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A 57-year-old male patient presented with an immobile ellipsoid mass of 6-cm diameter in the right occipitoparietal region. Cranial computed tomography showed the mass with dense contrast enhancement causing bone destruction. After embolization of the mass, total resection was performed. Histological examination showed the mass had a capsule, with no invasion of the dura mater or dermis, and the follicles of various sizes covered with mono-lined thyrocytes were full of colloid. Immunohistochemical examination showed positive staining for thyroglobulin. Postoperatively, levels of thyroid hormones were normal, and thyroid ultrasonography and technetium-99m scintigraphy showed no abnormalities. Fine needle aspiration biopsy performed at various locations of the thyroid gland revealed no atypical thyroid cells. Whole body technetium-99m scintigraphy found no abnormal bone involvement. The histological evidence was suggestive of follicular carcinoma metastasis. Surgical treatment was planned for the thyroid gland, but the patient did not consent. Two years later, the patient presented with the pain and sensitivity in the sacrum, the right iliac wing, and the right caput femoris. Computed tomography revealed lytic lesions in these areas. Bone metastases were identified. Whole body scintigraphy showed increased activity in these regions, but the cranium and all other tissues were normal. The patient underwent total thyroidectomy under a diagnosis of follicular carcinoma. The present case of a lytic skull lesion associated with normal thyroid tissue on admission but finally treated as follicular thyroid cancer emphasizes the difficulty in histological discrimination of follicular carcinoma from normal thyroid tissue.

A 67-year-old woman was admitted to our clinic with symptoms of normal pressure hydrocephalus, lower cranial nerve pareses, and pyramidal and cerebellar signs associated with respiratory disturbances. Computed tomography (CT) and magnetic resonance imaging revealed a 4.7 x 5.4 cm quadrigeminal arachnoid cyst causing severe compression of the tectum and entire brain stem, aqueduct, and cerebellum, associated with moderate dilation of the third and lateral ventricles. Emergency surgery was undertaken due to sudden loss of consciousness and impaired breathing. The cyst was totally removed by midline suboccipital craniotomy in the prone position. Postoperatively, her symptoms improved except for the ataxia and impaired breathing. She was monitored cautiously for over 15 days. CT at discharge on the 18th postoperative day revealed decreased cyst size to 3.9 x 4.1 cm. Histological examination confirmed the diagnosis of the arachnoid cyst of the quadrigeminal cistern. The patient died of respiratory problems on the 5th day after discharge. Quadrigeminal arachnoid cysts may compress the brain stem and cause severe respiratory disturbances, which can be fatal due to apneic spells. Patients should be monitored continuously in the preoperative and postoperative period until the restoration of autonomous ventilation is achieved.

A 44-year-old woman presented with a thoracic chordoma with intrathoracic extension manifesting as complaints of lower extremity weakness, hypesthesia below the levels of T5-6, and sphincter incontinence. Almost total resection combined with anterior interbody fusion and stabilization was possible through a left transpleural transthoracic approach. She suffered recurrence after 2 years and was considered inoperable. Biopsy revealed a malignant chordoma with no sarcomatous differentiation. Chordoma is an uncommon malignant bone tumor originating from remnants of the embryonal notochord, occurring mostly along the axial skeleton, at the extremity of the vertebral spine, and is least common in the thoracic region. Differential diagnosis is problematic and biopsy is helpful particularly if considered inoperable. Thoracic chordomas of the malignant type manifest as cord or root compression. Classical malignant chordomas must be distinguished from chondroid, benign, or other types of chordomas, since the biological behavior and clinical features are distinct. However, the differential diagnosis cannot be based on histological examination, but long-term follow up is required. Most patients have extradural and intraspinal tissue extension at the time of diagnosis, which makes complete resection impossible. Aggressive surgery without violation of surgical borders is the best choice in the treatment of thoracic chordoma. Thoracic chordoma is a recurring neoplasm and is prone to dissemination and sarcomatous differentiation despite its slow-growing nature.

A 40-year-old female was admitted to the hospital with complaints of headache worsening gradually over a 1-month duration. Her past history included surgery to treat a left cerebellar cystic lesion 3 years before, and an untreated small solid right supracerebellar lesion of 1 cm diameter. On admission, magnetic resonance imaging showed that the right cerebellar lesion had grown to approximately 4 cm diameter abutting the tentorium and causing obstructive hydrocephalus. She also had two more small lesions, a right supratentorial solid lesion with cystic component near the splenium and an intramedullary cystic lesion at the C-2 level. Right suboccipital craniectomy was done. The vascular attachments between the superior aspect of the tumor and the tentorium were coagulated and the tumor was totally removed. C1-2 laminectomy was also performed to drain the intramedullary cyst. The patient deteriorated and lost consciousness with respiratory arrest 6 hours postoperatively and was reoperated for intracerebellar hematoma due to oozing from the tentorial vessels. Histological investigation revealed hemangioblastoma. Dural tentorial vascular attachments in solid hemangioblastomas located subjacent to the tentorium may cause early postoperative complications of hematoma at the site of vascular attachment following the resection. Computed tomography study in the early postoperative period is helpful to identify this problem.

A 17-year-old male presented with a wound on the right temporal region, oozing hemorrhagic necrotic brain tissue and cerebrospinal fluid, following a fall. Computed tomography showed temporoparietal and petrous apex fractures on the right. Neurological examination revealed abducens nerve paresis, ptosis, and myosis on the right side. The patient was treated surgically for the removal of the free bony fragments at the fracture site and to close the dural tear. The abducens nerve paresis, ptosis, and myosis persisted at the 3rd monthly postoperative follow-up examination. The anatomy of the abducens nerve at the petroclival region was studied in four cadaveric heads. Two silicone-injected heads were used for microsurgical dissections and two for histological sections. The abducens nerve has three different angulations in the petroclival region, located at the dural entrance porus, the petrous apex, and the lateral wall of the cavernous segment of the internal carotid artery. The abducens nerve had fine anastomoses with the trigeminal nerve and the periarterial sympathetic plexus. There were fibrous connections extending inside the venous space of the petroclival area. The abducens nerve seems to be vulnerable to damage in the petroclival region, either directly by trauma to its dural porus and petrous apex or indirectly by stretching of the nerve through the nervous and/or fibrous connections. Concurrent functional loss of the abducens nerve and the periarterial sympathetic plexus clinically manifested as incomplete Horner's syndrome in our patient.

A 39-year-old woman was admitted with complaints of headache and nasal discharge on the left for 3 months which was later on proved to be cerebrospinal fluid (CSF). Neurological examination found no abnormalities except bilateral papilledema. Neuroimaging demonstrated enlargement of the lamina cribrosa foramina through which the olfactory nerves pass, as well as empty sella and cerebral cortical atrophy. Bone mineral densitometry showed osteopenia. CSF Ca++ and blood parathyroid hormone levels were elevated. CSF pressure was 280 mmH2O. Bilateral frontal craniotomy was performed to expose the anterior fossa. Foraminal enlargement at the lamina cribrosa was confirmed, and islands of extra-osseous calcifications on the arachnoid membrane were identified. The base of the anterior fossa was repaired intradurally with fascial graft and fibrin glue on both sides. No CSF leakage was noted at 1-year follow up. Spontaneous CSF leakage probably resulted from enlargement of the foramina at the lamina cribrosa due to Ca++ mobilization from bones and pseudotumor cerebri not to the extent of hydrocephalus caused by poor CSF absorption at the arachnoid granulations obliterated by extra-osseous calcareous accumulation.

A 17-year-old female presented with a very rare case of primary Ewing's sarcoma of the skull involving the occipitotemporal region. Systemic examination found no evidence of metastasis. The tumor was surgically removed, and the patient underwent radiotherapy and chemotherapy. Fourteen months after surgery there has been no recurrence of the tumor. Cranial primary Ewing's tumor has a good prognosis after radical surgery and adjuvant therapy.

A 44-year-old woman presented with a thoracic chordoma with intrathoracic extension manifesting as complaints of lower extremity weakness, hypesthesia below the levels of T5-6, and sphincter incontinence. Almost total resection combined with anterior interbody fusion and stabilization was possible through a left transpleural transthoracic approach. She suffered recurrence after 2 years and was considered inoperable. Biopsy revealed a malignant chordoma with no sarcomatous differentiation. Chordoma is an uncommon malignant bone tumor originating from remnants of the embryonal notochord, occurring mostly along the axial skeleton, at the extremity of the vertebral spine, and is least common in the thoracic region. Differential diagnosis is problematic and biopsy is helpful particularly if considered inoperable. Thoracic chordomas of the malignant type manifest as cord or root compression. Classical malignant chordomas must be distinguished from chondroid, benign, or other types of chordomas, since the biological behavior and clinical features are distinct. However, the differential diagnosis cannot be based on histological examination, but long-term follow up is required. Most patients have extradural and intraspinal tissue extension at the time of diagnosis, which makes complete resection impossible. Aggressive surgery without violation of surgical borders is the best choice in the treatment of thoracic chordoma. Thoracic chordoma is a recurring neoplasm and is prone to dissemination and sarcomatous differentiation despite its slow-growing nature.

A 35-year-old woman presented with a solitary neurofibroma in an unusual presacral location without neurofibromatosis manifesting as bilateral chronic sciatica for 2 years. She was initially considered as having a giant right ovarian mass, but was referred with a prediagnosis of solitary giant sacral nerve sheath tumor. The initial differential diagnosis was based on neuroimaging. A right-sided J incision with the extraperitoneal approach provided good exposure and handling of the tumor bed. Almost total excision without neurological deficit was possible. The histological diagnosis was neurofibroma. Benign retroperitoneal neural sheath tumors in patients without von Recklinghausen's disease are quite rare. Intrapelvic tumors are often diagnosed at a later stage. Neuroimaging is very helpful to delineate this unusual site and the extent of tumor development, and to determine the appropriate surgical intervention. A clear understanding of retroperitoneal anatomy is essential for safe removal of such tumors. Complete resection is preferred to prevent local recurrence and malignant transformation. Although root section is inevitable, neurological deficit is unlikely.