| Examining the Larynx |
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There are a variety of ways to examine the larynx and each has its strengths and limitations. Often times more than one technique is needed for a complete evaluation. The following describes the various methods that are used in the evaluation of voice disorders.
Indirect laryngoscopy using a dental (angled) mirror is a quick, easy, and cheap method of looking grossly at the larynx. The patient's tongue is held out, the dental mirror is placed in the back of the mouth, and the patient says "eeee." This method's limitations are that it may induce a gag reflex, often times does not allow adequate viewing of the entire larynx, does not allow for video documentation, and it does not allow examination during normal speech or singing.
Flexible fiberoptic laryngoscopy visualizes the larynx by using a small, flexible scope that can be fed through the nose or mouth after anesthetic spray is applied. This can be connected to a video for recording and stroboscopic evaluation (see below) can be performed. The resolution is adequate but somewhat distorted. However, when fed through the nose, this method is the best in evaluating speaking and singing techniques in their normal, unaltered state.
Rigid intraoral laryngoscopy uses a rod-like scope with a 90-degree lens that is fed straight into the back of the mouth to visualize the larynx. Topical anesthetic spray is sometimes used to suppress the gag reflex. The magnification and resolution of this scope is the best for analyzing laryngeal anatomic and physiologic details. It can be connected to a video recorder as well as stroboscope for more detailed evaluations.
Stroboscopic evaluation utilizes a strobe light attached to a scope to flicker at a frequency determined by a subject's voice. This strobe lighting then gives the perception of the vocal cords moving in slow motion and allows a much more detailed analysis of vocal cord function and anatomy. The vocal cord mucosal wave, produced by the vocal cord's mucous membrane flowing over its muscle as air flows past, can only be visualized with the strobe light, high-speed photography or possibly digital photography.
Electromyography (EMG) measures electrical activity in a given muscle group. By placing a needle into the vocal cord muscle, it can be determined whether the muscle is being supplied by a nerve. This is helpful in vocal cord paralysis as it can help predict if vocal cord function may return. It is also of assistance in localizing the vocal muscle as is needed when injecting Botox for spasmodic dysphonia. EMG of the vocal muscle is usually performed by placing a special needle through the lower-middle aspect of the neck, through the cricothyroid membrane and into the vocal cord. It is done with a injection of local anesthetic and is usually very well tolerated.
Voice Analysis is a computerized means of breaking down and analyzing a voice into many different aspects. It is helpful as a way of objectively evaluating a voice, as way of "seeing" on paper the irregularities of a voice and as a way of comparing pre- and post-treatment. This last benefit can serve as a means for biofeedback for the patient in helping them learn and understand their own voice better
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