Preoperative imaging features: Are they useful tools for predicting IDH1 mutation status in gliomas Grades II-IV?

Background: It is already known that gliomas biomolecular parameters have a reliable prognostic value. However, an invasive procedure is required to determine them. Our aim was to better understand the clinical characteristics of gliomas Grades II-IV and to assess the usefulness of imaging features in magnetic resonance imaging (MRI) to predict the isocitrate dehydrogenase one (IDH1) mutation. Methods: Preoperative MRI characteristics were retrospectively reviewed and molecular diagnosis of gliomas was tested in adult patients between 2014 and 2021 in two institutions. We applied a biological criterion to divide the brain in cerebral compartments. Results: A total of 108 patients met the inclusion criteria. Contrast enhancement (CE) in MRI was significantly associated with wild-type IDH1 (IDH1-Wt) (P < 0.00002). Furthermore, the positive predictive value of CE for IDH1-Wt was of 87.1%. On the other hand, the negative predictive value of non-CE for mutated IDH1 (IDH1-Mut) was of 52.6%; 60.2% of gliomas were located in the neocortical and 24.1% in the allocortical/mesocortical telencephalon. Considering gliomas Grades II-III, 66.7% of IDH1-Mut and 28.6% of IDH1-Wt gliomas were located in the neocortex, without statistical significance. Conclusion: Our research revealed that CE is useful for predicting IDH1-Wt in gliomas. On the contrary, nonCE is not useful for predicting IDH1-Mut gliomas. Thus, the traditional concept of associating non-CE MRI with a low-grade glioma should be reviewed, as it can lead to an underestimation of the potential aggressiveness of the tumor. If this association was validated with the future prospective studies, a noninvasive tool would be available for predicting gliomas IDH1 mutation status.

Algoritmo para el diagnóstico integrado de los gliomas 2021. Nuestra experiencia / Algorithm for the integrated diagnosis of gliomas 2021. Our experience

Resumen La aplicación de las diferentes técnicas moleculares para el diagnóstico de los gliomas según la clasificación de la OMS, sigue sin estar al alcance de todos en nuestro país. Nuestro objetivo fue describir el protocolo diagnóstico desarrollado en función de los recursos disponibles, conforme con la clasificación vigente (2021). También, describir el perfil epidemiológico de los gliomas diagnosticados entre 2018-2021 en el Instituto Roffo y contrastarlo con la literatura. Se evaluó la mutación en IDH1-R132H, ATRX, el estado del 1p19q, CDKN2A, EGFR y del p53. Se incluyeron 94 pacientes, 53.2% fueron masculinos, con una edad promedio de 50.9 años. El diagnóstico más frecuente fue el de GB IDH1-no mutado (63.8%). Considerando únicamente a los gliomas grado 2 y 3, el astrocitoma difuso IDH1-Mutado/ATRX-Mutado/p53-sobreexpresado, grado 2 (11.7%) fue el más frecuente. En cuanto a su localización, el 67% de los tumores se ubicaron en el telencéfalo neocortical: 24.5% del total en el lóbulo frontal. En el 95.7% de los casos se arribó a un diagnóstico integrado concluyente siguiendo el algoritmo propuesto. Las características epidemiológicas coinciden con lo publicado en la literatura. La biología molecular nos permitió diferenciar nítidamente enfermedades que suponíamos emparentadas desde un punto de vista histológico, pero que observando su historia natural, su genética y su respuesta a tratamientos instaurados eran tumores distintos, aunque todos fueran llamados "gliomas". Los estándares internacionales no conciben su diagnóstico sin la biología molecular. No es aceptable que se siga diagnosticando únicamente con estándares histológicos. El algoritmo propuesto podría ser una alternativa viable y confiable.

Abstract The utilization of the different molecular techniques for the diagnosis of gliomas according to the WHO classification is still not available to everyone in our country. Our objective was to describe the diagnostic algorithm devel oped based on available resources, in accordance with the current classification (2021). Also, to describe the epidemiological profile of gliomas diagnosed between 2018-2021 at the Roffo Institute and compare it with the international literature. IDH1-R132H and ATRX mutation, as well as 1p19q status, CDKN2A, EGFR, and p53 were evaluated. 94 patients were included, 53.2% were male, with a mean age of 50.9 years. The most frequent diagnosis was GB IDH1-wild type (63.8%). Considering only grade 2 and 3 gliomas, diffuse astrocytoma IDH1- Mutated / ATRX-Mutated / p53-overexpressed, grade 2 (11.7%) was the most frequent diagnosis. Regarding their location, 67% of the tumors were located in the neocortical telencephalon: 24.5% of the total in the frontal lobe. In 95.7% of cases, a conclusive integrated diagnosis was reached following the proposed algorithm. The epidemiological characteristics coincide with what has been published in the literature. Molecular biology allowed us to clearly differentiate pathologies that we assumed were related from a histological point of view, but which, observing their natural history, their genetics and their response to established treatments were different tumors, although they were all called "gliomas". International standards do not conceive CNS tumor diagnosis without molecular biology. It is not acceptable to continue to diagnose only with histological standards. The proposed algorithm could be a viable and reliable alternative.

[Algorithm for the integrated diagnosis of gliomas 2021. Our experience]. / Algoritmo para el diagnóstico integrado de los gliomas 2021. Nuestra experiencia.

The utilization of the different molecular techniques for the diagnosis of gliomas according to the WHO classification is still not available to everyone in our country. Our objective was to describe the diagnostic algorithm developed based on available resources, in accordance with the current classification (2021). Also, to describe the epidemiological profile of gliomas diagnosed between 2018-2021 at the Roffo Institute and compare it with the international literature. IDH1-R132H and ATRX mutation, as well as 1p19q status, CDKN2A, EGFR, and p53 were evaluated. 94 patients were included, 53.2% were male, with a mean age of 50.9 years. The most frequent diagnosis was GB IDH1-wild type (63.8%). Considering only grade 2 and 3 gliomas, diffuse astrocytoma IDH1-Mutated / ATRX-Mutated / p53-overexpressed, grade 2 (11.7%) was the most frequent diagnosis. Regarding their location, 67% of the tumors were located in the neocortical telencephalon: 24.5% of the total in the frontal lobe. In 95.7% of cases, a conclusive integrated diagnosis was reached following the proposed algorithm. The epidemiological characteristics coincide with what has been published in the literature. Molecular biology allowed us to clearly differentiate pathologies that we assumed were related from a histological point of view, but which, observing their natural history, their genetics and their response to established treatments were different tumors, although they were all called "gliomas". International standards do not conceive CNS tumor diagnosis without molecular biology. It is not acceptable to continue to diagnose only with histological standards. The proposed algorithm could be a viable and reliable alternative.

La aplicación de las diferentes técnicas moleculares para el diagnóstico de los gliomas según la clasificación de la OMS, sigue sin estar al alcance de todos en nuestro país. Nuestro objetivo fue describir el protocolo diagnóstico desarrollado en función de los recursos disponibles, conforme con la clasificación vigente (2021). También, describir el perfil epidemiológico de los gliomas diagnosticados entre 2018-2021 en el Instituto Roffo y contrastarlo con la literatura. Se evaluó la mutación en IDH1-R132H, ATRX, el estado del 1p19q, CDKN2A, EGFR y del p53. Se incluyeron 94 pacientes, 53.2% fueron masculinos, con una edad promedio de 50.9 años. El diagnóstico más frecuente fue el de GB IDH1-no mutado (63.8%). Considerando únicamente a los gliomas grado 2 y 3, el astrocitoma difuso IDH1-Mutado/ATRX-Mutado/p53-sobreexpresado, grado 2 (11.7%) fue el más frecuente. En cuanto a su localización, el 67% de los tumores se ubicaron en el telencéfalo neocortical: 24.5% del total en el lóbulo frontal. En el 95.7% de los casos se arribó a un diagnóstico integrado concluyente siguiendo el algoritmo propuesto. Las características epidemiológicas coinciden con lo publicado en la literatura. La biología molecular nos permitió diferenciar nítidamente enfermedades que suponíamos emparentadas desde un punto de vista histológico, pero que observando su historia natural, su genética y su respuesta a tratamientos instaurados eran tumores distintos, aunque todos fueran llamados "gliomas". Los estándares internacionales no conciben su diagnóstico sin la biología molecular. No es aceptable que se siga diagnosticando únicamente con estándares histológicos. El algoritmo propuesto podría ser una alternativa viable y confiable.

Navegando por la fisura silviana: anatomía microquirúrgica, neuroimágenes y técnica quirúrgica / Navigating the sylvian fissure: microsurgical anatomy, neuroimaging, and surgical technique

Objetivo: Describir la anatomía quirúrgica de la fisura silviana (FS) a través de disecciones cadavéricas y neuroimágenes; desarrollar su aplicación microquirúrgica. Materiales y métodos: Se estudiaron 10 hemisferios cadavéricos humanos fijados y un cráneo humano en seco, a través de la disección de fibras blancas y de la anatomía arterial y neural, utilizando un microscopio quirúrgico. Las arterias cerebrales fueron inyectadas con silicona coloreada. La anatomía quirúrgica fue correlacionada con la anatomía neuroimagenológica. Finalmente, se recolectó la experiencia microquirúrgica adquirida y, a su vez, la anatomía del Complejo Silviano, fue revisada. Resultados: La FS se extiende desde la cara basal a la lateral del cerebro. Cada superficie tiene una parte superficial (tronco silviano y sus ramos), intermedia (compartimientos anterior y opercular lateral) y profunda (compartimiento esfenoidal, hendidura insular anterior y lateral y la región retroinsular). En 7 de los 10 hemisferios, el surco central no se intersectó con la FS en la superficie lateral del cerebro. En el 80% de los hemisferios, la principal bifurcación de la arteria cerebral media se localizó en o proximal al limen insular. Debajo de la pars triangularis se localiza el punto más ancho de la superficie lateral de la FS. Los autores comienzan la disección de la misma en o proximalmente a este punto. Conclusiones: El conocimiento anatómico profundo y su aplicación a las neuroimágenes, son herramientas esenciales para el planeamiento prequirúrgico y son requisitos mandatorios para operar con seguridad a través y alrededor de la FS

Objective: The aim of this study is to describe the microsurgical anatomy of the sylvian fissure, through cadaveric dissections and neuroimaging and to elucidate its clinical application for microsurgery. Methods: One human skull and ten cadaveric human hemispheres were studied through white matter fiber dissections and arterial and neural anatomy of the sylvian fissure and insular dissections under the microscope. The cerebral arteries were perfused with colored latex. The surgical anatomy was correlated with neuroimaging anatomy. Finally, the microsurgical experienced gained applying this anatomical knowledge was gathered, and the literature about the anatomy of the sylvian complex was revised, as well. Results: The Sylvian fissure extends from the basal to the lateral surface of the brain. Each surface has a superficial (sylvian stem and its rami), intermediate (anterior and lateral opercular compartments) and deep parts (sphenoidal compartment, anterior and lateral insular clefts and retroinsular region). In 7 out of 10 hemispheres, the central sulcus did not intersect with the sylvian fissure on the lateral surface of the brain. In 80% of the hemispheres, the middle cerebral artery main bifurcation was localized at or proximal to the limen insulae. Beneath the pars triangularis, the widest point of the lateral surface of the sylvian fissure is located. The authors start dissecting the sylvian fissure at this point. Conclusion: The thorough anatomical knowledge with its clinical application in modern neuroimaging are essential tools for preoperative planning and are mandatory requisites to safely operate through and around the sylvian fissure anatomical complex.

Single Neuron Coding of Identity in the Human Hippocampal Formation.

Experimental findings show the ubiquitous presence of graded responses and tuning curves in the neocortex, particularly in visual areas [1-15]. Among these, inferotemporal-cortex (IT) neurons respond to complex visual stimuli, but differences in the neurons' responses can be used to distinguish the stimuli eliciting the responses [8, 9, 16-18]. The IT projects directly to the medial temporal lobe (MTL) [19], where neurons respond selectively to different pictures of specific persons and even to their written and spoken names [20-22]. However, it is not clear whether this is done through a graded coding, as in the neocortex, or a truly invariant code, in which the response-eliciting stimuli cannot be distinguished from each other. To address this issue, we recorded single neurons during the repeated presentation of different stimuli (pictures and written and spoken names) corresponding to the same persons. Using statistical tests and a decoding approach, we found that only in a minority of cases can the different pictures of a given person be distinguished from the neurons' responses and that in a larger proportion of cases, the responses to the pictures were different to the ones to the written and spoken names. We argue that MTL neurons tend to lack a representation of sensory features (particularly within a sensory modality), which can be advantageous for the memory function attributed to this area [23-25], and that a full representation of memories is given by a combination of mostly invariant coding in the MTL with a representation of sensory features in the neocortex.

Depression and Temporal Lobe Epilepsy: Expression Pattern of Calbindin Immunoreactivity in Hippocampal Dentate Gyrus of Patients Who Underwent Epilepsy Surgery with and without Comorbid Depression.

PURPOSE: Changes in calbindin (CB) expression have been reported in patients with temporal lobe epilepsy (TLE) with controversial implications on hippocampal functions. The aim of this study was to determine the CB immunoreactivity in hippocampal dentate gyrus of patients who underwent epilepsy surgery for drug-resistant TLE with and without comorbid depression and/or memory deficits. METHODS: Selected hippocampal samples from patients with TLE who underwent epilepsy surgery were included. Clinical and complementary assessment: EEG, video-EEG, MRI, psychiatric assessment (structured clinical interview, DSM-IV), and memory assessment (Rey auditory verbal learning test, RAVLT; Rey-Osterrieth complex figure test, RCFT), were determined before surgery. Hippocampal sections were processed using immunoperoxidase with the anti-calbindin antibody. The semiquantitative analysis of CB immunoreactivity was determined in dentate gyrus by computerized image analysis (ImageJ). RESULTS: Hippocampal sections of patients with TLE and HS (n = 24) and postmortem controls (n = 5) were included. A significant reduction of CB+ cells was found in patients with TLE (p < 0.05, Student's t-test). Among TLE cases (n = 24), depression (n = 12) and memory deficit (n = 17) were determined. Depression was associated with a higher % of cells with the CB dendritic expression (CB-sprouted cells) (F(1, 20) = 11.81, p = 0.003, hp2 = 0.37), a higher CB+ area (µm2) (F(1, 20) = 5.33, p = 0.032, hp2 = 0.21), and a higher optical density (F(1, 20) = 15.09, p = 0.001, hp2 = 0.43) (two-way ANOVA). The GAF scale (general assessment of functioning) of DSM-IV inversely correlated with the % of CB-sprouted cells (r = -0.52, p = 0.008) and with the CB+ area (r = -0.46, p = 0.022). CONCLUSIONS: In this exploratory study, comorbid depression was associated with a differential pattern of CB cell loss in dentate gyrus combined with a higher CB sprouting. These changes may indicate granular cell dysmaturation associated to the epileptic hyperexcitability phenomena. Further investigations should be carried out to confirm these preliminary findings.

Case Report of Worth Syndrome and Chiari I Malformation: Unusual Association and Surgical Treatment.

BACKGROUND: Worth syndrome or autosomal dominant endosteal hyperostosis (ADEH) is an extremely rare genetic disease involving increased bone density. To the author's knowledge, this is the second case report of a family with neurologic involvement associated with this condition along with its surgical treatment. The most effective treatment for clinically significant neurologic symptoms in this scenario is currently unknown, and there is sparse experience on surgical treatment for this condition reported in the literature. Therefore we aim to make a contribution to the identification of a standard and consistently successful surgical management. CASE DESCRIPTION: Two patients, mother (Patient 1) and daughter (Patient 2), were diagnosed with Worth syndrome. Both presented with the typical facial characteristics described for ADEH. Interestingly, Patient 1 presented the novel mutation in the LRP5 gene that is associated with different conditions involving increased bone density. Although neurologic symptoms are infrequent in ADEH, both referred chronic headache, nausea, and vomiting. Neuroimaging showed an increased cranial bone density and Chiari I malformation. The patients underwent a midline suboccipital craniectomy with excision of the posterior arch of C1 and duroplasty. However, due to a symptomatic recurrence 5 years after surgery, Patient 1 was reoperated on. We extended the craniectomy and also carried out a C2 laminectomy. CONCLUSION: After surgical interventions, patients' neurologic symptoms were successfully resolved. This report shows that posterior fossa decompression including duroplasty may be a valid treatment option in case of neurologic involvement.

Análisis video-electroencefalográfico de crisis epilépticas con inicio ictal de difícil lateralización, en epilepsia temporal mesial / Video-electroencephalographic analysis of epileptic seizures with ictal onset of difficult lateralization, in mesial temporal epilepsy

El propósito del trabajo fue analizar las características clínicas y electrofisiológicas de pacientes que presentaron crisis originadas en ambas regiones temporales en los registros de Video- EEG de scalp. Del total de la población con epilepsia temporal mesial (ET), resistente a las drogas, que ingresó a la Unidad de Video-EEG del Hospital Municipal Ramos Mejía y del Hospital de Alta Complejidad en Red El Cruce Dr. Néstor C. Kirchner, desde marzo de 2009 a marzo de 2014 (n=150), se seleccionaron 9 pacientes con crisis originadas en ambas regiones temporales (40 crisis focales con compromiso de la conciencia). Del total de los pacientes con epilepsia del lóbulo temporal fármaco-resistente, candidatos a cirugía de la epilepsia, en un 6% de los casos resultó difícil lateralizar la zona epileptógena con el registro de Video-EEG de scalp.

Psychiatric outcome of epilepsy surgery in patients with psychosis and temporal lobe drug-resistant epilepsy: a prospective case series.

OBJECTIVES: Temporal lobe resistant epilepsy has been associated with a high incidence of psychotic disorders; however, there are many controversies; while some patients get better after surgery from their psychiatric condition, others develop psychosis or de novo depression. The aim of this study was to determine the psychiatric and seizure outcome after epilepsy surgery in patients with a previous history of psychoses. METHODS: Surgical candidates with temporal lobe drug-resistant epilepsy and a positive history of psychosis diagnosed during the presurgical psychiatric assessment were included. A two-year prospective follow-up was determined after surgery. The DSM-IV Structural Interview, GAF (global assessment of functionality, DSM-IV), Ictal Classification for psychoses, and Engel's classification were used. The Student t test and chi-square-Fisher tests were used. RESULTS: During 2000-2010, 89 patients were admitted to the epilepsy surgery program, 14 patients (15.7%) presented psychoses and were included in this series. After surgery, six patients (43%) did not develop any psychiatric complications, three patients (21%) with chronic interictal psychosis continued with no exacerbation, three patients (21%) developed acute and transient psychotic symptoms, and two patients (14%) developed de novo depression. Seizure outcome was Engel class I-II in 10 patients (71%). Total GAF scores were higher after surgery in patients found to be in Engel class I-II (p<0.05). CONCLUSIONS: Patients with comorbid psychosis and temporal lobe drug-resistant epilepsy may benefit from epilepsy surgery under close psychiatric supervision.

Postoperative neuropsychological outcome in patients with mesial temporal lobe epilepsy in Argentina.

The aim of the present study is to compare pre- and postsurgical neuropsychological outcome in individuals suffering from mesial temporal lobe epilepsy (mTLE), in order to evaluate prognosis. The selected thirty-five patients had medically mTLE and had undergone an anterior temporal lobectomy (ATL). Neuropsychological evaluation was performed in three different stages: before ATL, 6 months after resection, and a year afterwards. Neuropsychological protocol evaluated attention, verbal memory, visual memory, executive function, language, intelligence, and handedness. There was a significant improvement (P = 0.030) in the group with visual memory deficit after surgery, whereas no changes were observed across patients with verbal memory deficit. No changes were observed in language after surgery. Executive function showed significant improvement 6 months after surgery (P = 0.035). Postoperative outcome of cognitive impairments depends on baseline neuropsychological status of the patients with TLE. In our case series, deficits found in patients with mTLE after ATL did not result in a subjective complaint.

Psychosis after epilepsy surgery: report of three cases.

Temporal lobe epilepsy surgery has become a successful alternative in patients with refractory epilepsy. However, the outcome of epilepsy surgery may be affected by the occurrence of postsurgical psychiatric symptoms, such as psychosis. This report describes three cases of refractory temporal lobe epilepsy and hippocampal sclerosis, which, after anterior temporal lobectomy, presented with acute psychosis. One of them had a history of acute psychosis, and all of them met criteria for Cluster A personality disorder (schizoid/schizotypal) during psychiatric assessment prior to surgery. The three cases had a good seizure outcome (Engel I), but, on follow-up during the first year after surgery, developed an acute psychotic episode compatible with schizoaffective disorder; brief psychotic disorder; and a delusional disorder, respectively, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Treatment with low-dose risperidone was successful.

Doublecortin (DCX) immunoreactivity in hippocampus of chronic refractory temporal lobe epilepsy patients with hippocampal sclerosis.

INTRODUCTION: Status epilepticus increases the production of new neurons (hippocampal neurogenesis) and promotes aberrant migration. However chronic experimental models of epilepsy and studies performed in human epilepsy showed controversial results suggesting a reduction in hippocampal neurogenesis in late stages of the disease. Doublecortin (DCX) has been validated to determine alterations in the production of new neurons in the human hippocampus. OBJECTIVES: Determine DCX expression in human hippocampal sclerosis (HS) from patients who underwent epilepsy surgery for refractory temporal lobe epilepsy (TLE). METHODS: Hippocampal sections of 9 patients with HS and TLE who underwent surgery, were processed using immunoperoxidase for DCX. Archival material from 5 normal post-mortem hippocampus were simultaneously processed. RESULTS: Significantly lower staining intensity was observed in DCX-positive neurons localized in dentate gyrus (DG) and in CA1 of epileptic hippocampus; lower DCX reactive area was observed in pyramidal layers of CA1; and a reduced in the mean number of DCX-positive neurons were determined in DG compared to normal hippocampus (p<0.05). CONCLUSIONS: This study found a decrease in DCX expression in hippocampus of patients with HS and chronic and refractory TLE suggesting alterations in NG and hippocampal synaptogenesis with potential cognitive and emotional repercussion.

NADPH diaphorase reactive neurons in temporal lobe cortex of patients with intractable epilepsy and hippocampal sclerosis.

Several studies have demonstrated a controversial involvement of NO in epileptogenesis. The aim of this study is to compare the NADPH diaphorase (NADPH-d) reactivity in the temporal cortex between surgical specimens of patients with intractable epilepsy and hippocampal sclerosis and autopsy controls. Brain samples of patients and postmortem controls were stained with the NADPH-d technique. Sprouting and larger areas of NADPH-d reactive neurons were found in the temporal cortex of epileptic patients.

MR imaging of the trigeminal ganglion, nerve, and the perineural vascular plexus: normal appearance and variants with correlation to cadaver specimens.

BACKGROUND AND PURPOSE: MR imaging is the method of choice for evaluating the trigeminal nerve. Detection of abnormalities such as perineural tumor spread requires detailed knowledge of the normal MR appearance of the trigeminal nerve and surrounding structures. The purpose of this study was to clarify the normal MR appearance and variations of the trigeminal ganglion, maxillary nerve (V2), and mandibular nerve (V3) with their corresponding perineural vascular plexus. METHOD: S: MR images obtained in 32 patients without symptoms referable to the trigeminal nerve were retrospectively reviewed. The trigeminal ganglion in Meckel's cave, V2 within the foramen rotundum, and V3 at the level of foramen ovale were assessed for visualization and enhancement. The configuration of the perineural vascular plexus was recorded. Correlation to cadaver specimens was made. RESULTS: The trigeminal ganglion and V3 were observed to enhance in 3-4% of patients unilaterally. V2 and V3 were well visualized 93% of the time. The perineural vascular plexus of V2 was observed 91% of the time, and that of V3 in 97% of instances. CONCLUSION: This study characterizes the normal MR appearance of the trigeminal ganglion and its proximal branches. The trigeminal ganglion, V2, and, V3 are almost always reliably seen on thin-section MR studies of the skull base. Enhancement of the perivascular plexus is routinely seen; however, enhancement of the trigeminal ganglion, V2, or V3 alone is seen only on occasion as supported by the avascular appearance of these anatomic structures in cadaver specimens.

Masteidectomia minima: nueva variante del abordaje presigmoideo / Minimal mastoidectomy: a new variation of the presigmoid approach

Los abordajes a la patología de la región petroclival han aumentado en complejidad con el desa-rrollo de nuevas técnicas para la cirugía en base de cráneo. Entre ellas el abordaje presigmoideo retro-laberíntico es el que ha tenido mayor aceptación debido a la amplitud de exposición sumado a la baja morbilidad. Aun siendo baja su morbilidad esta puede ser de importancia debido a la necesidad de exponer el nervio facial, los canales semícirculares y el bulbo de la yugular. Para comprobar si efectivamente es necesario arriesgar dichas estructuras para exponer la región petroclival se diseñó en el laboratorio una variante del abordaje pre-sigmoideo pero con mastoidectomia minima en la cual las mismas permanecían indemnes. Fueron utilizadas diez cabezas cadavérícas y cinco cráneos a los efectos de comparar ambos abordajes. Curiosamente observa-mos que la mastoidectomia minima ofreció el mismo angulo de exposición así como similar cercanía a la región petroclival comparado con la variante retrolaberíntica pero sin la morbilidad que significa exponer las estructuras neurovasculares y otológicas escondidas en la profundidad del hueso temporal, Futuras pruebas clínicas utilizando esta nueva variante del abordaje presigmoideo aclararan su real valor en la resolución de las lesiones ubicadas en la región petroclival.