The theories of abnormal embryogenesis suggested as explanations for the various forms of SBA and occult spinal dysraphism appear in some instances too all encompassing, as in Gardner's hydrodynamic theory or Padget's neuroschisis theory, or too limited, as in the theory of arrested development proposed by Daniel and Strich for the ACM, or just too speculative in many cases. The observation of a completed defect does not allow one to venture backwards in development to a specific time and cause with any accuracy. Perhaps several different causes striking different tissues at different times can set up a series of aberrations that lead to morphologically similar mature anomalies. The ability of developmental processes to heal themselves, as shown experimentally, may obscure the true mechanism and timing of occurrence although the final morphological expression may be dramatic. Since the study of human embryogenesis in the experimental laboratory is ethically unacceptable although technically feasible, the elucidation of the mechanisms of these neural defects will be long in coming.

Retrospective analysis of 200 cases of documented head trauma demonstrated an accuracy approaching 100% in the diagnosis of intra- and extracerebral collections of blood. Caution must be exercised in the evaluation of trauma 1 to 5 weeks old, since subdural hematomas have the same density as normal brain tissue, and angiography may be necessary. The clinical diagnosis of brainstem contusion is associated with a remarkably high level (54%) of surgically correctable lesions. The use of computed tomography in the evaluation of other traumatic intracranial lesions is discussed.

✓ Nineteen carotid arteries were examined post mortem after endarterectomy had been performed from 1 hour to 11 years previously. The sequential morphological changes at the endarterectomy site were divided into acute, reparative, and mature phases. All nine occluded arteries thrombosed during the acute phase postoperatively. The degree of medial necrosis, acute inflammation and adventitial exposure was more marked in these thrombosed acute phase arteries. By 30 days new intima covered the endarterectomy site and thereafter thrombosis was not seen. Avoidable technical errors led to thrombosis of three arteries. Anticoagulation after surgery may reduce the incidence of postoperative thrombosis. Recurrent symptomatic atheroma occurred in two cases at the original endarterectomy site 16 months and 11 years after operation.

The radiographic evaluation of a spectrum of vascular cerebral damage is presented, ranging from simple porencephaly to the most severe form, classic hydranencephaly. With a combination of clinical materal and computed tomography, it is possible in most cases to arrive at a specific diagnosis of hydranencephaly or severe bilateral porencephaly. Pictorially similar entities, such as massive congenital subdural hematomas or hygromas, alobar holoprosencephaly, massive hydrocephalus, and massive postanoxic or infective encephalopathies, are discussed.

No abstract