Thoracic Myelopathy Resulting from a Ventral Osteosclerotic Lesion: A Rare Case Report

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Abstract

INTRODUCTION

Melorheostosis, first described by Leri and Joanny in 19227), is characterized by benign hyperostosis along the bone cortex. The term “melorheostosis” is derived from the Greek words “Melos” (limb) and “Rheos” (flow), reflecting the radiographic appearance of the condition, which resembles “melting or dripping candle wax.” This condition is extremely rare, with an incidence of approximately 0.9 per million individuals17). Since its initial description, only 400 cases have been reported in the literature. The onset of melorheostosis ranges from 2 to 64 years, with older patients generally exhibiting slower disease progression3,18).

Melorheostosis primarily affects appendicular bones, such as the hands, feet, and long bone diaphyses, more frequently in the lower extremities. Spinal melorheostosis is relatively unusual and can result in symptoms such as stiffness, motion-related back pain, radiculopathy, and progressive myelopathy. Treatment is typically symptom-based. Due to its insidious onset and mild early-stage symptoms, spinal melorheostosis is often overlooked, particularly in adults, who tend to experience slow disease progression4). Sclerotic bone formation within the spinal canal poses a significant threat to the spinal cord, considering the limited space available in the spinal canal. In addition, because of the low incidence of spinal melorheostosis, no specific treatment guideline has been established, and only a few cases involving surgical management have been reported.

Here, we present a rare case of a 67-year-old patient with mild myelopathy resulting from spinal melorheostosis, who was treated with surgical decompression and posterior screw fixation. The clinical aspects, pathophysiology, and surgical technique employed in this case were reviewed in this study.

CASE REPORT

A 67-year-old female with no significant medical history visited our outpatient with incidental findings on thoracic vertebral imaging from a preoperative chest computed tomography (CT) scan performed for shoulder surgery. The patient presented with gait disturbances and mild, motion-related back pain, which had lasted for approximately 2 to 3 years, along with a recent symptom of mild tingling sensations in both feet. Physical examination revealed weakly positive ankle clonus bilaterally, though sensory and motor functions were intact. Chest radiography revealed hyperostotic masses in the right vertebral part of T3-4, the right costovertebral joint of T5, and right 4^th rib extending into the spinal canal of T4 and T5 (Fig. 1). Sclerotic lesions observed on a preoperative T-spine X-ray in the right vertebral part of T3-4, the right head of the 4th rib, and the right T5 costovertebral joint were further evaluated in detail (Fig. 2A, B). Thoracic spine CT revealed characteristic “dripping candle wax” cortical osteosclerotic lesions spreading on the right side of the T3 and T4 vertebral bodies, compromising the right lamina, the T4 transverse process, and the head of 4^th rib. Axial CT imaging of the thoracic spine revealed an ossification of the posterior longitudinal ligament-like mass that significantly compressed the ventral side of the spinal cord. Spinal magnetic resonance imaging (MRI) confirmed spinal cord compression caused by hyperostosis protruding into the ventral side of the spinal canal at the T3-4 level (Fig. 3A). Moreover, bone scintigraphy showed increased uptake at these sites, with no additional lesions detected in other locations on imaging (Fig. 4). Following consultation with radiology, a diagnosis of “spinal melorheostosis” was considered based on the characteristic imaging findings. Consequently, we opted for surgical resection for pathological confirmation and spinal cord decompression.

Fig. 1.

Anteroposterior chest X-ray. Radiographs taken at the time of the visit showing sclerotic lesions in the right vertebral part of T3-T4, the right head of the fourth rib, and the right T5 costovertebral joint.

Fig. 2.

Preoperative thoracic spine X-rays in anteroposterior (A) and lateral (B) views, and postoperative thoracic spine X-rays in anteroposterior (C) and lateral (D) views. (A, B) The sclerotic lesions observed on the preoperative thoracic spine X-ray in the right vertebral part of T3-T4, the right head of the fourth rib, and the right T5 costovertebral joint were further evaluated in detail. (C, D) Posterior screw fixation was performed at the T2, T3, T5, and T6 levels.

Fig. 3.

Preoperative magnetic resonance imaging (MRI) in sagittal and axial (A) viewing, and postoperative MRI in sagittal and axial (B) views. Both axial views are at the T3-T4 disc level. (A) Preoperative MRI showing hyperostotic ventral lesions at T4 compressing the spinal cord. (B) Postoperative spinal MRI shows the cross-link material at the T4 level with a bright appearance and revealing full decompression of the spinal cord.

Fig. 4.

Radionuclide bone scanning showing increased radiopharmaceutical accumulation in the lesions at T3, T4, and T5.

Given the kyphotic nature of the thoracic spine and the anterior compression of the spinal cord by the sclerotic mass, we planned a T3/4 and T4/5 facetectomy to create space for ventral spinal cord access, along with unavoidable pedicle screw fixation for stabilization. Prior to spinal cord decompression, posterior screw fixation was performed at the T2, T3, T5, and T6 levels (Fig. 2C, D). Hypertrophic bony lesions were observed on the right lamina of T3 and T4 and the head of the 4th rib. To gain a broader surgical field and access the ventral side of the spinal cord, we performed a total laminectomy of T3 and T4, bilateral facetectomy of T3/4 and T4/5 (Fig. 5A), bilateral T4 pediculectomy, and removal of the 4th rib head. Partial corpectomies were performed bilaterally to create adequate ventral space, and the osteosclerotic mass was carefully removed by pushing it into the created space. The dura, which was adhered to the adjacent bony lesion, was detached using a reverse curette without causing cerebrospinal fluid (CSF) leakage. Following the removal of the sclerotic lesion, a dural defect was identified at the site of chronic compression by the ventral sclerotic lesions. Duroplasty was performed by surrounding the dural sac with artificial dura and suturing it in several places, as the primary suture of the ventral dural defect was not feasible. The space created by the laminectomy was packed with tricortical iliac bone, which was secured with a miniplate and screws. A Hemovac drain was not placed to avoid additional CSF leakage (Fig. 5B).

Fig. 5.

(A) Intraoperative photographs. To achieve a wide surgical field and access the ventral side of the spinal cord, we performed total laminectomy at T3 and T4, removed the head of the right fourth rib. (B) Towards the end of the surgery, partial corpectomy and duroplasty were performed, and the removal of the rib head exposed the pleural fat. The area (asterisk) indicates the pleural fat.

The pathological features of melorheostosis include thickened cortical bone and an irregular bone matrix containing enlarged lacunae. Histologically, thickened cortical bone and prominent cement lines are frequently observed, which are associated with excessive bone matrix production3,16). These common features were also identified in the specimen obtained in our case (Fig. 6). Postoperatively, no additional CSF leakage or wound complications were observed. The patient experienced an improvement in both back pain and mild tingling sensation in both feet, although motor function revealed slightly weakened bilateral iliopsoas muscle strength (4/5). Postoperative spinal CT at one year (Fig. 7C, D) and MRI at one week (Fig. 3B) revealed a fully decompressed spinal cord and the complete disappearance of cortical sclerotic lesions. Over the 12-month period after surgery, the motor function of the patient fully recovered, with no evidence of melorheostosis recurrence.

Fig. 6.

Photomicrograph of an intraoperative specimen showing enlarged bone trabeculae without cellular atypia, along with thickened cortical bones and prominent cement lines.

Fig. 7.

Preoperative computed tomography (CT) in axial (A) and sagittal (B) views, and postoperative CT in axial (C) and sagittal (D) views. (A, B) The preoperative axial and sagittal CT images of the T3-T4 vertebral body show osteosclerotic changes on the right side, involving the vertebral body of T3-T4 with posterior column involvement compromising the right lamina and the costovertebral joint of T4. (C, D) One-year postoperative CT images show complete disappearance of the cortical sclerotic lesions with no evidence of recurrence.

DISCUSSION

Melorheostosis is a rare sclerosing bone dysplasia, with an incidence of approximately 0.9 per million individuals17). It predominantly affects the appendicular skeleton, such as the hands, feet, and long bones, with more frequent involvement in the lower extremities3,18). Involvement of the spine is extremely uncommon, and the slow progression of the disease in adults often leads to the early stages being asymptomatic or overlooked4,8).

The etiology of melorheostosis remains unclear, but several hypotheses have been proposed. Murray and McCredie11) suggested that it may be related to specific infections or injuries affecting the “sclerotomes,” the embryologically formed segments of the skeleton supplied by individual sensory nerves. Additionally, mutations in MAP2K1 have been associated with conditions that increase bone density, exhibiting the characteristic "dripping candle wax" appearance observed in melorheostosis16).

Patients with spinal melorheostosis may present with symptoms such as stiffness, motion-related back pain, radiculopathy, and progressive myelopathy5,9,12,13,15,19). Surgical intervention is typically considered in cases with significant neurological deficits or intractable pain that cannot be managed conservatively5,12,13). In our case, the patient presented with mild but significant clinical symptoms, including gait disturbances and motion-related pain, indicating early neurological involvement.

While radiological imaging, including CT and MRI, is essential for identifying the characteristic sclerotic lesions of melorheostosis, clinical decision-making should not rely solely on imaging findings. Radiographic studies provide essential information regarding the extent of bone involvement and the degree of spinal cord compression2,6,10). However, relying exclusively on radiological criteria without considering the patient's clinical symptoms can lead to an incomplete understanding of the disease’s impact.

In this case, both the patient’s neurological symptoms and imaging findings indicating spinal cord compression were considered in the decision to pursue surgical treatment. The surgical approach involved decompression and posterior screw fixation, leading to a favorable outcome with significant symptomatic relief over a 12-month follow-up period. This result aligns with other reported cases where surgical intervention led to positive outcomes5,13-15).

Due to the rarity of spinal involvement and the absence of established treatment guidelines, individualized treatment plans are essential for managing spinal melorheostosis. A multidisciplinary approach that includes careful symptom monitoring, regular imaging, and clinical evaluation is crucial for optimizing patient outcomes. The potential for recurrence of vertebral melorheostosis further underscores the imperative for careful deliberation1). Several case reports have described different approaches to the management of spinal melorheostosis, with varying degrees of success depending on the patient’s symptoms, radiological findings, and response to treatment. Table 1 summarizes key details from these cases, highlighting both conservative and surgical treatment methods along with their respective outcomes5,9,12,15,19).

Table 1.

Summary of treatment methods for cases of spinal melorheostosis

CONCLUSION

Spinal melorheostosis is a rare but typically benign condition that is often managed conservatively. However, surgical intervention may be necessary when neurological deficits or significant symptoms arise. This case emphasizes the importance of a comprehensive evaluation that incorporates both clinical and radiological findings. Treatment strategies should be individualized based on the patient’s symptoms and imaging results, ensuring timely and appropriate intervention.

The findings of this case demonstrate that surgical decompression, when indicated, can provide significant symptomatic relief and prevent further neurological deterioration. Careful consideration of both radiological factors and clinical symptoms is essential for deciding the appropriate course of treatment in patients with spinal melorheostosis.

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