Evaluation of Bell's palsy in the cerebellopontine angle: An MRI study.

BACKGROUND: Evaluation of cranial nerve morphology through measuring cross-sectional area (CSA) on magnetic resonance imaging (MRI) is increasing day-by-day in clinical diseases. In Bell's palsy (BP), the manifestation of the enlarged CSA of the facial nerve (FN) may be used for diagnosis. This study aims to evaluate whether there is an enlargement of the cisternal FN in BP. METHODS: This retrospective study included 43 patients diagnosed with BP. In the reconstructed MRI, the long (LD) and short (SD) diameters of the paralytic and normal sides of the FNs located in the cerebellopontine angle were measured, and the CSA was calculated using the Radinsky formula. Before the radiologic measurement, a preliminary experiment was carried out on the rat sciatic nerve to be able to determine the actual nerve boundary on MRI. FINDINGS: There was a statistically significant relationship between paralytic and normal sides in the measurements of LD, SD, and CSA. The paralytic side was larger than the normal side in the cisternal FN. According to the Receiver Operating Characteristic (ROC) curve, BP can be estimated with 60% sensitivity and 70% specificity by the CSA of the FN more than 1.04 mm2 . As a result of the preliminary experiment, it was found that the actual nerve boundary was at approximately 50% intensity between the minimum and maximum values. CONCLUSION: Although entrapment of FN in the labyrinthine segment in BP was known, this study showed that the cisternal FN, which could be evaluated more conveniently, enlarged in the paralytic side compared with the normal side, and revealed the necessity of performing the comparison amongst the MRI studies on BP patients by a standardised measurement method. This study will also help clinicians to make a decision in the diagnosis of BP by giving a cut-off value for the CSA.

Anatomic features of the cranial aperture of the optic canal in children: a radiologic study.

OBJECTIVE: This study aimed to peruse anatomic features of the cranial aperture of the optic canal (CAOC) for obtaining an extended morphometric dataset in children. METHODS: Computed tomography images of 200 children were included in this retrospective work to analyze the shape, location and diameters of the CAOC. RESULTS: The CAOC area, width and height were observed as 17.53 ± 2.80 mm2, 6.12 ± 0.84 mm, and 4.35 ± 0.64 mm, respectively. The angle of the optic canal in axial plane was found as 39.28 ± 5.13°, while in sagittal plane as 16.01 ± 6.76°. The distance between the CAOC and the midsagittal line was 7.17 ± 1.48 mm. The CAOC was measured as 54.04 ± 5.23 mm and 42.55 ± 3.28 mm away from the anterior and lateral boundary of the anterior skull base, respectively. The CAOC shape was described as the tear-drop (186 foramina, 46.5%), triangular (156 foramina, 39%), oval (47 foramina, 11.8%), and round (11 foramina, 2.8%). CONCLUSION: The depth, angle and diameter measurements belonging to the CAOC were changing according to its shape or demographic data (e.g., sex and age). Therefore, preoperative radiologic evaluation containing the shape, location and size of the CAOC should be considered by multidisciplinary operating teams in terms of surgical interventions such as implant positioning.

Quantitative Analysis of the Vascular and Neural Compartments of the Jugular Foramen in Dry Skulls.

AIM: To compare the right and left sides and the endo?exocranial orifices of the jugular foramen (JF) considering the vascular compartment (VC) and the neural compartment (NC). MATERIAL AND METHODS: A total of 20 human dry skulls belonging to the inventory of Medical Faculty, Department of Anatomy, were included in this study. Numerical values were obtained using direct anatomical and also computed tomography measurements. RESULTS: The endocranial and exocranial VC occupied wider areas on the right side than on the left side (p < 0.05). However, there was no statistically significant difference between the surface area of the endocranial and exocranial NC in terms of the sides (p > 0.05). The length of the endocranial VC was greater on the right than on the left side. The right exocranial VC was wider than the left exocranial VC. However, the widths and lengths of the endocranial and exocranial NC showed no statistically significant difference between the sides (p > 0.05). CONCLUSION: The right-sided dominance of JF observed in this study was attributed to the length of endocranial VC and the width of exocranial VC.

Fetal Anatomy of the Optic Strut and Prechiasmatic Sulcus with a Clinical Perspective.

OBJECTIVE: The main objective of the study was to show the morphologic features of optic strut (OS) and prechiasmatic sulcus (PS) in the fetal skull base with a surgical anatomical perspective. METHODS: Twenty-three fetal cadavers (9 female, 14 male) with an average age of 21.70 ± 3.12 (range: 16-28) weeks of gestation in the inventory of the Anatomy Department were included in the study. Measurements were made with a digital image analysis software and goniometer. RESULTS: The sulcal length, interoptic distance, planum length, and sulcal angle were detected as follows: 3.91 ± 0.74 mm, 6.88 ± 1.04 mm, 6.55 ± 1.51 mm, and 24.52 ± 9.51°, respectively. Considering the location of the posteromedial margin of OS according to PS, OS was identified as the sulcal in 56.5% (13 cases), postsulcal in 30.4% (7 cases), and asymmetric in 13% (3 cases). According to the sulcal length and angle, PS was identified as type 1 in 26.1% (6 cases), type 2 in 21.7% (5 cases), type 3 in 30.4% (7 cases), and type 4 in 21.7% (5 cases). CONCLUSIONS: Our findings suggest that the sulcal length and angle reach adult size in utero. Taking into account the fetal and the gathered adult measurements, the high percentage of steep angle compared to flat angle show that after birth, PS become more flat, probably depending on the variations of the sphenoid sinus pneumatization. Thus, more studies conducted on the alterations in PS and OS types relative to the pneumatization are needed in terms of patient positioning, selection of appropriate surgical approach, and intraoperative decision-making.

Growth dynamic of the geniculate ganglion in children: a retrospective computed tomography study.

PURPOSE: The main aim of this retrospective computed tomography (CT) study was to examine the morphometric development of the geniculate ganglion (GG) in children aged between 1 and 18 years for surgical approaches. METHODS: This study was placed on 41 patients (20 females and 21 males) including cochlear implantation cases aged from one to 18 (at mean, 6.44 ± 5.79) years. All the measurements belonging to the length, width and area of GG were performed with a CT scanner. RESULTS: The morphometric values of GG were not different in terms of sex or side, statistically (p > 0.05). The length (p = 0.155) of GG was not correlated with the increasing ages from one to 18 years; however, its area (p < 0.001) and width (p = 0.003) were found to be increased in the childhood period. Linear functions for the length, width and area of GG were calculated as y = 2.028 + 0.011 × age (years), y = 1.496 + 0.014 × age (years), and y = 3.239 + 0.035 × Age (years), respectively. The dehiscence of GG was found in 22 (26.8%) out of 82 temporal bones. CONCLUSION: Our data suggested that the area and width of GG were progressively increasing with age in the childhood period. The calculated formula representing the growth dynamic of GG in children and the incidence of the presence of the dehiscent GG can be useful for radiologists and otologists to estimate its size and to avoid iatrogenic injury during early childhood surgeries.

Radioanatomic Assessment of the Geniculate Ganglion Dehiscence and Dimension: A Cadaveric Study.

OBJECTIVE: The main aim of this study placed on cadavers was to compare the data related to geniculate ganglion (GG) dehiscence and dimension obtained from computed tomography (CT) with dissection values. METHODS: This study was conducted on 20 temporal bones obtained from 10 cadavers (4 female, 6 male) aged between 45 and 92 (71.50 ± 15.98) years. All the measurements related to GG dimension were performed with a CT scanner and microdissection. RESULTS: The size of GG including its area, length, and width did not show statistically significant differences in terms of sex, side, and assessment method (CT and cadaveric dissections). The dehiscent GG was observed in 6 (30%) and 5 (25%) out of 20 temporal bones in CT and cadaveric dissections, respectively. The presence and absence of GG dehiscence in CT and dissection were similar in 75%. CONCLUSIONS: Our findings based on dissection data suggest that radiologic evaluation of dehiscent GG detection might be erroneous by 25%, which highlights that surgeons should be careful when lifting the dura to prevent GG injury during middle cranial fossa surgical approaches. On the other hand, there was no statistical difference between CT and dissection measurements related to GG dimension.

Evaluation of the Foramen Magnum Area Calculated by Different Methods: A Radioanatomic Study.

PURPOSE: The main objective of the study was to evaluate the probable diversity in the area of the foramen magnum (FM) calculated by different measuring methods. METHODS: The study was conducted on 24 dry skulls, present in the collection of the Anatomy Department, Faculty of Medicine, Mersin University. The area of FM was calculated by different measurement methods including automatic field setting, Teixeria and Radinsky formulas obtained from anatomic (ASM), photographic (PSM) and radiologic (RSM) skull measurements. RESULTS: The areas of FMs calculated by Teixeria formula in RSM, PSM, and ASM were as follows: 857.96 ±â€Š99.97 mm, 796.68 ±â€Š105.08 mm, and 820.86 ±â€Š96.40 mm, respectively. The areas calculated by Radinsky formula in RSM, PSM, and ASM were as follows: 851.37 ±â€Š99.68 mm, 792.63 ±â€Š104.18 mm, and 814.85 ±â€Š94.99 mm, respectively. Lastly, the areas calculated by the automatic field setting of RSM and PSM software were as follows: 799.75 ±â€Š103.38 mm and 752.83 ±â€Š105.60 mm, respectively. CONCLUSION: Statistical significance was observed between the areas of FM obtained from RSM, ASM, and PSM when calculated by the automatic field setting, Teixeria formula, and Radinsky formula. The authors think that considering the amorphous shape of FM, the automatic field setting of the software should be used to obtain the most accurate numerical data related to the area of FM.

Morphometric Assessment of the Carotid Foramen for Lateral Surgical Approach.

OBJECTIVES: This study aimed to compare the right and left sides of the carotid foramen (CF) to determine its precise location according to certain anatomical landmarks. MATERIALS AND METHODS: Twenty human dry skulls were included in the study. A digital caliper and a digital image analysis software were used to obtain direct anatomical numerical values. Then, the same parameters on dry skulls were assessed with computed tomography (CT). RESULTS: CF was found to be round shaped (62.5%), oval shaped (32.5%), and tear-drop shaped (5%). In all cases, the position of CF was seen as just postero-laterally of the foramen lacerum. According to the jugular foramen, CF was seen to be anterior in 85% and antero-medial in 15% of the cases. Regarding the morphometric values of the surface area, the length and width of CF were observed to be 37.86±11.24 mm2, 8.02±1.09 mm, and 6.86±0.90 mm at direct anatomical measurements and 39.69±10.07 mm2, 7.89±1.14 mm, and 6.41±0.90 mm at CT, respectively. The angles between the supramastoid crest-CF-zygoma root and the supramastoid crest-CF-mastoid process were determined as 37.11±6.87º and 42.22±6.40º at direct anatomical measurements and 36.59±4.94º and 43.71±4.55º at CT, respectively. CONCLUSION: A significant difference in sides was not observed in relation with the numerical data of CF obtained from CT or from direct anatomical measurements of dry skulls. Moreover, a significant difference was not found between radiological and direct anatomical measurements. Therefore, precise radiological assessment of this region by an experienced neuroradiologist may be assumed as a fundamental need for successful surgeries of the skull base, in addition to thorough anatomical knowledge of neurootologists and neurosurgeons.

Morphometric properties of the facial canal in children: A retrospective computed tomography study.

PURPOSE: The main objective of the study was to examine the morphometric development of the facial canal in temporal bones aged from one to 18 years for pediatric otosurgeons and neurosurgeons. METHODS: The study was performed on 41 patients including cochlear implantation cases (20 females and 21 males) with a mean age of 6.44 ±â€¯5.79 years. All the measurements belonging to the facial canal including the length, width and angles of its segments were performed using the data of computed tomography assessment. RESULTS: The numerical data of the facial canal segments were not different in terms of sexes or sides, statistically (p > 0.05). The width of the labyrinthine segment (p = 0.145), the length of the tympanic segment (p = 0.555), the first (p = 0.067) and second (p = 0.060) genu angles seemed to reach adult size at two years of age. In addition, the length of the labyrinthine segment (p = 0.064) and the width of the mastoid segment (p = 0.264) seemed to attain adult size at four years, while the width of the meatal foramen (p = 0.264) seemed to arrive adult size at seven years. However, the length of the mastoid segment and the width of the tympanic segment were developing independently of increasing age between 1 and 18 years. CONCLUSION: Our data suggested that, contrary to the general acceptance in the literature, the dimension of the facial canal segments show remarkable changes during the transition from intrauterine life to adult life. The regression equations representing the facial canal growth dynamic in children may be useful for otosurgeons to estimate the size of its segments and to prevent iatrogenic injury during early childhood surgeries such as cochlear implantation.

The Predictability Precision of Superior Semicircular Canal Through Radiological Assessment and Microanatomical Dissection.

OBJECTIVE: There is still ongoing research on the relationship of arcuate eminence (AE) and superior semicircular canal (SSC). We aimed to evaluate the precision of predictability of SSC through the morphology of AE via radiological means. MATERIALS AND METHODS: This investigation is performed on 12 dry skulls belonging to Mersin University Medical Faculty department of anatomy. Computed tomography (CT) assessment is performed with 0.5-mm-thin sections temporal bone algorithm on dry skulls which were marked with fixated copper wire by scotch tapes on the most prominent part of the middle fossa floor assuming the location of AE. The data are reformatted on the workstation with vitrea 2.0. The distances of the determined three points including lateral (A), apical (B), and medial (C) of the SSC and the copper wire are measured radiologically. Also, the height between the most apical part of the SSC to the floor of the skullbase (H) is measured. The angles between the placed copper wires and the SSC (E) are calculated. The angle between SSC and the midpoint of the IAC (F) and SSC to the sulcus of the greater GSPN (G) were measured. The nearest distance was measured between the most posterior part of the SSC and the point marked by the perpendicular line drawn from the medial border of the petrous bone to the most posterior part of the internal auditory canal (IAC) (D). RESULTS: The right and left A, B, and C distances are 2.54+/- 2.75, 3.67+/-3.16, 5.85+/-3.77; 2.92+/-2.24, 3.68+/-2.93, 6.09+/-3.40, respectively. We could not find any statistical significance when the right A, B, and C distances were compared with the left values. Examination of the values revealed that C distance is greater than the A distance of the same side both for right (p=0.040) and left (p=0.022) measurements. The calculated left and right E angles are 30.313+/-12.838, and 35.558+/-18.437 degrees, respectively. Statistical significance was not found between the right and left angles. The right and left F, G angles were 53.17, 47.25; 93.58, 100.92 degrees; and D distances are 8.01, 8.13 millimeters, respectively. Statistical significance was not found when right and left E, F, G angles and D distances were compared. Among 12 left and 12 right sides, the copper wire was found to be nearly overlapping to SSC in two in the right and only one in the left. CONCLUSION: This study reveals that there is a great variability predicting the exact location of SSC through the prominence of AE. Complementary studies are needed with greater number of dry skulls and cadavers. Comparison of different hypothesis including the effect of temporal lobe sulcus is to be discussed to better enlighten the exact relationship of the aforementioned anatomical structures.

Variations in the origins of the thyroid arteries on CT angiography.

OBJECTIVE: To investigate the anatomical variations in the origins of the thyroid arteries on CT angiography images. METHODS: The presence and the origins of the superior thyroid artery, the inferior thyroid artery, and the thyroidea ima artery were retrospectively evaluated based on carotid CT angiography examinations. The bifurcation level of the common carotid artery with respect to the cervical vertebrae and disc spaces was also determined. A total of 640 patients were included in the study. RESULTS: The right and left superior thyroid arteries arose from the external carotid artery in 413 (64.5%) and 254 (39.7%) patients, from the bifurcation of the common carotid artery in 131 (20.5%) and 148 (23.1%) patients, and from the common carotid artery in 90 (14.1%) and 226 (35.3%) patients, respectively. We could not observe the right and the left superior thyroid arteries in 6 (0.9%) and 12 (1.9%) of the patients, respectively. However, the right and left inferior thyroid arteries were not identified in 14 (2.2%) and 45 (7%) of the patients, respectively. The thyroidea ima artery was detected in 2.3% of the patients. CONCLUSION: The visualization of thyroid arteries on CT angiography images enables the anatomy of the arterial supply system of the thyroid gland to be explored in a noninvasive manner prior to surgery.

The evaluation of the right inferior phrenic artery diameter in cirrhotic patients.

PURPOSE: The purpose of this study is to evaluate the relationship between right inferior phrenic artery diameter and portal hypertension in cirrhotic patients. METHODS: CT examinations of 38 patients with chronic liver disease (patient group) and 40 patients without any liver disease (control group) were evaluated. The right inferior phrenic artery diameter of the patient and control group were measured. CT findings of portal hypertension, which were accepted as ascites, collaterals, splenomegaly and portal vein diameter greater than 13 mm, were determined and scored in the patient group. Patients obtained scores between one and four with respect to portal hypertension findings, and the scores were compared with phrenic artery diameters. Child-Pugh and MELD scores of the patients were also calculated. RESULTS: The mean diameter of the right inferior phrenic artery in the patient group was larger than that in the control group (p < 0.001). The mean phrenic artery diameter of the patients with score 1 was significantly different from those with score 2 (p = 0.028), score 3 (p = 0.001) and score 4 (p = 0.005). We found a linear and moderate relationship between phrenic artery diameter values and Child-Pugh scores (p = 0.012, r = 0.405). CONCLUSION: Dilatation of the right inferior phrenic artery in cirrhotic patients may be a nonspecific sign of developing portal hypertension.

Stent-Assisted Coil Embolization of Posttraumatic Dissecting Carotid Aneurysm Causing Ophthalmoplegia.

BACKGROUND: Ophthalmoplegia secondary to a traumatic dissecting aneurysm in the cavernous segment of internal carotid artery (ICA) is a relatively rare entity. Anticoagulant or antiplatelet therapy is the preferred treatment option for carotid dissections. However, endovascular interventions are noninvasive and alternative methods to surgery, especially in cases of aneurysms that do not respond to medical therapy. CASE REPORT: We report of a 19-year-old man presenting with left-sided, total ophthalmoplegia after a traffic accident. Magnetic resonance imaging (MRI) and digital subtraction angiography (DSA) revealed a dissection beginning at the cervical segment of internal carotid artery (ICA) together with a dissecting aneurysm in the cavernous segment. A stent was placed in the narrowed and dissected segment of ICA, and the dissecting aneurysm of the cavernous segment was successfully managed with a stent-assisted coil embolization. After the endovascular treatment of the aneurysm, a full recovery of cranial nerve function was achieved. CONCLUSIONS: Immediate diagnosis and appropriate therapy of dissecting aneurysms is necessary for good clinical outcomes in cases of ophthalmoplegia.

Bilateral thalamic lesions: A pictorial review.

Bithalamic lesions are uncommon, however, both focal and systemic disorders may present bilateral abnormalities in the thalamus in different acute and chronic clinical situations. Neuroimaging, in particular magnetic resonance imaging, plays an essential role in diagnostic approach. Imaging features such as signal alterations, diffusion restriction or contrast enhancement are helpful in characterization of these abnormalities. The location of the lesions may provide key information because some pathologies typically involve a certain part of the thalamus. In addition to thalamic findings, neuroimaging findings in other parts of the brain associated with the clinical and laboratory information should be taken into account to make a correct diagnosis.

Diabetic striatopathy in a patient with hemiballism.

Diabetic striatopathy is a rare and life-threatening manifestation of diabetes mellitus. The disease commonly affects individuals of Asian descent, females, and the elderly. Patients usually present with hemiballism-hemichorea caused by nonketotic hyperglycemia. Hemiballism-hemichorea is defined as involuntary continuous random appearing movement involving one side of the body. This movement disorder may develop secondary to stroke, diabetic striatopathy, neoplasm, infection, Wilson's disease, and thyrotoxicosis. Despite being rare, prompt recognition of a hyperglycemia-induced hemiballism-hemichorea is essential because the symptoms are reversible with correction of hyperglycemia. Diagnosis is possible based on blood analysis and neuroimaging findings. Laboratory tests reveal raised blood glucose and hemoglobin A1C levels which indicate poorly controlled diabetes. Neuroimaging provides suggestive findings of diabetic striatopathy which are hyperattenuation on computed tomography and hyperintensity on T1-weighted magnetic resonance imaging in the basal ganglia. In this case report, our aim is to present neuroimaging findings in an adult man with sudden onset of hemiballism associated with nonketotic hyperglycemia.

Nonodontogenic mandibular lesions: differentiation based on CT attenuation.

Mandibular lesions are classified as odontogenic and nonodontogenic based on the cell of origin. Odontogenic lesions are frequently encountered at head and neck imaging. However, several nonodontogenic pathologies may also involve mandible and present further diagnostic dilemma. Awareness of the imaging features of nonodontogenic lesions is crucial in order to guide clinicians in proper patient management. Computed tomography (CT) may provide key information to narrow diagnostic considerations. Nonodontogenic mandibular lesions may have lytic, sclerotic, ground-glass, or mixed lytic and sclerotic appearances on CT. In this article, our aim is to present various nonodontogenic lesions of the mandible by categorizing them according to their attenuations on CT.

Microsurgical anatomy and variations of the anterior clinoid process.

AIM: The aim of this study was to better define the microsurgical anatomy of the supra/parasellar region and describe variations of the anterior clinoid process (ACP). MATERIAL AND METHODS: Fifteen formalin-fixed cadaver heads and 25 dry skulls were used to define the microsurgical anatomy of the ACP and related structures. The presence of the caroticoclinoid foramen (CaCF) as well as other relevant measurements were all noted. Radiological examination of the CaCF was also demonstrated on dry skulls. RESULTS: Interosseous bridges, which form between the anterior and middle clinoid processes or connect all three (anterior, middle and posterior) clinoid processes, were found in 30% of the specimens. The average basal width, length and thickness of the ACP were 7.3 mm, 9.7 mm and 5.4 mm, respectively. Length of the optic nerve (ON) up to the falciform ligament (FL) was 10.9 mm; length of the ON under the FL was 2.7 mm; length of ON after removal of the ACP and unroofing the optic canal was 21.1 mm. CONCLUSION: This study contributes to the relationship of important vascular, neural, bone and dural layers of this region and also demonstrates the variations of ACP by means of microsurgical dissections and radiological examinations.

Recurrent and atypical posterior reversible encephalopathy syndrome in a child with hypertension.

Posterior reversible encephalopathy syndrome (PRES) is a clinical and radiologic entity with typical symptoms including headache, seizures, visual disturbance, altered mental status, vomiting, nausea and focal neurologic signs. In this article, we report recurrent and atypical PRES in a child with hypertension due to end-stage renal disease (ESRD) who was on a peritoneal dialysis program for 6 months. After the second hypertension attack, PRES findings did not recover and persisted as encephalomalacia. As far as we know, this case is the first child with ESRD who developed encephalomalacia after recurrent episodes of PRES. When a patient with a history of PRES presented with new clinical and neuroradiological findings, recurrent PRES should be considered.

The importance of early diagnosis and appropriate treatment in Grisel's syndrome: report of two cases.

Grisel's syndrome designates subluxation of atlanto-axial joint unrelated to trauma or bone disease. Atlanto-axial subluxation is seen after the upper neck inflammatory processes of head and neck region. Moreover, this rare clinical entity has been observed after various otolaryngological surgical approaches including adenoidectomy, tonsillectomy and mastoidectomy. An 8-year-old girl and 14 year-old boy presented with complaints of painful torticollis. The first patient was operated on at another health center due to adenoid hypertrophy. She was referred to our clinic on the postoperative 5th day with painful torticollis. The diagnosis was established by computerized tomography and three-dimensional reconstructions. The second patient had a history of throat infection. Radiological investigation demonstrated atlantoaxial subluxation. The patients were treated with external fixation, antibiotic therapy, muscle relaxants, and anti-inflammatory therapy. Early diagnosis and appropriate treatment resulted in a good outcome in our patients. Grisel's syndrome must be considered in the differential diagnosis in children with painful torticollis associated with upper respiratory tract infection and after various otolaryngological surgical procedures. We report two cases of Grisel's syndrome which emphasize on the importance of early diagnosis for appropriate and successful treatment.

Anatomical variations of the foramen magnum, occipital condyle and jugular tubercle.

AIM: The foramen magnum (FM) is a unique and complex anatomical region. The occipital condyle (OC) and jugular tubercle (JT) are the main bony structures which obscure the anterolaterally situated lesions of the FM.The aim of this study was to revisit the anatomy of the FM region and assess variations of the surrounding structures. MATERIAL AND METHODS: Observations, on thirty dry skulls (dried specimens, 60 sides) and ten formalin-fixed cadaveric heads with perfused vessels, were carried out to define the microsurgical anatomy of the FM region. Morphometric analysis and variations of the FM, OC, JT and hypoglossal canal (HC) were noted. Radiological assessment (3D-computed tomography) of the OC, JT, HC were also conducted on dry skulls. RESULTS: The short and long OC were demonstrated in 5% and 33% of the specimens, respectively. Flat formation of the JT was determined in 10% and tall JT was found in 23% of the specimens. The comparison of the anatomical measurements and the correspondent radiological mean values did not achieve statistical significance. CONCLUSION: The OC and JT are the main bony prominences obstructing the anterolateral surface of the brainstem. Neurosurgeons should be familiar with variations of the structures surrounding the FM in order to perform the safest and widest exposure possible.