Keywords
ligamentum flavum hematoma - radiculopathy - pars interarticularis defect - spinal
instability
Introduction
Ligamentum flavum (LF) is the longest ligamentous structure in the human body. Its
main function is maintaining the upright position. Different pathological changes
can occur in LF including hypertrophy, calcification/ossification, and cyst formation.
In addition, rarely hematoma may occur in the LF and it is an extremely rare cause
of nerve root and spinal cord compression. The first case of LF hematoma (LFH) in
the literature was reported by Sweasey et al in 1992.[1] Although LF is extended from the C2 vertebra to the sacrum, the majority of reported
cases of LFH are located at the mobile segments of spine, most frequently at lumbar
region.[2] The cervical and lumbar spine receives transmitted pressure to the epidural space
due to their spinal mobility. Therefore, most intraligamentous hemorrhages are observed
in the mobile cervical and lumbar regions. In the literature, the reported cases are
older aged, most frequently older than 60 years old, and most patients are males.[2] The etiology and pathogenesis of LFH are not clearly defined. Thus, further studies
and additional case reports will contribute to the present data. We report a case
of LFH that occurred in association with spinal instability in a patient whose complaints
were resolved rapidly following L5/S1 decompression surgery.
Case Presentation
A 60-year old man presented with a 3-week history of worsening low back pain radiating
to the left leg. He had no recent history of trauma or lumbar surgery. His complaints
were worsening during walking at approximately 50 m. Neurological examination revealed
left posterolateral leg pain on stretching and hypoesthesia on the left S1 dermatomes.
In addition, straight leg raising test was positive on the left side. His left Achilles
reflex was hypoactive and there was also loss of left dorsiflexor muscle strength
(3–4/5). Laboratory tests were unremarkable. Magnetic resonance imaging (MRI) without
contrast was performed and revealed a left posterior epidural mass compressing the
thecal sac at the left L5–S1 level. On the sagittal fat-suppressed T1-weighted image,
there was a 1-cm hyperintense lesion that may be compatible with subacute stage hematoma
([Fig. 1A]). On the T2-weighted images, the lesion was heterogeneously hypointense to spinal
cord with hyperintense foci ([Fig. 1B]
[C]). Axial T2-weighted image showed compression of the thecal sac by the lesion at
L5–S1 level ([Fig. 1C]). Computed tomography (CT) images revealed the pars interarticularis defect at L5–S1
level ([Fig. 2A]
[B]). Surgical resection of the epidural lesion and transpedicular stabilization was
recommended but the patient refused the application of instrumentation. Therefore,
he underwent only left L5–S1 partial hemilaminectomy with excision of the epidural
lesion under the aid of operation microscope. On early postoperative MRI, the lesion
was seen as totally excised ([Fig. 3A]
[B]). He recovered rapidly after surgery with resolution of neurological symptoms and
low back pain. Histopathological examination of the surgical specimen revealed presence
of erythrocytes in ligamentous connective tissue and confirmed the diagnosis of LFH.
There was no evidence of neural tissue or malignancy ([Fig. 4]). When the blood biochemistry of the patient was examined retrospectively, no pathological
finding that could cause bleeding diathesis were found.
Fig. 1 Preoperative MRI of the lumbar spine without contrast showing left posterolateral
epidural lesion, that is hyperintense on (A) sagittal T1-weighted MRI and heterogeneous on (B) sagittal T2-weighted MRI. This lesion exerts compression to the thecal sac at L5–S1
level on (C) axial T2-weighted MRI. MRI, magnetic resonance imaging.
Fig. 2 Preoperative CT imaging of the lumbar spine showing the pars interarticularis defect
at L5–S1 level on (A) the sagittal CT image and (B) the axial CT image. CT, computed tomography.
Fig. 3 Early postoperative MRI of the lumbar spine without contrast demonstrating the complete
removal of the hematoma on (A) sagittal fat-suppressed T1-weighted MRI (B) axial T1-weighted MRI. MRI, magnetic resonance imaging.
Fig. 4 Histological examination of the surgical specimen showing erythrocytes (red area)
in ligamentous connective tissue (yellow area).
Discussion
The LF is composed of elastic fibers (80%) and collagen (20%) and is poorly vascularized,
having only a few small vessels pass through it in young healthy people. Therefore,
intraligamentous bleeding is very rare.[3]
[4]
[5] Although the pathogenesis of the development of hematoma is still unclear, it is
thought to be a degenerative process. The most commonly accepted mechanism is the
bleeding of the irregular small vessels of the degenerated and hypertrophied LF.[6] Significant microangiogenesis around the ruptured collagen and elastic fibers during
the degenerative changes in the LF has been reported.[7] Epidemiological studies have showed the evidence of a causal role of mechanical
stress due to spinal instability in initiating the pathological pathway of LF hypertrophy.[8]
[9] In our patient, LFH was associated with the degenerated LF near the pars interarticularis
defect at L5–S1 level. As a precipitating factor for hematoma, the most potential
suspect is minor trauma resulting from daily activities or sports. In addition, percutaneous
procedures like lumbar puncture or epidural interventions and increased intra-abdominal
pressure are also accused for the tearing of these vessels.[10] However, it may also occur as an idiopathic form without provacation.[11]
[12] The clinical presentation of LFH is with radiculopathy or myelopathy according to
the location of pathology, similar with the other more common causes of neural compression
like disc herniation. When LFH occurs in the lumbar spine, the presentation is often
with low back and/or leg pain accompanied by various neurological deficits as in our
patient. LFH usually occurs acutely. Chronic LFH is rarely seen and a less common
cause of severe neural compression.[2] In the diagnosis, MRI is the most important tool for the detection of the relationship
between the lesion in the epidural space and LF.[1] In most LFH cases, lesions are hyperintense on T1-weighted MRIs, while heterogeneous
intensity is seen on T2-weighted images. In our case, the LFH was also hyperintense
on T1-weighted fat-suppressed MRIs that may be compatible with the subacute stage
of hematoma. However, the intensities of the lesion can vary in relation to the stage
of the hemoglobin breakdown during the aging of the blood.[6] Therefore, it is sometimes very difficult to differentiate LFH from other epidural
lesions like intraspinal cystic tumors or facet cysts.[13] Contrast-enhanced MRI may help in the differentiation, because enhancement is much
more rare in hematoma unlike spinal tumors.[14] However, in LFH, slight-to-moderate peripheral enhancements may occur.[15] In addition, there are reported cases of LFH with marked enhancement which causes
preoperative suspicion that the lesion was likely to be neoplasm.[16] Facet cysts are usually not enhanced, but they may also show rim enhancement.[17] Consecutive MRIs may help the preoperative diagnosis by revealing signal intensity
changes in relation to the stage of clothing. However, it may not be possible if the
symptoms of the patient is severe. In patients who have severe pain and neurologic
deficits, the standard care is surgical excision with rapid and favorable outcomes.[3]
[18]
[19] In our patient, we performed decompressive microsurgical excision of the lesion
due to the presence of S1 radiculopathy. The prognosis of the patient after surgery
was excellent. The diagnosis of LFH was made with the histopathological evaluation
of the surgical specimen. Surgery is also recommended in some cases for the exact
diagnosis.[2] However, in stable patients, initial observation and conservative management may
be warranted.[20]
Conclusion
LFH is an extremely rare cause of radiculopathy and/or myelopathy. However, it should
be remembered in the differential diagnosis of the epidural lesions, especially when
it is seen in the lumbar region in older-aged male patients. Spinal instability that
plays a role in the pathogenesis of hypertrophy and degeneration of LF is one of the
cause of LFH. The patients who have severe pain and neurological deficit should be
surgically managed immediately.
