Significance of MRI changes after surgery of the skull base

Extending the traditional resection limits of squamous cell carcinoma of the anterior skull base

Objective

Preliminary report to evaluate the efficacy of resection of squamous cell carcinomas that demonstrate intracra-nial invasion.

Methods

A retrospective review of all cases of extracranial squamous cell carcinomas that extend intracranially treated by a single surgeon.

Results

A total of 21 cases were reviewed. In 6 cases, there was noted to be overt brain invasion. Complete resection of the intracranial disease was achieved in each of the remaining 15 cases. There were no instances of CSF leak, meningitis, brain abscess, stroke, or other intracranial complication noted either acutely or secondarily. In follow-ups that ranged from 10 months (single patient died of disease at 10 months) to 6 years (average, 3.8 years), there were no instances of intracranial recurrence. There was a disease-free control rate of 67.7% at an average follow-up of 4.1 years.

Conclusions

Extending the resection of squamous cell carcinoma into the intracranial vault judiciously as outlined appears to be associated with acceptable outcomes in the treatment of advanced squamous cell carcinoma of the skull base.

Endoscopic transnasal craniotomy and the resection of craniopharyngioma

OBJECTIVES/HYPOTHESIS

To describe the utility of a large transnasal craniotomy and its reconstruction in the surgical management of patients with craniopharyngioma.

STUDY DESIGN

Observational retrospective cohort study.

METHODS

Retrospective review of patients treated in an academic neurosurgery/rhinology practice between 2000 and 2007. Patient characteristics (age, sex, follow-up), tumor factors (size, position extension, previous surgery), type of repair (pedicled mucosal flaps, free mucosal grafts), and outcomes (visual, endocrine, and surgical morbidity) were defined and sought in patients who had an entirely endoscopic resection of extensive craniopharyngioma (defined as requiring removal of the planum sphenoidale in addition to sella exposure in the approach).

RESULTS

Seven patients had an entirely endoscopic resection of extensive craniopharyngioma during the study period. Mean age was 23.4 years (standard deviation +/- 16.3). Mean tumor size was 3.2 cm (standard deviation +/- 2.0). The majority of these pathologies had extensive suprasellar disease, and two (28.6%) had ventricular disease. Cerebrospinal fluid leak rate was 29% (2 of 7). These leaks occurred only in reconstructions with free mucosal grafts. There were no cerebrospinal fluid leaks in patients who had vascularized pedicled septal flap repairs.

CONCLUSIONS

The endoscopic management of large craniopharyngioma emphasizes recent advancements in endoscopic skull base surgery. The ability to provide exposure through a large (4 cm+) transnasal craniotomy, near-field assessment of neurovascular structures, and the successful reconstruction of a large skull defect have significantly advanced the field in the past decade. The use of a two-surgeon approach and bilateral pedicled septal mucosal flaps have greatly enhanced the reliability of this approach.

Posttreatment imaging of the skull base

Imaging the skull base after surgery can be challenging because anatomic structures may have been destroyed by an underlying process or removed at surgery. Foreign substances may be introduced to fill a void left by tumor resection, for hemostasis, and to repair dural defects. Previous imaging studies must be available for comparison to understand the characteristics of an underlying lesion. By following the progression of a lesion on subsequent imaging studies, the nature of treatment-related changes and residual or recurrent pathology is best realized.

Magnetic resonance navigation for head and neck lesions

OBJECTIVE

Review applications of interventional magnetic resonance imaging and describe methods, procedures, and additional instrumentation for the magnetic resonance "operating theater." Describe advantages of magnetic resonance navigation for biopsies of head and neck tumors.

STUDY DESIGN

Patients with palpable and nonpalpable head and neck and cranial base tumors were recruited into the study. Patients underwent magnetic resonance-guided biopsy. Retrospective analysis of 21 patients was conducted.

METHODS

0.5 Tesla superconducting open magnetic resonance imaging was used for navigation of the biopsy needle. Patient records and magnetic resonance images were reviewed. The type, size, and location of the lesions were tabulated. Type of anesthesia and monitoring method were analyzed. The histopathologic correlation was conducted in patients who required further surgeries or open surgical biopsies.

RESULTS

Twenty-two biopsies were carried out in the magnetic resonance suite. One patient required general anesthesia and the other biopsies were conducted under intravenous sedation. There was only one case of nonconcurrence in a patient with Wegener's granulomatosis of the posterior orbit. Overall, a 92% concurrence rate between image-directed fine-needle aspiration, open biopsy, and surgical therapy was encountered. No complications occurred.

CONCLUSIONS

The use of interventional magnetic resonance imaging to assist with fine-needle aspiration core biopsy has made the biopsy procedure safer and more accurate. Potentially morbid and disfiguring surgeries have been avoided in some patients. Deeper lesions have been more easily approached, as the needle for biopsy is under constant magnetic resonance guidance. Improved visualization for critical structures allows safer performance of biopsies. The primary difficulties of open magnetic resonance imaging relate to the need for nonferromagnetic instrumentation and equipment and their high costs. An inverse relationship exists between the imaging quality and the "dead time" required to acquire images.