Spinal arachnoid calcifications.

Arachnoid calcifications have been imaged on axial-CT and MRI. These often clinically asymptomatic deposits have been attributed to trauma, myelography (particularly with the use of oil-based contrast), subarachnoid hemorrhage, and spinal anesthesia. This report describes calcified arachnoid plaques in an 86-year-old male cadaver located in the dorsal thoracic level. A laminectomy from C4 to the lumbo-sacral junction was performed and the dura mater was transected and pinned aside. Three plaques between T2-T3, 3 at T7, 2 at T9 were noted. Plaques were 1.0 mm in thickness and ranged from 0.5 cm to 1.0 cm in diameter. The spinal cord or nerve roots were not displaced. The plaques stained positively with Von Kossa and Alizarin Red S staining, confirming that the deposits included calcium phosphate and calcium. Arachnoid calcifications are an incidental finding in cadavers and typically do not compress the spinal cord or nerve roots. However such plaques may be precursors to spinal arachnoid ossificans, a more serious condition that may cause spinal cord or nerve root compression.