Tibialis anterior branch involvement in fibular intraneural ganglia

Fibular (peroneal) intraneural ganglia classically present with predominant tibialis anterior weakness, for which there is no clear anatomical explanation. We identified a new imaging pattern, which consisted of involvement of a proximal tibialis anterior branch, in patients with fibular intraneural ganglia. This study characterizes the cystic involvement of this tibialis anterior branch and evaluates its significance. The magnetic resonance imaging (MRI) and clinical data of 23 patients with fibular intraneural ganglia were retrospectively reviewed. The tibialis anterior branch was consistently involved with the cyst, and this involvement, although variable, was more prominent than the cystic involvement of other terminal branches of the fibular nerve. The finding of cyst extension within a muscle end-organ branch seems likely to explain, in part, the characteristic clinical finding of preferential foot drop in patients with fibular intraneural ganglia.