Anatomical and histological study of the deep neck fasciae: does the alar fascia exist?

PURPOSE: The aim of this study was to determine whether the alar fascia is a distinct layer of the deep cervical neck fasciae. The present study also aimed to elucidate the anatomical limits of this fascia.
METHODS: Neck dissections of ten adult cadavers were performed, layer by layer, in the retropharyngeal region, under a powered operating microscope. Detailed dissections revealed the anatomical limits of the deep neck fasciae. Histological descriptions were also performed on large tissue samples collected from three cervical dissections.
RESULTS: In the ten dissections, three layers of fascia were identified and dissected in the retropharyngeal region: a visceral fascia, a prevertebral fascia and an alar fascia. The alar fascia appeared like a connecting band derivative of the visceral fascia, between both vascular sheaths. It fused completely with the visceral fascia anteriorly at the level of T2 and with the prevertebral fascia posteriorly at the level of C1. No sagittal connection between the visceral fascia and the prevertebral fascia was identified. The stained histological sections confirmed the presence of the visceral and prevertebral fasciae at the oropharyngeal level, with a third intermediate layer closely connected with the visceral fascia.
CONCLUSION: The alar fascia is a layer of the cervical neck fascia connected with the visceral fascia from C1 to T2 levels. The anatomical limits of this alar fascia and its relationships with the internal carotid artery are important in the surgical management and the prognosis of deep neck infections and retropharyngeal lymph node metastases.