From the Guidelines
Cranial nerves are 12 pairs of nerves that emerge directly from the brain and brainstem, controlling various functions in the head and neck, including sensory and motor functions, and are designated by numbers from I to XII. These nerves are responsible for a wide range of functions, including:
- Sensory functions such as smell, vision, taste, hearing, and balance
- Motor functions such as eye movement, facial expression, swallowing, and tongue movement
- Other functions like internal organ function and neck movement The 12 pairs of cranial nerves are:
- Olfactory (CN I)
- Optic (CN II)
- Oculomotor (CN III)
- Trochlear (CN IV)
- Trigeminal (CN V)
- Abducens (CN VI)
- Facial (CN VII)
- Vestibulocochlear (CN VIII)
- Glossopharyngeal (CN IX)
- Vagus (CN X)
- Spinal accessory (CN XI)
- Hypoglossal (CN XII) As noted by 1, the cranial nerves arise from nuclei within the brain and brain stem and supply sensory and motor innervation to the head and neck region. Understanding the functions and anatomy of the cranial nerves is essential for clinicians to diagnose and treat conditions affecting the brain and nervous system, and to improve patient outcomes in terms of morbidity, mortality, and quality of life. The proper functioning of these nerves is crucial for daily activities and quality of life, and damage to these nerves can result in various symptoms depending on which nerve is affected, such as loss of smell, vision problems, facial paralysis, or difficulty swallowing, as discussed in 1.
From the Research
Definition and Function of Cranial Nerves
- Cranial nerves are pairs of nerves that control motor and sensory functions of the head and neck 2.
- There are 12 pairs of cranial nerves in the human body 2.
Examples of Cranial Nerves
- The trigeminal nerve is the largest and most widely distributed in the supra-hyoid neck, providing sensory input from the face and motor innervation to the muscles of mastication 3.
- The oculomotor, abducens, facial, and hypoglossal nerves are examples of cranial nerves that can be affected by various disease conditions 4.
- The third and seventh cranial nerves can be congenitally absent, which can be diagnosed using high-resolution cranial nerve magnetic resonance (MR) imaging 5.
Imaging and Evaluation of Cranial Nerves
- Magnetic resonance imaging (MRI) is considered the gold standard in the study of cranial nerves 2.
- Computed tomography (CT) can provide an indirect view of the nerve and is useful to demonstrate the intraosseous segments of cranial nerves, the foramina through which they exit the skull base, and their pathologic changes 2.
- Electrophysiological techniques, such as visual evoked potentials, brain stem auditory evoked potentials, and facial motor nerve conduction studies, can be used to evaluate cranial nerve abnormalities 6.