Abstract 522 Endocrinology I Poster Symposium, Saturday, 5/1

A decrease in ventricular size on head CT scan is a common pretreatment finding in young diabetic patients with DKA. We sought to identify histopathologic changes that might accompany the diabetic state to determine if brain edema is a prominent feature.

We studied six control New Zealand White rabbits (C) and twelve New Zealand White rabbits with alloxan-induced diabetes, (75 mg/kg i.v. × 1) eight of which remained healthy-appearing with normal serum bicarbonate concentrations (D) and four of which developed DKA requiring euthanasia prior to the end of the six week study period. Histology was performed on all organs in all animals.

The mean serum glucose values for C, D and the DKA subgroup were 134, 365 and 713 mg/dl, respectively. At study termination, the mean serum bicarbonate values were normal for C and D, and 4.6 mEq/L for DKA animals. Brain water content of D and DKA animals did not differ significantly from C as measured by wet weight - dry weight comparisons.

Three histopathologic brain lesions were identified by light microscopy: vascular congestion, neuronal cytoretraction (cell shrinkage) and patchy edema. Each finding was semiquantitatively scored (0 to 4) based on extent of lesion and compared between groups. For vascular congestion, the only statistically significant difference was between C and DKA with mean scores of 1.0 vs. 3.3, respectively (p < .03). For neuronal cytoretraction, mean scores for C vs. D were 1.2 vs. 2.4 respectively (p < .01); mean scores for C vs DKA were 1.2 vs. 2.8, respectively (p < .03). For patchy edema, mean scores for C vs. D were 0.3 vs. 3.0, respectively (p < .001); mean scores for C vs. DKA were 0.3 vs. 3.3, respectively (p < .001). There was no statistical difference between D and DKA for either lesion.

When the three lesion scores were combined there was a significant difference between C vs. D with mean scores of 2.5 vs. 7.6, respectively (p < .001), between C vs. DKA with mean scores of 2.5 vs. 9.3, respectively (p < .001), and between D vs. DKA with mean scores of 7.6 vs. 9.3, respectively (p < .03). The histology of all other organs was normal except for degeneration of the pancreatic islets in groups D and DKA due to alloxan treatment.

These data suggest that patchy brain edema and neuronal cytoretraction are prominent features of the uncontrolled diabetic state and that DKA need not be present for the development of brain histopathology.