep 16. PubMed PMID: 27636184.
9)

Sun JQ, Han DM, Li YX, Gong SS, Zan HR, Wang T. Combined endoscope-assisted translabyrinthine subtemporal keyhole approach for vestibular Schwannoma and auditory midbrain implantation: Cadaveric study. Acta Otolaryngol. 2010 Oct;130(10):1125-9. doi: 10.3109/00016481003699674. PubMed PMID: 20367538.
10)

Wong RH, De Los Reyes K, Alikhani P, Sivaknathan S, van Gompel J, van Loveren H, Agazzi S. The Subtemporal Approach to Retroinfundibular Craniopharyngiomas: A New Look at an Old Approach. Neurosurgery. 2015 Aug 18. [Epub ahead of print] PubMed PMID: 26287553.

Update: NeuroVR

CAE Healthcare NeuroVR Surgical Simulator from CAE Healthcare on Vimeo.

https://caehealthcare.com/surgical-simulation/neurovr


Simulation technology identifies neurosurgical residency applicants with differing levels of technical ability. These results provide information for studies being developed for longitudinal studies on the acquisition, development, and maintenance of psychomotor skills. Technical abilities customized training programs that maximize individual resident bimanual psychomotor training dependant on continuously updated and validated metrics from virtual reality simulation studies should be explored 1).


“Experts” display significantly more automaticity when operating on identical simulated tumors separated by a series of different tumors using the NeuroVR platform. These results support the Fitts and Posner model of motor learning and are consistent with the concept that automaticity improves after completing residency training. The potential educational application of the findings is outlined related to neurosurgical resident training 2).


Ultrasonic aspirator force application was continually assessed during resection of simulated brain tumors by neurosurgeons, residents, and medical students. The participants performed simulated resections of 18 simulated brain tumors with different visual and haptic characteristics. The raw data, namely, coordinates of the instrument tip as well as contact force values, were collected by the simulator. To provide a visual and qualitative spatial analysis of forces, the authors created a graph, called a force pyramid, representing force sum along the z-coordinate for different xy coordinates of the tool tip.

Sixteen neurosurgeons, 15 residents, and 84 medical students participated in the study. Neurosurgeon, resident and medical student groups displayed easily distinguishable 3D “force pyramid fingerprints.” Neurosurgeons had the lowest force pyramids, indicating application of the lowest forces, followed by resident and medical student groups. Handedness, ergonomics, and visual and haptic tumor characteristics resulted in distinct well-defined 3D force pyramid patterns.

Force pyramid fingerprints provide 3D spatial assessment displays of instrument force application during simulated tumor resection. Neurosurgeon force utilization and ergonomic data form a basis for understanding and modulating resident force application and improving patient safety during tumor resection 3).

1)

Winkler-Schwartz A, Bajunaid K, Mullah MA, Marwa I, Alotaibi FE, Fares J, Baggiani M, Azarnoush H, Zharni GA, Christie S, Sabbagh AJ, Werthner P, Del Maestro RF. Bimanual Psychomotor Performance in Neurosurgical Resident Applicants Assessed Using NeuroTouch, a Virtual Reality Simulator. J Surg Educ. 2016 Nov – Dec;73(6):942-953. doi: 10.1016/j.jsurg.2016.04.013. Epub 2016 Jul 7. PubMed PMID: 27395397.
2)

Bugdadi A, Sawaya R, Olwi D, Al-Zhrani G, Azarnoush H, Sabbagh AJ, Alsideiri G, Bajunaid K, Alotaibi FE, Winkler-Schwartz A, Del Maestro R. Automaticity of Force Application During Simulated Brain Tumor Resection: Testing the Fitts and Posner Model. J Surg Educ. 2017 Jul 3. pii: S1931-7204(17)30114-9. doi: 10.1016/j.jsurg.2017.06.018. [Epub ahead of print] PubMed PMID: 28684100.
3)

Azarnoush H, Siar S, Sawaya R, Zhrani GA, Winkler-Schwartz A, Alotaibi FE, Bugdadi A, Bajunaid K, Marwa I, Sabbagh AJ, Del Maestro RF. The force pyramid: a spatial analysis of force application during virtual reality brain tumor resection. J Neurosurg. 2017 Jul;127(1):171-181. doi: 10.3171/2016.7.JNS16322. Epub 2016 Sep 30. PubMed PMID: 27689458.

Update: Navigated transcranial magnetic stimulation for language mapping

In respect to language mapping with repetitive nTMS, literature reports have yielded variable results, and it is currently not routinely performed for presurgical language localization.

The expert panel recommends nTMS motor mapping in routine neurosurgical practice, as it has a sufficient level of evidence supporting its reliability. The panel recommends that nTMS language mapping be used in the framework of clinical studies to continue refinement of its protocol and increase reliability 1).

Although language mapping by repetitive navigated transcranial magnetic stimulation (rTMS) gains importance in neuropsychological research and clinical utility, neuroscientists still use different mapping protocols including different stimulation frequencies.

The stimulation frequency has to be adapted to the aim of the rTMS language investigation 2).

2015

Ille et al. performed multimodal language mapping in 35 patients with left-sided perisylvian lesions by using rTMS, fMRI, and DCS. The rTMS mappings were conducted with a picture-to-trigger interval (PTI, time between stimulus presentation and stimulation onset) of either 0 or 300 msec. The error rates (ERs; that is, the number of errors per number of stimulations) were calculated for each region of the cortical parcellation system (CPS). Subsequently, the rTMS mappings were analyzed through different error rate thresholds (ERT; that is, the ER at which a CPS region was defined as language positive in terms of rTMS), and the 2-out-of-3 rule (a stimulation site was defined as language positive in terms of rTMS if at least 2 out of 3 stimulations caused an error). As a second step, the authors combined the results of fMRI and rTMS in a predefined protocol of combined noninvasive mapping. To validate this noninvasive protocol, they correlated its results to DCS during awake surgery.

The analysis by different rTMS ERTs obtained the highest correlation regarding sensitivity and a low rate of false positives for the ERTs of 15%, 20%, 25%, and the 2-out-of-3 rule. However, when comparing the combined fMRI and rTMS results with DCS, the authors observed an overall specificity of 83%, a positive predictive value of 51%, a sensitivity of 98%, and a negative predictive value of 95%.

In comparison with fMRI, rTMS is a more sensitive but less specific tool for preoperative language mapping than DCS. Moreover, rTMS is most reliable when using ERTs of 15%, 20%, 25%, or the 2-out-of-3 rule and a PTI of 0 msec. Furthermore, the combination of fMRI and rTMS leads to a higher correlation to DCS than both techniques alone, and the presented protocols for combined noninvasive language mapping might play a supportive role in the language-mapping assessment prior to the gold-standard intraoperative DCS 3).

2013

nTMS and MEGI were performed on 12 subjects. nTMS yielded 21 positive language disruption sites (11 speech arrest, 5 anomia, and 5 other) while DCS yielded 10 positive sites (2 speech arrest, 5 anomia, and 3 other). MEGI isolated 32 sites of peak activation with language tasks. Positive language sites were most commonly found in the pars opercularis for all three modalities. In 9 instances the positive DCS site corresponded to a positive nTMS site, while in 1 instance it did not. In 4 instances, a positive nTMS site corresponded to a negative DCS site, while 169 instances of negative nTMS and DCS were recorded. The sensitivity of nTMS was therefore 90%, specificity was 98%, the positive predictive value was 69% and the negative predictive value was 99% as compared with intraoperative DCS. MEGI language sites for verb generation and object naming correlated with nTMS sites in 5 subjects, and with DCS sites in 2 subjects. CONCLUSION: Maps of language function generated with nTMS correlate well with those generated by DCS. Negative nTMS mapping also correlates with negative DCS mapping. In our study, MEGI lacks the same level of correlation with intraoperative mapping; nevertheless it provides useful adjunct information in some cases. nTMS may offer a lesion-based method for noninvasively interrogating language pathways and be valuable in managing patients with peri-eloquent lesions 4).


Twenty patients with tumors in or close to left-sided language eloquent regions were examined by repetitive nTMS before surgery. During awake surgery, language-eloquent cortex was identified by DCS. nTMS results were compared for accuracy and reliability with regard to DCS by projecting both results into the cortical parcellation system.

Presurgical nTMS maps showed an overall sensitivity of 90.2%, specificity of 23.8%, positive predictive value of 35.6%, and negative predictive value of 83.9% compared with DCS. For the anatomic Broca’s area, the corresponding values were a sensitivity of 100%, specificity of 13.0%, positive predictive value of 56.5%, and negative predictive value of 100%, respectively.

Good overall correlation between repetitive nTMS and DCS was observed, particularly with regard to negatively mapped regions. Noninvasive inhibition mapping with nTMS is evolving as a valuable tool for preoperative mapping of language areas. Yet its low specificity in posterior language areas in the current study necessitates further research to refine the methodology 5).

1)

Krieg SM, Lioumis P, Mäkelä JP, Wilenius J, Karhu J, Hannula H, Savolainen P, Lucas CW, Seidel K, Laakso A, Islam M, Vaalto S, Lehtinen H, Vitikainen AM, Tarapore PE, Picht T. Protocol for motor and language mapping by navigated TMS in patients and healthy volunteers; workshop report. Acta Neurochir (Wien). 2017 Jul;159(7):1187-1195. doi: 10.1007/s00701-017-3187-z. Epub 2017 Apr 29. Review. PubMed PMID: 28456870.
2)

Hauck T, Tanigawa N, Probst M, Wohlschlaeger A, Ille S, Sollmann N, Maurer S, Zimmer C, Ringel F, Meyer B, Krieg SM. Stimulation frequency determines the distribution of language positive cortical regions during navigated transcranial magnetic brain stimulation. BMC Neurosci. 2015 Feb 18;16(1):5. PubMed PMID: 25880838.
3)

Ille S, Sollmann N, Hauck T, Maurer S, Tanigawa N, Obermueller T, Negwer C, Droese D, Zimmer C, Meyer B, Ringel F, Krieg SM. Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation. J Neurosurg. 2015 Jul;123(1):212-25. doi: 10.3171/2014.9.JNS14929. Epub 2015 Mar 6. PubMed PMID: 25748306.
4)

Tarapore PE, Findlay AM, Honma SM, Mizuiri D, Houde JF, Berger MS, Nagarajan SS. Language mapping with navigated repetitive TMS: proof of technique and validation. Neuroimage. 2013 Nov 15;82:260-72. doi: 10.1016/j.neuroimage.2013.05.018. Epub 2013 May 20. PubMed PMID: 23702420; PubMed Central PMCID: PMC3759608.
5)

Picht T, Krieg SM, Sollmann N, Rösler J, Niraula B, Neuvonen T, Savolainen P, Lioumis P, Mäkelä JP, Deletis V, Meyer B, Vajkoczy P, Ringel F. A comparison of language mapping by preoperative navigated transcranial magnetic stimulation and direct cortical stimulation during awake surgery. Neurosurgery. 2013 May;72(5):808-19. doi: 10.1227/NEU.0b013e3182889e01. PubMed PMID: 23385773.