Fig. 4

a CT image of the head of the adult alpaca (soft tissue window). A partially mineralized soft-tissue mass originated at the level of the right ear and caused severe destruction of the temporal bone, midline shift of the brain and hydrocephalus (not seen on these planes), b corresponding macroscopic section to A of the cranium on the height of the ear canal, arrowheads depict the thin capsule of fibrous tissue around the abscess; A + B: the left ear canal is clearly visible, while the right ear canal and cranium is replaced by the abscess, causing severe midline shift and displacement of the brain to the left. c histologic overview of the brain abscess. Neuropil in the left third, abscess capsule in the middle third, necrotic center in the right third of the picture (HE-staining). Bottom left insert: detail of abscess capsule with granulation tissue and collagenous fibers to the left, degenerated neutrophils and necrotic cell debris to the right (HE-staining). Bottom right insert: Collagenous fibers (dark blue) in the abscess capsule (Masson’s trichrome staining). d brain-abscess interface, abscess capsule to the right. Cerebral edema, gliosis and marked loss of neurons in the neuropil of the cerebral cortex, arrows: remaining neurons. Vascular proliferation and activation of endothelial cells and perivascular infiltration of lymphocytes (HE-staining). e brain-abscess interface, abscess capsule to the right. Infiltration of vessels from the abscess capsule into the neuropil (SMA-IHC). f severe diffuse astrogliosis (brown signal) in the neuropil of the cerebral cortex adjacent to the abscess capsule (GFAP-IHC)