A 31-year-old female presented with localised pain in the lower back region for the past 6 months, worsening over the past month. She described the pain to be most severe during extension of the back with partial relief during flexion. No history of trauma or fever were elicited.
Abnormal T1W hypointense and T2W hyperintense signal was seen in the soft tissues between the spinous process of L3 and L4 vertebrae. Similar signal changes were also seen involving the L3 and L4 spinous processes with associated mild flattening of the adjacent margins of these spinous processes. The signal changes were better visualised on STIR images. A mild diffuse disc bulge was noted at L4/L5 level but no significant nerve root compression or neural foraminal narrowing was seen (not shown).
Post contrast images revealed significant enhancement involving the L3 and L4 spinous processes and the interspace between these spinous processes suggestive of inflammation. The characteristic location of the signal changes and enhancement along with typical patient history aided in confirming the diagnosis of interspinous bursitis.
Baastrup’s disease is characterised by close approximation of adjacent spinous processes with inflammation and adventitious bursa formation in the intervening soft tissues. The condition has also been described as ‘kissing spines’. Patients typically present with localised lumbar pain exacerbated by extension of the spine [1, 2]. Although the condition is commoner in older subjects, cases have been reported in young individuals [1]. Athletes have also been described to be more prone to develop this condition [3]. Single level involvement is commoner than multilevel involvement with L4-L5 level being most commonly affected [1].
The condition is thought to occur due to repeated strain on the interspinous ligaments [1, 3]. Excessive flexion, strains the ligament near its bony attachment resulting in bony spur formation with repeated extension causing compression of adjacent inflamed structures and impeding healing. An adventitious bursa forms in the interspinous region due this repeated stress [1]. Repeated lower back strain during domestic work was the likely underlying cause of interspinous bursitis in our subject who was a housewife.
MRI clearly demonstrates the adventitious bursa as fluid signal between adjacent spinous processes on T2W and STIR sequences. Structural alterations like expansion, flattening and approximation of the involved spinous processes described as diagnostic features on plain radiography and CT can also be well demonstrated on MRI [4]. IV contrast administration during MRI is not essential for diagnosis but the degree of contrast enhancement may correlate with the extent of inflammation. The marked contrast enhancement in our case likely indicates significant bursitis with inflammatory marrow oedema in adjacent spinous processes.
Interspinous bursitis has been reported to be associated with bulging discs, central spinal canal stenosis and anterolisthesis [5]. Disc degeneration and mild diffuse disc bulge were seen at L4-L5 level in our case. Another characteristically described association is a posterior epidural cyst, seen as a small fluid signal lesion anterior to the ligamentum flavum. Communication between the interspinous bursa and the posterior epidural cyst has been documented during bursography confirming the cyst to be extension of the interspinous bursa. The epidural cyst may cause spinal canal stenosis in some cases [2].
Steroid injection into the interspinous bursa has been used with success in the management of Baastrup’s disease [3]. Symptomatic relief after excision of part of the involved spinous process has also been described [2]. Spontaneous reduction in size of the interspinous bursa after spinal fixation for anterolisthesis has also been reported [6].
Lumbar interspinous bursitis (Baastrup's disease) at L3-L4 level
Based on the provided lumbar spine MRI images (sagittal and axial sequences), the following findings are observed:
• The adjacent lumbar spinous processes (mainly noted at the L4-L5 level) are close to each other, showing apparent “contact” or “kissing” signs.
• T2W and STIR hyperintense spaces or cystic signals are visible between adjacent spinous processes, suggesting possible synovial cysts or fluid accumulation, indicative of tendon bursitis/mucinous bursa.
• Some adjacent spinous processes exhibit morphological changes (mild hypertrophy or bony reaction), with increased signal intensity in nearby soft tissues, suggesting edema or inflammation.
• At the L4-L5 level, the intervertebral disc shows mild degenerative changes with slight bulging, but there is no significant canal stenosis or severe compression noted.
• No obvious vertebral fractures, significant ligament tears, or extensive abnormal soft tissue proliferation are observed.
Based on the patient’s age, clinical symptoms (low back pain that worsens on extension and partially relieves on flexion), and MRI findings, the following diagnoses may be considered:
Considering the patient’s clinical presentation (low back pain that correlates with extension), imaging findings (adjacent spinous processes unusually close with T2 hyperintensity indicating bursitis/synovial effusion), and exclusion of other infectious or significant degenerative causes, the most likely diagnosis is Baastrup’s Disease (Baastrup’s disease).
1. Conservative Treatment:
2. Injection or Minimally Invasive Treatment:
3. Rehabilitation Training Prescription (FITT-VP Principle):
4. Lifestyle Guidance:
Avoid frequent and strenuous extension movements in daily activities; during work or house chores, take intermittent breaks and use back protection measures. Schedule regular follow-up visits and imaging to evaluate improvements.
Disclaimer: This report is provided for reference only and does not replace a face-to-face consultation or professional medical advice. If you have any questions or if your symptoms worsen, please seek medical attention for further evaluation and treatment.
Lumbar interspinous bursitis (Baastrup's disease) at L3-L4 level
