Long-Term Progression of Lipomatosis of Nerve

Objective Lipomatosis of nerve (LN) is a condition of massive peripheral nerve enlargement due to proliferation of fibrous and adipose tissue within the nerve, the natural history of which is currently unknown. We measured the pattern of growth in individuals with long-term radiologic follow-up. Methods Review of the searchable records for LN at our institution found 52 patients, confirmed by pathology or pathognomic appearance on MRI. Ten patients had serial MRI of the same anatomic region for more than 2 years of clinical follow-up. Volumetric analysis was performed using regions of interest on serially imaged segments of affected nerves. Adjustment for skeletal growth was performed for pediatric patients. Results LN enlarged in 7 of 10 individuals, often both longitudinally along the nerve and in cross-sectional volume. Regarding cross-sectional volume, 2 of the 10 patients demonstrated volume growth more than doubling and 5 additional patients had a >20% increase in nerve volume; the remaining 3 patients were quiescent, where change in the nerve volume was within the error range of volumetric analysis. All cases with growth remained >20% after adjustment for skeletal growth. Five of 10 individuals had longitudinal extension, even with correction for skeletal growth. More significant growth was noted in younger patients ( P = 0.02). Growth rates more than 5% per year correlated with surgery, without statistical significance in this small population ( P = 0.14). Conclusions Serial MRI reveals progressive enlargement of LN. The rate of growth was more profound in youth, but also occurred in early adulthood.