The authors discuss the diagnostic criteria of iniencephaly based on data from the literature and eleven additional, new cases. The most important differential diagnostic problems involve anencephaly with spinal retroflexion and the Klippel‐Feil syndrome. Ultrasound indicated cranio‐spinal alterations while amniotic fluid AFP estimation and exfoliative cytology substantiated abnormal closure of the neural tube, thus comprising helpful means for prenatal diagnosis of iniencephaly. The authors emphasize the need for median‐sagittal sectioning through the spinal column for accurate evaluation of vertebral abnormalities. This, together with close observation of the occiput and the foramen magnum, helps the precise diagnosis of iniencephaly and once regularly applied will most likely result in more frequent recognition of this developmental abnormality.

Systematic human pathological background to brain tumor radiosurgery explaining biological and pathophysiological effects of focused irradiation barely exists. The goal of this study was to explore histopathological changes evoked by single high-dose irradiation in a set of different brain tumors following Gamma Knife radiosurgery (GKRS). Light microscopy revealed that GKRS evokes degenerative and proliferative pathological changes in the parenchyma, stroma and vessels of the irradiated tumors. Three main histological types of gamma radiolesions, that is acute, subacute and chronic variants of tissue reactions were recognized in different neoplasms irrespective of their ontogenetic nature. Acute type gamma radiolesions were characterized mainly with necrotic changes and appeared either early or in a delayed time interval. Subacute type gamma radiolesions expressed resorptive activity also with early or delayed chronology. Chronic type lesions showed a reparative tendency but presented only at the delayed stage. These changes seem to follow each other consecutively. There was no significant relation between morphological characteristics of the generated tissue reaction and the time interval elapsed after GKRS. This relative time and environment autonomy of the developed pathological lesions with similar histological picture in different neoplasms suggests either a vascular mechanism or/and a genetically directed origin presumably induced by the ionizing energy of high-dose irradiation.

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