Nerve atrophy in trigeminal neuralgia due to neurovascular compression and its association with surgical outcomes after microvascular decompression

Idiopathic trigeminal neuralgia (TN) is caused by neurovascular compression and is often related to morphological changes in the trigeminal nerve. The aim of this study was to quantitatively measure atrophic changes of trigeminal nerves in patients with TN, and to further investigate whether nerve atrophy affected the efficacy of microvascular decompression (MVD). We conducted a prospective case-control study of 60 consecutive patients with TN and 30 sex- and age-matched healthy controls. All subjects underwent high-resolution three-dimensional MRI. The volume of the cisternal segment of trigeminal nerves was measured and compared using 3D Slicer software. Patients with TN underwent primary MVD and regular follow-up for at least 2 years. Associations of nerve atrophy with patient characteristics and operative outcomes were analyzed. The mean volume of the affected trigeminal nerve was significantly reduced in comparison to that of the nonaffected side (65.8 +/- 21.1 versus 77.9 +/- 19.3 mm(3), P = 0.001) and controls (65.8 +/- 21.1 versus 74.7 +/- 16.5 mm(3), P = 0.003). Fifty-two patients (86.7%) achieved complete pain relief without medication immediately after surgery, and 77.6% of patients were complete pain relief at the 2-year follow-up. The Spearman correlation test showed that there was a positive correlation (r = 0.46, P = 0.018) between the degree of trigeminal nerve indentation and nerve atrophy. In multivariate logistic regression analysis, two factors, indentation on nerve root (OR = 2.968, P = 0.022) and degree of nerve atrophy (OR = 1.18, P = 0.035), were associated with the long-term outcome. TN is associated with atrophy on the affected nerve. Furthermore, greater nerve atrophy is associated with more severe trigeminal nerve indentation and better long-term outcome following MVD.