Baastrup disease

Baastrup disease/syndrome (also referred to as kissing spines) is a cause of low back pain characterized 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.

Epidemiology

It tends to be more common in the elderly ¹.

Associations

• older age

• anterolisthesis 

• central canal stenosis ⁷

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

It is named after Christian Ingerslev Baastrup, Danish radiologist (1855-1950) ³.