Facial paralysis is accompanied by numerous restrictions in the mouth and cheek area. Due to the lack of nerve stimulation, atrophy of the facial musculature occurs, resulting in tissue loss and slackening of the overlying skin. This is comparable to the natural aging process in which fat deposits are reduced and the connective tissue loses tension[1]. Facial paralysis patients experience "faster aging", but only on one side. This is not only noticeable with regard to symmetry, but also affects the patient during food intake and articulation[2].
For example, the buccinator muscle ensures that the food bolus is pushed back into the middle during chewing movements. If this muscle fails to function, food remains in the cheek pockets. Inadequate muscle tension also leads to impaired "sealing" of the mouth (orbicularis oris muscle), which results in oral incompetence especially when drinking. Here, more so in older patients, the oral continence (amount of drink that can be kept in the mouth) is limited to less than 20 ml[3]. Exceeding this amount leads to a drooling mouth effect (unilateral oral incontinence).
During articulation, it is noticeable that the pronunciation is less clear than in non-affected people due to the slackening of one half of the face[4].
The insertion of a muscle graft in the cheek area or the reanimation of the original musculature can not only restore symmetry but also improve the problems mentioned above by tightening the tissue[5].
This 3D model clearly shows the complexity of the mimic musculature. In addition, you can also visualize the position of the parotid gland (Glandula parotidea), between whose superficial and deep part the Plexus parotideus of the N. facialis is located. In the clinical picture of mumps the parotid gland is classically swollen.
Source: "danielmclogan". Head Anatomy for Artist. 2020. sketchfab.com/3d-models/head-anatomy-for-artist-99717ac9c0434ac59fc5efd3d1dc3471. Accessed on 11/15/2020. CC BY-SA 4.0. creativecommons.org/licenses/by-sa/4.0.
sources:
[1] Stuzin JM. Restoring facial shape in face lifting: the role of skeletal support in facial analysis and midface soft-tissue repositioning. Plast Reconstr Surg 2007; 119(1):362-76; discussion 377-8.
[2] Swart BJM de, Verheij JCGE, Beurskens CHG. Problems with eating and drinking in patients with unilateral peripheral facial paralysis. Dysphagia 2003; 18(4):267–73.
[3] Seçil Y, Aydogdu I, Ertekin C. Peripheral facial palsy and dysfunction of the oropharynx. J Neurol Neurosurg Psychiatry 2002; 72(3):391–3.
[4] Movérare T, Lohmander A, Hultcrantz M, Sjögreen L. Peripheral facial palsy: Speech, communication and oral motor function. Eur Ann Otorhinolaryngol Head Neck Dis 2017; 134(1):27–31.
[5] Myckatyn TM, Mackinnon SE. The surgical management of facial nerve injury. Clinics in Plastic Surgery 2003; 30(2):307–18.