Ahmed Aly, MD1, Tarek Aly, MD, PhD.2*
1Tanta University Hospitals
2Orthopedic department, Tanta university, Faculty of medicine, 48th Sarwat street, Tanta 31111, Egypt.
*Corresponding Author: Tarek Aly, MD, PhD, Orthopedic department, Tanta university, Faculty of medicine, 48th Sarwat street, Tanta 31111, Egypt.
Abstract
Lumbar spinal stenosis is a common bone disease in the elderly. The thickness of ligamentum flavum plays a significant role in the pathogenesis of lumbar spinal stenosis. Lumbar spine stenosis secondary to Ligamentum flavum hypertrophy is expected in older people, most of whom are in the L4/5 level. Ligamentum flavum hypertrophy was associated with quantitative and qualitative lipid changes and demonstrated total lipid accumulation in hypertrophied ligamentum flavum patients. Many researchers suggest a relation between the severity of COVID-19 and the extent of phospholipid changes.
This study presents the case of a 27-year-old female patient with Lumbar spinal canal stenosis with hypertrophy of ligamentum flavum following affection with COVID-19 coronavirus.
Keywords: Ligamentum flavum, Lumbar spinal stenosis, Covid19, Coronavirus.
Introduction
Lumbar spinal stenosis is one of the most common spinal degenerative diseases, and it has a high incidence among elderly individuals. Lumbar spinal stenosis is usually caused by hypertrophied ligamentum flavum [1-4]. Thickening of ligamentum flavum can cause spinal stenosis and compress the nerve roots or cauda equina, leading to back pain and intermittent claudication [5]. Various factors, including age, activity level, genetic composition, and mechanical stress, accelerate the development of hypertrophied ligamentum flavum [6,7]. Most researchers agree that an abnormal stress level can accelerate the degradation and hypertrophy of ligamentum flavum [8-10].
The average human ligamentum flavum is an elastic structure of 80% and 20% collagen fibers [11]. Increased collagen fibers, broken elastic fibers, and increased cell numbers in human hypertrophied ligamentum flavum are associated with the increased expression of fibrosis-related factors [12,13].
The pathogenesis of thickening of the ligamentum flavum is not clear. There is still controversy about whether the thickening is due to tissue hypertrophy or deformation. Some studies state that the narrowing of the canal results from the ligament's hypertrophy, while others argue that deformities of the ligamentum flavum inside the spinal canal compress the nerve tissues [14,15]. Additionally, the terms "thickening" and "hypertrophy" are used interchangeably in the literature, although they are not necessarily the same thing [16]. Sakamaki described the thickening of the ligamentum flavum as being caused by hypertrophied or deformed tissue, and they questioned whether it was related to disc degeneration in the MRI exams [15].
The relationship between the thickness of the ligamentum flavum, the degeneration of the intervertebral disc, and disc height at L3-L4, L4- L5, and L5-S1 was examined, and the investigators confirmed that the thickness of the ligamentum flavum at levels L3-L4, L4-L5, and L5- S1 was not significantly greater in patients with grade IV and V degeneration than in those with grade I to III degeneration. These results suggest that the thickening of the ligamentum flavum is not due to the deformation of this ligament inside the vertebral canal because of disc degeneration [17].
We presented a case of hypertrophy of ligamentum flavum with manifestations of lumbar spinal stenosis following Coronavirus infection.
Case Presentation
A 27-year-old female presented with complaints of radiating pain along the back of both thighs, more on the right side than the left, for 2 months. The patient described the pain as a sharp shooting sensation in the back of the thighs, more on the right side. The pain is associated with numbness and tingling in both the lower extremities. A worsening numbness in both legs (right more than left) was also described. The patient had tried various conservative measures for lower back pain. Decreased walking distance with intermittent claudication was also reported. The patient denied any recent onset of bowel or bladder dysfunction.
The patient had a recent onset of fever, with flu-like symptoms 3 months before the back and leg symptoms. The diagnosis of Coronavirus was confirmed.
CT chest was done and confirmed CORADS 4th degree affection of the lungs with ground glass appearance. CT of the lumbar spine showed marked hypertrophy of ligamentum flavum at L5-S1 (4.7 mm on the right side) level with narrowing of the spinal canal to 8.5 mm in AP diameter at the same level.
Figure 1: Ground glass appearance of both lungs on CT scan.
Figure 2: CT scan of L5-S1 level showing marked hypertrophy of ligamentum flavum with narrowing of spinal canal (Red arrow).
Discussion
Lumbar spinal canal stenosis is a common cause of low back and lower extremity pain, particularly in elderly patients (18). Hypertrophy of ligamentum flavum is a significant component in developing lumbar spinal canal stenosis with radiculopathy, in addition to degenerative changes occurring in lumbar vertebrae [19]. Many factors, such as aging, mechanical stress, transforming growth factor-beta, and matrix metalloproteinases, are presumed to be involved in the degeneration of ligamentum flavum [20-22].
We presented a case of a young female presented with manifestations of lumbar spinal canal stenosis following COVID-19 affection with Coronavirus.
The ligamentum flavum thickness is an age-dependent phenomenon. Significant changes in LF thickness were witnessed at the L4-L5 and L5-S1 spinal levels as age increased [23].
Abbas et al. [16] and Altinkaya et al. [24] have found that the ligamentum flavum thickness was significantly more significant at the L4-L5 level than the L3-L4 level in subjects with spinal stenosis. In contrast, at the L5-S1 level, no significant difference was seen between patients with spinal stenosis and those without spinal stenosis. They explained this phenomenon by attributing it to the relative hypermobility of these two segments compared with the L5- S1 segment, which is stabilized by illio-lumbar ligaments and the extensive transverse process of the L5 vertebra. In addition, the articular facets of S1 are more coronally oriented, acting to decrease the shearing stress in that segment.
The mean thickness of ligamentum flavum was assessed in many previous studies in correlation to the age in the population between 20-40 years at the L5-S1 level. Sakamaki [15] found it to be 2.5 mm. Altinkaya [24] measured it as 2.7 mm. Kolte [23] found it to be 3.6 mm.
In the patient studied in this study, the ligamentum flavum hypertrophy was calipered as 4.7 mm in L5-S1 level, which was found to be more than the above studies leading to lumbar spinal canal stenosis manifestations.
The impact of COVID-19 on lipid metabolism was discussed by many researchers [25-28]. Yamada et al. [29] found that hypertrophy of the ligamentum flavum was associated with quantitative and qualitative lipid changes and demonstrated total lipid accumulation. Among different types of phospholipase A2 that target cell membrane phospholipids, there is increasing focus on the inflammatory secretory phospholipase A2 IIA (sPLA2-IIA) associated with the severity of COVID-19. Analysis indicates increased sPLA2-IIA levels together with eicosanoids in the sera of COVID patients.
Lysophospholipids, such as lysophosphatidylcholine, could be metabolized by autotaxin (ATX) and converted to lysophosphatidic acid (LPA). Increased ATX has been found in the serum of patients with COVID-19 [30].
Zhou et al. described that Lysophosphatidic acid concentration in the cerebrospinal fluid of patients with hypertrophied ligamentum flavum was higher than those in subjects with non-hypertrophied ligament, and Lysophosphatidic acid-induced hypertrophy of ligamentum flavum [31].
Conclusion
The ligamentum flavum tends to thicken with increasing age. Statistically significant increases in thickness were observed at the L4-L5 and L5-S1 spinal levels. The thickening of the ligamentum flavum is an age-dependent degenerative change. However, according to many previous studies, subjects in the younger age group (20-40) showed a thickness of <4 mm. We presented a case of a young lady less than 30 with hypertrophied ligamentum flavum at an L5-S1 level of more than 4.5 mm and assumed that this hypertrophy may be due to Covid-19 Coronavirus infection.
Conflict of Interests: The authors now represent that they have no conflict of interest to declare. These authors contributed equally to this manuscript/work.
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