Spontaneous Regression of a Clival Chordoma: An Unusual Case Report.

INTRODUCTION: Chordoma is a malignant and aggressive tumor originating from remnants of the primitive notochord and usually involving the axial skeleton. Spontaneous regression of clival chordomas was described recently. We present the third case report of spontaneous regression of a clival chordoma and discuss similarities of cases and implications for clinical practice. CASE DESCRIPTION: We present the case of a previously healthy 21-year-old Caucasian woman who presented with progressive holocranial headache for 3 months, which encouraged image investigation. Magnetic resonance imaging (MRI) revealed an osteolytic clival lesion hyperintense in T2 and hypointense in T1 images. After 2 months of initial evaluation and surgical proposal, she repeated MRI to allow use for intraoperative neuronavigation. Surprisingly, there was tumor regression. DISCUSSION: The present reported case is somehow different from previous ones and does not share an underlying inflammatory/immunological recognizable fact, being interpreted by us as a spontaneous partial regression of the tumor. We highlight the need for continuous investigation of chordoma regression to uncover the underlying mechanisms.

The relationship of the posterior cranial fossa with age and sex / Relación de la fosa craneal posterior con la edad y el sexo

SUMMARY: This paper determined the morphometric measurements of posterior cranial fossa using MRI in Turkish healthy population. Two hundred thirty one (231; 131 females and 100 males) subjects ranging from 20 up to 85 years were included in this study. Measurements of the posterior cranial fossa were taken from subjects having brain MRI in the Radiology Department, Adana, Turkey. Statistical analysis were done by SPSS 21.00 package programme. ANOVA Test and Chi-Square Test were used to determine the relation between measurements and age groups. The p<0.05 value was considered as significant. The overall means and standard deviations of the measurements were: Clivus length,31.10?5.45 mm; McRae line, 32.59?3.89 mm; Supraocciput length,41.99 ? 4.37 mm; Twining line, 79.23?5.53 mm; Posterior cranial fossa height, 66.76?5.06 mm; Cerebellum height, 55.17?5.29 mm; Clival angle, 125.59??6.57?; Cerebellar tentorium angle, 128.30??7.77? mm, Occipital protuberance angle, 93.27??8.02? and hindbrain vertical length, 50.56?3.47 mmin females, respectively, whereas the corresponding values were 32.43?5.99 mm; 32.85?3.77 mm; 42.46?4.68 mm; 80.95?5.94 mm; 69.70?4.67mm; 57.01?3.43 mm; 123.90??7.12? 128.80?8.33?; 95.35?9.19? and 52.71?3.33 mm in males, respectively. Significant difference was found in some parameters such as twining line, posterior cranial fossa height, cerebellum height and hindbrain vertical length between sex (p<0.05). Also, ages were divided into six groups as decades. Significant difference between six decades was also found in parameters including McRae line, twining line, posterior cranial fossa height, cerebellum height, clival angle, cerebellar tentorium angle, occipital tuberance angle and hindbrain vertical length (p<0.05). The posterior cranial fossa dimensions of healthy population provides important and useful knowledge in terms of comparison of abnormalities clinically, and data can be used as an anatomical landmark during surgery involving posterior cranial fossa.

RESUMEN: Se determinaron las medidas morfométricas de la fosa craneal posterior mediante resonancia magnética en una población turca. Se incluyeron doscientos treinta y un (231; 131 mujeres y 100 hombres) sujetos sanos con edades entre los 20 y los 85 años. Por medio de una resonancia magnética cerebral se tomaron medidas de la fosa craneal posterior de sujetos en el Departamento de Radiología de Adana, Turquía. El análisis estadístico se realizó mediante el programa de SPSS 21.00. Se utilizó la prueba ANOVA y la prueba de chi-cuadrado para determinar la relación entre las medidas y los grupos de edad. Se consideró significativo el valor de p <0,05. Las medias generales y las desviaciones estándar de las medidas en las mujeres fueron: longitud del clivus, 31,10 ? 5,45 mm; Línea McRae, 32,59 ? 3,89 mm; Longitud del supraoccipucio, 41,99 ? 4,37 mm; línea de Twining (desde el tubérculo selar hasta la confluencia de los senos), 79,23 ? 5,53 mm; Altura posterior de la fosa craneal, 66,76 ? 5,06 mm; Altura del cerebelo, 55,17 ? 5,29 mm; Ángulo clival, 125,59 ? ? 6,57 ?; Ángulo del tentorio cerebeloso, 128,30 ? ? 7,77 ? mm, Angulo de protuberancia occipital, 93,27 ? ? 8,02 ? y Longitud vertical del rombencéfalo, 50,56 ? 3,47 mm. En los hombres los valores obte- nidos fueron 32,43 ? 5,99 mm; 32,85 ? 3,77 mm; 42,46 ? 4,68 mm; 80,95 ? 5,94 mm; 69,70 ? 4,67 mm; 57,01 ? 3,43 mm; 123,90 ? ? 7,12 ? 128,80 ? 8,33 ?; 95,35 ? 9,19 ? y 52,71 ? 3,33 mm, respectivamente. Se encontraron diferencias significativas entre ambos sexos (p <0,05) en algunos de los parámetros, como la línea de Twining, la altura de la fosa craneal posterior, la altura del cerebelo y la longitud vertical del rombencéfalo. También se encontró una diferencia significativa entre las edades de los individuos (división en seis décadas) en los parámetros que incluyen la línea de McRae, la línea de Twining, la altura de la fosa craneal posterior, la altura del cerebelo, el ángulo de clivación, el ángulo de la tienda del cerebelo, el ángulo de protuberancia occipital y la longitud vertical del rombencéfalo (p <0,05). La población estudiada nos proporciona información importante y útil en términos de comparación clínica de anomalías y los datos pueden eventualmente ser utilizados como un punto de referencia anatómico durante la cirugía que involucra la fosa craneal posterior.

Resection of Clival Chordoma Through the Anterior Clivectomy: 2-Dimensional Operative Video.

Clival chordomas are rare malignant behaving tumors that grow, locally invade, metastasize, and seed, and they have a high recurrence rate.1,2 The longest disease control is achieved by radical resection followed by high doses of radiation therapy, commonly proton beam.3 To achieve radical tumor removal, multiple surgical procedures through different approaches might be required.4 Since the chordoma's origin is, and remains, extradural, an extradural approach is preferred, and can lead to intradural extension. Anterior approach is frequently utilized to remove the midline-located tumor and the eroded clivus.5 Several midline approaches were utilized, including the transbasal, transfacial, transcervical, open door, and Lefort's maxillotomies1; however, the same tumor removal can be achieved with a simple extension of the trans-sphenoidal approach, by resecting the anterior maxillary wall, of the contralateral to the lesion preponderant side.5 This approach coupled with the use of neuronavigation on mobile head and endoscopic-assisted technique allowed to achieve a wide and direct exposure, with the ability to resect extra- and intradural tumors.2,5 Lately, the endonasal endoscopic technique became popular as an alternative4; however, we found a great advantage in the ability to combine the stereoscopic microsurgical technique with the endoscopic dissection, in addition to avoiding the extensive nasal dissection and its complications. We present a case of a 63-yr old woman with an upper clivus chordoma compressing the brainstem who underwent a gross total resection by endoscopic-assisted microscopic techniques through an anterior clivectomy approach. Patient consented to the procedure and publication of her images.

Petroclival Meningiomas: A Simple System That Could Help in Selecting the Approach.

BACKGROUND: Petroclival meningiomas (PCM) represent a neurosurgical challenge due to their strategic location close to the brainstem. OBJECTIVE: To assess the applicability of a retrosigmoid approach (RSA) by analyzing the degree of displacement of the middle cerebellar peduncle (MCP) elicited by PCM. METHODS: Patients with PCM were prospectively included and divided into those whose imaging studies showed that the posterior end of the MCP was displaced by the tumor and were eligible for and underwent RSA (group A) and those who were not eligible for RSA and who underwent surgery via a posterior transpetrosal approach (group B). We compared tumor behavior, clinical characteristic of patients and surgical results. RESULTS: Twenty patients with PCM were enrolled and allocated to group A (n = 15) or group B (n = 5). The clinical manifestations were more severe in group B; tumors in this group were larger and gross total removal was achieved in only 1 patient (20%). In comparison, in 12 cases on group A, tumors could be totally removed (80%) and all of these patients could recover their quality of life after surgery. CONCLUSION: To our knowledge, this study is the first to consider displacement of the MCP when establishing a suitable surgical approach for PCM. Our results suggest that the RSA becomes increasingly suitable when peduncle displacement is greater. By using this method, it was also possible to identify two types of tumors: petroclivals (group A) and clivopetrosals (group B), that show some specific clinical and surgical differences.

Tortícolis como forma de presentación de quiste de la bolsa de Blake. Diagnóstico ecográfico en atención primaria / Torticolis as a form of presentation of Blake's pouch cyst. Ultrasound diagnosis in primary care

La tortícolis es un signo clínico definido por la inclinación lateral del cuello y rotación de la cabeza, que puede ser fija o flexible y acompañarse o no de dolor cervical. Aparece en trastornos de diferente complejidad. Ante un caso de tortícolis, es preciso realizar una historia clínica cuidadosa y un examen físico completo, y, en caso de ser persistente, solicitar pruebas de imagen.Se hace referencia a una causa de tortícolis no descrita en la literatura. Se trata de una tumoración quística compresiva en la fosa craneal posterior, quiste de la bolsa de Blake, en una lactante pequeña diagnosticada mediante ecografía en la consulta de Pediatría de Atención Primaria. Tras el diagnóstico, se remitió al centro hospitalario de referencia, donde se intervino de urgencia por Neurocirugía Pediátrica, mediante fenestración de la tumoración por ventriculostomía endoscópica y derivación ventrículo-peritoneal. Actualmente, se encuentra asintomática y sin secuelas.

Torticollis is a clinical sign defined by the lateral inclination of the neck and rotation of the head, which can be fixed or flexible and accompanied or not by cervical pain. It appears in disorders of different complexity. In a case of torticollis it is necessary to carry out a careful medical history and a complete physical examination and, if persistent, request imaging tests.Reference is made to a cause of torticollis not described in the literature. This is a compressive cystic tumor in the posterior cranial fossa, Blake's pouch cyst, in a small infant diagnosed by ultrasound in the Primary Care Pediatrics office. After diagnosis, she was referred to the referral hospital, where emergency intervention was performed by pediatric neurosurgery, by fenestration of the tumor by endoscopic ventriculostomy and ventriculo-peritoneal shunt. She is currently asymptomatic and without sequelae.

[Torticolis as a form of presentation of Blake's pouch cyst. Ultrasound diagnosis in primary care]. / Tortícolis como forma de presentación de quiste de la bolsa de Blake. Diagnóstico ecográfico en atención primaria.

Torticollis is a clinical sign defined by the lateral inclination of the neck and rotation of the head, which can be fixed or flexible and accompanied or not by cervical pain. It appears in disorders of different complexity. In a case of torticollis it is necessary to carry out a careful medical history and a complete physical examination and, if persistent, request imaging tests. Reference is made to a cause of torticollis not described in the literature. This is a compressive cystic tumor in the posterior cranial fossa, Blake's pouch cyst, in a small infant diagnosed by ultrasound in the Primary Care Pediatrics office. After diagnosis, she was referred to the referral hospital, where emergency intervention was performed by pediatric neurosurgery, by fenestration of the tumor by endoscopic ventriculostomy and ventriculo-peritoneal shunt. She is currently asymptomatic and without sequelae.

La tortícolis es un signo clínico definido por la inclinación lateral del cuello y rotación de la cabeza, que puede ser fija o flexible y acompañarse o no de dolor cervical. Aparece en trastornos de diferente complejidad. Ante un caso de tortícolis, es preciso realizar una historia clínica cuidadosa y un examen físico completo, y, en caso de ser persistente, solicitar pruebas de imagen. Se hace referencia a una causa de tortícolis no descrita en la literatura. Se trata de una tumoración quística compresiva en la fosa craneal posterior, quiste de la bolsa de Blake, en una lactante pequeña diagnosticada mediante ecografía en la consulta de Pediatría de Atención Primaria. Tras el diagnóstico, se remitió al centro hospitalario de referencia, donde se intervino de urgencia por Neurocirugía Pediátrica, mediante fenestración de la tumoración por ventriculostomía endoscópica y derivación ventrículo-peritoneal. Actualmente, se encuentra asintomática y sin secuelas.

The role of clivus length and cranial base flexion angle in basilar invagination and Chiari malformation pathophysiology.

BACKGROUND: The craniovertebral junction is an anatomically well-defined transitional zone located between the skull and the cervical spine. Multiple malformations can affect this region with the most prominent being basilar invagination (BI) and Chiari malformation (CM). Despite numerous studies, the origin, pathophysiology, and classification of these pathologies remain controversial. The objective of this study was to evaluate the implication of cranial base flexion angle and clivus length in the development of these conditions. METHODS: Midline tomography and magnetic resonance imaging of normal subjects and patients diagnosed with BI (types I and II) and Chiari malformation were evaluated. A craniometric study of the skull base was performed. Linear and angular measurements were used for comparisons between groups. RESULTS: 109 images from patients with craniovertebral junction malformation and controls were evaluated. Seventeen had BI-I, 26 had BI-II, 36 had CM, and 30 were normal subjects. Demographic data for the two groups were not significantly different. Craniometric analysis of images revealed a gradation in linear and angular variables from controls to CM, BI-I, and BI-II patients. Clivus length was significantly smaller in BI-II patients compared with other groups, while basal angle was greater. Moderate or strong correlations were noted among all variables analyzed. CONCLUSION: Data suggest that clivus length and basal angle may play a role in pathophysiology of BI and CM.

Dermoid cyst with cerebellar meningoencephalocele at different locations accompanied by posterior fossa abnormalities: case report

ABSTRACT CONTEXT: Dermoid cysts are well-defined cysts containing sebaceous glands and dermal structures. In the literature, dermoid cysts and associated closure defects have been described in the same locations. CASE REPORT: In this case, a dermoid cyst was found at the base of the mouth with a coexisting closure defect in the occipital calvarium. Additional abnormalities were also observed, including posterior myeloschisis, right cerebellar dysgenesis, vermian hypogenesis and posterior fusion of the second and third vertebrae. The finding of a dermoid cyst located at the base of the mouth is discussed here, with additional imaging findings. CONCLUSION: Dermoid cysts in the head and neck region may be accompanied by posterior fossa abnormalities.

A Primary Clival Defect: Endoscopic Binostril Approach With Nasal Septal Flap Closure and Preservation of Septal Integrity.

Primary spontaneous cerebrospinal fluid (CSF) rhinorrhea is an unusual phenomenon that may occur anywhere along the skull base. However, CSF leaks originating from clival defects are rarely reported in the literature. The majority of reported cases were managed with microscopic techniques, using free grafts. The present study discusses a case of spontaneous CSF rhinorrhea from a clival defect closed with our transnasal operative approach using endoscopic techniques. The skull base defect was successfully managed with an endoscopic binostril approach to create a nasal septal flap pedicled at the sphenopalatine artery, while also preserving the integrity of the nasal septum.

Role of Transnasal Endoscopic Surgery in the Treatment of Superficial Siderosis of Central Nervous System Secondary to Clivus Arachnoidocele: Report of Successful Case and Literature Review.

BACKGROUND: Superficial siderosis (SS) of the central nervous system is a disease characterized by deposition of hemosiderin in the leptomeninges (arachnoid and pia mater) due to chronic intradural bleeding. One of the etiologic mechanisms proposed is a dural breach secondary to trauma with a consequent arachnoidocele in contact with an exuberant venous plexus. We describe a unique case of clival arachnoidocele treated by an endoscopic endonasal approach and closure of the defect with fat and nasoseptal flap. CASE DESCRIPTION: A 35-year-old man with a history of severe head trauma 20 years ago presented with hearing deficit and a mild motor ataxia impairing gait. Magnetic resonance imaging disclosed hemosiderin deposition throughout the brain cortical layer and in the cerebellum, affecting the dentate nucleus as well. A computed tomography revealed an osteolytic formation in the clivus, involving the inner bone table and bone marrow. The patient was then submitted to an endoscopic endonasal transclival approach to close the defect. CONCLUSIONS: SS may be a result of several etiologies generating repetitive meningeal bleeding. Our patient had the diagnosis of posttraumatic clival arachnoidocele and SS probably related to trauma with some dural injury. An endoscopic endonasal approach with tear reconstruction is feasible and successful to address clival arachnoidoceles and, in this case, to avoid progression of the SS.

Dermoid cyst with cerebellar meningoencephalocele at different locations accompanied by posterior fossa abnormalities: case report.

CONTEXT: Dermoid cysts are well-defined cysts containing sebaceous glands and dermal structures. In the literature, dermoid cysts and associated closure defects have been described in the same locations. CASE REPORT: In this case, a dermoid cyst was found at the base of the mouth with a coexisting closure defect in the occipital calvarium. Additional abnormalities were also observed, including posterior myeloschisis, right cerebellar dysgenesis, vermian hypogenesis and posterior fusion of the second and third vertebrae. The finding of a dermoid cyst located at the base of the mouth is discussed here, with additional imaging findings. CONCLUSION: Dermoid cysts in the head and neck region may be accompanied by posterior fossa abnormalities.

Three-Dimensional Volume Imaging to Increase the Accuracy of Surgical Management in a Case of Recurrent Chordoma of the Clivus.

BACKGROUND The clivus is a depression in the anterior occipital bone of the skull base, posterior to the dorsum sellae, at the junction with the sphenoid bone. Chordoma is a rare tumor arising from embryonic remnants of the notochord and can be locally aggressive with a tendency to recur. The optimal management of this rare tumor remains controversial. A report of a case of recurrent chordoma of the clivus is presented to illustrate the value of volumetric three-dimensional (3-D) reconstruction with computed tomography (CT) and magnetic resonance imaging (MRI) to determine optimal surgical management. CASE REPORT A 53-year-old man presented with pain in the right orbital cavity, right proptosis, swelling of the right cheek, and bilateral loss of vision. He also had adrenal insufficiency. CT and contrast-enhanced (gadolinium) T1-weighted MRI with multiplanar acquisition were performed with volumetric 3-D reconstruction of the tumor, to increase the chances of treatment success. Surgical resection was performed to remove the tumor and reduce the risk of recurrence. Histology of the tumor was consistent with chordoma, supported by positive immunohistochemical staining for S-100 and epithelial membrane antigen (EMA). CONCLUSIONS This report highlighted the value of 3-D volume imaging in the diagnosis and treatment planning in a rare case of recurrent chordoma of the clivus. Analysis of tumor volume may be an indicator of the efficacy of surgery, complementing the Response Evaluation Criteria In Solid Tumors (RECIST) system and as a valuable tool to predict treatment outcome.

The intracranial and posterior cranial fossa volumes and volume fractions in children: a stereological study / Los volúmenes de la fosa craneal intracraneal y posterior y las fracciones de volumen en los niños: un estudio estereológico

SUMMARY: The size of intracranial cavity (IC) and posterior cranial fossa (PCF) plays an important role in the pathophysiology of various disorders. In this study, we aimed at establishing normal volume data of the IC and PCF in Turkish population according to age and sex by using stereological method. This study was carried out retrospectively on 339 individuals (168 females and 171 males) between 0 and 18 years old with no medical or neurological disorders that affected the skeletal morphology of the cranial cavity. Volumetric estimations were determined on computed tomography (CT) images using point-counting approach of stereological methods. Intracranial volume (ICV) and posterior cranial fossa volume (PCFV) were increased with age in both sexes. They reached adult dimensions at 5 years of age during the teenage years. According to sex; the mean ICV and PCFV were 1594.51±245.57cm3 and 244.89±53.86 cm3 in males, 1456.34±241.85 cm3 and 228.24±41.38 cm3 in females, respectively. Generally, significant differences were determined in ICV and PCFV according to sex after they reached maximum growth period. According to age the volume ratios of PCF to IC was ranged from 13.03 to 17.48 in males and 12.06 to 18.54 in females. This study demonstrated that these volume ratios could help the physician for both patient selections for surgery, and for the assessment of any surgical technique used to treatment of PCF malformations. However current study revealed that point counting method can produce accurate volume estimations and is effective in determining volume estimation of IC and PCF.

RESUMEN: El tamaño de la cavidad intracraneal (CI) y la fosa craneal posterior (FCP) desempeñan un papel importante en la fisiopatología de diversos trastornos. En este estudio, se pretende establecer los datos de volumen normal de la CI y FCP en la población turca, de acuerdo a la edad y el sexo, mediante el uso de métodos estereológicos. Este estudio se realizó retrospectivamente en 339 individuos (168 mujeres y 171 hombres) entre 0 y 18 años sin trastornos médicos o neurológicos que afectaron la morfología esquelética de la cavidad craneal. Las estimaciones volumétricas se determinaron en imágenes de tomografía computarizada (TC) utilizando el conteo de puntos de los métodos estereológicos. El volumen intracraneal (VIC) y el volumen posterior de la fosa craneal (VFCP) aumentaron con la edad en ambos sexos. Alcanzaron dimensiones adultas a los 5 años de edad durante la adolescencia. Según el sexo, el promedio de VIC y VFCP fue de 1594,51 ± 245,57 cm3 y de 244,89 ± 53,86 cm3 en los hombres, 1456,34 ± 241,85 cm3 y 228,24 ± 41,38 cm3 en las mujeres, respectivamente. En general, se determinaron diferencias significativas en VIC y VFCP de acuerdo con el sexo después de alcanzar el período de crecimiento máximo. Según la edad, las proporciones de volumen de FCP a CI oscilaban entre 13,03 a 17,48 en los hombres y 12,06 a 18,54 en las mujeres. Este estudio demostró que estas proporciones de volumen podrían ayudar al médico tanto en la selección de pacientes para la cirugía, como para la evaluación de cualquier técnica quirúrgica utilizada en el tratamiento de malformaciones de FCP. Además, el estudio actual reveló que el método de conteo de puntos puede producir estimaciones precisas de volumen siendo eficaz para determinar la estimación de volumen de IC y FCP.

3-D simulation of posterior fossa reduction in Chiari I.

We proposed a 3D model to evaluate the role of platybasia and clivus length in the development of Chiari I (CI). Using a computer aided design software, two DICOM files of a normal CT scan and MR were used to simulate different clivus lengths (CL) and also different basal angles (BA). The final posterior fossa volume (PFV) was obtained for each variation and the percentage of the volumetric change was acquired with the same method. The initial normal values of CL and BA were 35.65 mm and 112.66º respectively, with a total PFV of 209 ml. Ranging the CL from 34.65 to 29.65 - 24.65 - 19.65, there was a PFV decrease of 0.47% - 1.12% - 1.69%, respectively. Ranging the BA from 122.66º to 127.66º - 142.66º, the PFV decreased 0.69% - 3.23%, respectively. Our model highlights the importance of the basal angle and clivus length to the development of CI.

3-D simulation of posterior fossa reduction in Chiari I / Simulação em 3D da redução da fossa posterior no Chiari do tipo I

ABSTRACT We proposed a 3D model to evaluate the role of platybasia and clivus length in the development of Chiari I (CI). Using a computer aided design software, two DICOM files of a normal CT scan and MR were used to simulate different clivus lengths (CL) and also different basal angles (BA). The final posterior fossa volume (PFV) was obtained for each variation and the percentage of the volumetric change was acquired with the same method. The initial normal values of CL and BA were 35.65 mm and 112.66º respectively, with a total PFV of 209 ml. Ranging the CL from 34.65 to 29.65 – 24.65 – 19.65, there was a PFV decrease of 0.47% – 1.12% – 1.69%, respectively. Ranging the BA from 122.66º to 127.66º – 142.66º, the PFV decreased 0.69% – 3.23%, respectively. Our model highlights the importance of the basal angle and clivus length to the development of CI.

RESUMO No presente estudo, propusemos a criação de um modelo computacional em 3D com elaboração de software onde dois arquivos em formato DICOM com uma TC e RNM de crânio foram usados para simular diferentes mensurações na extensão do clivus (EC) e no ângulo basal (AB). O volume final da fossa posterior (VFP) foi obtido em cada variação, bem como a percentagem de volume alterada. O tamanho inicial da EC era de 35,65 mm e o do AB era de 112.66º, com um VFP de 209 ml. Variando a EC de 34,65 para 29,65 – 24.65 e 19.65, houve uma diminuição do VFP de 0.47%, 1.12% e 1.69%, respectivamente. Variando o AB de 122,66º para 127,66º e 142,66º, o VFP diminui para 0.69% e 3.23%, respectivamente. Nosso modelo enfatiza a importância da patogênese do aumento do AB e do encurtamento do clivus no desenvolvimento do Chiari I.

Assessment of an image-guided neurosurgery system using a head phantom.

OBJECTIVE: To acknowledge the challenges and limitations of image-guided neurosurgery systems, we compared the application accuracy of two different image registration methods for one commercial system. (VectorVision, BrainLab, Germany). METHODS: We used an anthropomorphic head phantom for radiosurgery and a custom built add-on to simulate surgical targets inside the brain during an image-guided neurosurgery. We used two image registration methods, fiducial registration using attachable surface markers for computed tomography (CT) and surface registration using infrared laser face scanning. After simulation, we calculated the three-dimensional (3D) distance between the predicted position of a target, and its actual position using a registered pointer and an infrared camera. Deviations were measured for both superficial fiducial markers and internal surgical targets by five different users. RESULTS: Deviations from the location of fiducial markers after each registration method were 2.15 ± 0.93 mm after CT surface marker registration and 1.25 ± 0.64 mm after infrared face scanner registration. The mean target registration errors were 2.95 ± 1.4 mm using fiducial registration and 2.90 ± 1.3 mm using surface registration. The largest deviations (6.2 mm) were found for the targets in the skull base and posterior cranial fossa. Fiducial deviations and target registration errors were statistically uncorrelated. The total application accuracy was 4.87 ± 0.97 mm after CT surface marker registration and 4.14 ± 0.64 mm after infrared face scanner registration. CONCLUSIONS: Despite others have reported differences, we did not find significant variations between both registration methods for the target registration error, although application accuracy was slightly better after surface face registration. Superficial registration errors, but not the target registration error, can be routinely evaluated in the operating room. Since both errors were uncorrelated, surgeons may neglect the achievable accuracy of the procedure. The described method is recommended to assess application accuracy in the operating room.