From the Guidelines
Facial paresis, or facial paralysis, is primarily caused by pathology affecting the facial nerve (CN VII), including intra-axial conditions, tumors, vascular lesions, inflammation, and trauma, as well as conditions affecting the nerve's intracranial and extracranial segments. To understand the causes of facial paresis, it is essential to consider the complex functions and course of the facial nerve, which contains branchial motor, visceral motor, general sensory, and special sensory functions 1. The facial nerve's intracranial course includes pontine, cisternal, and intratemporal segments, and it may be affected by various conditions, such as:
- Intra-axial conditions like infarction, vascular malformations, tumors, and multiple sclerosis within the pons 1
- Facial and vestibular schwannomas, meningiomas, vascular lesions, inflammation, cholesteatomas, paragangliomas, trauma, and intrinsic bone tumors as the nerve exits the brainstem and courses through the temporal bone 1
- Conditions affecting the extracranial segment, including parotid tumors, inflammation, and conditions of the neighboring anatomic spaces and skull base, such as carcinomas, sarcomas, trauma, and inflammatory disease 1 The most recent and highest quality study, published in 2022, highlights the complexity of the facial nerve and its potential causes of paralysis, including Bell palsy, which is the most common cause of acute peripheral facial nerve palsy, attributed to inflammation of the facial nerve, which may be idiopathic or due to herpes simplex virus 1. Therefore, a comprehensive evaluation and diagnosis are crucial to determine the underlying cause of facial paresis and guide appropriate treatment. Key points to consider in the evaluation and diagnosis of facial paresis include:
- Clinical presentation, such as facial droop, pain around the jaw or ear, hyperacusis, tinnitus, reduced taste, and decreased lacrimation or salivation 1
- Imaging studies, such as MRI or CT scans, to rule out underlying conditions like tumors or vascular lesions 1
- Electrophysiological tests, such as electromyography (EMG) or nerve conduction studies (NCS), to assess the function of the facial nerve 1
From the Research
Causes of Facial Paresis
The provided studies do not directly address the causes of facial paresis (facial paralysis). However, they do provide information on the neural basis of facial action recognition, the organization of central control of facial muscles, and the relationship between facial expression analysis and muscle mass.
Related Factors
- The study 2 discusses the organization of central control of muscles of facial expression in man, which may be related to the causes of facial paresis.
- The study 3 identifies a consistent and differential coding of action units in the brain, which could be relevant to understanding the neural basis of facial paresis.
- The study 4 analyzes the relationship between facial expression analysis and muscle mass, which may be related to the causes of facial paresis.
Key Findings
- The study 2 found that co-contraction of facial muscles during some facial expressions is accompanied by the presence of common synaptic drive to the motoneurones supplying the muscles involved.
- The study 3 found that the brain region responsible for the processing of changeable aspects of the face can decode the presence of specific action units in an image.
- The study 4 found a positive correlation between the integrated expression intensity value (IEIV) and the muscle mass, and that subjects with high IEIV and expressive face had thicker facial expression muscles and little fat infiltration into the muscles.
Potential Causes
- Damage to the facial nerve or its branches, which can result from trauma, infection, or tumors, may cause facial paresis 2.
- Abnormalities in the central control of facial muscles, such as those found in the study 2, may also contribute to facial paresis.
- Muscle weakness or paralysis, which can result from a variety of causes, including neurological disorders or muscle disease, may also cause facial paresis 4.