Subarachnoid hemorrhage-induced hydrocephalus in rats

Abstract

Background and purpose: Hydrocephalus is an important complication of subarachnoid hemorrhage (SAH). We investigated the occurrence of acute hydrocephalus in a rat SAH model.

Methods: SAH was induced by endovascular perforation in adult male Sprague-Dawley rats (n=36). Sham rats (n=8) underwent the same procedure without perforation. MRI was performed 24 hours after SAH and the volume of the ventricular system and extent of T2* hypointensity lesions were measured. We defined hydrocephalus as ventricular volume > +3 SDs above the mean in sham animals. SAH grade was determined and brains were used for histology, immunohistochemistry, Perls staining, and Western blot analysis. Ventricular wall damage was defined as percentage of ependymal surface disruption.

Results: All surviving rats (n=27) after SAH had ventricular enlargement (33.6 ± 4.7 versus 13.5 ± 1.4 mm(3) in sham animals, P<0.01). Ventricular volume correlated with SAH severity (r=0.48; P<0.05). Out of 27 SAH rats, 12 demonstrated hydrocephalus and all had intraventricular blood accumulation. Rats with hydrocephalus had more severe ventricular wall damage (7.4 ± 1.2%) than the sham animals (0.6 ± 0.2%; P<0.01) and rats without hydrocephalus (1.1 ± 0.2%; P<0.01). Periventricular iron deposition was observed and heme oxygenase-1 and Iba-1 expression were markedly increased in hydrocephalus rats.

Conclusions: SAH causes ventricular enlargement in a rat endovascular perforation model, with hydrocephalus occurring in 44% of animals at 24 hours. Rats with hydrocephalus had more severe SAH, intraventricular hemorrhage, and greater ventricular wall damage.

Fig. 1

Coronal T2 and T2* images, photomicrographs and hematoxylin and eosin sections 24 hours after endovascular perforation(A) or sham procedure(B). HE: hematoxylin and eosin staining.

Fig. 2

Ventricular volume 24 hours after endovascular perforation or sham procedure (A). Correlation of ventricular volume and SAH grade at 24 hours (B). Coronal T2* images of sham and SAH animals with or without hydrocephalus at 24 hours. Rats with hydrocephalus have a larger hypointensity volume than the sham animals or rats without hydrocephalus (C). Hematoxylin and eosin staining of sham and SAH animals with or without hydrocephalus. Note the presence of intraventricular hemorrhage in the hydrocephalic rat. Boxes show intact ependyma (sham, SAH without hydrocephalus) and disrupted ependyma with intraventricular hemorrhage (SAH with hydrocephalus). SAH animals with hydrocephalus have more ventricular wall damage compared to sham or SAH animals without hydrocephalus (D). *p<0.05 and #p<0.01. Values are mean±SEM. Scale bar=200μm. SAH-subarachnoid hemorrhage; HC-hydrocephalus.

Fig. 3

(A) Perls’ reaction (with or without 3,3′Diaminobenzidine, DAB, enhancement) showed iron-positive cells (brackets or arrowheads) in ependyma and subependyma in hydrocephalic SAH rats but not sham and non-hydrocephalic rats. The inserts in A: show DAB staining alone which only showed erythrocytes on the ependymal surface. Periventricular HO-1 immunoreactivity of sham and SAH animals with or without hydrocephalus. Western blot analysis demonstrated higher HO-1 levels in SAH animals with hydrocephalus compared with sham controls (#p<0.01; n=3–4) (B). Periventricular Iba-1 immunoreactivity of sham and SAH animals with or without hydrocephalus. Western blot analysis demonstrated higher Iba-1 levels in hydrocephalic SAH rats compared with SAH animals without hydrocephalus and sham controls (*p<0.05; n=3–4) (C). Scale bars=20 or 200μm. Values are mean±SEM. SAH-subarachnoid hemorrhage; HC-hydrocephalus.