Thoracic spine arachnoid ossification with and without cord cavitation. Report of three cases.

Thoracic spine arachnoid ossification is a relatively rare disease that affects mainly women and causes sensory, motor, and sphinctal symptoms associated with inferior limb pain. Based on three cases, the authors comment on pathogenic and surgery-related aspects of the disease. The patient in Case 1 was followed over the course of 23 years. Spinal cavitation is highlighted in Case 2, and yellow, gross, half-ring ossification is described in Case 3. Calcium deposits usually occur in the middle and lower thoracic spine where the majority of trabeculated arachnoid cells are located. Operative treatment does not interrupt the ossification process, which continues over time, causing progressive deterioration in the patient. Spinal cavitation can occur due to spinal cord tethering, stretching, and central cord edema formation, accompanied by cerebrospinal fluid blockage and pulse pressure changes. The results of surgical intervention are poor, offering short-term recovery with later deterioration. Multiple pathogenic factors are involved in this clinical syndrome including metabolic changes.