Paradoxic hypertrophy of the sciatic nerve in adult patients after above-knee amputation

Abstract

Paradoxic hypertrophy of nerve tissue at an amputation stump without neuroma formation rarely develops in young patients, in contrast to atrophy of the nerve in older patients. Herein, we present the magnetic resonance imaging (MRI) findings of adult patients (older than 20 years old) who underwent above-knee amputation, one of whom had a palpable mass suggesting a recurrent lesion. MRI ruled out the recurrent lesion and demonstrated paradoxic hypertrophy of the sciatic nerve in all patients.

Sonographic evaluation of the sciatic nerve in patients with lower‐limb amputations

“…Regarding the pathogenesis of sciatic nerve enlargement, young age has been suggested to play a role in the initial study by Hill et al1 In the report of Kerimoglu and Canyigit2 and in our study nerve hypertrophy is also encountered in older ages. In cases with malignancies, the pathogenesis has also been linked to chemotherapy and tumor relapse 1, 2. In accordance with our above‐quoted results, we believe that the mechanisms related to distal neuroma formation might be responsible for proximal enlargement of the peripheral nerve as well.…”

“…Sciatic nerve hypertrophy following lower‐limb amputation has been mentioned previously in only two reports 1, 2. Both were MRI findings of above‐knee amputees including seven osteogenic sarcomas in one study1 and two osteogenic sarcomas and one synovial sarcoma cases in the other 2. However, clinical data regarding the type of prosthesis or pain assessment were lacking in both reports.…”

“…In our study we included below‐knee amputees in addition to individuals with above‐knee amputations. Moreover, we also analyzed whether certain clinical parameters had any impact on the sciatic nerve enlargement; in other words, whether these changes are really “paradoxic” as described in the aforementioned studies 1, 2…”

“…Paradoxic hypertrophy of the sciatic nerve after lower‐limb amputation has been mentioned in two anecdotal reports in the literature. One was a series of seven amputees,1 and a second was a report of three cases 2. Both studies comprised patients who had undergone above‐knee amputations due to lower‐limb sarcoma, and magnetic resonance imaging (MRI) was used to visualize the sciatic nerves.…”

Review of the principal extra spinal pathologies causing sciatica and new MRI approaches

“…Rarely, paradoxical sciatic nerve stump hypertrophy can develop in young patients who underwent limb amputation, in contrast to neural atrophy, which is characteristic in older patients [33,34] (Figure 9). Residual limb pain post amputation is often referred to as ''stump pain'' and has been described in up to 60% of patients [35].…”