By: Catherine Joachin
Cranial Nerve VII
What is Cranial Nerve VII?
The facial nerve, also referred to as cranial nerve VII, is the seventh set of twelve cranial nerve pairs in the brain (Cleveland Clinic, 2024). It stimulates the muscles of facial expression as well as those involved in mouth and tongue movements such as swallowing, tongue elevation and complex jaw motion (Dulak & Naqvi, 2023).
Anatomy and Function
Originating in the brainstem, the facial nerve travels through the facial canal before exiting the base of the skull via the stylomastoid foramen — a small, external opening on the temporal bone — and entering the parotid gland (Dulak & Naqvi, 2023; Tewari, Gupta & Palimar, 2022). From there, it divides into terminal branches, including five motor branches, each needed for the expression of specific facial muscles:
- The frontal (temporal) branch controls forehead muscles.
- The zygomatic branch controls blinking.
- The buccal branch controls the cheek muscles.
- The (marginal) mandibular branch controls.
- The cervical branch controls the chin and lower mouth muscles via the platysma muscle.
(Cleveland Clinic, 2024; Dulak & Naqvi, 2023)
The facial nerve also performs sensory and parasympathetic functions.
- Sensory nerve fibers of the facial nerve innervate the ear canal, the eardrum and the outer ear, assuming a crucial role in hearing (Cleveland Clinic, 2024). They also relay taste sensation from the anterior two-thirds of the tongue (Cleveland Clinic, 2024).
- Parasympathetic nerve fibers of the facial nerve innervate the muscles of the oral cavity and lacrimal glands, which are responsible for saliva secretion and tear production, respectively (Cleveland Clinic, 2024.; Dulak & Naqvi, 2023).
Clinical Significance
Injury to the facial nerve may cause various motor and sensory problems, including muscle weakness, loss of secretion from the associated glands, loss of taste from the anterior parts of the tongue and increased sensitivity to loud sound (Penn Medicine, 2025). These can be caused by several different situations such as a stroke, head trauma, infection or facial surgery (Cleveland Clinic, 2024; Penn Medicine, 2025).
A notable example of facial nerve paralysis is Bell’s palsy, an idiopathic condition characterized by sudden, unexplained muscle weakness on one side of the face (Dulak & Naqvi, 2023).
Symptoms of Bell’s palsy may include:
- Drooping eyelid, eyebrow and mouth on the affected side
- Dry eyes
- Facial pain
- Slurred speech
- Difficulty blinking or controlling eyes
- Hypersensitivity to sound in the one ear
- Difficulty eating and drinking
- Diminished sense of taste
(Cleveland Clinic, 2024)
Although this form of facial palsy is usually described as temporary, rare cases have resulted in long-term or permanent facial dysfunction (Dulak & Naqvi, 2023). Residual symptoms include tearing, contracture, and synkinesis, in which voluntary muscle movements cause simultaneous involuntary facial contractions (Dulak & Naqvi, 2023).
Research
Although research has established that stimulation of the trigeminal and vagus nerves, cranial nerves V and X, respectively, exerts therapeutic anticonvulsant effects on patients with drug-resistant epilepsy, no study to date has explored electrical stimulation of the facial nerve as a candidate treatment option for the condition.
Very few studies have looked into the relationship between epilepsy and cranial nerve VII. A 1991 article on delayed facial nerve palsy following temporal lobectomy (i.e., surgical removal of part of the temporal lobe) for drug-resistant epilepsy found that heat transmission through the outermost membrane of the brain to the geniculate ganglion below the site of resection offers a potential avenue to explore the pathophysiology of ipsilateral facial nerve palsy (Anderson, Awad & Hahn, 1991). However, the three instances documented in this report were not sufficient to establish a cause-and-effect relationship between the epilepsy surgery and the onset of ipsilateral Bell’s palsy.
Conclusion
Cranial nerve VII is a mixed nerve carrying motor, sensory, and parasympathetic fibers that play important roles in innervating the muscles of facial expression, taste, tongue sensation, and secretion of salivary and lacrimal glands. Damage to this nerve may cause severe facial dysfunction in the form of unilateral facial paralysis, a lopsided appearance, and involuntary muscle movements; however, these symptoms do not appear to be related to epilepsy.
References
Anderson, J., Awad, I. A., & Hahn, J. F. (1991). Delayed facial nerve palsy after temporal lobectomy for epilepsy: report of four cases and discussion of possible mechanisms. Neurosurgery, 28(3), 453–456. https://doi.org/10.1097/00006123-199103000-00022
Cleveland Clinic (2024). Facial nerve. Cleveland Clinic. Retrieved August 29, 2025, from https://my.clevelandclinic.org/health/body/22218-facial-nerve
Dulak, D., & Naqvi, I. A. (2023, July 24). Neuroanatomy, Cranial nerve 7 (Facial). StatPearls – NCBI Bookshelf. Retrieved August 29, 2025 from https://www.ncbi.nlm.nih.gov/books/NBK526119/
Penn Medicine. (2025). Facial nerve disorders – Symptoms and causes. The Trustees of the University of Pennsylvania. Retrieved from https://www.pennmedicine.org/conditions/facial-nerve-disorders
Tewari, S., Gupta, C., & Palimar, V. (2022). A Morphometric Study of Stylomastoid Foramen with Its Clinical Applications. Journal of Neurological Surgery. Part B, Skull Base, 83(1), 033–036. https://doi.org/10.1055/s-0040-1716674
