Vincent Chong

Nasopharyngeal carcinoma with intracranial spread: CT and MR characteristics.

PURPOSE Nasopharyngeal carcinoma (NPC) frequently spreads intracranially. We compare CT and MRI in identifying intracranial spread and reexamine the route of infiltration. METHOD One hundred fourteen consecutive patients with proven NPC were evaluated prospectively with T1-, T2-weighted, contrast-enhanced MRI and CT. RESULTS MRI showed 35 (31%) patients with middle cranial fossa involvement. Twenty-nine (25%) patients had cavernous sinus infiltration, while six (5%) showed only dural thickening. The most common route of spread is through the foramen ovale (FO) (12/35 patients, 34%), followed by skull base destruction (6/35 patients, 17%), foramen lacerum (FL) (6/35 patients, 17%), sphenoid sinus (6/35 patients, 17%), and combined FO and FL (5/35 patients, 14%). Using MRI as a standard, CT demonstrated the following involvement: cavernous sinus in 26 of 29 (90%) patients, FO in 9 of 12 patients, skull base in 6 of 6 patients, FO and FL in 3 of 5 patients, FL in 6 of 6 patients, sphenoid sinus in 6 of 6 patients and dura in 0 of 18 patients. CONCLUSION It is believed that NPC most commonly spreads intracranially via the FL or by direct erosion. Perineural spread through the FO is an important route, which explains why with CT evidence of cavernous sinus involvement there may be no skull base erosion. These findings are best seen on MRI.

Skull base erosion in nasopharyngeal carcinoma: Detection by CT and MRI

It is generally accepted that computed tomography (CT) is superior to magnetic resonance imaging (MRI) in demonstrating bony erosion while MRI is better in delineating soft tissue abnormality. The ability to detect skull base erosion by CT and MRI was compared in a retrospective study of 114 patients with nasopharyngeal carcinoma (NPC). Involvement of the following structures was demonstrated on CT and MRI: pterygoid plates [CT--10 (9%) patients, MRI--8 (7%) patients]; pterygoid process [CT--22 (19%) patients, MRI--22 (19%) patients]; clivus [CT--17 (15%) patients, MRI--26 (23%) patients]; petrous apex [CT--20 (18%) patients, MRI--34 (30%) patients]; sphenoid body/sinus [CT--31 (27%) patients, MRI--32 (28%) patients]; sphenoid wing [CT--12 (11%) patients, MRI--16 (14%) patients]. Erosion of the foramen ovale could be seen on CT in 19 (17%) patients but tumour was noted in the foramen in 28 (25%) patients using MRI. Contrary to common belief, MRI appears to be more sensitive in detecting bony involvement in the petrous apex, the clivus and the sphenoid wing. MRI is, therefore, the preferred technique in demonstrating skull base involvement.

Retropharyngeal lymphadenopathy in nasopharyngeal carcinoma

PURPOSE This study reports the incidence, numer, size and distribution of enlarged lateral retropharyngeal (LRP) nodes in patients with nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS One-hundred and fourteen patients with histopathologically proven NPC were staged prospectively with magnetic resonance imaging (MRI) and computed tomography (CT). T1-weighted, gadolinium-DTPA enhanced, T2-weighted images and CT were obtained. RESULTS Ninety-one (80%) patients showed enlargement of both LRP and cervical nodes. LRP lymphadenopathy was detected in 59 (65%) of these 91 patients. A total of 347 neck nodes were identified. There were 72 enlarged LRP nodes (average 13 mm, range 6-34 mm). Sixteen groups of fused nodes were also seen (average 24 mm, range 15-40 m). Thirty-two patients (35%) with cervical lymphadenopathy showed no LRP lymphadenopathy. LRP nodes were seen at the following levels: C1, 35 (49%) nodes; C1/C2, 23 (32%); C2, 13 (18%) and C2/C3, one (1%). It is not known if all these nodes are due to metastasis or hyperplasia as no histopathological proof is available. CONCLUSION LRP lymphadenopathy may be seen in up to 65% of NPC patients with neck node enlargement. All the retropharyngeal nodes were located in the lateral group. Although medial retropharyngeal nodes are mentioned in the literature, they were not seen in this study. LRP nodes should be documented when surgical resection is contemplated in malignancy of the head and neck.

MRI features of cervical nodal necrosis in metastatic disease

Magnetic resonance imaging (MRI) is increasingly used to evaluate head and neck tumours but its place in the assessment of nodal metastasis is still unclear. This study compares the MRI findings with the computed tomography (CT) sign of nodal necrosis in 114 patients with confirmed nasopharyngeal carcinoma (NPC). Ninety-one (80%) patients showed neck node enlargement on both MRI and CT. Thirty-one (34%) of these patient with lymphadenopathy showed nodal necrosis. Seventy-two necrotic nodes were seen on CT. Using CT as the standard, the sensitivity and specificity of individual MRI sequences are as follows: T1-weighted (36%, 100%), T2-weighted (47%, 98%) and enhanced T1 (67%, 100%). In combination (when one or more sequences are positive), the sensitivity and specificity are as follows: T1 and T2-weighted (60%, 99%), T1-weighted and enhanced scan (67%, 100%) and T1-, T2-weighted and enhanced scan (78%, 99%). Only 26 (36%) nodes with nodal necrosis could be recognised on T1-weighted MRI as an area of low signal intensity. Paradoxically, eleven (15%) nodes, showed slightly hyperintense necrotic areas. Contrast enhanced MRI showed 48 (67%) NN thus improving detection rate. High signal intensity with or without a rim of lower signal intensity could be seen in 39 (54%) nodes on T2-weighted images. Five nodes (7%), curiously showed low signal necrotic centres. Ideally, staging of the primary tumour and nodes should be performed using a single modality. The tumour is often more advantageously evaluated by MRI. However, CT should be considered if MRI findings of nodal involvement are equivocal.

Temporal lobe changes following radiation therapy: imaging and proton MR spectroscopic findings

Abstract Radiation therapy for nasopharyngeal carcinoma affects the temporal lobes. This paper characterizes proton MR spectroscopic findings of the temporal lobes and correlates them with imaging changes. Single-voxel proton MR spectroscopic examinations were acquired from 13 healthy adult volunteers (25 spectra) and 18 patients (28 spectra). All patients had biopsy-confirmed nasopharyngeal carcinoma and were previously treated with radiation therapy. Six patients (33 %) had a single treatment and12 (67 %) patients had two treatments. Point resolved spectroscopy (PRESS) method was used (TR = 3000 ms, TE = 135 ms) and data processed automatically using the LCModel software package for metabolite quantification. Voxel size and geometry were adapted to the lesion to reduce skull-base lipid contamination. The metabolites were quantitated relative to water signal. For each location, an additional non-water-suppressed reference scan in fully relaxed conditions was performed. The imaging findings were divided into four categories: I, normal; II, edema only; III, contrast-enhancing lesions; and IV, cystic encephalomalacia. The N-acetyl-aspartate levels were reduced in 27 (96 %) spectra. Choline was increased in 3 (11 %), normal in 4 (14 %), and reduced in 21 (75 %) spectra. The creatine level was normal in 8 (29 %) spectra and reduced in 20 (71 %) spectra. Imaging showed 4 (14 %) spectra with category-I imaging findings; 5 (18 %) spectra with category-II findings; 15 (54 %) spectra with category-III findings; and 4 (14 %) spectra with category-IV findings. Magnetic resonance spectroscopy showed reduced N-acetyl-aspartate in radiation-induced temporal lobe changes. Creatine levels were relatively more stable. Choline levels may be increased, normal, or reduced. Imaging findings ranged from normal to contrast-enhancing lesions and cystic encephalomalacia.

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.

Pterygopalatine fossa and maxillary nerve infiltration in nasopharyngeal carcinoma

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

Malignancy of the temporal bone and external auditory canal

A retrospective study of 18 patients with malignant tumors of the external auditory canal and temporal bone was undertaken to gain an Asian perspective of this rare disease. Of these patients, 15 (83%) had squamous cell carcinoma (SCC) and 61% had stage T3 tumors at presentation. The mean age was 56 years (range 38-82 years). Seven (39%) of the 18 patients had radiation-associated tumors (RATs), and all had undergone radiotherapy for treatment of nasopharyngeal carcinoma. The 1-year cumulative recurrence for the RAT group was 100%, but there was no recurrence in the non-RAT group (P = 0.001). In malignancies of the external auditory canal and temporal bone, a different classification and staging system for patients with RATs may be warranted to better guide treatment strategies.

Nasopharyngeal carcinoma: review of how imaging affects staging.

Imaging plays an important role in the staging of carcinoma of the nasopharynx. Accurate staging is necessary as the treatment is directly dependent on stage. Clinical examination provides information on mucosal involvement but is unable to determine the deep extension or presence of skull base invasion or intracranial spread. The 1997 International Union Against Cancer (UICC) and American Joint Committee on Cancer (AJCC) staging manuals were a collaborative project that provided a unified classification for nasopharyngeal carcinoma (NPC). The majority of staging can be identified only on imaging and not by clinical examination. The intent of this article is to provide information on the specific imaging findings that will directly affect the stage and treatment of NPC.

Temporal bone tumours in patients irradiated for nasopharyngeal neoplasm

Radiation-associated tumours are rare complications of radiotherapy. This study seeks to highlight and discuss the clinically challenging problem of radiation-associated tumours (RATs) in the temporal bones of seven patients previously irradiated for nasopharyngeal neoplasm. Seven patients (six males and one female) with radiation-associated temporal bone tumours are presented (five squamous cell carcinomas, one osteogenic sarcoma and one chondrosarcoma). The initial nasopharyngeal disease for which radiotherapy was indicated was nasopharyngeal carcinoma (six patients) and nasopharyngeal lymphoma (one patient). The latency period between radiotherapy and presentation of temporal bone tumours ranged from five years to 30 years with a mean of 12.9 years. All the patients underwent surgical tumour resection. Three patients had post-operative radiotherapy and one patient underwent pre- and post-operative chemotherapy. Two patients died from the disease within three months of treatment with one patient surviving 36 months at the time of writing. One patient died from an unrelated medical condition three months after surgery. With refinement in radiotherapy techniques and the resultant increase in patient survival, there may be more patients with radiation-associated tumours in the future. It remains imperative for clinicians to be vigilant when patients previously irradiated for nasopharyngeal carcinoma present with otological symptoms as the key to the successful management of this condition lies in the early detection and expedient treatment of this difficult disease.