Bilateral temporal lobectomy for necrosis induced by radiotherapy for nasopharyngeal carcinoma

Cerebral radionecrosis in patients with nasopharyngeal carcinoma

This study involved seven patients with cerebral radionecrosis following radiation therapy for nasopharyngeal carcinoma (NPC). Their charts were reviewed and the relationship of extracranial malignancies to cerebral radionecrosis was investigated. The radiation dose ranged from 70 to 135 Gy, and the latency was from 6 to 39 months. Two of seven patients died of NPC-related complications during follow-up. The crude incidence of cerebral radionecrosis in patients with NPC was 0.93% in our series. Improvement of symptoms could be achieved by corticosteroid therapy, with or without surgery. In a review of the literature, there were 306 cases of cerebral radionecrosis in extracranial malignancies. The nasopharynx is the most common primary site in cerebral radionecrosis of extracranial malignancies, followed by the scalp and sinonasal tract. The 3-year overall survival rate in our series was 68.57%, as provided by the Kaplan-Meier product limited method. Cerebral radionecrosis in NPC patients should be differentiated from tumor recurrence, in order to apply the appropriate treatment.

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.

Pathogenesis of irradiation-induced cognitive dysfunction

Neurocognitive dysfunction is a common sequela of cranial irradiation that is especially severe in young children. The underlying mechanisms of this disorder have not been described. The present review describes the role of the hippocampus and the anatomically related cortex in memory function and its marked susceptibility to ischemic and hypoxic injury. Based on studies of animal models of human amnesia and histopathological findings in the irradiated brain, the neurocognitive sequela of cranial irradiation can be seen to be mediated through vascular injury, resulting in ischemia and hypoxia in the hippocampal region. Recognition of the site and mechanisms of this injury may lead to the development of techniques to minimize the risks.