Osteomyelitis of the skull base.

Three cases of osteomyelitis of the skull base with associated problems in diagnosis and therapy are discussed. Patients with atypical skull base osteomyelitis are difficult to diagnose as they have no ear abnormalities, but they often develop multiple cranial nerve deficits mimicking symptoms of a posterior fossa mass. We conclude that computed tomographic scans, magnetic resonance imaging studies, bone scans indium-labeled white blood cell scans, and gallium scans are useful in making the diagnosis. A biopsy of the bony lesion often is needed to identify the causative organism and to rule out a tumor. Intravenously administered antibiotics are the mainstay of therapy and should be continued until 1 week after the gallium scan shows no abnormalities. Follow-up gallium scans then are done at 1 week and 3 months after the cessation of antibiotic therapy to search for a recurrence.     

Neuronavigation in skull base tumors.

OBJECTIVE: Computer-assisted neuronavigation was used in 87 cases of skull base lesions (SBLs). Preoperative planning and intraoperative identification of anatomic landmarks is especially important in SBLs since it helps to avoid or minimize surgical morbidity and mortality. In this study, we assessed the accuracy and the clinical usefulness of a frameless system based on the optical digitizer in SBLs. PATIENTS AND METHODS: Between April 2000 and March 2003, eighty-seven patients with SBLs were operated on in our department using cranial neuronavigation. A passive-marker-based neuronavigation system was used for intraoperative image guidance. There were 56 women and 31 men. The patient's ages ranged from 4 to 76 years (average: 45.7 year). The locations of the tumors reported in this series were as follows: frontobasal, 24 cases; sellar/parasellar, 32 cases; petroclival, 16 cases; tentorial/subtemporal, 15 cases. RESULTS: The computer-calculated registration accuracy ranged between 0.3 and 1.7 mm (mean, 1.1 mm). Gross total removal of the SBLs was accomplished in 82 out of 87 patients as was confirmed on postoperative CT and MRI scans. The follow-up period ranged from 1 month to 48 months (average: 20.1 months). Overall mortality and severe morbidity (meningitis, permanent cranial nerve deficits, and cerebrospinal fluid fistulae) rates were 4.6 % and 33.3 %, respectively. CONCLUSION: The image-guided surgery is a valuable aid for safe, helpful and complete removal of SBLs of the brain where accurate localization of the lesion is critical. Although our preliminary series is not large, interactive image guidance provides a constant display of surgical instrument position during surgery and its relationship with the SBLs components, surrounding normal brain, and vascular structures, providing valuable guidance to the surgeon during an operation. Our experience with the neuronavigation suggests that image guidance is helpful in this type of lesions, providing better anatomic orientation during skull base surgery, delineating tumor margins and their relation to critical neurovascular structures.     

Pediatric skull, skull base, and meningeal tumors.

Calvarial neoplastic and non-neoplastic tumors are routinely encountered by all neurosurgeons. Benign and malignant skull base and meningeal tumors are relatively rare lesions in children. Interdisciplinary approaches to those tumors more frequently encountered in the pediatric population in these locations are discussed. Unique aspects of the diagnosis, treatment, and prognosis for infants and children are discussed.     

Blastomycosis of the skull base

Blastomycosis is usually considered a pulmonary or cutaneous disease. A patient with blastomycosis of the infratemporal fossa temporal bone and sinuses without pulmonary disease is presented. Extensive skull base involvement required surgical debridement for relief of pain, and long-term systemic antifungal therapy. The literature is reviewed and discussed.     

Chondrosarcoma of the skull base

Chondrosarcoma of the skull base is an uncommon neoplasm that comprises 0.15% of all intracranial tumors and 6% of skull base lesions. Compression of vital neurologic structures by tumor expansion as well as the histologic characteristics contribute to the malignant potential of these neoplasms. Tumor recurrence has been associated with incomplete resection in this traditionally surgically inaccessible region. This review of five cases of chondrosarcoma of the skull base examines the surgical approaches to resection in a chronologic fashion to emphasize that total gross resection of these lesions has become possible through the evolution of lateral skull base techniques. The difficulty in pathologic diagnosis and the efficacy of postoperative radiotherapy in enhancing survival are also addressed.     

Endoscopic endonasal skull base surgery: Part 1--The midline anterior fossa skull base.

OBJECTIVE: An endonasal endoscopic surgery to the anterior fossa skull base was developed in cadaver dissection as a minimally invasive surgical technique and, subsequently, used in patient treatment. METHODS: Six cadaver head specimens were used. Ideal head positioning and various surgical routes were studied. To estimate the extent of surgical exposure provided by this technique, the width of the exposed anterior cranial fossa was measured between the medial margin of the orbits, the optic nerves and the carotid arteries. Three demonstrative patient cases are presented. RESULTS: Ideal head positioning was discovered to be at 15-degree extension of the forehead-chin line. Paraseptal, middle meatal and middle turbinectomy approaches were developed. The average width between the medial orbits was measured to be 24 mm (range 22-29 mm) at the crista galli level, 27 mm (range 24-30 mm) at the planum sphenoidale, 18 mm (range 15-22 mm) between the optic nerves, and 17 mm (range 13-21 mm) between the rostral carotid siphons. This technique, when it was applied in patient care, proved to be minimally invasive. CONCLUSIONS: This endoscopic endonasal approach provided a direct "short-cut" access to the midline anterior fossa skull base. This technique can be used for the surgical treatment of cerebrospinal fluid (CSF) leak, meningiomas, craniopharyngiomas, pituitary adenomas, and other midline intracranial anterior skull base lesions. This is the first report in the English literature describing endonasal endoscopy for the surgical treatment of primary intracranial anterior fossa skull base lesions.     

Unusual tumors of the posterior fossa skull base.

Five unusual cases of posterior skull base tumors were treated through different skull base approaches. Two or more staged operations were required to achieve total or near-total excision and decompression of two extensive tumors. Total excision of an extensive en plaque meningioma of the foramen magnum that encircled the brain stem and cervical spinal cord could not be achieved through the extreme lateral and suboccipital craniectomy approach. However, the vital structures were decompressed and the patient's postoperative morbidity was acceptable. An extended middle fossa approach was required to excise a hemangiopericytoma of the middle and posterior fossae in a 12-year-old. Extension of the tumor into the posterior fossa precluded a retromastoid approach because the mass draped the lower cranial nerves posteriorly. Two men had undifferentiated adenocarcinomas involving the jugular foramen and middle to posterior fossa, respectively. The origin of one was renal in a 37-year-old man. A 63-year-old man survived 1.5 years after a good decompression of his extensive tumor and irradiation. The histological diagnosis of paraganglioma of the occipital bone was a surprise in a 25-year-old man with pure bony involvement. These cases indicate that the appropriate selection of skull base approaches and their combination can provide the needed access to achieve adequate excision or decompression of masses located in challenging anatomical regions of the skull base. Furthermore, good surgical excision improves palliation in radioresistant metastatic tumors of the skull base.     

LINAC radiosurgery in skull base meningiomas.

LINAC radiosurgery has provided increasing access and changed treatment strategies in patients with benign skull base meningiomas in recent years. From January 1996 to January 2003, 37 patients with skull base meningiomas were treated with LINAC radiosurgery. A combination of the University of Florida system and the X Knife System, developed by Radionics, was used in all patients. Eight patients were treated by microsurgical resection before radiosurgery, in two patients tumor recurrence was treated and in 29 patients LINAC radiosurgery was the initial treatment procedure. The median treatment volume was 5.9 mL (0.7 to 22 mL) and the median given dose was 14.6 Gy (12.8 to 18 Gy) prescribed to the 80 percent isodose line. The follow-up period is between 12 and 96 months, median 66 months. 12 patients (32.4 %) showed a significant reduction in tumor size, in 11 patients (29.7 %) there was significantly less contrast enhancement and in 13 patients (35.1 %) the skull base meningioma was without any change. In one patient (2.8 %) there was tumor growth 48 months after radiosurgery, so the tumor control rate was 97.2 %. Two patients (5.6 %) showed neurological worsening after radiosurgery, whereas the symptoms were transient in one patient. LINAC radiosurgery offers us an effective treatment modality and changes treatment strategies in skull base meningiomas towards a less aggressive surgical approach. By combining microsurgery and radiosurgery we can achieve high tumor control rates with an acceptable low morbidity and a high level of quality of life.     

Preparation of the human skull for skull base anatomic study

Human skulls are unsurpassed in the ability to provide three-dimensional instruction in osteology as well as understanding the sites of soft tissue insertion and the intricate course of neurovascular structures in the skull base. Recent geopolitical developments in Asia have led to extreme difficulty in obtaining human skull specimens. The purpose of this article is to present a method for the preparation of dried human skulls from fresh and frozen cadavers using commonly available chemicals. The technique, requiring about 8 weeks total time and basic equipment, consists of maceration accelerated by several enzymes followed by defatting, washing, and bleaching. The skulls produced are of excellent quality and durability with no preparation artifacts. An economical source of skulls has now been reestablished to facilitate learning of the intricate relationships of the skull base.     

Endoscope-assisted far-lateral transcondylar approach to the skull base.

The far-lateral transcondylar approach was used in this cadaveric study in an attempt to evaluate the usefulness of endoscope-assisted microsurgery in this region of the skull base. The study was carried out using 4 latex-injected, formalin-fixed cadaver heads. After initial examination of intradural structures under an operating microscope, a zero degree 4 mm diameter solid-rod endoscope lens was introduced and guided into position under the direction of the operating microscope. Photographs of the regional anatomy were taken through this lens and through a 30 degree angled lens and compared to photographs of the anatomy taken through the microscope. Clear close-up views of the dural portals and intradural course of the cranial nerves were obtained using the endoscope. The endoscope was introduced through three corridors enclosed with cranial nerves, providing the surgeon with panoramic views of the vertebrobasilar arteries and anterior brainstem surface. The endoscope can be guided through narrow corridors and placed immediately adjacent to a region of interest at the skull base. It enables the surgeon to look around blind corners and work behind structures that are hidden from microscopic view.     

Malignant PEComa of the skull base

Perivascular epithelioid cell tumors (PEComas) are rare, usually benign lesions comprising a family of neoplasms including angiomyolipoma, lymphangioleiomyomatosis, clear cell "sugar" tumors, and clear cell myomelanocytic tumors. This report describes an apparent case of a malignant PEComa of the skull base in a 49-year-old woman, a previously undescribed location for this lesion.     

Salmonella osteomyelitis of the skull base

A case of skull base osteomyelitis caused by Salmonella is reported. The patient, a diabetic immunosuppressed man, had a insidious presentation of nasopharyngeal and cranial nerve findings. His radiologic studies showed a striking destruction of the skull base. He died despite antibiotic therapy. Relevant literature is discussed.     

Transmandibular exposure of the skull base

The combined transmandibular-transcervical approach to the skull base ensures a wide field exposure to the lateral and midline compartments of the middle cranial fossa with attendant vascular control. Splitting the lip and mandible in the midline and dividing the floor of the mouth structures along the lateral border of the tongue exposes the parapharyngeal space, infratemporal fossa (lateral compartment), and clivus, nasopharynx, and cervical spine (midline compartment). A variety of benign and malignant intracranial and extracranial skull base lesions have been treated using this approach.     

Meningioma of the posterior skull base

Combined intratemporal and cerebellopontine angle meningiomas are rejatively rare. There are unsolved problems with the stability of the skull and spine and the lower cranial nerves and there is a marked tendency for the tumor to involve the spinal cord. This article reports on five cases of combined intratemporal and cerebellopontine angle meningiomas.     

Inflammatory pseudotumors of the skull base

Inflammatory pseudotumor is a rare affliction of the skull base with a propensity for locally aggressive growth. Frequently, the location of involvement does not lend itself to conventional biopsy techniques, resulting in diagnostic and treatment dilemma. A retrospective review of three unusual cases of skull base inflammatory pseudotumors is reported. These lesions illustrate the difficulty of management by virtue of their histopathology and behavior. They are clinically and radiographically indistinguishable from invasive neoplasms. One involved the petrous apex with bony erosion; a second case presented with pain and trigeminal paresthesia secondary to an infiltrative lesion in the clivus and the sphenoid sinus; and the third case involved peritubal soft tissues of the infratemporal fossa, with mandibular paresthesia and middle ear effusion. All three lesions were resected via lateral skull base approaches with no evidence of recurrence. Because of the inherent nature of this lesion and its rarity, inflammatory pseudotumor should remain a diagnosis of exclusion. When suspected, surgical approaches should be designed to allow complete extirpation with limited morbidity.     

Cancer surgery of the skull base

Squamous-cell carcinomas are the most common type of malignant tumors arising in the region of the tonsils and palatine arch. This article describes surgical resection of such tumors with extension to the nasopharynx. The author's experience with over 40 patients confirms the safety of the procedure.