Tumor invasion of the anterior skull base: a comparison of MR and CT studies

Imaging of Skull Base and Orbital Invasion in Sinonasal Cancer: Correlation with Histopathology

Simple Summary

Pretreatment assessment of local extension in sinonasal cancer is essential for prognostic evaluation and surgical planning. It essentially relies on CT and MRI imaging whose performance is not accurately described in the scientific literature. The aim of this study was to assess the diagnostic performance of CT and MRI for the diagnosis of skull base and orbital invasion in sinonasal cancer by comparing imaging findings to histopathological data. A total of 176 patients were included. Objective data about the diagnostic value of pretreatment imaging in patients with sinonasal cancer were obtained: they suggest that pretreatment assessment of orbital invasion is difficult, even with the combination of CT and MRI.

Abstract

Background: Pretreatment assessment of local extension in sinonasal cancer is essential for prognostic evaluation and surgical planning. The aim of this study was to assess the diagnostic performance of two common imaging techniques (CT and MRI) for the diagnosis of skull base and orbital invasion by comparing imaging findings to histopathological data. Methods: This was a retrospective two-center study including patients with sinonasal cancer involving the skull base and/or the orbit operated on between 2000 and 2019. Patients were included only if pre-operative CT and/or MRI, operative and histopathologic reports were available. A double prospective blinded imaging review was conducted according to predefined radiological parameters. Radiologic tumor extension was compared to histopathological reports, which were considered the gold standard. The predictive positive value (PPV) for the diagnosis of skull base/orbital invasion was calculated for each parameter. Results: A total of 176 patients were included. Ethmoidal intestinal-type adenocarcinoma was the most common type of cancer (41%). The PPV for major modification of the bony skull base was 78% on the CT scan, and 89% on MRI. MRI signs of dural invasion with the highest PPVs were: contact angle over 45° between tumor and dura (86%), irregular deformation of dura adjacent to tumor (87%) and nodular dural enhancement over 2 mm in thickness (87%). Signs of orbital invasion had low PPVs (<50%). Conclusions: This retrospective study provides objective data about the diagnostic value of pretreatment imaging in patients with sinonasal cancer.

Skull Metastasis from Hepatocellular Carcinoma

CT, MR and angiographic findings of 6 patients with 9 skull metastases from hepatocellular carcinoma (HCC) were reviewed. In 3 of 6 patients, local pain or neurologic deficit was the initial main manifestation of the disease, although all had been treated for chronic liver disease. In the remaining 3 patients, skull metastases were detected following treatment of HCC. The metastatic lesions appeared as expansile osteolytic masses on CT and as hypervascular masses on angiography. All lesions were demonstrated on MR imaging. Compared with the brain parenchyma, the lesions were iso- or hypointense on T1-weighted and T2-weighted MR images. The lesions were moderately to markedly enhanced by Gd-DTPA. Flow voids were shown in the tumors in 5 lesions. HCC should be included in the differential diagnosis of an osteolytic hypervascular lesion of the skull, especially in Oriental patients. The relatively hypointense tumor on T2-weighted MR images associated with flow void, different from primary skull tumors or directly invasive tumors, may support the diagnosis of HCC metastasis.

Magnetic resonance imaging, computed tomography, and 68Ga-DOTATOC positron emission tomography for imaging skull base meningiomas with infracranial extension treated with stereotactic radiotherapy--a case series

Introduction

Magnetic resonance imaging (MRI) and computed tomography (CT) with ⁶⁸Ga-DOTATOC positron emission tomography (⁶⁸Ga-DOTATOC-PET) were compared retrospectively for their ability to delineate infracranial extension of skull base (SB) meningiomas treated with fractionated stereotactic radiotherapy.

Methods

Fifty patients with 56 meningiomas of the SB underwent MRI, CT, and ⁶⁸Ga-DOTATOC PET/CT prior to fractionated stereotactic radiotherapy. The study group consisted of 16 patients who had infracranial meningioma extension, visible on MRI ± CT (MRI/CT) or PET, and were evaluated further. The respective findings were reviewed independently, analyzed with respect to correlations, and compared with each other.

Results

Within the study group, SB transgression was associated with bony changes visible by CT in 14 patients (81%). Tumorous changes of the foramen ovale and rotundum were evident in 13 and 8 cases, respectively, which were accompanied by skeletal muscular invasion in 8 lesions. We analysed six designated anatomical sites of the SB in each of the 16 patients. Of the 96 sites, 42 had infiltration that was delineable by MRI/CT and PET in 35 cases and by PET only in 7 cases. The mean infracranial volume that was delineable in PET was 10.1 ± 10.6 cm³, which was somewhat larger than the volume detectable in MRI/CT (8.4 ± 7.9 cm³).

Conclusions

⁶⁸Ga-DOTATOC-PET allows detection and assessment of the extent of infracranial meningioma invasion. This method seems to be useful for planning fractionated stereotactic radiation when used in addition to conventional imaging modalities that are often inconclusive in the SB region.

Potential impact of (68)Ga-DOTATOC PET/CT on stereotactic radiotherapy planning of meningiomas

PURPOSE

Since meningiomas show a high expression of somatostatin receptor subtype 2, PET with (68)Ga-DOTATOC was proposed as an additional imaging modality beside CT and MRI for planning radiotherapy. We investigated the input of (68)Ga-DOTATOC-PET/CT on the definition of the "gross tumour volume" (GTV) in meningiomas, in order to assess the potential value of this method.

METHODS

Prior to radiotherapy, 42 patients with meningiomas (26 f, 16 m, mean age 55) underwent MRI and (68)Ga-DOTATOC-PET/CT examinations.

HISTORY

operated n = 24, radiotherapy n = 1, operation and radiotherapy n = 8, no treatment n = 9. PET/CT and MRI data were co-registered using a BrainLAB workstation. For comparison, the GTV was defined first under consideration of CT and MRI data, then using PET data.

RESULTS

3/42 patients were excluded from the analysis (two with negative PET results, one with an extensive tumour, not precisely delineable by MRI or PET/CT). The average GTV(CT/MRI) was 22(+/-19)cm(3); GTV(PET) was 23(+/-20)cm(3). Additional GTV, obtained as a result of PET was 9(+/-10)cm(3) and was observed in patients with osseous infiltration. In some pre-treated patients there were intratumoural areas (as identified in CT/MRI) without SR-expression (7(+/-11)cm(3)). Common GTV as obtained by both CT/MRI and PET was 15(+/-14)cm(3). The mean bi-directional difference between the GTV(CT/MRI) and GTV(PET) accounted to 16(+/-15)cm(3) (93%, p < 0.001). In a subgroup of seven patients with multiple meningiomas, PET showed a total of 19 lesions; nine of them were not recognizable by CT or MRI.

CONCLUSION

(68)Ga-DOTATOC-PET enables delineation of SR-positive meningiomas and delivers additional information to both CT and MRI regarding the planning of stereotactic radiotherapy. The acquisition on a PET/CT scanner helps to estimate the relation of PET findings to anatomical structures and is especially useful for detection of osseous infiltration. (68)Ga-DOTATOC-PET also allows detection of additional lesions in patients with multiple meningiomas.

Assessment of Upper Respiratory Tract and Ocular Irritative Effects of Volatile Chemicals in Humans

Accurate assessment of upper respiratory tract and ocular irritation is critical for identifying and remedying problems related to overexposure to volatile chemicals, as well as for establishing parameters of irritation useful for regulatory purposes. This article (a) describes the basic anatomy and physiology of the human upper respiratory tract and ocular mucosae, (b) discusses how airborne chemicals induce irritative sensations, and (c) reviews practical means employed for assessing such phenomena, including psychophysical (e.g., threshold and suprathreshold perceptual measures), physiological (e.g., cardiovascular responses), electrophysiological (e.g., event-related potentials), and imaging (e.g., magnetic resonance imaging) techniques. Although traditionally animal models have been used as the first step in assessing such irritation, they are not addressed here since (a) there are numerous reviews available on this topic and (b) many rodents and rabbits are obligate nose breathers whose nasal passages differ considerably from those of humans, potentially limiting generalization of animal-based data to humans. A major goal of this compendium is to inform the reader of procedures for assessing irritation in humans and to provide information of value in the continued interpretation and development of empirical databases upon which future reasoned regulatory health decisions can be made.

[Skull base tumors]

Modern imaging techniques have great importance in the diagnosis and therapy of skull-base pathologies. Many of these lesions, especially in relation to their specific location, can be evaluated using CT and MR imaging. Tumors commonly found in the anterior skull base include carcinoma, rhabdomyosarcoma, esthesioneuroblastoma and meningioma. In the central cranial fossa, nasopharyngeal carcinoma, metastases, meningioma, pituitary adenoma and neurinoma have to be considered. The most common neoplasms of the posterior skull base, including the CP angle, are neurinoma, meningioma, nasopharyngeal carcinoma, chordoma and paraganglioma. One major task of imaging is the evaluation of the exact tumor extent as well as its relationship to the neighboring neurovascular structures. The purpose of this review is to recapitulate the most important anatomical landmarks of the skull base. The typical imaging findings of the most common tumors involving the skull base are also presented.

Comprometimento órbito-craniano por tumores malignos sinonasais: estudo por tomografia computadorizada

Tumores malignos das cavidades sinonasais são raros e freqüentemente diagnosticados em estágio avançado da doença. A extensão destes tumores para locais críticos como a órbita e o crânio gera dificuldades no tratamento destas lesões. Dez pacientes com neoplasia maligna sinonasal, sem qualquer tratamento prévio e com evidência radiológica de extensão órbito-craniana, foram estudados por tomografia computadorizada. Dos dez tumores, cinco (50%) foram neoplasias epiteliais, tendo sido a mais comum o carcinoma epidermóide (três casos). O sítio de origem tumoral mais comum foi o seio etmoidal, em quatro pacientes (40%), seguido pelo seio maxilar (30%) e pela fossa nasal (30%). Dezesseis órbitas foram comprometidas, já que seis pacientes (60%) apresentaram acometimento orbitário tumoral bilateral. Os tumores se estenderam mais freqüentemente para as órbitas através de erosão da parede medial e do soalho orbitários. A maioria das órbitas teve todos os compartimentos acometidos. Extensão dos tumores para a cavidade craniana foi mais comum através do teto etmoidal (70%) e teto orbitário (30%). A fossa craniana anterior foi acometida em oito casos (80%), seguida pela fossa craniana média (40%) e pelo lobo frontal (excluindo-se a fossa anterior) (30%). Trinta e sete regiões da face foram acometidas pelos dez tumores, excluindo-se o sítio de origem da neoplasia e a região órbito-craniana, corroborando a grande extensão loco-regional do tumor no momento do diagnóstico.

Osteosarcoma of the jaw bones

Osteosarcoma of the jaw bone is comparatively rare and accounts for about 6.5% of all osteosarcomas. We treated eight cases of osteosarcoma of the jaw bone involving the mandible and maxilla in equal proportions between 1986-1992. The median age was 31 years and male: female ratio was 5:3. Swelling and bony expansion were the most common presentations. Radiologically six patients had lytic lesions, and histopathologically they were osteoblastic (n = 4), chondroblastic (n = 3) and fibroblastic (n = 1). Three patients, two with mandibular and one with maxillary osteosarcoma underwent radical surgery and six courses of cisplatinum-based chemotherapy. All were alive and disease free 24, 30, and 54 months after treatment. Histologically all three were chondroblastic. Five patients had incomplete or palliative treatment. All patients died of progressive or locally recurrent disease within 2 years.

Significance of MRI changes after surgery of the skull base

Magnetic resonance (MR) imaging is commonly used in the followup of patients who have undergone surgical removal of tumors from the cranial base to assess the possibility of tumor recurrence, persistence, or surgical complications. Interpretations of this study must be cautious because postoperative enhanced signals are encountered frequently. Although technological improvements continue to enhance the usefulness of MR images for followup, problems remain in differentiating between fibrotic, reconstructive changes, and tumor recurrence. In this study, the hospital records and MR findings of 215 patients who had undergone skull base surgery were reviewed. The study was prompted by negative operative exploration in three patients in whom postoperative MR images strongly suggested tumor recurrence. One-year follow-up images were available in 174 patients. Of these, 94% showed signal enhancement on the 1-year follow-up study. Progressive changes were observed in 14% of patients. The correlation of preoperative MR findings and surgery, with regard to dural involvement, vascular involvement, cranial nerve infiltration, and extent of intracranial infiltration, was analyzed in 28 patients. Methods to facilitate the detection of tumor recurrence using MR images are reviewed.

Contemporary imaging methodology for diagnosis of lesions of the head and upper neck

CT and MRI are the primary imaging modalities used to evaluate the various regions of the head and neck. From the preceding discussion one can see clearly that the choice of the appropriate imaging modality depends on a number of variables. There is no indisputable "winner" under all anatomical or pathological circumstances. The advantages and disadvantages of CT and MRI in certain clinical settings have been discussed. The information provided will enable one to exercise a rational choice in the selection of imaging modalities.