Transcranial magnetic stimulation for diagnosis of residual limb neuromas.

OBJECTIVE

To analyze the mechanism and examine the potential diagnostic contribution of transcranial magnetic stimulation (TMS) in diagnosing painful, clonic, and/or autonomic manifestations in amputees' residual limbs.

DESIGN

Prospective study.

SETTING

Regional rehabilitation institute at a medical school in France.

PARTICIPANTS

Thirty-four amputees (24 with myoclonus, stump pain, or trophic skin disorders; 10 controls with no stump symptoms).

INTERVENTIONS: Not applicable.

MAIN OUTCOMES MEASURES: TMS performed before and after correcting prosthesis adaptation.

RESULTS

TMS induced pain in 12 amputees, clonic manifestations in 4, and autonomic manifestations in 2. Twelve patients underwent magnetic resonance imaging that showed neuromas in all 12. After neuroma resection in 9 amputees, TMS no longer provoked abnormal manifestations. TMS did provoke abnormal manifestations after resection in 3 patients who had postoperative recurrent neuromas. The response to TMS was negative in subjects with a clinically silent neuroma (n=7). The response was also negative in all patients with other stump anomalies whose clinical manifestations fully regressed after conservative treatment. There was a highly significant correlation between the presence of a pathologic neuroma and TMS-induced abnormal manifestations (P<.0001).

CONCLUSIONS

TMS can provoke symptoms in patients who experience spontaneous or evoked symptoms related to a neuroma. Induced symptoms are proportional to spontaneous symptoms. Removing the neuroma can stop stump symptoms and reverse the TMS effect. The response to TMS was negative in the control subjects with clinically silent neuromas; conservative treatment was successful in these cases. TMS-induced abnormal manifestations underlying mechanisms are discussed (ephaptic transmission in neuromas).