![]() ![]() Cranial nerve IV (the trochlear nerve_ innervates the superior oblique muscles, which moves the eye downward and outward. Cranial nerve III innervates the superior, medial, and inferior rectus muscles, as well as the inferior oblique muscle, which together function to move eyes medially and in the vertical plane. ![]() Cranial nerve exam includes assessment of the extraocular movements, which are controlled by cranial nerves III, IV and VI. ![]() Testing of the pupillary responses also assesses the function of cranial nerve III (the oculomotor nerve), parasympathetic fibers of which form the efferent limb of the pupillary reflex. Its axons convey visual information and compose the afferent limb of the pupillary reflex. Cranial nerve II (the optic nerve) is the only cranial nerve that can be directly visualized as it exits from the central nervous system. The 12 Cranial Nerves and Their Basic FunctionsĬranial nerve I (the olfactory nerve) is a purely sensory nerve that conveys the sense of smell, and is not routinely tested during most examinations. Strength of sternocleidomastoids and trapezius muscles Movement and sensation of palate, pharynx, gag reflex, guttural sounds Movement of pharynx, sensation of pharynx, posterior tongue (including taste of posterior tongue), and most of ear canal Horizontal eye movements (adduction), efferent pupillary responseĭownward vertical eye movement, internal rotation of eyeįacial movement and strength, taste, dampening of loud sounds, sensation anterior wall of external ear canal Visual acuity, afferent pupillary response A physician should approach the examination in a systematic fashion and go through the cranial nerves in their numerical order. The cranial nerves are symmetrical therefore, while performing the examination, the examiner should compare each side to the other. The cranial nerve examination is applied neuroanatomy. Importantly, a variety of pathological conditions that are associated with alterations in mental status (such as some neurodegenerative disorders or brain lesions) can also cause cranial nerve dysfunction therefore, any abnormal findings during a mental status exam should prompt a careful and complete neurological exam. However, in many cases a patient's history doesn't directly suggest cranial nerve pathologies, as some of them (such as sixth nerve palsy) may have subtle manifestations and can only be uncovered by a careful neurological exam. In some cases, cranial nerve dysfunction is readily apparent: a patient might mention a characteristic chief complaint (such as loss of smell or diplopia), or a visually evident physical sign of cranial nerve involvement, such as in facial nerve palsy. Kaplan, MD Neurology, Brigham and Women's/Massachusetts General Hospital, Boston, Massachusetts, USAĭuring each section of the neurological testing, the examiner uses the powers of observation to assess the patient. ![]()
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