Imaging and surgical findings of spinal epidural abscess caused by direct intraspinal spread of paraspinal infection: Correlation with spinal pneumorrhachis and its clinical implication

Background: The clinical outcome of spinal epidural abscess (SEA) can deteriorate rapidly especially in immune-compromised patient. Awareness of all possible causes is key to expeditious diagnosis and treatment of SEA. Purpose: To report and analyze the imaging and clinical presentations characterizing an uncommon cause of SEA due to direct extension of intra-thoracic infections in immune compromised patients. Methods: Medical histories and CT/MRI findings of 2 cases presented with intrathoracic infections with subsequent development of SEA and 1 case with pneumorrhachis were retrospectively analyzed. Further investigation into the anatomic pathways from intrathoracic cavities to epidural space was also carried out on a cadaver. Results: One case with advanced esophageal adenocarcinoma on systemic chemotherapy complicated with esophageal obstruction and perforation requiring stomach pull-through surgery. MRI showed direct connection of thoracic infection to cervical and thoracic SEA which was caused by GI tract Candida Albicans. One case with systemic lupus erythematosus (SLE) on immune suppression therapy developed thoracic empyema, which directly extended into thoracic epidural space. The third case of pneumorrhachis and cadaveric study demonstrated the pathway from paraspinal tissue to the spinal epidural space. Conclusions: Our data confirmed that the direct connections between thoracic and paraspinal compartments to spinal epidural space which could serve as a potential conduit to spread infections. It is likely more commonly occur in immune compromised patient. Its awareness should be raised to justify early spinal imaging in such patient groups even with only mild neurological symptoms. Keywords: Epidural abscess, Paraspinal infection, Pneumorrhachi