[Normal Anatomy of the Pituitary Gland].

This study describes the anatomy of the pituitary gland during endoscopic endonasal surgery. Before surgery, the extent of pneumatization of the sphenoid sinus and bony septations in the sphenoid sinus should be evaluated using computed tomography. After wide sphenoidotomy, several important surgical landmarks, including the medial and lateral opticocarotid recesses and carotid protuberances, can be observed in the sphenoid sinus. The pituitary gland is composed of two components: the adenohypophysis and neurohypophysis. Two small vessels, the superior and inferior hypophyseal arteries, supply the pituitary gland. Several vital structures exist inside the cavernous sinus, including the internal carotid artery and cranial nerves. Understanding the surgical anatomy is mandatory for treating lesions around the pituitary fossa via the endoscopic endonasal approach.

Chronic epidural hematoma with frontal skull-base destruction mimicking osteogenic tumor, associated with coagulopathy due to chronic hepatitis C.

Background: Intracranial epidural hematoma is generally evoked by acute coup-injury. Though rare, it has a chronic clinical course and can be a non-traumatic event. Case Description: The patient was A thirty-five-year-old man with a complaint of one-year history of hand tremor. He was suspected diagnosis of osteogenic tumor with differential diagnosis of epidural tumor, or abscess in the right frontal skull base bone, associated with chronic type C hepatitis because of his plain CT and MRI. Results: Results of examinations and surgery, the extradural mass was chronic epidural hematoma without skull fracture. We diagnosis he is the rare case of chronic epidural hematoma caused by coagulopathy due to chronic hepatitis C. Conclusion: We reported a rare case of chronic epidural hematoma caused by coagulopathy due to chronic hepatitis C. The repeated spontaneous hemorrhage in the epidural space formed the capsule and destruction of skull base bone, just mimicking skull base tumor.

Pathology of Crooke Cells in the Human Pituitaries: A Timely Review.

Crooke cell change was first found in the regressed and suppressed corticotroph (adrenocorticotropic hormone-producing) cells, and now is known to occur in pituitary tumors. The tumor cells of this type can be recognized by morphology with immunohistochemistry, and are well known to predict aggressive behavior such as invasion and rare metastases. This is one of the representative neuroendocrine tumors in the pituitary which is now considered to have malignant potential as proposed in the pancreas and gastrointestinal tracts. It is important to emphasize the pituitary tumor pathology such as Crooke cell change for prognostication and appropriate therapies. This review article describes the evolution from the Crooke cells to Crooke cell tumors which is timely along with the Fifth WHO classification 2022 published online.

Analysis of Insulinoma-Associated Protein 1 Expression in Pituitary Neuroendocrine Tumors.

Insulinoma-associated protein 1 (INSM1) is a representative diagnostic marker of neuroendocrine neoplasms (NENs); however, it has not yet been used to diagnose pituitary neuroendocrine tumors (PitNETs), according to the 2022 World Health Organization (WHO) classification of pituitary tumors. This study aimed to examine the expression of INSM1 using immunohistochemistry, in the various cell lineages of PitNET classified by hormone secretion and transcription factor expression. INSM1 expression in PitNETs (different subtypes) and normal pituitary tissues was immunohistochemically assessed. The results were interpreted as scores of 0 (negative), 1 (focally positive), or 2 (frankly positive), depending on the proportion of cell staining. Twenty-eight of 35 PitNET cases (80%) showed INSM1 positivity in their nuclei. The staining in each histological subtype of PitNETs was as follows: somatotroph tumors, score 0 = 3/5, score 1 = 1/5, score 2 = 1/5; lactotroph tumors, score 0 = 2/5, score 1 = 1/5, score 2 = 2/5; thyrotroph tumors, score 2 = 5/5; corticotroph tumors: score 1 = 1/9, score 2 = 8/9; gonadotroph tumors, score 0 = 2/10, score 1 = 0/10, score 2 = 8/10; and unclassifiable tumor, score 1 = 1/1. INSM1 expression in most PitNETs was obtained, similar to that in the normal pituitary gland; thus, INSM1 may maintain the characteristics of anterior pituitary cells and pituitary tumors.

Immunohistochemical Analyses of Mammalian Target of Rapamycin (mTOR) Expression in Pituitary Neuroendocrine Tumors (PitNETs): mTOR as a Therapeutic Target for Functional PitNETs.

Current therapeutic modalities for pituitary neuroendocrine tumors (PitNETs) include medication, surgery, and radiotherapy. Some patients have tumors that are refractory to current modalities. Therefore, novel treatment options are needed for patients with intractable diseases. Consequently, we examined the pathological data of PitNETs to study medical therapies. We retrospectively studied 120 patients with histologically diagnosed PitNETs. We used the data for the histopathological examination of hormones, such as growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone, thyroid stimulating hormone, luteinizing hormone, follicle-stimulating hormone, and α-subunit, together with the immunohistochemical studies of the phospho-mammalian target of rapamycin (mTOR), cytokeratin (CAM5.2), somatostatin receptor (SSTR) type 2 and 5, Pit-1 (POU1F1/GHF-1), steroidogenic factor-1 (SF-1), and Tpit. GH-, PRL-, and SSTR5-immunopositive PitNETs had significantly higher percentage of mTOR-positivity, compared with GH-, PRL-, and SSTR5-immunonegative Pit NETs. Our results show that activation of the AKT/phosphatidylinositol-3-kinase pathway, including mTOR activation, might be related the development of PitNETs, especially GH- and PRL-producing PitNETs. Thus, mTOR is a potential target for treating functional PitNETs.

Double pituitary neuroendocrine tumors in a patient with normal growth hormone level acromegaly: A case report and review of the literature.

Background: Acromegaly is a rare disease caused by growth hormone (GH) hypersecretion caused by a pituitary neuroendocrine tumor (PitNET). However, some acromegaly patients show normal GH levels, and they can be a pitfall in clinical diagnosis. Moreover, rarely, synchronous true double or multiple PitNETs are encountered. Moreover, these PitNETs increase the risk of a left lesion during surgical exploration. Case Description: The patient, who was a 73-year-old female, was referred to our hospital with a chief complaint of headache. Assessment of basal anterior pituitary function revealed a slightly high level of insulin-like growth factor-1 (IGF-1) (standard deviation, 2.4), and her physical findings exhibited mild acromegalic features. The endocrine evaluation confirmed acromegaly and magnetic resonance imaging (MRI) showed a macro PitNET with suprasellar extension. Endoscopic endonasal surgery (EES) was performed to remove the macro PitNET. Although postoperative MRI showed complete removal of the macro PitNET, endocrinological testing indicated no improvement in GH or IGF-1 excess. Pathological examination of the surgical specimen revealed a gonadotropic PitNET. Therefore, we repeated the MRI scan and found a micro PitNET in the thin left normal pituitary gland. A second EES was successfully performed to remove the micro PitNET completely, and both endocrinological and pathological examinations confirmed that the disease was cured. Conclusion: Diagnosing acromegaly with low GH levels requires close monitoring. Double PitNETs are relatively rare and can cause incomplete remission of functional PitNETs.

A case of aggressive pituitary neuroendocrine tumour with extremely rapid progression: possible diagnostic value of TERT promoter methylation.

Most pituitary adenoma/neuroendocrine tumours (PitNET) are histologically benign and grow slowly; however, a subset of these tumours exhibit a more aggressive clinical course characterized by local invasiveness and early recurrence. These high-risk PitNETs often require multiple surgeries and radiation over several years and may eventually acquire carcinomatous characteristics, such as metastasis in some cases. Herein, we report a rare case of PitNET causing oculomotor paresis with extremely rapid recurrence only 3 months after initial surgery, followed by lethal liver metastasis. Preoperative magnetic resonance imaging and intraoperative findings were consistent with typical PitNETs, other than moderate invasion of the cavernous sinus. Pathological examination of the specimen obtained from the initial transsphenoidal surgery revealed increased mitosis and elevated rates of cells positive for Ki-67 and p53. Based on the immunohistochemical assessment for transcription factors and pituitary hormones, the diagnosis was determined to be a silent sparsely granulated corticotroph PitNET with focal malignant transformation. Aggressive features represented by Ki-67 and p53 positivity were more robust in recurrent and metastatic specimens, but hormone immunostaining was decreased. Epigenetic analysis revealed methylation of the telomerase reverse transcriptase (TERT) promoter in the tumour, resulting in TERT upregulation. Despite extensive research, markers for distinguishing extremely aggressive PitNETs have not been determined. Although further analysis is needed, our case demonstrates the possible usefulness of assessing TERT promoter methylation status in the stratification of recurrence risk in extremely high-risk variants of PitNET.

Cathepsin D Inhibits Angiogenesis in Pituitary Neuroendocrine Tumors.

Prolactin and growth hormone can acquire anti-angiogenic properties after undergoing proteolytic cleavage by Cathepsin D and bone morphogenetic protein 1 (BMP-1) into fragments known as vasoinhibins. Little is known about the effect of vasoinhibins on angiogenesis through the involvement of key cleavage enzymes Cathepsin D and BMP-1 in pituitary neuroendocrine tumors (PitNETs, formerly pituitary adenomas). The purpose of this study was to investigate the mechanism of action of Cathepsin D and BMP-1 on angiogenesis in PitNETs compared with that of pro-angiogenic factors, including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor-2 (FGF2). A total of 43 patients were enrolled in a retrospective analysis and 22 samples were suitable for RNA extraction, including 16 nonfunctional PitNETs and six somatotroph tumors. The mRNA and protein levels of Cathepsin D, BMP-1, VEGF, and FGF2 were compared with those of von Willebrand factor, which was assessed to determine the vascularization of PitNETs. Cathepsin D and FGF2 were significantly correlated with vascularization in PitNETs. Both Cathepsin D and FGF2 are highly involved in angiogenesis in PitNETs, although the effect of Cathepsin D as an anti-angiogenic factor is dominant over that of FGF2 as a pro-angiogenic factor.

Molecular, functional, and histopathological classification of the pituitary neuroendocrine neoplasms.

In 2017, WHO published an updated classification of the pituitary adenomas according to the lineages defined by the transcription factors, PIT1, SF1 and TPIT. Nomenclature of the pituitary tumors follows the mature cell types such as somatotroph (GH), lactotroph (LH), thyrotroph, corticotroph, and gonadotroph (FSH, LH). Null cell adenomas are defined by the absence of expression of any hormones and transcription factors. Not infrequently, the pituitary adenomas are invasive to the adjacent structures and are designated as aggressive adenomas. Knosp grading is often used to define the aggressiveness of the tumor. Sparsely granulated somatotroph adenomas and Crooke cell corticotroph adenomas are representative aggressive adenomas. Recently, genomics regarding various adenomas have been clarified, such as GNAS for somatotrophs and USP8 for corticotrophs. Familial pituitary adenomas are another aspect which has been clarified such as MEN1, Carney's complex, familial isolated pituitary adenoma and McCune-Albright syndrome. The pituitary adenomas often produce GH or PRL, hormones of PIT1 transcription factor. It has been agreed that the pituitary adenomas share the characteristics of neuroendocrine neoplasms. The terminology of pituitary neuroendocrine tumor has been discussed. This review article covers various aspects of pituitary adenomas.

A Case of Dermoid Cyst Arising in the Temporal Lobe.

Intracranial dermoid cysts are rare congenital lesions that result from abnormal sequestration of ectodermal cells during neural tube formation. These tumors are especially rare in lateral areas such as in the temporal lobe. In this study, we report a case of dermoid cyst located in the right temporal lobe. A 50-year-old man was referred for further treatment of a tumor. CT revealed a low-density mass lesion in the right temporal lobe, with calcification. MRI showed the lesion with high signal intensity on diffusion-weighted imaging, high-low mixed signal intensity on T1-weighted imaging, and iso-high signal mixed intensity on T2-weighted imaging; the capsule was enhanced with gadolinium. Differential diagnosis included dermoid cyst, epidermoid cyst, teratoma, and neurenteric cyst. We decided to perform surgery for the improvement of his symptom, histopathological diagnosis, and radical cure. A right temporal craniotomy was performed, and the tumor was found adherent to the surrounding brain tissue. The tumor was completely removed under subpial dissection. Hair was confirmed in the tumor content. On histopathology, the cyst wall was lined with stratified squamous epithelium, sebaceous glands, small vessel aggregates, and inflammatory infiltrate. Keratinized material and hair were found in the lumen. The patient was discharged 7 days after surgery with no new neurologic deficits. This case was unusual in terms of the effect of gadolinium enhancement on MRI, and the presence of adipose tissue and calcification were useful for diagnosis. It is vital to consider prevention of chemical meningitis due to intrathecal dissemination of the tumor content intraoperatively.

The orbitopterygoid corridor as a deep keyhole for endoscopic access to the paranasal sinuses and clivus.

OBJECTIVE: The anteromedial triangle (AMT) is the triangle formed by the ophthalmic (V1) and maxillary (V2) nerves. Opening of this bony space offers a limited access to the sphenoid sinus (SphS). This study aims to demonstrate the utility of the orbitopterygopalatine corridor (OPC), obtained by enlarging the AMT and transposing the contents of the pterygopalatine fossa (PPF) and V2, as an entrance to the SphS, maxillary sinus (MaxS), and nasal cavity. METHODS: Five formalin-injected cadaveric specimens were used for this study (10 approaches). A classic pterional approach was performed. An OPC was created through the inferior orbital fissure, between the orbit and the PPF, by transposing the PPF inferiorly. The extent of the OPC was measured using neuronavigation and manual measurements. Two illustrative cases using the OPC to access skull base tumors are presented in the body of the article. RESULTS: Via the OPC, the SphS, MaxS, ethmoid sinus (EthS), and nasal cavity could be accessed. The use of endoscopic assistance through the OPC achieved better visualization of the EthS, SphS, MaxS, clivus, and nasal cavity. A significant gain in the area of exposure could be achieved using the OPC compared to the AMT (22.4 mm2 vs 504.1 mm2). CONCLUSIONS: Opening of the AMT and transposition of V2 and the contents of the PPF creates the OPC, a potentially useful deep keyhole to access the paranasal sinuses and clival region through a middle fossa approach. It is a valuable alternative approach to reach deep-seated skull base lesions infiltrating the cavernous sinus and middle cranial fossa and extending into the paranasal sinus.

A Case of Nervus Intermedius Neuralgia.

BACKGROUND: Nervus intermedius neuralgia is an extremely rare craniofacial neuralgia characterized by paroxysmal episodes of pain located deep in the ear, typically triggered by sensory or mechanical stimuli at the wall of the auditory canal without underlying pathology. Pain is sometimes associated with disorders of lacrimation, salivation, and taste. CASE DESCRIPTION: We present a case of a surgically treated 68-year-old man with left paroxysmal deep ear pain for 20 years before presentation. Preoperative 3-dimensional magnetic resonance cisternography/magnetic resonance angiography (3D-MRC/MRA) fusion imaging showed severe compression of the facial nerve by the anterior inferior cerebellar artery in the cisternal portion with associated nerve deformity. We suspected nervus intermedius neuralgia and decided to perform microvascular decompression of the facial nerve. Transposition of the artery led to sufficient decompression of the nerve. The pain disappeared immediately after surgery. CONCLUSIONS: It is important to keep in mind the possibility of nervus intermedius neuralgia in patients who present with intermittent episodes of pain located deep in the ear. Furthermore, 3D-MRC/MRA fusion imaging is useful for decision-making in surgery. Microvascular decompression was highly effective in our case. Based on radiological findings, microvascular decompression should be considered a viable treatment option.

Effects of olive leaf powder supplemented to fish feed on muscle protein of red sea bream.

Olive leaf is known to have the high polyphenol content of 6-9% in dry weight. We investigated the effects of olive leaf powder (OLP) supplemented to fish feed on muscle protein of red sea bream (Pagrus major). Fish reared with feed containing 8% OLP for 40 days had 1.4 times higher myofibril content and 2.2 times higher acid-soluble collagen content than fish reared with control feed for the same period. On the other hand, sarcoplasmic protein content and collagenase activity of the muscle were almost the same between the control fish and OLP-diet fish. Microstructure observation of fish muscle showed that OLP-diet fish has more rigid endomysium structure than that of the control-diet fish. Since collagen fiber in endomysium is responsible for the texture of the muscle, feeding OLP to aquaculture fish will lead to a harder muscle texture. The present study suggests that OLP is a useful feed additive to enhance the texture of aquaculture red sea bream muscle through strengthening of the collagen structure in the muscle.

Surgical Anatomy for the Endoscopic Endonasal Approach to the Ventrolateral Skull Base.

The authors describe the surgical anatomy for the endoscopic endonasal approach (EEA) to the ventrolateral skull base. The ventrolateral skull base can be divided into two segments: the upper lateral and lower lateral skull base. The upper lateral skull base includes the cavernous sinus and the orbit, while the lower lateral skull base includes the petrous apex, Meckel's cave, parapharyngeal space, infratemporal fossa, etc. To gain access to the upper lateral skull base, a simple opening of the ethmoid sinus provides sufficient exposure of this area. To reach the lower lateral skull base, a transpterygoid approach, following ethmoidectomy, is a key procedure providing wide exposure of this area. Understanding of surgical anatomy is mandatory for treating ventrolateral skull base lesions via EEA. An appropriate, less-invasive approach should be applied depending on the size, location, and type of lesion.

New Technique for Chiasmapexy Using Iliac Crest Bone Graft: 2 Cases of Visual Impairment Caused by Empty Sella Syndrome.

BACKGROUND: Chiasmapexy is used to treat empty sella syndrome, and various materials are used for the elevation of the optic chiasm. However, the use of artificial substances may have the risk of graft infection, and fat and muscle may be absorbed over the long term after surgery. In addition, bone and cartilage may be unavailable in adequate amounts. Here, we describe a new technique for chiasmapexy using an iliac crest bone graft. CASE DESCRIPTION: The first patient was a 71-year-old woman who had undergone transsphenoidal surgery twice for the treatment of pituitary adenoma and Rathke cleft cyst. The optic chiasm collapsed after the second surgery and her visual field worsened gradually. We performed chiasmapexy using fat, fascia, and a septal mucosal flap, but the optic chiasm did not remain in the normal position because of graft shrinkage. Finally, we used an iliac crest bone graft, which resulted in good visual function. The second patient was a 58-year-old man who was incidentally diagnosed with empty sella syndrome. The patient's bitemporal hemianopia gradually progressed. As in the first case, we used an iliac crest bone graft, which halted the deterioration of visual function after chiasmapexy. CONCLUSIONS: The advantages of iliac bone are that it is less likely to absorb and become infected than synthetic materials. This method may be suitable for reoperative cases, especially those wherein the septal cartilage has been removed in a previous surgery. This method will halt visual deterioration and may be one of the considerable options for chiasmapexy operations.

Training model for control of an internal carotid artery injury during transsphenoidal surgery.

OBJECTIVES: As the adoption of endoscopic endonasal approaches (EEA) continues to proliferate, increasing numbers of internal carotid artery (ICA) injuries are reported. The objective of this study was to develop a synthetic ICA injury-training model that could mimic this clinical scenario and be portable, repeatable, reproducible, and without risk of biological contamination. METHODS: Based on computed tomography of a human head, we constructed a synthetic model using selective laser sintering with polyamide nylon and glass beads. Subsequently, the model was connected to a pulsatile pump using 6-mm silicon tubing. The pump maintains a pulsatile flow of an artificial blood-like fluid at a variable pressure to simulate heart beats. Volunteer surgeons with different levels of training and experience were provided simulation training sessions with the models. Pre- and posttraining questionnaires were completed by each of the participants. RESULTS: Pre- and posttraining questionnaires suggest that repeated simulation sessions improve the surgical skills and self-confidence of trainees. CONCLUSION: This ICA injury model is portable; reproducible; and avoids ethical, biohazard, religious, and legal problems associated with cadaveric models. A synthetic ICA injury model for EEA allows recurring training that may improve the surgeon's ability to maintain endoscopic visualization, control catastrophic bleeding, decrease psychomotor stress, and develop effective team strategies to achieve hemostasis. LEVEL OF EVIDENCE: NA Laryngoscope, 127:38-43, 2017.

Comparative analysis of the anterior transpetrosal approach with the endoscopic endonasal approach to the petroclival region.

OBJECTIVE The endoscopic endonasal approach (EEA) offers direct access to midline skull base lesions, and the anterior transpetrosal approach (ATPA) stands out as a method for granting entry into the upper and middle clival areas. This study evaluated the feasibility of performing EEA for tumors located in the petroclival region in comparison with ATPA. METHODS On 8 embalmed cadaver heads, EEA to the petroclival region was performed utilizing a 4-mm endoscope with either 0° or 30° lenses, and an ATPA was performed under microscopic visualization. A comparison was executed based on measurements of 5 heads (10 sides). Case illustrations were utilized to demonstrate the advantages and disadvantages of EEA and ATPA when dealing with petroclival conditions. RESULTS Extradurally, EEA allows direct access to the medial petrous apex, which is limited by the petrous and paraclival internal carotid artery (ICA) segments laterally. The ATPA offers direct access to the petrous apex, which is blocked by the petrous ICA and abducens nerve inferiorly. Intradurally, the EEA allows a direct view of the areas medial to the cisternal segment of cranial nerve VI with limited lateral exposure. ATPA offers excellent access to the cistern between cranial nerves III and VIII. The quantitative analysis demonstrated that the EEA corridor could be expanded laterally with an angled drill up to 1.8 times wider than the bone window between both paraclival ICA segments. CONCLUSIONS The midline, horizontal line of the petrous ICA segment, paraclival ICA segment, and the abducens nerve are the main landmarks used to decide which approach to the petroclival region to select. The EEA is superior to the ATPA for accessing lesions medial or caudal to the abducens nerve, such as chordomas, chondrosarcomas, and midclival meningiomas. The ATPA is superior to lesions located posterior and/or lateral to the paraclival ICA segment and lesions with extension to the middle fossa and/or infratemporal fossa. The EEA and ATPA are complementary and can be used independently or in combination with each other in order to approach complex petroclival lesions.

[A Case of Thrombotic Thrombocytopenic Purpura in a Patient Undergoing FOLFOX6 plus Panitumumab Therapy for Unresectable Recurrent Rectal Cancer with a Rapidly Progressive Course].

A 71-year-old male patient began FOLFOX6 plus panitumumab treatment for unresectable recurrent rectal cancer. He developed thrombocytopenia after 2 courses of treatment and therefore a platelet transfusion was performed. The day after transfusion, the patient developed jaundice and hematuria. His lactate dehydrogenase levels had increased and a peripheral blood smear review revealed the presence of schistocytes. Anti-ADAMTS13 antibodies were present, and there was a reduction in ADAMTS13 activity. The patient was diagnosed with thrombotic thrombocytopenic purpura and treated with a plasma exchange. The day after the plasma exchange, his clinical condition rapidly worsened and he died. Thrombocytopenia due to chemotherapy often appears as myelosuppression. If conditions such as jaundice, indirect bilirubinemia, or hematuria appear during the course of chemotherapy, this condition must be considered as a differential diagnosis.

Growth stabilization and regression of meningiomas after discontinuation of cyproterone acetate: a case series of 12 patients.

BACKGROUND: The relationship between meningiomas and exogenous sex hormones is well known, but cyproterone acetate (CA), a progesterone agonist, seems to have a stronger influence on tumor growth. OBJECTIVE: To show the close relationship between CA treatment and meningioma growth. METHODS: Since 2010, all patients referred to our clinic for a suspicion of meningioma were questioned specifically about exogenous sex hormone intake and more specifically about CA intake. Twelve patients harboring one or multiple meningiomas and treated with CA were identified. CA was stopped in all cases. Tumor volumes and diameters were measured on serial MRIs and compared to the last MRI before CA withdrawal. RESULTS: Ten patients with multiple tumors had been taking the drug for a longer period of time (mean of 20.4 years) than the two patients with one tumor (10 years). Two patients with multiple tumors underwent surgery because of rapidly decreased visual acuity at the time of diagnosis. Discontinuation of CA led to tumor shrinkage in 11 patients and a stop in tumor growth in one [mean tumor volume reduction was around 10 cm(3)/year; range (0.00; 76)]. There was no regrowth during a mean follow-up period of 12 months (range: 5-35). CONCLUSION: For patients diagnosed with a meningioma and treated with CA, medication withdrawal followed by observation should be the first line of treatment. Care should be taken with long-term use of high doses of CA, and serial brain MRIs should be considered after several years of CA.

Endoscopic endonasal cranial base surgery simulation using an artificial cranial base model created by selective laser sintering.

Mastery of the expanded endoscopic endonasal approach (EEA) requires anatomical knowledge and surgical skills; the learning curve for this technique is steep. To a great degree, these skills can be gained by cadaveric dissections; however, ethical, religious, and legal considerations may interfere with this paradigm in different regions of the world. We assessed an artificial cranial base model for the surgical simulation of EEA and compared its usefulness with that of cadaveric specimens. The model is made of both polyamide nylon and glass beads using a selective laser sintering (SLS) technique to reflect CT-DICOM data of the patient's head. It features several artificial cranial base structures such as the dura mater, venous sinuses, cavernous sinuses, internal carotid arteries, and cranial nerves. Under endoscopic view, the model was dissected through the nostrils using a high-speed drill and other endonasal surgical instruments. Anatomical structures around and inside the sphenoid sinus were accurately reconstructed in the model, and several important surgical landmarks, including the medial and lateral optico-carotid recesses and vidian canals, were observed. The bone was removed with a high-speed drill until it was eggshell thin and the dura mater was preserved, a technique very similar to that applied in patients during endonasal cranial base approaches. The model allowed simulation of almost all sagittal and coronal plane EEA modules. SLS modeling is a useful tool for acquiring the anatomical knowledge and surgical expertise for performing EEA while avoiding the ethical, religious, and infection-related problems inherent with use of cadaveric specimens.