One of the fundamental problems posed by multiple sclerosis is concerned with the distribution of the pathological lesions called plaques. The The fixed cerebral hemispheres were cut coronally at 1 cm. intervals, the first cut being made immediately in front of the mammillary bodies. This procedure is the usual practice in the Department of Pathology, and the resulting coronal slices anterior to the first cut are called Al, 2, 3, etc. and those posterior P1, 2, 3, etc. The inspection of these 1 cm. coronal slices formed the basis of our investigation and it was not thought to be invalidated by the exclusion of small plaques occurring between cuts and the appearance of large plaques in more than one slice.The cut coronal slices were photographed from the posterior aspect. On life size prints each plaque was outlined in ink, and its position recorded (Fig. 1). Every plaque was then represented by a dot on one of a series of photographs of normal coronal brain slices (Figs. 2 to 15). The dot was placed in the position of the apparent centre of the plaque, and in this way every plaque from all the cases was assigned to an anatomical situation. The amassed dots were then counted and assigned to various topographical categories, the first division being into left and right hemispheres. Four broad divisions were then made, namely, cortex, white matter, central grey matter, and the junction of cortex with white matter. Plaques were assigned to the last category only when they clearly appeared to be astride the boundary. These categories were further divided first into lobes and subsequently into named gyri. RESULTSThe total number of plaques counted was 1,594, making the average for each case 72. Their relative distribution is recorded in Tables I and lI. The percentages for the right and left hemispheres were 51 and 49, and this equality appeared not only in the totals but also in every anatomical structure considered.In order to compare the incidence of plaques in the various lobes of the cerebrum the area occupied TABLE

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Subependymomas of the fourth ventricle are generally considered incidental postmortem findings, and have received scant attention from neurosurgeons. The authors present a surgical series of 12 cases of this disorder diagnosed over a 13-year period. The clinical and radiological findings were reviewed and correlations made with pathological studies. The subependymoma is a histologically benign tumor that tends to be calcified. It has a predilection for the fourth ventricle and a peak incidence in the fifth decade of life. It is usually of considerable size with extensive attachment at the time of its detection, and is associated with significant surgical morbidity. The authors believe that magnetic resonance imaging may be the best method of investigation. Intraoperative disturbance of circulatory or respiratory control should suggest to the surgeon that the operation be abandoned. A laser or ultrasonic aspirator may be very helpful in removing these tumors. Postoperative care must include monitoring for apnea.

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The monoclonal antibody UJ13A was raised following immunization of mice with human foetal brain and subsequent somatic cell hyridization of spleen cells with the mouse myeloma cell line P3-X63-AG8-653. The antibody is of the IgG1 subclass and has been shown by indirect immunofluorescence studies on normal foetal, paediatric and adult tissues to selectively bind to most tissues of neuroectodermal origin. Many tumours of neural origin also express the UJ13A antigen and the reagent can be used to distinguish primary intracranial neural tumours from secondary carcinomas and lymphomas. UJ13A is also useful as one of a panel of reagents employed for the identification of metastatic spread of neuroblastoma cells to bone marrow and cerebrospinal fluid. Knowledge of the full spectrum of normal and malignant tissues binding UJ13A suggests that the antibody may have a role in the radioimmunolocalization of neuronal tumours such as neuroblastoma.