Radiation-induced temporal lobe changes: CT and MR imaging characteristics

OBJECTIVE

This article documents the CT and MR imaging characteristics of patients with temporal lobe changes after radiation therapy for nasopharyngeal carcinoma. These characteristics may serve to differentiate radiation-induced changes from intracranial tumor recurrence.

MATERIALS AND METHODS

We reviewed the imaging records of 1916 patients with nasopharyngeal carcinoma examined over a 5-year period. Forty-seven patients (2.5%) had temporal lobe changes. Thirty-four patients underwent CT (55 examinations), and 26 patients underwent MR imaging (32 examinations). Thirteen patients underwent CT and MR imaging. These studies were independently analyzed according to imaging technique and were categorized as follows: location of lesions, characteristics of gray or white matter changes, and patterns of late changes.

RESULTS

On CT, 12 patients (35%) had unilateral temporal lobe changes, and 22 patients (65%) had bilateral temporal lobe changes. The following patterns were noted: ill-defined contrast enhancement in 27 patients (79%); solid enhancement in six patients (18%); and ring enhancement in one patient (3%). On MR imaging, 11 patients (42%) had unilateral lesions, and 15 patients (58%) had bilateral lesions. Simultaneous gray and white matter lesions were noted in 17 patients (65%), and nine patients (35%) had lesions localized to the gray matter. Three patients (6%) had cerebral atrophy, and two patients (4%) had encephalomalacia.

CONCLUSION

The temporal lobes show characteristic CT and MR imaging features after radiation injury. Familiarity with these changes may assist in differentiating temporal lobe changes from progressive nasopharyngeal carcinoma.

Facial lymphadenopathy in nasopharyngeal carcinoma

AIMS

This paper reports the findings of facial nodal metastasis in nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

The film records of 1916 patients with histologically confirmed NPC seen over a 5-year period were reviewed.

RESULTS

Eight facial nodes were demonstrated in three (0.2%) patients. There were three buccinator, two malar, two infraorbital and one mandibular nodes.

CONCLUSION

Facial nodal metastasis in NPC is unusual, but may be seen at presentation or during recurrence.

Imaging the sphenoid sinus: pictorial essay

This paper focuses on the spectrum of sphenoid sinus lesions that may be seen radiologically and the mapping of disease extent. Imaging plays a central role in the assessment of sphenoid sinus disease. Although primary sphenoid sinus disease is uncommon, this sinus is nevertheless affected secondarily by a variety of pathological processes.

Identification of a pre-S2 mutant in hepatocytes expressing a novel marginal pattern of surface antigen in advanced diseases of chronic hepatitis B virus infection

BACKGROUND AND AIMS

The expression of hepatitis B viral (HBV) antigens in liver tissue reflects the replicative status of chronic HBV infection. We have previously recognized a novel marginal pattern of hepatitis B surface antigen (HBsAg) in hepatocytes, which usually clusters in groups and emerges at the late non-replicative phase. This study was designed to investigate whether the marginal-type HBsAg represented the gene product of a specific HBV-surface mutant.

METHODS

Microdissection of cirrhotic nodules homogeneously expressing marginal HBsAg was performed on two of 12 resected livers from HBsAg-seropositive patients with hepatocellular carcinoma. The gene presumably encoding marginal HBsAg was polymerase chain reaction (PCR)-cloned, sequenced and analysed. In vitro transfection and expression of the cloned surface mutant plasmids were performed on the Huh7 cell line to illustrate intrahepatic HBsAg expression.

RESULTS

Immunohistochemical staining revealed that the marginal HBsAg was positive for pre-S1 and thus contained large surface proteins. The PCR cloning and sequencing of the genes presumably encoding marginal-type HBsAg in both cases revealed the same deletion at the 5' terminus (nt 2-55) of pre-S2. A point mutation on the small-surface (S) antigen was also found in one case. The pre-S2 deletion sequence and the mutation sites of the S gene coincide with human lymphocyte antigen-restricted T- and/or B-cell epitopes. In vitro transfection of the mutant plasmid revealed a blot-like retention or accumulation of HBsAg in the cytoplasm or at the periphery of hepatocytes, accompanied by a decreased secretion of HBsAg in the culture supernatant, mimicking intrahepatic expression.

CONCLUSION

A natural pre-S2 deletion mutant was identified in hepatocytes expressing a novel marginal pattern of HBsAg, which probably contains mutant, large, surface proteins. The biological significance of the pre-S2 deletion mutant should be interesting in view of the clustering proliferation of hepatocytes expressing marginal HBsAg.

Radiology of the nasopharynx: pictorial essay

The nasopharynx, located just below the central skull base, is a difficult area to evaluate clinically. Endoscopic examination provides useful information but cannot delineate submucosal disease. Benign lesions of the nasopharynx are relatively uncommon. They include Thornwaldt cyst, juvenile angiofibroma, haemangioma, haemangiopericytoma, Kimura's disease, branchial cleft cyst, oncocytoma, amyloidoma, and non-ossifying fibromyxoid tumours. The most common malignant lesions are carcinomas and lymphomas. Other malignant neoplasms such as adenocystic carcinomas are rarely seen. The purpose of the present pictorial review is to highlight the salient normal anatomy of the nasopharynx and the spectrum of pathological anatomy.

Meningeal infiltration in recurrent nasopharyngeal carcinoma

Permeative infiltration of the meninges appears to be a distinct form of recurrent nasopharyngeal carcinoma (NPC). The present report of eight patients with recurrent NPC illustrates meningeal infiltration following basal foramina extension. Seven of the eight patients (88%) showed jugular foramen involvement. Three patients had concomitant infiltration of the foramen magnum. There was one patient showing spread through the foramen lacerum. Only four (50%) of these patients had clinically detectable tumour in the nasopharynx, while the other half showed deep submucosal recurrence with endoscopically unremarkable findings. Permeative meningeal infiltration appears to be a distinct form of NPC recurrence. It is important to recognize this phenomenon so as to optimize the treatment options.

Temporal lobe necrosis following radiation therapy for nasopharyngeal carcinoma: 1H MR spectroscopic findings

PURPOSE

To observe the patterns of radiation-induced temporal lobe necrosis (TLN) following radiation therapy for nasopharyngeal carcinoma (NPC).

METHODS AND MATERIALS

Twenty-five proton magnetic resonance spectroscopic (1H MRS) examinations were acquired from 13 healthy adult volunteers for comparison with data from the patient population. There were 18 patients (28 spectra) with radiologic evidence of TLN and all patients were confirmed cases of NPC treated with radiation therapy. Six patients (33%) had a single treatment while 12 (67%) patients had two treatments. All 1H MRS examinations were performed on a 2-T whole body system (Bruker) using the point-resolved spectroscopy (PRESS) method with TE = 135 ms, TR = 3000 ms, and data processed automatically using the LCModel software package for metabolite quantification.

RESULTS

The N-acetyl-aspartate (NAA) levels were reduced in all except one spectrum (96%). Choline (Cho) was increased in 3 (11%), normal in 4 (14%), and reduced in 21 (75%) spectra. The creatine (Cr) level was normal in 8 (29%) spectra and reduced in 20 (71%) spectra. In four patients with normal imaging findings 1H MRS was abnormal.

CONCLUSION

1H MRS can characterize radiation-induced TLN. Spectra with increased Cho can be mistaken for neoplasm. Spectroscopy can also identify metabolic derangement before imaging.

Radiology of the orbital apex

The orbital apex, formed by the superior orbital fissure and optic canal, is the cross-road between the orbit and the intracranial structures. Pathological processes may extend intracranially via the superior orbital fissure and vice versa. In addition to intrinsic soft tissue lesions, various pathological processes may involve the surrounding osseous anatomy. Malignant lesions arising from adjacent structures or from haematogeneous metastasis may also infiltrate this region.

Parotid gland involvement in nasopharyngeal carcinoma

PURPOSE

This study documents the imaging findings of parotid gland involvement in nasopharyngeal carcinoma (NPC).

METHOD

This study reviewed the film records of 1,916 patients with NPC seen over a 5 year period. There were 27 (1.4%) patients with parotid involvement. There were 27 CT and 4 MR studies, and the pattern of involvement was categorized into the following groups: (1) parotid nodal involvement; (2) parotid invasion from extracapsular cervical nodal spread; (3) direct invasion by NPC; and (4) diffusely infiltrated gland not related to (2) or (3).

RESULTS

In the subset of 27 patients, parotid nodal involvement was seen in 11 (41%) patients. Ten (37%) patients had cervical extranodal spread into the parotid gland. Three patients (11%) showed direct invasion by NPC, and another three patients (11%) showed an isolated and diffusely infiltrated parotid gland.

CONCLUSION

Metastatic NPC may involve parotid nodes. The parotid gland may also be involved by extracapsular spread from enlarged cervical nodes or infiltrated directly by the primary lesion in the nasopharynx.

Pictorial review: radiology of the sphenoid bone

The sphenoid bone is located in the central skull base and forms part of the floor of the anterior and middle cranial fossae. The optic foramen, superior orbital fissure, foramen rotundum, foramen ovale and foramen spinosum are found within this complex bone. These foramina form important transition zones between intracranial and extracranial structures. Imaging plays a central role in delineating lesions within the sphenoid bone and the associated fissures and neural foramina. The purpose of this pictorial review is to highlight the pertinent normal and pathological anatomy of the sphenoid bone.

Carcinoma of the nasopharynx

Nasopharyngeal carcinoma (NPC) is an intriguing disease that shows a distinct geographical distribution with well-defined, high-risk ethnic groups. This neoplasm exhibits strong associations with the Epstein-Barr virus, dietary and genetic factors. Radiation therapy is the mainstay of treatment and imaging plays a central role in tumor mapping and radiation therapy planning. NPC provides an excellent model for the study of normal and pathological anatomy of the skull base. It also provides an excellent model in the study of consequences of radiation therapy.

Computed tomographic and magnetic resonance imaging findings in paranasal sinus involvement in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) may spread to the paranasal sinuses. This retrospective study describes the features of paranasal sinus involvement in NPC on computed tomography (CT) and magnetic resonance imaging (MRI). One hundred and fourteen patients with histologically proven NPC underwent staging with both CT and MRI. Maxillary sinus infiltration was demonstrated on MRI in 10 patients; sphenoid sinus infiltration in 24 patients; and, ethmoid sinus involvement in 4 patients. CT could separate inflammatory changes from tumour in all maxillary sinuses but is less helpful in the sphenoid and ethmoid sinuses. Contrast-enhanced MRI could differentiate tumour from inflammatory changes in all sinuses. Using MRI as the standard, the rates of CT separating tumour from inflammation are: maxillary sinus (100%), sphenoid sinus (43%) and ethmoid sinus (25%). Histological confirmation of tumour involvement in the paranasal sinuses is not available. It is important to separate sinusitis from tumour infiltration as prognosis and treatment planning may be affected.

Comparison of CT and MRI features in sinusitis

OBJECTIVE

To correlate the features of inflammatory changes in the paranasal sinuses on magnetic resonance imaging (MRI) with computed tomography (CT).

METHODS AND PATIENTS

One hundred and fourteen patients with histologically proven nasopharyngeal carcinoma (NPC) were staged with both CT and MRI. All CT and MRI images of patients with mucosal thickening but no tumour involvement of the sinuses were retrospectively analysed.

RESULTS

There were inflammatory changes in 36 maxillary, 21 sphenoid and 16 ethmoid sinuses. These changes include mucosal thickening, retention cysts, retained secretions, inspissated secretions and dystrophic calcification. MRI is superior to CT in separating thickened mucosa, retained secretions and retentions cysts.

CONCLUSION

It is important to appreciate CT changes of sinusitis and the corresponding spectrum of MRI features.

Functional endoscopic sinus surgery (FESS): what radiologists need to know

The place of coronal computed tomography (CT) in the assessment of patients prior to functional endoscopic sinus surgery (FESS) is well established. The ability to accurately correlate radiological and surgical anatomy enhances precision and safety during FESS. This pictorial essay reviews the conceptual anatomical framework that forms the basis of FESS.

Radiology of the parapharyngeal space

The parapharyngeal space (PPS) is a central space in the deep neck. Intrinsic lesions within this space are limited. Other spaces in the neck are closely related to the PPS and the direction of displacement of this space often suggests the origin of a lesion. The morphology of a lesion, together with the site of origin, helps in narrowing the diagnostic possibilities. The behaviour of the PPS often helps to determine whether a lesion is an intrinsic abnormality or whether it arises from a neighbouring space. Such information is crucial in the planning of surgical approach and the placement of drains.

Hypoglossal nerve palsy in nasopharyngeal carcinoma

The carotid space and the last four cranial nerves are at risk when nasopharyngeal carcinoma (NPC) recurs or spreads posterolaterally. The objective of this study is to document the features of hypoglossal nerve infiltration and the appearance of the paralysed tongue. We reviewed hypoglossal nerve palsy in 16 patients with NPC. The following features were analysed: tumour morphology (submucosal spread), hypoglossal canal erosion, perineural infiltration or intracranial spread, other lower cranial nerve palsies, and appearance of the tongue. These findings were correlated with clinical records. All 16 patients had tumour recurrence following radiation therapy. In 7 patients (44 %), recurrence was submucosal. Hypoglossal canal involvement was seen in 12 patients (75 %). Isolated hypoglossal nerve palsy was noted in 5 patients (31 %) and 7 patients (44 %) had posterior cranial fossa tumour spread. Posterior displacement of the tongue was consistently well seen. In conclusion, tumour recurrence should be suspected in the presence of hypoglossal nerve palsy even when endoscopic findings are negative. Posterior displacement of the tongue, which has not been emphasised in the literature, is an easily recognisable sign and may indicate early hypoglossal nerve palsy.

Radiology of the jugular foramen

The jugular foramen, a complex bony canal, transmits vessels and nerves from the posterior cranial fossa through the skull base into the carotid space. It is inaccessible to clinical examination and radiology plays a central role in evaluating this region. Familiarity with the normal anatomy of this area will help in the formulation of differential diagnosis and the assessment of disease extent. Both intracranial and extracranial lesions may affect the jugular foramen in addition to intrinsic abnormalities. Normal variants and artefacts seen on magnetic resonance imaging (MRI) should not be mistaken for pathological processes.

The retropharyngeal space: route of tumour spread

The retropharyngeal space is a potential route for the spread of infection and malignancy. We present patients with squamous cell carcinoma of the larynx and tongue with superior contiguous spread along the retropharyngeal space resulting in skull base erosion. The fascia defining the retropharyngeal space is attached to the skull base and pathological processes can extend superiorly to destroy the skull base.

Temporal lobe necrosis in nasopharyngeal carcinoma: pictorial essay

Nasopharyngeal carcinoma (NPC) shows a high frequency of skull base erosion and intracranial spread. This tumour is usually treated with radiation therapy. The medial and inferior portions of both temporal lobes are included within the radiation portals. These areas are therefore potential sites of radiation-induced necrosis. It is important to recognize this complication and separate it from intracranial tumour recurrence because the treatments of these entities are different.

Pathogenesis of middle-ear effusion in nasopharyngeal carcinoma: a new perspective

The theory that middle-ear effusion (MEE) associated with nasopharyngeal carcinoma (NPC) is merely the result of tensor veli palatinus destruction is deficient because recent studies have shown that many patients with NPC have MEE but no tensor veli palatinus dysfunction. The present study evaluates the relationship between MEE and Eustachian cartilage erosion by NPC and examines the pathogenesis of NPC-associated MEE from a new perspective. Thirty-five patients with NPC were studied by magnetic resonance scans taken along the lengths of the Eustachian tubes. Twenty-four patients had tumour involvement of both sides of the nasopharynx so that 59 ears were available for study. Eighteen ears had MEE of which 12 had Eustachian cartilage erosion (p < 0.00001), Fischer's Exact Test). In ears with MEE, Eustachian cartilage erosion was frequently but not necessarily associated with tensor veli palatinus destruction. We postulate that altered Eustachian tubal compliance as a result of cartilage erosion by tumour is an important reason why middle-ear effusions develop in patients with NPC.

Pterygopalatine fossa and maxillary nerve infiltration in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) may infiltrate the pterygopalatine fossa (PPF) and the maxillary nerve. This study illustrates involvement of the maxillary nerve in the PPF with perineural spread to the cavernous sinus.

METHODS

One hundred and fourteen patients with proven NPC were studied using magnetic resonance imaging (MRI) and computed tomography (CT). The images were retrospectively reviewed for PPF infiltration and maxillary nerve involvement.

RESULTS

Seventeen (15%) patients showed infiltration of the PPF. Four patients had maxillary nerve involvement and a perineural spread to the cavernous sinus. Of the 17 patients with PPF infiltration, 8 (47%) patients showed hypoesthesia in the distribution of the infraorbital nerve. All 4 patients with contrast-enhancement of the maxillary nerve exhibited infraorbital neuropathy.

CONCLUSION

Infiltration of the maxillary nerve in the PPF with intracranial spread is uncommon but should be suspected in patients with infraorbital neuropathy. This is important as it affects both prognosis and radiation treatment planning.

Sequence analysis of the small cryptic Xanthomonas campestris pv. vesicatoria plasmid pXV64 encoding a Rep protein similar to gene II protein of phage 12-2

The complete nucleotide sequence (1,851 bp) was determined for the Xanthomonas campestris pv. vesicatoria plasmid pXV64. Sequence analysis revealed an intergenic region (IG) of 355 bp and two oppositely running open reading frames, ORF1 and ORF2, encoding polypeptides of 39 and 16 kDa, respectively. While the function of ORF2 is not known, ORF1 is suggested to be the gene encoding Rep protein based on (i) similarity in amino acid sequence to that of the gene II protein (gIIP) of filamentous phage 12-2, (ii) presence of a sequence in the ori-containing region which is similar to the sequence around the Rep nicking site in some rolling circle-replicating replicons, and (iii) ability to support replication in trans of the region containing pXV64 ori (392 bp) which is located within the region including IG and a short stretch in the N-terminus of ORF2.