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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.
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 ...
Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. [1] A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portion of the orbicularis oculi, not the full open and close.
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.
For an adequate test, vision must not be entirely lost. In dim room light, the examiner notes the size of the pupils. The patient is asked to gaze into the distance, and the examiner swings the beam of a penlight back and forth from one pupil to the other, and observes the size of pupils and reaction in the eye that is lit.
Another way of testing the VOR response is a caloric reflex test, which is an attempt to induce nystagmus (compensatory eye movement in the absence of head motion) by pouring cold or warm water into the ear. Also available is bi-thermal air caloric irrigations, in which warm and cool air is administered into the ear.
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.
Diagram illustrating the locations of extraocular muscles and ocular cranial nerves. Paresis of the oculomotor nerve (CNIII) reduces the strength of medial rectus, superior rectus, inferior rectus, and inferior oblique muscles, while trochlear nerve (CNIV) and abducens nerve (CNVI) paralysis affect superior oblique muscle and lateral rectus muscle respectively.