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It can also be used to diagnose the cause of vertigo, dizziness or balance dysfunction by testing the vestibular system. [1] Electronystagmography is used to assess voluntary and involuntary eye movements. [2] It evaluates the cochlear nerve and the oculomotor nerve (CN III). [2] The ENG can be used to determine the origin of various eye and ...
Unilateral loss indicates a possible nerve lesion or deviated septum. This test is usually skipped on a cranial nerve exam. [1] The short axons of the first cranial nerve regenerate on a regular basis. The neurons in the olfactory epithelium have a limited life span, and new cells grow to replace the ones that die off.
Videonystagmography (VNG) is a type of testing used to assess vestibular and central nervous system function through the use of eye movement tracking, specifically evaluating nystagmus. [1] The older version of technology used to perform these tests, known as electronystagmography (ENG), leverages electrophysiological signals.
When the optic nerve is damaged, the sensory (afferent) stimulus sent to the midbrain is reduced. The pupil, responding less vigorously, dilates from its prior constricted state when the light is moved away from the unaffected eye and towards the affected eye. This response is a relative afferent pupillary defect (or Marcus Gunn pupil). [1]
The head impulse test can be done at the bed side and used as a screening tool for problems with a person's vestibular system. [25] It can also be diagnostically tested by doing a video-head impulse test (VHIT). In this diagnostic test, a person wears highly sensitive goggles that detect rapid changes in eye movement.
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of the eye and that raise the eyelid.
Light from a single point of a distant object and light from a single point of a near object being brought to a focus. The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size.
Emergency physicians routinely test pupillary light reflex to assess brain stem function. Abnormal pupillary reflex can be found in optic nerve injury, oculomotor nerve damage, brain stem lesion (including brain stem death), and depressant drugs, such as barbiturates. [5] [6] Examples are provided as below: