This communication deals solely with a group of cases, hitherto rather obscure, in which damage to the cervical part of the spinal cord occurs without radiographic evidence of vertebral injury or displacement. Two alternative explanations of such injury have been postulated. The first is that the spinal cord pressure is due to acute massive prolapse of an intervertebral disc : but our limited experience of this lesion suggests that as a rule this is recognisable on radiographic examination by narrowing of the intervertebral space. The second explanation is that paraplegia is due to hyperfiexion dislocation which undergoes spontaneous reduction ; but it is doubtful whether this occurs at all, because forward flexion or dislocation of the cervical spine which is sufficient to damage the cord would necessarily be associated with locking of the articular facets, or crush fracture of a vertebra, or both. Neither of these lesions undergoes spontaneous reduction, and moreover both are demonstrable by radiographic examination. \Ve suggest that the usual mechanism of these injuries, in which radiographic examination reveals no significant displacement, is forced hyperextension.

Aneurysms occasionally develop from the great cerebral vein as a result of congenital arteriovenous fistulae. In a recent review Hirano and Terry (1958) referred to 18 cases, nine of which were confirmed at necropsy. The example of this rare condition reported here presented as a case of hydrocephalus showing certain noteworthy features. The condition responded well to surgical treatment, but the patient died after a fall. The connexions of the aneurysm were defined at necropsy. Case ReportA baby girl of 6 months was brought for neurosurgical consultation because of obvious hydrocephalus in February, 1954. The pregnancy and delivery and the early development of the infant had been normal, and five weeks before she was examined she had been able to sit up almost unaided. At the time her balance had become impaired and she no longer raised her head spontaneously. The skull was seen to be expanded and superficial scalp veins were prominent. The skull circumference was 515 cm.; the fontanelle was half closed but tense. Eye movements and pupillary reactions were normal; no other abnormalities were detected. In radiographs of the skull, opening of sutures and finger markings of the vault were seen but there was no evidence of the cause of the increased pressure. The transverse sinuses were in their normal position and the posterior fossa was not unduly shallow. At ventriculography, the intracranial pressure was high and an obstruction of the aqueduct was demonstrated, but not with the flaskshaped outline usually found in aqueduct stenosis. The obstruction (Fig. I) began 2 cm. below the third ventricle and increased caudally giving rise to a "rat tail" shadow. The aqueduct was displaced forwards and downwards suggesting a space-occupying lesion behind the pineal. To define this further, air was subsequently introduced by the lumbar route after the ventricular pressure had been lowered. The radiological appearances then were surprising (Fig. 2). All the subarachnoid cisterns were greatly dilated, particularly the cistema ambiens. The sulci of the cerebral convexities were considerably enlarged up to the midline. These findings were interpreted to indicate defective absorption of fluid at the sagittal sinus as the primary cause of the hydrocephalus. 224It was thought that the resultant rise in fluid pressure in the subarachnoid space had caused dilatation of the cisterns to such a degree that the cistema ambiens had obstructed the aqueduct and so produced a type of hydrocephalus which was at least intermittently noncommunicating. To reverse this sequence an anastomosis between the spinal theca and the peritoneal cavity was made with polythene tubing on February 25, 1954. The immediate result was highly satisfactory: skull expansion ceased, the scalp veins became less distended, and normal development was resumed. At the age of I year the child could stand with support; the skull circumference had increased by only 2 cm. At 18 months she could stand unaided; the fontanelles were closed. She had a normal vocabulary and t...

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The differential diagnosis of obstructive hydrocephalus in childhood involves a consideration of two main groups of cases, cerebellar tumours and obstructive lesions of a non-neoplastic nature. The most common of the non-neoplastic conditions are stenosis of the aqueduct of Silvius and obliteration of the outlet of the fourth ventricle.In the literature on obstructive hydrocephalus the radiological distinctions between the neoplastic and the non-neoplastic groups have been well drawn mainly by improved techniques in ventriculography. The pathological aspects have been described by Russell (1949) Matria Twenty-three cases were studied, 15 with cerebellar tumours and eight with non-neoplastic obstructions; of the latter four were stenoses of the aqueduct and four occlusion of the foramina of the fourth ventricle. The ages in the two groups were comparable, varying from 3 to 15 years.The tumours were either medulloblastomas or astrocytomas, the obstructions in the fourth ventricle were all caused by arachnoid adhesions, the type produced by congenital atresia not being represented. The aetiology in the aqueduct stenosis group is not known but is usually a subependymal gliosis of uncertain origin.