Evaluation of sensibility of non-innervated, intraoral, microsurgically transferred flaps"

Abstract

Background: This study investigated the sensory recovery of microvascular free flaps in the oral cavity with functional magnetic resonance imaging (fMRI) to assess the activation in the primary sensory cortex (S1).

Methods: The study included 20 patients with sensory recovery at the flap site in the tongue and/or mouth floor after ablative cancer surgery that involved unilateral resection of the lingual nerve and reconstruction with a radial free forearm flap, anterolateral thigh flap or lower leg perforator flap without nerve readaptation between 2012 and 2019. The control non-flap and contralateral flap sites were electrically stimulated with a patient-specific, sensation-inducing voltage for 10 min with 30s on/off intervals. During this process, a fMRI was conducted simultaneously to assess the signal area and level in S1.

Results: The stimulation voltage was higher at the flap site than at the control non-flap site (6.0 V vs. 3.0 V, p<0.001). The signal area activated upon stimulation of the flap and control non-flap sites was located in the cortical area representing the lingual nerve. The signal level in S1 upon stimulation of the flap site was similar to that upon stimulation of the control non-flap site (3.2 T vs. 3.5 T, p=0.751).

Conclusions: Activation of the cortical area representing the lingual nerve upon stimulation of the flap site implies that sensory recovery of microvascular free flaps in the tongue and mouth floor region involves nerve ingrowth from the remaining lingual nerve into the flap tissue.