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Neuroradiology Case of the Week

Case 188

Ben Wandtke, MD, Akio Hiwatashi, MD
and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 68-year-old female with a history of right hemilaminectomy at L4/5 presents with low back pain and right lower extremity weakness and parasthesia.

Radiological Findings: Plain radiographs and CT myelogram were obtained.

Differential Diagnosis: Chronic osteomyelitis

Diagnosis: Baastrup’s sign

Synonyms: Baastrup’s disease, kissing spine, osteoarthrosis interspinalis, Michotte's syndrome

Discussion: Baastrup’s sign was first reported by the Danish radiologist Christian Baastrup in 1931 describing hypertrophied spinous processes of adjacent vertebrae in close approximation or actual contact which may undergo reactive sclerosis or degeneration. It is hypothesized that excessive lordosis or extensive disc space loss leads to close approximation and contact of spinous processes and to degeneration of intervening ligaments. Interspinous bursal fluid in patients with Baastrup's sign can extend into the posterocentral epidural space and cause various degrees of central canal stenosis.  Bursae are found when the interspinous distance is small compared with the total height of the lumbar spine ('bursal index'). Postmortem analysis of a random population reveal that nearly all bursal spaces show some sign of inflammation and a few show severe bony erosion. Crystal deposits are also described.

References:

1. Resnick, D. Diagnosis of Bone and Joint Disorders. 3rd edition, W.B. Saunders, 1995, p. 363.
2. Chen CK, Yeh L, Resnick D, Lai PH, Liang HL, Pan HB, Yang CF. Intraspinal posterior epidural cysts associated with Baastrup's disease: Report of 10 patients. AJR Am J Roentgenol. 2004 Jan;182(1):191-4. [Medline]
3. http://www.whonamedit.com/synd.cfm/1296.html
4. Bywaters EG, Evans S. The lumbar interspinous bursae and Baastrup's syndrome. An autopsy study. Rheumatol Int. 1982;2(2):87-96. [Medline]