High risk low grade glioma

July 20, 2019

High risk low grade glioma

On the basis of two randomized studies from the European Organization for Research and Treatment of Cancer (EORTC) ¹⁾ ²⁾. and a synthesis by Pignatti et al, ³⁾ high-risk low grade glioma LGG were defined by any three of five characteristics, including astrocytic histology, large tumor size (> 6 cm in diameter), midline tumor involvement, neurologic deficits ascribed to the tumor and not to surgery, and age older than 40 years.

This definition differ significantly from the definition used in the RTOG 9802 trial⁴⁾.

Radiation Therapy Oncology Group (RTOG) 9802 has established postoperative radiation therapy (RT) and chemotherapy sequentially as the new standard of care for patients with high-risk low-grade glioma (LGG) meeting trial criteria. Although this trial investigated sequential chemoradiation therapy (sCRT) with RT followed by chemotherapy, it is unknown whether concurrent chemoradiation therapy (cCRT) may offer advantages over sCRT.

The National Cancer Database (NCDB) was queried for newly diagnosed World Health Organization (WHO) grade II glioma. Patients with unknown surgery, RT, or chemotherapy status were excluded, along with patients below 40 years old who underwent gross total resection to coincide with RTOG 9802 exclusion criteria. The χ, the Fisher exact, or Wilcoxon rank-sum tests evaluated differences in characteristics between groups. Kaplan-Meier analysis was used to evaluate overall survival (OS) between groups (sCRT vs. cCRT). Cox proportional hazards modeling determined variables associated with OS.

In total, 496 patients were analyzed (n=416 [83.9%] cCRT, n=80 [16.1%] sCRT). Sequencing or concurrency of therapy did not independently influence survival on univariable/multivariable analysis. Factors associated with worse OS on multivariable analysis included advanced age (P<0.001), whereas mixed glioma (P=0.017) and oligodendroglioma (P=0.005) were associated with better OS than astrocytoma histologies.

This is the only analysis of which we are aware of cCRT versus sCRT for LGG. There is no evidence that cCRT improves outcomes over sCRT ⁵⁾.

The level of evidence for adjuvant treatment of diffuse WHO grade II glioma (low-grade glioma, LGG) is low. In so-called “high risk low grade glioma” patients most centers currently apply an early aggressive adjuvant therapy after surgery. The aim of a assessment was to compare progression free survival (PFS) and overall survival (OS) in patients receiving radiation therapy (RT) alone, chemotherapy (CT) alone, or a combined/consecutive RT+CT, with patients receiving no primary adjuvant treatment after surgery.

Based on a retrospective multicenter cohort of 288 patients (≥ 18 years old) with diffuse WHO grade II gliomas, a subgroup analysis of patients with confirmed isocitrate dehydrogenase mutation was performed. The influence of primary adjuvant treatment after surgery on PFS and OS was assessed using Kaplan-Meier estimates and multivariate Cox regression models, including age (≥ 40 years), complete tumor resection (CTR), recurrent surgery, and astrocytoma versus oligodendroglioma.

One hundred forty-four patients matched the inclusion criteria. Forty patients (27.8%) received adjuvant treatment. The median follow-up duration was 6 years (95% confidence interval 4.8-6.3 years). The median overall PFS was 3.9 years and OS 16.1 years. PFS and OS were significantly longer without adjuvant treatment (p = 0.003). A significant difference in favor of no adjuvant therapy was observed even in high-risk patients (age ≥ 40 years or residual tumor, 3.9 vs 3.1 years, p = 0.025). In the multivariate model (controlled for age, CTR, oligodendroglial diagnosis, and recurrent surgery), patients who received no adjuvant therapy showed a significantly positive influence on PFS (p = 0.030) and OS (p = 0.009) compared to any other adjuvant treatment regimen. This effect was most pronounced if RT+CT was applied (p = 0.004, hazard ratio [HR] 2.7 for PFS, and p = 0.001, HR 20.2 for OS). CTR was independently associated with longer PFS (p = 0.019). Age ≥ 40 years, histopathological diagnosis, and recurrence did not achieve statistical significance.

In this series of IDH-mutated LGGs, adjuvant treatment with RT, CT with temozolomide (TMZ), or the combination of both showed no significant advantage in terms of PFS and OS. Even in high-risk patients, the authors observed a similar significantly negative impact of adjuvant treatment on PFS and OS. These results underscore the importance of a CTR in LGG. Whether patients ≥ 40 years old should receive adjuvant treatment despite a CTR should be a matter of debate. A potential tumor dedifferentiation by administration of early TMZ, RT, or RT+CT in IDH-mutated LGG should be considered. However, these data are limited by the retrospective study design and the potentially heterogeneous indication for adjuvant treatment ⁶⁾.

There was no significant difference in progression-free survival in patients with low-grade glioma when treated with either radiotherapy alone or temozolomide chemotherapy alone. Further data maturation is needed for overall survival analyses and evaluation of the full predictive effects of different molecular subtypes for future individualised treatment choices.

The effect of temozolomide chemotherapy or radiotherapy on HRQOL or global cognitive functioning did not differ in patients with low grade glioma. These results do not support the choice of temozolomide alone over radiotherapy alone in patients with high-risk low-grade glioma ⁷⁾.

References

¹⁾

van den Bent MJ, Afra D, de Witte O, et al. (2005) Long term efficacy of early versus delayed radiotherapy for low-grade astrocytoma and oligodendroglioma in adults: The EORTC 22845 randomised trial. Lancet 366:985–990.

²⁾

Karim AB, Afra D, Cornu P, et al. (2002) Randomized trial on the efficacy of radiotherapy for cerebral low-grade glioma in the adult: European Organization for Research and Treatment of Cancer Study 22845 with the Medical Research Council Study BRO4—An interim analysis. Int J Radiat Oncol Biol Phys 52:316–324.

³⁾

Pignatti F, van den Bent M, Curran D, et al. (2002) Prognostic factors for survival in adult patients with cerebral low-grade glioma. J Clin Oncol 20:2076–2084.

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Chamberlain MC. Does RTOG 9802 change practice with respect to newly diagnosed low-grade glioma? J Clin Oncol. 2013 Feb 10;31(5):652-3. doi: 10.1200/JCO.2012.46.7969. Epub 2013 Jan 7. PubMed PMID: 23295807.

⁵⁾

Ryckman JM, Appiah AK, Lyden E, Verma V, Zhang C. Concurrent Versus Sequential Chemoradiation for Low-grade Gliomas Meeting RTOG 9802 Criteria. Am J Clin Oncol. 2019 Feb 12. doi: 10.1097/COC.0000000000000519. [Epub ahead of print] PubMed PMID: 30768441.

⁶⁾

Paľa A, Coburger J, Scherer M, Ahmeti H, Roder C, Gessler F, Jungk C, Scheuerle A, Senft C, Tatagiba M, Synowitz M, Wirtz CR, Schmitz B, Unterberg AW. To treat or not to treat? A retrospective multicenter assessment of survival in patients with IDH-mutant low-grade glioma based on adjuvant treatment. J Neurosurg. 2019 Jul 19:1-8. doi: 10.3171/2019.4.JNS183395. [Epub ahead of print] PubMed PMID: 31323633.

⁷⁾

Reijneveld JC, Taphoorn MJ, Coens C, Bromberg JE, Mason WP, Hoang-Xuan K, Ryan G, Hassel MB, Enting RH, Brandes AA, Wick A, Chinot O, Reni M, Kantor G, Thiessen B, Klein M, Verger E, Borchers C, Hau P, Back M, Smits A, Golfinopoulos V, Gorlia T, Bottomley A, Stupp R, Baumert BG. Health-related quality of life in patients with high-risk low-grade glioma (EORTC 22033-26033): a randomised, open-label, phase 3 intergroup study. Lancet Oncol. 2016 Nov;17(11):1533-1542. doi: 10.1016/S1470-2045(16)30305-9. Epub 2016 Sep 27. PubMed PMID: 27686943.

APOEε4

July 20, 2019

APOEε4

Apolipoprotein E (ApoE) is a glycoprotein with a major role in brain lipoprotein metabolism. It has three isoforms encoded by distinct alleles: APOEε2, APOEε3 and APOEε4.

The presence of this genotype portends a worse prognosis following traumatic brain injury ¹⁾

Furthermore, the incidence of severe traumatic brain injury in individuals with the apoE-4 allele greatly exceeds the rate of the allele in the general population ²⁾. This allele is also a risk factor for Alzheimer’s disease ³⁾ ⁴⁾ ⁵⁾ as well as for chronic traumatic encephalopathy.

Among patients with lobar hemorrhage, those with the apoE ε4 allele typically have their first hemorrhage >5 yrs earlier than noncarriers (73 ± 8 yrs vs./ 79 ± 7 yrs) ⁶⁾.

Findings suggested that APOEε4 allele is a risk factor to brain function aggravation in the early stage of aneurysmal subarachnoid hemorrhage, and it may contribute to early brain injury after SAH ⁷⁾.

Finding also suggests that the patients with APOEε4 allele predispose to cerebral vasospasm after spontaneous SAH ⁸⁾.

The presence of APOE ε4, an elevated international normalized ratio, and a higher glucose level (≥ 10 mmol/L) are predictors of progressive traumatic intracerebral hemorrhage. Additionally, APOE ε4 is not associated with traumatic coagulopathy and patient outcome ⁹⁾.

APOE ε4 and ε2 alleles appear to affect lobar ICH risk variably by race/ethnicity, associations that are confirmed in white individuals but can be shown in Hispanic individuals only when the excess burden of hypertension is propensity score-matched; further studies are needed to explore the interactions between APOE alleles and environmental exposures that vary by race/ethnicity in representative populations at risk for ICH ¹⁰⁾.

APOEε4 may induce cerebral perfusion impairment in the early phase, contributing to early brain injury (EBI) following aneurysmal subarachnoid hemorrhage (aSAH), and assessment of APOE genotypes could serve as a useful tool in the prognostic evaluation and therapeutic management of aSAH ¹¹⁾.

The APOΕε4 polymorphism was analysed in 147 patients with aSAH. Allele and genotype frequencies were compared to those found in a gender- and area-matched control group of healthy individuals (n = 211). Early cerebral vasospasm (CVS) was identified and treated according to neurointensive care unit (NICU) guidelines. Neurological deficit(s) at admittance and at 1-year follow-up visit was recorded. Neurological outcome was assessed by the National Institute of Health Stroke Scale, Barthel Index and the Extended Glasgow Outcome Scale.

APOEε4 and non-APOEε4 allele frequencies were similar in aSAH patients and healthy individuals. The presence of APOEε4 was not associated with the development of early CVS. We could not find an influence of the APOE polymorphism on 1-year neurological outcome between groups. Subgroup analyses of patients treated with surgical clipping vs endovascular coiling did not reveal any associations.

The APOEε4 polymorphism has no major influence on risk of aSAH, the occurrence of CVS or long-term neurological outcome after aSAH ¹²⁾.

References

¹⁾

Friedman G,Froom P,Sazbon L,et al. Apolipoprotein E-e4 Genotype Predicts a Poor Outcome in Survivors of Traumatic Injury. Neurology. 1999; 52:244– 248

²⁾

Nicoll JAR, Roberts GW, Graham DI. Apolipoprotein Ee4 Allele is Associated with Deposition of Amyloid ß-Protein Following Head Injury. Nature Med. 1995; 1:135–137

³⁾

Mayeux R, Ottman R, Tang MX, et al. Genetic Susceptibility and Head Injury as Risk Factors for Alz- heimer’s Disease Among Community-Dwelling Elderly Persons and Their First Degree Relatives. Ann Neurol. 1993; 33:494–501

⁴⁾

Roberts GW, Gentleman SM, Lynch A, et al. ß Amyloid Protein Deposition in the Brain After Severe Head Injury: Implications for the Pathogenesis of Alzheimer’s Disease. J Neurol Neurosurg Psychiatry. 1994; 57:419–425

⁵⁾

Mayeux R, Ottman R, Maestre G, et al. Synergistic Effects of Traumatic Head Injury and Apolipoprotein-e4 in Patients with Alzheimer’s Disease. Neurology. 1995; 45:555–557

⁶⁾

Greenberg SM, Rebeck GW, Vonsattel JPV, et al. Apolipoprotein E e4 and Cerebral Hemorrhage Associated with Amyloid Angiopathy. Ann Neurol. 1995; 38:254–259

⁷⁾

Lin B, Dan W, Jiang L, Yin XH, Wu HT, Sun XC. Association of APOE polymorphism with the change of brain function in the early stage of aneurysmal subarachnoid hemorrhage. Acta Neurochir Suppl. 2011;110(Pt 1):39-42. doi: 10.1007/978-3-7091-0353-1_7. PubMed PMID: 21116912.

⁸⁾

Wu HT, Zhang XD, Su H, Jiang Y, Zhou S, Sun XC. Association of apolipoprotein E polymorphisms with cerebral vasospasm after spontaneous subarachnoid hemorrhage. Acta Neurochir Suppl. 2011;110(Pt 1):141-4. doi: 10.1007/978-3-7091-0353-1_24. PubMed PMID: 21116929.

⁹⁾

Wan X, Gan C, You C, Fan T, Zhang S, Zhang H, Wang S, Shu K, Wang X, Lei T. Association of APOE ε4 with progressive hemorrhagic injury in patients with traumatic intracerebral hemorrhage. J Neurosurg. 2019 Jul 19:1-8. doi: 10.3171/2019.4.JNS183472. [Epub ahead of print] PubMed PMID: 31323634.

¹⁰⁾

Marini S, Crawford K, Morotti A, Lee MJ, Pezzini A, Moomaw CJ, Flaherty ML, Montaner J, Roquer J, Jimenez-Conde J, Giralt-Steinhauer E, Elosua R, Cuadrado-Godia E, Soriano-Tarraga C, Slowik A, Jagiella JM, Pera J, Urbanik A, Pichler A, Hansen BM, McCauley JL, Tirschwell DL, Selim M, Brown DL, Silliman SL, Worrall BB, Meschia JF, Kidwell CS, Testai FD, Kittner SJ, Schmidt H, Enzinger C, Deary IJ, Rannikmae K, Samarasekera N, Salman RA, Sudlow CL, Klijn CJM, van Nieuwenhuizen KM, Fernandez-Cadenas I, Delgado P, Norrving B, Lindgren A, Goldstein JN, Viswanathan A, Greenberg SM, Falcone GJ, Biffi A, Langefeld CD, Woo D, Rosand J, Anderson CD; International Stroke Genetics Consortium. Association of Apolipoprotein E With Intracerebral Hemorrhage Risk by Race/Ethnicity: A Meta-analysis. JAMA Neurol. 2019 Feb 6. doi: 10.1001/jamaneurol.2018.4519. [Epub ahead of print] PubMed PMID: 30726504.

¹¹⁾

Cheng C, Jiang L, Yang Y, Wu H, Huang Z, Sun X. Effect of APOE Gene Polymorphism on Early Cerebral Perfusion After Aneurysmal Subarachnoid Hemorrhage. Transl Stroke Res. 2015 Sep 14. [Epub ahead of print] PubMed PMID: 26370543.

¹²⁾

Csajbok LZ, Nylén K, Öst M, Blennow K, Zetterberg H, Nellgård P, Nellgård B. Apolipoprotein E polymorphism in aneurysmal subarachnoid haemorrhage in West Sweden. Acta Neurol Scand. 2015 Sep 16. doi: 10.1111/ane.12487. [Epub ahead of print] PubMed PMID: 26374096.

Localization

July 20, 2019

Localization

History

In the early days of neurosurgery the neurosurgeon was purely an operator acting under the guidance of the neurologist, who took the responsibility for the localization of the lesion and for the extent of the operative procedure.

The neurologist was at first almost entirely dependent on the history and the clinical findings in making his diagnosis and localization.

Valuable help came from the roentgen ray, and stereoscopic films of the skull X-rays.

Calcification in tumors was demonstrated quite frequently, and it was no longer difficult to determine whether the sella turcica shows pathological changes; the proliferation of the skull over a dural tumor may he an ingrowth of new bone, impossible to detect except with the roentgen ray; and localized erosions of the skull are frequently significant.

The most important advance came with the introduction of ventriculography or pneumoencephalography, by Walter Edward Dandy of Baltimore in 1918.

All tumors of the brain which give symptoms of pressure produce distortion or change in the size, shape or position of the ventricles. Dandy says that ten years ago less than 50 per cent of tumors of the brain could be exposed at operation; that now exposure is possible in 65 per cent because of better roentgen rays, better surgery and increased experience; and that all the remaining 35 per cent can be localized by the cerebral pneumogram. Have others been able to confirm this statement ? Grant ¹⁾ has collected 392 cases from the records of several neurosurgeons. The method was of value in 311 cases, but in 218 it confirmed a neurological diagnosis, or was unverified, or ruled out a suspected tumor. Ninety three tumors were localized and exposed at operation solely through the aid of the pneumogram. There were errors of technique in 10 per cent of the cases, and the mortality was 8 per cent. But the mortality of unlocalized tumors is 100 per cent, and of the ninety three tumors which could not have been localized otherwise, forty four were removed at operation. Grant’s figures substantiate Dandy’s claims, if we allow for inexperience with a new method. It is fair to conclude that, in the hands of those competent to do a cerebral pneumogram and to interpret the findings, it will reduce almost to the vanishing point the number of tumors of the brain which cannot be localized and exposed at operation ²⁾.

Subsequent advances in preoperative radiological localization included computed tomography (CT; 1971) and MRI (1977). Since then, other imaging modalities have been developed for clinical application although none as pivotal as CT and MRI. Intraoperative technological advances include the microscope, which has allowed precise surgery under magnification and improved lighting, and the endoscope, which has improved the treatment of hydrocephalus and allowed biopsy and complete resection of intraventricular, pituitary and pineal region tumors through a minimally invasive approach. Neuronavigation, intraoperative MRI, CT and ultrasound have increased the ability of the neurosurgeon to perform safe and maximal tumor resection. This may be facilitated by the use of fluorescing agents, which help define the tumor margin, and intraoperative neurophysiological monitoring, which helps identify and protect eloquent brain ³⁾.

Modern neurosurgery

The basic principle of modern neurosurgery is precise lesion localization that results in a minimally invasive approach ⁴⁾ ⁵⁾ ⁶⁾ ⁷⁾.

To achieve this goal, various methods have been developed to define the correct position of the craniotomy and are considered standard in today’s neurosurgical armamentarium ⁸⁾ ⁹⁾ ¹⁰⁾ ¹¹⁾ ¹²⁾ ¹³⁾.

In this sense, the use of surgical navigation systems is becoming an increasingly important part of planning and performing intracranial surgery ¹⁴⁾¹⁵⁾ ¹⁶⁾.

The aim of a study of Dho et al. from the Seoul National University Hospital, was to analyze the positional effect of MRI on the accuracy of neuronavigational localization for posterior fossa lesions when the operation is performed with the patient in the prone position.

Ten patients with posterior fossa tumors requiring surgery in the prone position were prospectively enrolled in the study. All patients underwent preoperative navigational MRI in both the supine and prone positions in a single session. Using simultaneous intraoperative registration of the supine and prone navigational MR images, the authors investigated the images’ accuracy, spatial deformity, and source of errors for PF lesions. Accuracy was determined in terms of differences in the ability of the supine and prone MR images to localize 64 test points in the PF by using a neuronavigation system. Spatial deformities were analyzed and visualized by in-house-developed software with a 3D reconstruction function and spatial calculation of the MRI data. To identify the source of differences, the authors investigated the accuracy of fiducial point localization in the supine and prone MR images after taking the surface anatomy and age factors into consideration.

Neuronavigational localization performed using prone MRI was more accurate for PF lesions than routine supine MRI prior to prone position surgery. Prone MRI more accurately localized 93.8% of the tested PF areas than supine MRI. The spatial deformities in the neuronavigation system calculated using the supine MRI tended to move in the posterior-superior direction from the actual anatomical landmarks. The average distance of the spatial differences between the prone and supine MR images was 6.3 mm. The spatial difference had a tendency to increase close to the midline. An older age (> 60 years) and fiducial markers adjacent to the cervical muscles were considered to contribute significantly to the source of differences in the positional effect of neuronavigation (p < 0.001 and p = 0.01, respectively).

This study demonstrated the superior accuracy of neuronavigational localization with prone-position MRI during prone-position surgery for PF lesions. The authors recommended that the scan position of the neuronavigational MRI be matched with the surgical position for more precise localization ¹⁷⁾.

References

¹⁾

Grant, Francis C.: Ventriculography, Arch. Neurol. and Fsychiat, 14:513 September, 1925.

²⁾

Towne EB. Neurosurgery: LOCALIZATION of Tumors of the Brain. Cal West Med. 1927 Mar;26(3):367-8. PubMed PMID: 18740275; PubMed Central PMCID: PMC1655419.

³⁾

Zebian B, Vergani F, Lavrador JP, Mukherjee S, Kitchen WJ, Stagno V, Chamilos C, Pettorini B, Mallucci C. Recent technological advances in pediatric brain tumor surgery. CNS Oncol. 2016 Dec 21. doi: 10.2217/cns-2016-0022. [Epub ahead of print] PubMed PMID: 28001090.

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Fischer G., Stadie A., Schwandt E., Gawehn J., Boor S., Marx J., Oertel J. Minimally invasive superficial temporal artery to middle cerebral artery bypass through a minicraniotomy: Benefit of three-dimensional virtual reality planning using magnetic resonance angiography. Neurosurg. Focus. 2009;26:E20.

⁵⁾ , ¹⁴⁾

Ganslandt O., Behari S., Gralla J., Fahlbusch R., Nimsky C. Neuronavigation: Concept, techniques and applications. Neurol. India. 2002;50:244–255.

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Recinos P.F., Raza S.M., Jallo G.I., Recinos V.R. Use of a minimally invasive tubular retraction system for deep-seated tumors in pediatric patients. J. Neurosurg. Pediatr. 2011;7:516–521.

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Stadie A.T., Kockro R.A., Reisch R., Tropine A., Boor S., Stoeter P., Perneczky A. Virtual reality system for planning minimally invasive neurosurgery. Technical. Note. J. Neurosurg. 2008;108:382–394.

⁸⁾ , ¹⁵⁾

Enchev Y.P., Popov R.V., Romansky K.V., Marinov M.B., Bussarsky V.A. Cranial neuronavigation-a step forward or a step aside in modern neurosurgery. Folia Med. 2008;50:5–10.

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Esposito V., Paolini S., Morace R., Colonnese C., Venditti E., Calistri V., Cantore G. Intraoperative localization of subcortical brain lesions. Acta Neurochir. 2008;150:537–542.

¹⁰⁾ , ¹⁶⁾

Schroeder H.W., Wagner W., Tschiltschke W., Gaab M.R. Frameless neuronavigation in intracranial endoscopic neurosurgery. J. Neurosurg. 2001;94:72–79.

¹¹⁾

Spivak C.J., Pirouzmand F. Comparison of the reliability of brain lesion localization when using traditional and stereotactic image-guided techniques: A prospective study. J. Neurosurg. 2005;103:424–427.

¹²⁾

Wagner W., Gaab M.R., Schroeder H.W., Tschiltschke W. Cranial neuronavigation in neurosurgery: Assessment of usefulness in relation to type and site of pathology in 284 patients. Minim. Inv. Neurosurg. 2000;43:124–131.

¹³⁾

Woerdeman P.A., Willems P.W., Noordmans H.J., Tulleken C.A., van der Sprenkel J.W. Application accuracy in frameless image-guided neurosurgery: A comparison study of three patient-to-image registration methods. J. Neurosurg. 2007;106:1012–1016.

¹⁷⁾

Dho YS, Kim YJ, Kim KG, Hwang SH, Kim KH, Kim JW, Kim YH, Choi SH, Park CK. Positional effect of preoperative neuronavigational magnetic resonance image on accuracy of posterior fossa lesion localization. J Neurosurg. 2019 Jul 19:1-10. doi: 10.3171/2019.4.JNS1989. [Epub ahead of print] PubMed PMID: 31323639.

Drilling

July 20, 2019

Drilling

Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of circular cross-section in solid materials. The drill bit is a rotary cutting tool, often multipoint. The bit is pressed against the workpiece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the workpiece, cutting off chips (swarf) from the hole as it is drilled.

Drilling of the clinoid process and tuberculum sellae, and optic canal unroofing are important surgical techniques, which may be performed relatively safely by a skilled neurosurgeon.

Skull base drilling is a necessary and important element of skull base surgery; however, drilling around vulnerable neurovascular structures has certain risks.

In a simulated surgical setting using human cadavers, a trial was conducted with 5 expert skull base surgeons from 3 different hospitals. They performed 10 AP approaches, using either the feedback method or standard image guidance. Damage to critical structures was assessed. Operative time, drill cavity sizes, and proximity of postoperative drill cavities to the cochlea and the internal acoustic meatus, were measured. Questionnaires were obtained postoperatively. Errors in the virtual drill cavities as compared with actual postoperative cavities were calculated. In a clinical setup, the method was used during AP.

Surgeons rated their intraoperative orientation significantly better with the feedback method compared with standard image guidance. During the cadaver trial, the cochlea was harmed on 1 occasion in the control group, while surgeons drilled closer to the cochlea and meatus without injuring them in the group using feedback. Virtual drilling under- and overestimation errors were 2.2 ± 0.2 and -3.0 ± 0.6 mm on average. The method functioned properly during the clinical setup.

The proposed feedback method improves orientation and surgical performance in an experimental setting. Errors in virtual drilling reflect spatial errors of the image guidance system. The feedback method is clinically practicable during anterior petrosectomy ¹⁾.

Manual cranial drilling is an old but in modern neurosurgery still established procedure which can be applied quickly and universally in emergencysituations. Electrical drilling requires more complex equipment and is usually reserved to the Operating Room (OR). It also seems desirable to apply an electrical drill for bedside usage but a suitable product does not exist so far.

An experimental study using a manually and an electrically driven skull drill included a total of 40 holes drilled into synthetic biomechanical sheets. Half of the holes were produced with a prototype electrical drilling machine of the company Kaiser Medical Technology and half of them with a traditional manual drill. Different drilling parameters such as the geometry of the borehole, the drilling forces and the drilling vibrations were captured during all experiments.

The electrical drilling needed higher vertical force by the operators and a longer time to penetrate the sheet. A reason was the relatively lower rotational speed provided by this particular drill. When drilling electrically the vibrations were substantially less which in turn led to a more precise shape of the holes (revealed by observation via a microscope).

The electrification of bedside drilling can in principle enable emergency craniostomies to be performed with greater ease and accuracy. The power of the electric drive, however, must be at least equivalent to the power of the traditional manual drill. Otherwise, the vertical forces exerted on the scull by the operator become inhibitive. The challenge is to combine cost-efficiency and re-sterilizability of an electrically driven drilling machine which at the same time is small and simple enough to qualify for emergency applications ²⁾.

see Transmeatal drilling

References

¹⁾

Voormolen EH, Diederen S, Cebula H, Woerdeman PA, Noordmans HJ, Viergever MA, Robe PA, Froelich S, Regli L, Berkelbach van der Sprenkel JW. Distance Control and Virtual Drilling Improves Anatomical Orientation During Anterior Petrosectomy. Oper Neurosurg (Hagerstown). 2019 Apr 24. pii: opz064. doi: 10.1093/ons/opz064. [Epub ahead of print] PubMed PMID: 31323686.

²⁾

Carolus A, Richter W, Fritzen CP, Schmieder K, Brenke C. Experimental investigations of a manually versus an electrically driven skull drill for bedside usage. PLoS One. 2019 Apr 18;14(4):e0215171. doi: 10.1371/journal.pone.0215171. eCollection 2019. PubMed PMID: 30998712.