Aims - To assess the possible role of hypoxia in the formation of axonal bu
lbs.
Methods - Study material comprised sections from 28 brains showing evidence
of cerebral hypoxia with no history of head injury, four with a history of
head trauma but no evidence of hypoxic change, eight with a history of hea
d trauma and hypoxic change, and four from control brains originally descri
bed as "diffuse axonal injury." These were subjected to microwave antigen r
etrieval and immunohistochemistry using monoclonal antibodies to beta amylo
id precursor protein (beta APP), glial fibrillary acid protein (GFAP;), and
CD68-PGM1.
Results - Positive staining for beta APP was seen in all four controls, all
four cases of head injury only, seven of eight cases of head injury and hy
poxic changes, and 12 of 28 cases of hypoxia without history of head injury
; 22 of 25 cases who had been ventilated showed positive staining. The majo
rity of cases showed evidence of cerebral swelling.
Conclusions - Axonal bulbs staining positively for beta APP may occur in th
e presence of hypoxia and in the absence of head injury. The role of hypoxi
a, raised intracranial pressure, oedema, shift effects, and ventilatory sup
port in the formation of axonal bulbs is discussed. The presence of axonal
bulbs cannot necessarily be attributed to shearing forces alone.