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BAASTRUP'S SIGN
Authored By: Brandon Peters and Jerold Wallis, Assoc Prof of Radiology.
Patient: 78 year old male
History: 78 year old male with back pain.
Image Size:[small][as-submitted]

Fig. 1
Whole body delayed bone scan.

Fig. 2
Saggital CT, bone windows
Image Size:[small][as-submitted]

Findings: Radiopharmaceutical:  21.5 mCi MDP

Whole body delayed bone scintigraphy images (Fig. 1) demonstrate a moderately intense focus of increased tracer uptake in the midline at the spinous process of L4.  Mild foci of increased uptake are demonstrated at the knees, primarily in the medial compartment, consistent with degenerative arthritis.

CT images of the lumbar spine (Fig. 2) demonstrate direct contact of the L3 and L4 spinous processes. 
Diagnosis: Baastrup's Sign
General Discussion: 78 Year old male with newly diagnosed prostate cancer with episodic back pain presented for evaluation for osseous metastases. 

Originally described by Danish radiologist Dr. Christian Baastrup, the syndrome consists of back pain, which is most severe in extension, is related to abnormally close or direct contact of adjacent spinous processes with subsequent reactive sclerosis and sometimes development of bursal fluid collections.  Occasionally, the bursal fluid can extend into the central posterior epidural space forming cysts causing canal stenosis.    
Specific Discussion: While a solitary metastasis is a possibility, this is not likely given the CT findings.
References: 1.  Bywaters EG, et al.  The lumbar interspinous bursae and Baastrup's syndrome.  An autopsy study.  Rheumatol Int.  1982; 2 (2):  87-96.

2.  Chen CK et al.  Intraspinal posterior epidural cysts associated with Baastrup's disease:  Report of 10 patients.  AJR 2004 Jan; 182(1): 191-4.
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Additional Details:

Case Number: 85001Owner(s): Brandon Peters and Jerold Wallis, Assoc Prof of RadiologyLast Updated: 02-07-2013
Anatomy: Skeletal System   Pathology: Trauma
Modality: CT, Nuc MedAccess Level: Readable by all users, writable by NucMed Certifiers
Keywords: bsnmACR: 30000.77000

Case has been viewed 67 times.
Certified by Jerold Wallis on 05-12-2008

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