Читать книгу Advances in Neurolaryngology - Группа авторов - Страница 18

The first step in visual neurolaryngology is for the examiner to have a mental map of laryngeal anatomy. Understanding the treelike branching of the laryngeal nerves will allow us to work both forwards and backwards from clinical information we have. If we know where and how an injury took place along the path of the nerve, then we will know the findings and impairments that we should see on an endoscopic examination. Likewise, we can work in the reverse direction. Based on the functional impairments that are seen on an endoscopic examination, we should be able to predict where along the path of the nerve the injury took or is taking place.

The larynx is supplied by the Xth cranial nerve, the vagus nerve. There are two important anatomic locations along the path of this nerve for the examiner to think about. The first location is where the 10th cranial nerve leaves the skull and heads towards the neck. It passes through a very narrow opening along with two other cranial nerves, the XIth and the XIIth cranial nerves. From a diagnostic perspective, this bottleneck then is a location where an injury to the nerve will likely affect not only the Xth cranial nerve but also the XIth and the XIIth cranial nerves. So, in our endoscopic upper airway examination, if there are problems with the tongue (XIIth cranial nerve) or with lifting the arm and shoulder up (XIth cranial nerve), in addition to problems in the larynx, we will know to focus our attention on this narrow opening at the base of the skull.

The second diagnostically important location is where the Xth cranial nerve descends in the neck, it gives off four branches to supply the throat and larynx. Knowing which of these branches are affected will tell us how high the location of the injury is in the neck. If only single branch of the nerve is involved, we know the injury is taking place very near to the larynx. If multiple branches are involved, we know the injury is taking place further away from the larynx and closer to the brain.

The extended path of the left recurrent laryngeal branch of the Xth cranial nerve descending into the chest and wrapping around the aorta and left bronchus while the right typically remains recurrent in the lower neck is one of the best known diagnostic asymmetries.

Since speech and voice overlap in function, assessment of the tongue, soft palate muscles and pharyngeal constrictors contribute to understanding laryngeal neurologic injury.