====== Localization ======

{{ ::localization.jpg?300|}}

===== 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 [[tumor]]s 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
((Grant, Francis C.: Ventriculography, Arch. Neurol. and Fsychiat, 14:513 September, 1925.))
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
((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.
)).
----
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
((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.
)).

===== Modern neurosurgery =====

The basic principle of modern [[neurosurgery]] is precise lesion localization that results in a minimally invasive approach
((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.))
((Ganslandt O., Behari S., Gralla J., Fahlbusch R., Nimsky C. Neuronavigation: Concept, techniques and applications. Neurol. India. 2002;50:244–255.))
((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.))
((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.)).

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

In this sense, the use of [[surgical navigation system]]s is becoming an increasingly important part of planning and performing intracranial surgery
((Ganslandt O., Behari S., Gralla J., Fahlbusch R., Nimsky C. Neuronavigation: Concept, techniques and applications. Neurol. India. 2002;50:244–255.))
((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.))
((Schroeder H.W., Wagner W., Tschiltschke W., Gaab M.R. Frameless neuronavigation in intracranial endoscopic neurosurgery. J. Neurosurg. 2001;94:72–79.)).

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 [[neuronavigation]]al [[localization]] for [[posterior fossa lesion]]s when the [[operation]] is performed with the [[patient]] in the [[prone]] [[position]].

Ten patients with [[posterior fossa tumor]]s 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 [[neuronavigation]]al 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
((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.
)).

===== References =====