Baastrup Disease¶

Definition¶

Baastrup disease (also called "kissing spines") is cause of low back pain in which adjacent spinous processes make contact and develop degenerative changes — including sclerosis, flattening, bursitis, and osteophyte formation — at their points of contact. It results from loss of disc height and lumbar hyperextension.

Pathophysiology¶

As disc height decreases, the interspinous space narrows
Adjacent spinous processes approximate and eventually contact each other
Repeated contact causes reactive sclerosis, cortical flattening, and sometimes a neobursa (interspinous bursa) between the spinous processes
Most common in the lumbar spine (L4–L5, L3–L4) where the spinous processes are large and lordosis brings them closer together

Imaging Findings¶

Radiography¶

Sclerosis and flattening of adjacent spinous process tips
Close approximation or contact between spinous processes
Best seen on the lateral view

CT¶

Sclerosis, flattening, and enlargement of opposing spinous process surfaces
May show cyst formation between the spinous processes

MRI¶

Finding	Appearance
Interspinous bursitis	T2-bright fluid signal between the sclerotic spinous processes
Marrow edema	T2/STIR hyperintensity within the opposing spinous processes
Sclerosis	Low T1 and T2 signal at the spinous process tips
Epidural extension	Rarely, the interspinous bursa can extend anteriorly into the posterior epidural space, mimicking an epidural cyst

Clinical Pearl

Baastrup disease can be a source of midline low back pain that is often overlooked. It is typically worse with extension (which brings the spinous processes closer together) and relieved with flexion. When a patient has midline tenderness and extension-provoked pain, look carefully at the interspinous spaces on sagittal MRI for T2-bright fluid signal and spinous process edema. An interspinous injection (steroid + anesthetic) under fluoroscopy can be both diagnostic and therapeutic.

Key Points¶

"Kissing spines" — adjacent spinous processes contact each other due to disc height loss
Most common in the lumbar spine at L3–L5
MRI shows interspinous bursitis (T2-bright fluid) and spinous process edema
An often-overlooked cause of midline, extension-provoked low back pain
Interspinous injection can be diagnostic and therapeutic

References¶

Filippiadis DK, Mazioti A, Argentos S, et al. Baastrup's disease (kissing spines syndrome): a pictorial review. Insights Imaging. 2015;6(1):123-128. doi:10.1007/s13244-014-0376-7. PMC4330238
Hatgis J, Granville M, Jacobson RE. Baastrup's Disease, Interspinal Bursitis, and Dorsal Epidural Cysts: Radiologic Evaluation and Impact on Treatment Options. Cureus. 2017;9(7):e1449. doi:10.7759/cureus.1449. PMC5590705
Maes R, Morrison WB, Parker L, Schweitzer ME, Carrino JA. Lumbar interspinous bursitis (Baastrup disease) in a symptomatic population: prevalence on magnetic resonance imaging. Spine (Phila Pa 1976). 2008;33(7):E211-E215. PubMed 18379391
Sağtaş E, Kurnaz B, Alver KH, Ufuk F. Baastrup's disease prevalence across various age groups and its association with degenerative changes: insights from STIR sequence in MRI. Eur Spine J. 2024;33(7):2763-2769. doi:10.1007/s00586-024-08280-z. PubMed 38687395
Carroll JF. Baastrup's Disease. Radsource MRI Web Clinic. December 2017. radsource.us/baastrups_disease
Baastrup disease. Radiopaedia. radiopaedia.org/articles/baastrup-disease-1