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Temporal lobe destruction with microvascular dissections following irradiation for rhinopharyngeal carcinoma

Sir: We describe a patient who developed severe temporal lobe radiation injury 5 years after irradiation for a rhinopharyngeal carcinoma. Extensive involvement of the microcirculation, consisting of a perivascular in ̄ammatory reaction and structural changes of the vessel wall were found after post-mortem. The observed dissections of the endothelium have not been earlier described in detail. Histopathological alterations in neuronal tissue exposed to radiation are predominantly seen in the white matter [6] and are probably the result of small vessel injuries [1,2,4,10±12,14,15]. Vascular endothelial cells have the most rapid turnover among the components of the central nervous system and are directly injured by the ionizing radiation, starting with ultrastructural changes in the capillary basement membrane. Subsequent histopathological alterations develop slowly and usually there is little brain tissue available for examination from patients who have been irradiated years before. A 55-year-old man was admitted with signs of loss of hearing, smell and taste. A carcinoma of the dorsal wall of the rhinopharynx was found. On computed tomography (CT) scan, the skull base, clivus and ventral part of the foramen magnum were in®ltrated with tumour. No intracranial spread was seen. The tumour was irradiated by lateral ports with 40 Gy in 32 fractions with a surdosage of 70 Gy at the tumour. The irradiation ®eld (40 Gy) extended from the skull base up to C-3. It was estimated that the temporal lobes received 50 Gy. Six months later the patient developed orthostatic hypotension. During the following 5 years, his character and intelligence changed. He became aggressive, depressed, developed memory de®cits, and was admitted several times at the psychiatric ward. A CT scan of the brain and skull base showed that the white matter in the temporal lobes became hypodense. The rhinopharyngeal carcinoma was in complete remission with no signs of metastasis. After an attempted suicide, the patient developed a pneumonia, from which he died at the age of 60 years. Autopsy revealed a severe pneumonia. The remainder of the systemic examination showed no signi®cant abnormalities. Remnants of the carcinoma diagnosed earlier were not found. The formalin-®xed brain weighed 1325 g; the temporal lobes were soft. Coronal slides through the brain revealed completely destroyed white matter in the temporal lobes with a relative sparing of the overlying cerebral cortex (Figure 1a). These slides show some gradation of changes from areas closest to the ®eld of radiation (medial) to farthest away (lateral). The temporal cortex, macroscopically normal, showed mild focal damage. Loss of neurones was obvious, but many were still intact. Glial ®brillary acidic protein (GFAP) and vimentin staining showed a strong diffuse astrocytosis. An extensive and diffuse microglial MHC class II-positive proliferation was observed in the irradiated parts of the cortex and in the brainstem. Some microglial proliferation was also present in areas of the cortex where the adjacent white matter was conserved. Apart from the near complete white matter destruction, the preserved myelinated areas in the ®eld of irradiation showed extensive gliotic changes. Neuro®lament and silver stains showed loss of axons but the remaining axons appeared intact. Rounded macrophages, Tal1B5 and CD68-positive, were sparse in the grey matter but abundant in the remaining white matter. Arterioles in the white matter showed thickened ®brotic vessel walls (Figure 1b). Endothelial cells were frequently swollen. Larger branching arteries of the circle of Willis appeared undamaged except for some atherosclerotic changes. Blood±brain barrier (BBB) damage, visualized with ®brinogen antibody staining, showed an enhanced reaction in the white but not in the grey matter. Leakage of ®brin into the surrounding tissue was focally present in the grey matter and slightly more extensive in the white matter. In both white and grey matter mild lymphocytic in®ltration was observed, in most cases around small vessels but occasionally focally in the parenchyma. The Neuropathology and Applied Neurobiology (2000), 26, 473±492