Compressive myelopathy from diffuse spinal dural calcifications in a patient with end-stage renal disease: illustrative case

Alexis Malecki Wayne State University School of Medicine, Detroit, Michigan; and

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Jacob Pawloski Department of Neurosurgery, Henry Ford Health, Detroit, Michigan

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Anthony Anzalone Department of Neurosurgery, Henry Ford Health, Detroit, Michigan

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Kelly Shaftel Department of Neurosurgery, Henry Ford Health, Detroit, Michigan

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Hassan Ali Fadel Department of Neurosurgery, Henry Ford Health, Detroit, Michigan

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Ian Lee Department of Neurosurgery, Henry Ford Health, Detroit, Michigan

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BACKGROUND

Diffuse spinal dural calcification is a rare disorder associated with hyperparathyroidism, including the secondary forms associated with renal failure, osteodystrophy, and chronic hypocalcemia. Here, the authors report a rare case of diffuse dural calcification causing spinal cord compression with myelopathy, requiring decompressive surgery with duraplasty to achieve adequate decompression.

OBSERVATIONS

A 46-year-old male with a history of renal failure on dialysis presented with 2 months of progressive neuropathic pain, lower-extremity weakness, and nonsustained clonus. Spine imaging showed severe renal osteodystrophy with multilevel compression fractures and diffuse dural calcifications with areas of invagination causing severe spinal cord compression. Decompressive surgery was recommended. In surgery, a thickened and calcified dura was encountered with areas of buckling causing spinal cord compression. The invaginated area of the dura was resected and reconstructed with patch duraplasty. The patient’s neurological status remained unchanged postoperatively, and at the 6-month follow-up, the patient reported significant improvement in pain and muscle spasms.

LESSONS

Diffuse dural calcifications are a rare complication of prolonged dialysis and secondary hyperparathyroidism. When there is resultant spinal cord compression, this condition requires an intradural approach that addresses the thickened, calcified dura directly to obtain adequate spinal cord decompression.

ABBREVIATIONS

CSF = cerebrospinal fluid; CT = computed tomography; ESRD = end-stage renal disease; GFR = glomerular filtration rate; MRI = magnetic resonance imaging; PTH = parathyroid hormone; XLHR = X-linked hypophosphatemic rickets

BACKGROUND

Diffuse spinal dural calcification is a rare disorder associated with hyperparathyroidism, including the secondary forms associated with renal failure, osteodystrophy, and chronic hypocalcemia. Here, the authors report a rare case of diffuse dural calcification causing spinal cord compression with myelopathy, requiring decompressive surgery with duraplasty to achieve adequate decompression.

OBSERVATIONS

A 46-year-old male with a history of renal failure on dialysis presented with 2 months of progressive neuropathic pain, lower-extremity weakness, and nonsustained clonus. Spine imaging showed severe renal osteodystrophy with multilevel compression fractures and diffuse dural calcifications with areas of invagination causing severe spinal cord compression. Decompressive surgery was recommended. In surgery, a thickened and calcified dura was encountered with areas of buckling causing spinal cord compression. The invaginated area of the dura was resected and reconstructed with patch duraplasty. The patient’s neurological status remained unchanged postoperatively, and at the 6-month follow-up, the patient reported significant improvement in pain and muscle spasms.

LESSONS

Diffuse dural calcifications are a rare complication of prolonged dialysis and secondary hyperparathyroidism. When there is resultant spinal cord compression, this condition requires an intradural approach that addresses the thickened, calcified dura directly to obtain adequate spinal cord decompression.

ABBREVIATIONS

CSF = cerebrospinal fluid; CT = computed tomography; ESRD = end-stage renal disease; GFR = glomerular filtration rate; MRI = magnetic resonance imaging; PTH = parathyroid hormone; XLHR = X-linked hypophosphatemic rickets

Spinal cord compression, regardless of the cause, can ultimately result in severe neurological dysfunction if left untreated. Although common etiologies such as tumors, herniated discs, and trauma are well elaborated in the literature, impingement of the spinal cord by a diffusely thickened, calcified dura is a much less common presentation. This case report delineates an unusual instance of spinal cord compression caused by buckling of a diffusely calcified dura in a patient experiencing end-stage renal disease (ESRD) complicated by secondary hyperparathyroidism.

Diffuse calcification of the dura is a rare event typically observed in specific clinical contexts such as chronic renal failure and hyperparathyroidism. In particular, hyperparathyroidism results in fluctuations in calcium and phosphate levels that can lead to aberrant deposition of calcium salts in tissues, including the dura mater. The renal system plays a pivotal role in mineral and bone homeostasis, and its failure often results in impaired phosphate excretion, decreased calcium absorption, and secondary hyperparathyroidism. In the setting of end-stage renal disease, parathyroid hormone (PTH) levels rise to counteract falling calcium levels and stimulate bone resorption. In the spine, these metabolic derangements can result in paradoxical responses, including weakened bones, aberrant calcium deposition, and other hallmarks of renal osteodystrophy.1–5

This case report endeavors to contribute to the literature by exploring the complex interplay among ESRD, renal spinal osteodystrophy, secondary hyperparathyroidism, and diffuse dural calcifications culminating in symptomatic spinal cord compression. We intend to spotlight this unique mechanism of injury to the spinal cord, discuss surgical management options, and advocate for heightened clinical suspicion and accelerated diagnostic evaluation for this rare cause of compressive myelopathy.

Illustrative Case

A 46-year-old male with a history of focal segmental glomerular sclerosis resulting in ESRD requiring intermittent hemodialysis, complicated by severe renal osteodystrophy with multiple chronic compression fractures, presented to the emergency department complaining of 2 months of painful muscle spasms, subjective weakness, and severe neuropathic pain in his lower extremities. The patient used a wheelchair at the time of presentation because of bilateral quadriceps tendon ruptures 9 months prior, from which he had been unable to regain ambulation. During physical therapy, he was able to ambulate with a walker for some time but noticed significant back pain radiating into the right thigh with activity, which was attributed to his prior compression fractures. Two weeks prior to presenting in our emergency department, he noticed progressively worsening lower-extremity weakness and was no longer able to transfer himself in and out of his wheelchair for dialysis as he had done previously. He also reported activity-related burning pains and muscle spasms in his anterior and posterior thighs. He denied any numbness, loss of temperature sensation, or bowel or bladder complaints. On neurological examination of the lower extremities, his motor strength was 4/5 in hip flexion and knee extension with nonsustained clonus bilaterally.

Cervical, thoracic, and lumbar spine computed tomography (CT) revealed changes related to severe renal spinal osteodystrophy, multiple compression fractures of varying chronicity in the thoracic and lumbar spine, and diffuse thickening and calcification of the spinal dura (Fig. 1). There were multiple areas of deformation of the posterior dura, most significantly at the T7–8 and T10–11 levels, with concern for spinal cord compression on CT myelography (Fig. 2). Preoperative magnetic resonance imaging (MRI) of the thoracic spine confirmed compression of the dorsal thoracic cord at T10–11 due to dural invagination at this level with moderate stenosis at the T7–8 level (Fig. 3).

FIG. 1
FIG. 1

Preoperative noncontrast CT imaging shows a thickened, calcified dura extending from the cervicothoracic junction caudally to the lumbar spine, primarily affecting the dorsal aspect of the dura (arrows). There are multiple areas of invagination, with the most significant at the T10–11 level.

FIG. 2
FIG. 2

Preoperative imaging. A: Three-dimensional reconstruction of the preoperative CT scan shows the chronic T12 compression fracture and resultant focal kyphotic deformity and coronal imbalance. B: CT myelography performed at the outside hospital reveals again the two areas of suspected spinal stenosis at the T7–8 and T10–11 levels.

FIG. 3
FIG. 3

Preoperative T2-weighted MRI. Sagittal (A and B) and axial (C) images show an area of mild to moderate stenosis at the T7–8 level. The dura at the T10–11 level is significantly more deformed, and there is no circumferential CSF signal around the spinal cord at this level, concerning for more severe stenosis and compression (DF).

Given that the patient had signs and symptoms of compressive myelopathy, operative decompression was recommended. On the day of surgery, the patient was thrombocytopenic; thus, a platelet transfusion was administered after dialysis. He was also administered desmopressin immediately preoperatively to counteract uremic platelet dysfunction. After fluoroscopic localization, a posterior approach for a standard T7–8 laminectomy was performed. The ligamentum flavum was noted to be normal in appearance. After completion of the laminectomy, the dura was found to be thickened and rigid from calcium deposition with a small area of dorsal invagination. Intraoperative ultrasound was used and showed a cleft of cerebrospinal fluid (CSF) separating the dura and the adjacent spinal cord, without significant deformation of the spinal cord. On the basis of intraoperative ultrasound findings, this area of the dura was not excised or reconstructed. Next, a T10–11 laminectomy was performed, which revealed a calcified, thickened dura with a more significant deformation and dorsal invagination. Intraoperative ultrasound at the T10–11 level revealed spinal cord displacement and compression without a CSF cleft. This area of calcified dura was sharply opened and resected, and sutures were used to suspend the dural edges away from the spinal cord. Care was taken to carefully elevate the thickened dural leaflets away from the compressed spinal cord. The resultant diamond-shaped dural defect was repaired via patch duraplasty using a bovine dural substitute. The wound was then closed in a multilayer, watertight fashion. No drains were left in the wound bed.

The patient’s neurological status remained unchanged immediately postoperatively, and no adverse complications were observed in the postoperative period. The patient was determined to be stable for discharge on postoperative day 3 and was discharged to inpatient rehabilitation. At the 6-week follow-up, the patient reported significant improvement in pain and muscle spasms. Although he remained nonambulatory, this was believed to be multifactorial and largely related to his patellar tendon injuries bilaterally and chronic deconditioning for which he used a wheelchair preoperatively. Thoracic spine MRI postoperatively showed the resolution of spinal stenosis at the symptomatic level (Fig. 4). At the 6-month follow-up, the patient was still using his wheelchair but had begun to stand during therapy and take steps with a wheeled walker; his lower-extremity function was continuing to improve; and his back pain was well controlled with oral pain medications.

FIG. 4
FIG. 4

Postoperative sagittal (A and B) and axial (C) T2-weighted MRI 6 months after surgery. The area of mild stenosis noted at T7–8 remains stable without interval change from surgery. There is resolution of the severe stenosis at T10–11 with the return of normal CSF signal around the spinal cord (DF).

Patient Informed Consent

The necessary patient informed consent was obtained in this study.

Discussion

The prevalence of clinically symptomatic heterotopic calcifications is about 0.5%–3% in patients undergoing dialysis, although postmortem studies have shown extraosseous calcifications in 45% of patients with chronic kidney disease and 80% of dialysis patients.1 Decreased glomerular filtration rates (GFRs) in chronic kidney disease lead to lower levels of activated vitamin D, serum hypocalcemia, and hyperphosphatemia. These metabolic abnormalities lead to increased PTH secretion with the goal of increasing calcium reabsorption and phosphate excretion. These calcium and phosphate abnormalities worsen as kidney disease progresses and the body can no longer compensate for the low GFR, resulting in significant metabolic derangements. The resulting electrolyte and endocrine abnormalities cause disordered bone resorption and the subsequent bone weakness and fragility that are typical in renal osteodystrophy. Paradoxical deposition of calcium phosphate nanocrystals leads to vascular and soft tissue calcifications, including, rarely, dural calcifications.2–5

Intracranial dural calcifications in the setting of renal failure are a known complication, with some studies reporting an incidence of intracranial dural calcification up to 9.6% in dialysis patients.6 Diffuse spinal dural calcification is much less frequently reported, and, to our knowledge, this case represents the first report of surgical decompression with duraplasty for the treatment of symptomatic spinal cord compression in the setting of diffuse dural calcification.7–10 Similar dural calcifications due to other etiologies have been reported in the literature, with most pathologies linked to underlying abnormalities in calcium or phosphate metabolism. One report discussed the case of a man with diffuse dural calcifications on CT, which aided in the diagnosis of adult hypophosphatasia.11 Najefi et al.12 reported the first known case of cervical dural calcification secondary to X-linked hypophosphatemic rickets (XLHR). Although their patient presented with spinal cord compression from a combination of calcified dural plaques and ligamentum flavum, laminectomy revealed a flexible and noncompressive dura. Other authors reported a similar case of a man with XLHR experiencing progressive lower-extremity weakness, who was found to have diffuse calcification of the posterior longitudinal ligaments causing severe central canal stenosis.13 Because the ligamentous soft tissues of the spinal canal can also become calcified, it is important to differentiate these related pathologies during surgical planning. It is also important that these pathologies be differentiated from focal dural calcifications, which can occur from meningiomas, previous spinal subdural hemorrhages, or dural osteomas and do not specifically imply any underlying metabolic abnormalities.14

Observations

The phenomenon of dural buckling, or invagination of the calcified dura as described in this case, represents a clinically significant consequence of diffuse dural calcifications in the setting of renal osteodystrophy. The calcification causes dural thickening and a loss of normal dural flexibility, which alters the ability of the dura to compensate for any change in the length of the vertebral column. We posit that the combination of diffuse dural calcification and multiple chronic compression fractures with vertebral body height loss, along with the tubular nature of the spinal dura, put this patient at high risk for the dura buckling toward the spinal cord, causing symptomatic spinal cord compression.

Surgical management in this case was achieved by thoracic laminectomy and direct decompression via resection of the offending calcified dura, with patch duraplasty to repair the resulting dural defect. As opposed to calcification of the ligamentum flavum or posterior longitudinal ligaments, in which a laminectomy alone may be sufficient, the nature of this pathology necessitates an intradural approach for adequate decompression. The use of intraoperative ultrasound can be instrumental in these cases to evaluate the degree of compression as well as for verification of adequate decompression at the conclusion of the case. After resection of the most invaginated area of the dura is completed, the edge of the remaining dural leaflets can be sutured under tension to ligament or soft tissue on the edges of the laminectomy bed, thus tenting the leaflets away from the spinal cord. Tenting the dural edges away from the spinal cord reduces the need to resect a larger portion of dura, which could complicate the dural repair. The repair of the diamond-shaped dural defect was achieved with a bovine dural substitute in this case. Duraplasty in the setting of diffuse dural calcification can be especially challenging, given the thickened but brittle nature of the calcified dura, and a watertight dural repair may not be feasible. In these cases, care must be taken to achieve a strong multilayer closure of the paraspinal soft tissue to reduce the chances of postoperative pseudomeningocele or CSF leakage.

Although the patient presented with a focal kyphotic deformity due to the severe T12 compression fracture, we chose not to address this pathology with a larger fusion-based operation for a number of reasons. The fracture was chronic at the time of presentation, and back pain was not a significant part of the patient’s presenting symptoms. The driving force behind the patient’s neurological decline and mobility limitation was believed to be primarily attributable to compressive myelopathy as opposed to spinal deformity or fracture-related back pain. Given his multiple medical comorbidities, including chronic thrombocytopenia, the chronicity of the fracture, and the very poor bone quality, we believed that a thoracolumbar fusion would expose the patient to an unnecessarily high perioperative risk.

Lessons

As with any report of a single case, these observations are limited, and there may be other pathological manifestations of spinal dural calcifications not described herein. Given these limitations, surgical decompression of diffuse spinal dural calcifications causing symptomatic spinal cord compression is feasible and can be effective at relieving symptoms of myelopathy. Diffuse dural calcifications are a rare complication of chronic dialysis patients, with the potential for neurological injury when present in conjunction with multilevel compression fractures. In the absence of the dural buckling phenomenon that resulted in spinal cord compression in this case, the diffuse dural calcifications were unlikely to become symptomatic in this patient. To achieve adequate spinal cord decompression, this condition requires an intradural approach that addresses the calcified dural invaginations directly.

Author Contributions

Conception and design: Pawloski, Anzalone, Shaftel, Fadel, Lee. Acquisition of data: Pawloski, Anzalone, Shaftel, Lee. Analysis and interpretation of data: Pawloski, Shaftel, Lee. Drafting the article: Pawloski, Malecki, Anzalone. Critically revising the article: Pawloski, Anzalone, Lee. Reviewed submitted version of manuscript: Pawloski, Shaftel, Lee. Approved the final version of the manuscript on behalf of all authors: Pawloski. Study supervision: Lee.

Supplemental Information

Previous Presentations

This case was presented as a digital abstract at the Congress of Neurological Surgeons Annual Meeting, Washington, DC, September 2023.

References

  • 1

    Molenaar FM, van Reekum FE, Rookmaaker MB, Abrahams AC, van Jaarsveld BC Extraosseous calcification in end-stage renal disease: from visceral organs to vasculature. Semin Dial. 2014;27(5):477487.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Ho LT, Sprague SM Renal osteodystrophy in chronic renal failure. Semin Nephrol. 2002;22(6):488493.

  • 3

    Jin DC, Yun SR, Lee SW, et al. Lessons from 30 years’ data of Korean end-stage renal disease registry, 1985–2015. Kidney Res Clin Pract. 2015;34(3):132139.

  • 4

    Silver J, Rodriguez M, Slatopolsky E FGF23 and PTH—double agents at the heart of CKD. Nephrol Dial Transplant. 2012;27(5):17151720.

  • 5

    Bartolomeo K, Tan XY, Fatica R Extraosseous calcification in kidney disease. Cleve Clin J Med. 2022;89(2):8190.

  • 6

    Savazzi GM, Cusmano F, Musini S Cerebral imaging changes in patients with chronic renal failure treated conservatively or in hemodialysis. Nephron. 2001;89(1):3136.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Ritchie WG, Davison AM Dural calcification: a complication of prolonged periodic haemodialysis. Clin Radiol. 1974;25(3):349353.

  • 8

    Koroglu M, Chen PS, Oto A, Koroglu BK Left atrial, pulmonary vein and dural calcification in a patient with arrhythmia and chronic renal failure. JBR-BTR. 2005;88(2):7879.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Besigye E, Johansen JG, Osnes S Total dural calcification with secondary hyperparathyoidism: a rare entity. Neuroradiology. 1978;15(2):107109.

  • 10

    Dorenbeck U, Leingärtner T, Bretschneider T, Krämer BK, Feuerbach S Tentorial and dural calcification with tertiary hyperparathyroidism: a rare entity in chronic renal failure. Eur Radiol. 2002;12(suppl 3):S11S13.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Chew LC, Tong C, Bryant C, Joshua F Recognizing the clinical triad and dural calcification in adult hypophosphatasia. Rheumatology (Oxford). 2017;56(6):868.

  • 12

    Najefi AA, Beder DB, Sabah SA, Rezajooi K Cervical dural calcification and cervical myelopathy in X-linked hypophosphataemic rickets: a case report and review of the literature. Br J Neurosurg. 2019;33(2):222223.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Fearon C, Abbas A, Ryan SA, Fitzgerald SJ, Looby S Compressive cervical myelopathy in X-linked hypophosphataemic rickets. Can J Neurol Sci. 2018;45(5):568570.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Lyndon D, Lansley JA, Evanson J, Krishnan AS Dural masses: meningiomas and their mimics. Insights Imaging. 2019;10(1):11.

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  • FIG. 1

    Preoperative noncontrast CT imaging shows a thickened, calcified dura extending from the cervicothoracic junction caudally to the lumbar spine, primarily affecting the dorsal aspect of the dura (arrows). There are multiple areas of invagination, with the most significant at the T10–11 level.

  • FIG. 2

    Preoperative imaging. A: Three-dimensional reconstruction of the preoperative CT scan shows the chronic T12 compression fracture and resultant focal kyphotic deformity and coronal imbalance. B: CT myelography performed at the outside hospital reveals again the two areas of suspected spinal stenosis at the T7–8 and T10–11 levels.

  • FIG. 3

    Preoperative T2-weighted MRI. Sagittal (A and B) and axial (C) images show an area of mild to moderate stenosis at the T7–8 level. The dura at the T10–11 level is significantly more deformed, and there is no circumferential CSF signal around the spinal cord at this level, concerning for more severe stenosis and compression (DF).

  • FIG. 4

    Postoperative sagittal (A and B) and axial (C) T2-weighted MRI 6 months after surgery. The area of mild stenosis noted at T7–8 remains stable without interval change from surgery. There is resolution of the severe stenosis at T10–11 with the return of normal CSF signal around the spinal cord (DF).

  • 1

    Molenaar FM, van Reekum FE, Rookmaaker MB, Abrahams AC, van Jaarsveld BC Extraosseous calcification in end-stage renal disease: from visceral organs to vasculature. Semin Dial. 2014;27(5):477487.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Ho LT, Sprague SM Renal osteodystrophy in chronic renal failure. Semin Nephrol. 2002;22(6):488493.

  • 3

    Jin DC, Yun SR, Lee SW, et al. Lessons from 30 years’ data of Korean end-stage renal disease registry, 1985–2015. Kidney Res Clin Pract. 2015;34(3):132139.

  • 4

    Silver J, Rodriguez M, Slatopolsky E FGF23 and PTH—double agents at the heart of CKD. Nephrol Dial Transplant. 2012;27(5):17151720.

  • 5

    Bartolomeo K, Tan XY, Fatica R Extraosseous calcification in kidney disease. Cleve Clin J Med. 2022;89(2):8190.

  • 6

    Savazzi GM, Cusmano F, Musini S Cerebral imaging changes in patients with chronic renal failure treated conservatively or in hemodialysis. Nephron. 2001;89(1):3136.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Ritchie WG, Davison AM Dural calcification: a complication of prolonged periodic haemodialysis. Clin Radiol. 1974;25(3):349353.

  • 8

    Koroglu M, Chen PS, Oto A, Koroglu BK Left atrial, pulmonary vein and dural calcification in a patient with arrhythmia and chronic renal failure. JBR-BTR. 2005;88(2):7879.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Besigye E, Johansen JG, Osnes S Total dural calcification with secondary hyperparathyoidism: a rare entity. Neuroradiology. 1978;15(2):107109.

  • 10

    Dorenbeck U, Leingärtner T, Bretschneider T, Krämer BK, Feuerbach S Tentorial and dural calcification with tertiary hyperparathyroidism: a rare entity in chronic renal failure. Eur Radiol. 2002;12(suppl 3):S11S13.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Chew LC, Tong C, Bryant C, Joshua F Recognizing the clinical triad and dural calcification in adult hypophosphatasia. Rheumatology (Oxford). 2017;56(6):868.

  • 12

    Najefi AA, Beder DB, Sabah SA, Rezajooi K Cervical dural calcification and cervical myelopathy in X-linked hypophosphataemic rickets: a case report and review of the literature. Br J Neurosurg. 2019;33(2):222223.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Fearon C, Abbas A, Ryan SA, Fitzgerald SJ, Looby S Compressive cervical myelopathy in X-linked hypophosphataemic rickets. Can J Neurol Sci. 2018;45(5):568570.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Lyndon D, Lansley JA, Evanson J, Krishnan AS Dural masses: meningiomas and their mimics. Insights Imaging. 2019;10(1):11.

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