Baastrup disease or syndrome (also referred to as kissing spines) is a cause of low back pain characterised by interspinous bursitis and other degenerative changes of the bones and soft tissues where adjacent spinous processes in the lumbar spine rub against each other.
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Epidemiology
It tends to be more common in the elderly 1.
Associations
older age
Clinical presentation
Focal midline pain and tenderness relieved by flexion and aggravated by extension.
Pathology
This process can result in degenerative hypertrophy, inflammatory change (as seen in case 1) and even a pseudoarthrosis with bursa formation. This interspinous bursa may extend between the ligamenta flava in the midline forming an epidural cyst and further contributing to the already existing canal stenosis 2.
This condition is usually seen in patients with excessive lordosis of the lumbar spine.
Radiographic features
Plain radiograph / CT
often shows close approximation and contact of adjacent spinous processes (kissing spines)
resultant enlargement, flattening, and reactive sclerosis of apposing interspinous surfaces
MRI
May demonstrate interspinous bursal fluid and posterocentral epidural cyst(s). MRI can be very helpful in determining whether there is resulting posterior compression of the thecal sac.
FDG PET-CT
May demonstrate FDG avidity when associated with an inflammatory response such as bursitis 5,6. The best diagnostic clue for avoiding misinterpretation may be scrutinising sagittal multiplanar reconstructions (MPR) and involvement being limited to spinous processes, which is rare in malignancy 6.
Treatment and prognosis
Local steroid injection into the interspinous processes/ligament region may often ease the back pain 8. Surgical options include interspinous process decompression devices.
History and etymology
The condition is named after Christian Ingerslev Baastrup (1855-1950), a Danish radiologist who first described its radiographic appearances in a paper in 1933 3,9,10.