Tissue banks in NHS histopathology laboratories and the Consensus Statement.

Correction of errors and misleading data is an educational precept, and Weller's misconception of cerebral (berry) aneurysm pathology 1 is a case in point. His illustration of their frequency distribution depicts basilar aneu-rysms arising from the crotch but other aneu-rysms arising at lateral angles of forks or junctions. Though this was perhaps inadvertent , it is grossly misleading: such localisation is rare. Furthermore he neglects the internal carotid bifurcation and incorrectly infers that posterior cerebral artery aneurysms are more common. Weller's concept of cerebral aneurysm aeti-ology ignores a substantial body of research on early human aneurysms 2 and experimental production of similar changes and berry aneurysms by haemodynamic means. 3 4 His study 5 involved random sections of several resin embedded forks which do not provide the necessary three dimensional structure. The localisation of intimal proliferation at branching sites is incorrect. 1 An oval pad at the extremities of flow dividers is depicted when, in neonates, intimal proliferation covers the entire flow divider, with separate pads just inside the daughter branches proxi-mally where flow separation would be expected. 2 Similar intimal proliferation occurs over the flow dividers of extracranial arteries 6 and step serial cross sections do not show encroachment on the lumen, which actually expands laterally by as much as 30%. 6 Due to poor methodology he underestimates the incidence of raphés (60% of subjects 1 5). Based on serial sections on several hundred human cerebral forks, I assert that medial raphés, rather than defects to indicate their true function, are universal in humans and other animals studied. 2 3 Serial sections are essential for successful detection of raphés and no localised luminal indentation or rounding of the carina would have been invoked with perfusion fixation. The assumption that pads cause loss of elasticity is false as elastic tissue changes precede intimal thickening 2 6 and early aneurysmal changes occur more often to the side of the apex and apical pad. 2 3 Early aneurysmal changes can be produced haemodynamically at experimental forks and in arteries feeding arteriovenous fistulae. 3 6 They commence as transverse tears of the internal elastic lamina with progressive tearing or fragmentation of medial elastic laminae and loss of smooth muscle until eventually only endothelium and an attenuated adventitia remain. 3 6 Such changes result in ectasia or more localised dilatation, and intimal proliferation may be superimposed. 3 6 That cerebral aneurysms consist only of …