Clinical features and pathogenesis of scoliosis due to spinal astrocytoma.

The aetiology of scoliosis remains unclear. Some studies have focused on the theory of possible muscular imbalance. The role of the spinal cord, which directly innervates the paraspinal muscles, in muscular imbalance has not yet been studied. Spinal astrocytomas often grow on one side of the spinal cord, destroying it asymmetrically. Asymmetrical damage to the spinal cord can lead to asymmetrical changes in paraspinal muscles. The present study investigated the effect of muscular imbalance on scoliosis by observing scoliosis caused by spinal astrocytomas. Patients diagnosed with spinal astrocytomas in a single centre were analysed, and the type and side of the symptoms, sagittal tumour position, scoliosis, end vertebrae and apical vertebrae of scoliosis were recorded. The tumour side was assumed from symptom type and side, and the cross-sectional area of the paraspinal muscles on both sides of the end vertebra was outlined and compared. The incidence of astrocytoma-induced scoliosis was significantly higher in patients with unilateral symptoms. The inferred tumour side was highly consistent with the convex side of scoliosis. The distal vertebral segments of scoliosis were consistent with the spinal cord segments involved in the astrocytomas. The apical vertebrae were more caudal in astrocytoma-induced scoliosis. The cross-sectional area of the multifidus muscle on the convex side of apical-level scoliosis was significantly smaller than that on the concave side. However, no significant differences were observed in the erector spinae muscles. Overall, spinal astrocytomas can cause asymmetric destruction of the corresponding spinal cord segment, resulting in asymmetric atrophy and weakness of the multifidus muscle innervated by the spinal cord segment, thereby causing scoliosis that is convex to the weaker side. This mechanism involves asymmetric lower neuron paralysis of the multifidus muscle. This is a type of scoliosis with several differences from idiopathic scoliosis.