Imaging diagnosis
Case 153
【Progress】
He was admitted to our hospital and given antibiotics and analgesics. His lumbago is gradually improving.
【Discussion】
Unlike cranial subdural space, spine subdural space is minimum and possible area between dura matter and subarachnoid membrane, and it does not have any bridging vein (1). Further, unlike cranial epidural space fixes to the skull, spinal epidural space does not attach to the vertebral bone. Anterior spinal epidural space exists between dura mater and posterior longitudinal ligament, and posterior epidural space exists between dura mater and flavum (yellow) ligament. Cranial epidural space does not communicate with spinal epidural space which is a separate space, containing epidural vessels, nerves and adipose tissue and extends from foramen magnum to sacrum S2/3 level (2).
When infectious spondylitis occurs via contagious or hematopoietic route, inflammation spreads to the surroundings of disk and epidural space avoiding dura matter or ligament. Dura matter and ligament compose of thick collagen tissue which can be a barrier for infectious spread. Anterior and posterior longitudinal ligaments do not always cover the entire vertebral column, indicating contiguous infection occurs from vertebral body to epidural space via the route of non-ligament-cover area. In other words, posterior and anterior longitudinal ligaments, and flavum ligament serve to block the invasion to the subdural space, subarachnoid space and/or spinal cord itself. But epidural space is susceptible to be eroded via the route of the non-ligament cover area by infectious spondylitis either pyogenic spondylitis or tuberculosis spondylitis. Both pyogenic spondylitis and tuberculous spondylitis cause epidural infection and/or abscess relatively easily (3-6).
Meanwhile, as for vertebral disk which is composed of collagen protein and mucoprotein, the degree of erosion is different between pyogenic spondylitis and tuberculosis spondylitis. Because mycobacterium tuberculosis lacks proteolytic enzyme (3), vertebral disk is usually preserved in tuberculous spondylitis, while because most bacteria own proteolytic enzymes, pyogenic spondylitis often erodes vertebral disk even in early phase (3-7).
Further, the degree of vertebral bone destruction is more severe in tuberculous spondylitis than pyogenic spondylitis. It is believed that the action of macrophages under tuberculous spondylitis makes the bone destruction much greater than the action of leukocytes under pyogenic spondylitis does (3-7). Furthermore, it is reported thoracic spine is commonly involved by tuberculous spondylitis, while lumbar spine is commonly involved by pyogenic spondylitis (3-7).
In our patient, the lumbar spine is involved and anterior longitudinal ligament, vertebral body and disk were eroded. It indicates the diagnosis of pyogenic spondylitis rather than tuberculous spondylitis.
【Summary】
We present a seventy two year-old male presented suffering from worsening lumbago and slight fever. Laboratory test revealed CRP 18.6 mg/dL, white blood cells 13040/mm3. Lumbar spine MRI showed erosion of vertebral body, disk and anterior longitudinal ligaments. Spinal subdural space is a minimum or suspected space which can be ignorable. Anterior spinal epidural space exists between dura mater and posterior longitudinal ligament and posterior epidural space exists between dura mater and flavum ligament. Pyogenic spondylitis and tuberculous spondylitis cause epidural infection and/or abscess relatively easily. Because mycobacterium tuberculosis lack the proteolytic enzymes which dissolve mucoprotein of the vertebral disk, vertebral disk is preserved in tuberculous spondylitis while vertebral disk is destroyed in pyogenic spondylitis. Meanwhile, vertebral body is commonly destructed in tuberculous spondylitis probably because of the action of macrophages, while vertebral body is preserved in pyogenic spondylitis. In our patient, lumbar disk, anterior subligamentous space and vertebral body were eroded by infectious spondylitis which indicates pyogenic spondylitis rather than tuberculous spondylitis.
【References】
1.Liu J, et al. Spinal subdural hematoma following cranial surgery: a case report and review of the literature. Neurology India. 59 (2): 281-4
2.Cloran F, et al. Extracranial epidural emphysema: pathway, aetiology, diagnosis and management. Br J Radiol. 2011;84 (1002): 570-5.
3.Lee KY, et al. Comparison of Pyogenic Spondylitis and Tuberculous Spondylitis. Asian Spine J. 2014 Apr; 8(2): 216–223.
4.Ansari S, Ashraf AN, Moutaery KA. Spine infection: a review. Neurosurg Q. 2001;11:112–123.
5.Buchelt M, et al. Comparison of tuberculous and pyogenic spondylitis: an analysis of 122 cases. Clin Orthop Relat Res. 1993;(296):192–199.
6.An HS, et al. Spinal infections: diagnostic tests and imaging studies. Clin Orthop Relat Res. 2006;444:27–33
7.Jung NY, et al. Discrimination of tuberculous spondylitis from pyogenic spondylitis on MRI. AJR Am J Roentgenol. 2004;182:1405–1410
2019.7.17