Ultrastructure of Arachnoid Cysts

Abstract Arachnoid cyst(AC) morphology has been studied in a few cases and described to be similar to that of the arachnoidmembrane. However, there are a rather large number of reports that describe cysts with a different morphological appearance compared to the classic description of AC. In a systematic study of 24 consecutive cases of ACs, three different types of cyst could be described, all residing in the subarachnoid space. This chapter gives an overview of the AC wall morphology as well as findings of immunohistochemical studies. A brief description of the differential diagnosis of ACs is also provided, followed by a discussion on the similarities in morphological appearance of the different intracranial cysts.