19-year-old female patient, keen amateur runner and gaelic football player, presented with acute on chronic symptoms of non-radicular lower back pain. Symptoms were exacerbated by sporting activities and on hyper-extension. On examination there was vague tenderness over the lumbar region in the midline. An MRI was performed.
MRI of lumbosacral spine (Fig. 1); On the T2 weighted sequence (Fig. 1b and 1c) there is a focal area of abnormal high signal intensity in the soft tissues between the L4 and L5 spinous processes. The use of fat suppression (Fig. 1c) improves the contrast between the focal area of abnormality and adjacent normal tissues. On the T1 weighted sequence (Fig. 1a) findings are much more subtle and consist of slight reduction in T1 signal and osteophyte formation of the undersurface of the posterior process of L4. Axial T1 and T2 slices(Fig. 2a and 2b) through the site of clinical interest reveal similiar signal changes.
Fluoroscopic assessment (Fig. 3a, b) of the abnormal focus identified on MRI was performed as part of a therapeutic procedure. A small volume of iodinated contrast was injected which demonstrated a small contained potential space/fluid collection.
Interspinous bursitis or Baastrup' disease is caused by chronic contact between adjacent spinous processes [1], repetitive flexion and extension is thought to strain the spinous ligaments. Chronic contact results in changes to the bone with hypertrophy, sclerosis, inflammatory changes and bursae can develop between affected spinous processes. [2] Repetitive activity aggravates symptoms and is thought to impair a normal healing process. [1] Bursae formation as occurred with our young patient, most commonly occur at L4-L5. [1]
Degenerative changes of the spine including Baastrup's disease are generally considered to be a disease of the older population [2, 3] and in symptomatic populations the condition is not infrequent. [2] Symptoms are typically those of pain on hyperextension [2] The condition has also been described with increased frequency in young athletes. [1]
Radiographic changes include enlargement of the spinous processes, reduced distances between adjacent spinous processes and reactive sclerotic changes.
Lumbar interspinous bursitis can be diagnosed on MRI as fluid signal between opposing spinous processes with high signal on T2 weighted sequences and low signal on T1 weighted sequences. [1, 2, 3, 4] Sagittal fat suppressed sequences can be useful adjunct to the standard imaging sequences of the lumbar spine. Associations have been demonstrated with anterolisthesis and central canal stenosis. [2]
Bone SPECT studies and PET scanning have also been shown to demonstrate increased uptake in this disease process related to osteoblastic activity and inflammatory changes respectively. [1]
Bursography is rarely necessary in the diagnosis of interspinous bursitis, it was performed in this patient to confirm appropriate location for thereaupeutic steriod injection and confirmed the presence of a bursae.
Treatment options include conservative measures with rest and targeted steriod injection. [1] In patients with persistent symptoms surgical options can be considered.
Teaching points
Although unusual in younger patients this condition should be considered among the differential of low back pain, particularily if pain is exacerbated by hyperextension and if there is a history of regular athletic activity.
MRI allows detection of interspinous abnormalities [1] and diagnosis of interspinous bursitis. Fat suppressed T2 weighted sequences can be helpful in identifying areas of inflammation/bursae formation.
Steriod injection has been demonstrated to be a successful form of conservative treatment. [1, 2, 4]
Interspinous bursitis (Baastrup's disease)
The patient is a 19-year-old female presenting with non-radicular lower back pain that worsens with movement and excessive lumbar extension. Upon examination, mild tenderness is noted in the midline lumbar region. MRI scans show an abnormal high signal between adjacent spinous processes in the mid to lower lumbar segments (most prominent around the L4-L5 space). On T2-weighted images, the lesion appears hyperintense, while on T1-weighted images the signal is relatively low, suggesting the presence of fluid or a bursa-like change. Mild sclerosis and hypertrophy can be seen in the adjacent bony structures, and certain sequences indicate a reduced distance between the spinous processes.
Repetitive lumbar flexion and extension can lead to excessive contact or friction between adjacent spinous processes, causing chronic irritation and inflammation. It often occurs in middle-aged individuals or younger people engaged in frequent physical activities.
Conditions such as lumbar facet joint arthritis or sprain of the supraspinous or interspinous ligaments can also cause lower back pain, which typically worsens with extension.
Common among athletes, caused by excessive lumbar extension and rotation that can lead to lower back pain. MRI and/or CT may be needed to confirm changes in the pars region.
Considering the patient’s young age, exercise habits (running, playing soccer), symptom characteristics (pain aggravated by extension), and imaging findings (bursa-like lesions between adjacent lumbar spinous processes, local bony sclerosis, and hypertrophy), the most likely diagnosis is Interspinous Bursitis (Baastrup’s Disease).
This includes rest, reducing or temporarily stopping strenuous lumbar extension exercises that provoke pain. NSAIDs or appropriate analgesics can be used for symptomatic relief during acute episodes.
With imaging guidance, corticosteroid injections can be administered into the interspinous bursa region to alleviate local inflammation and pain.
If conservative treatment and injections are ineffective and the patient’s symptoms significantly impair quality of life, surgical options such as decompression or corrective procedures may be considered.
Rehabilitation should follow the FITT-VP principle (Frequency, Intensity, Time, Type, Volume, and Progression).
During the entire rehabilitation process, closely monitor pain levels and functional changes. Adapt the type, intensity, and duration of exercises progressively. In case of significant pain or functional regression, seek medical advice promptly.
This report provides a reference analysis based on the available imaging and clinical information. It is not a substitute for in-person medical consultation or professional medical advice. If you have any concerns or changes in your condition, please consult a professional healthcare provider promptly.
Interspinous bursitis (Baastrup's disease)
