2022 Workshop Handout Bundle-EDX Evaluation of the Lower Cranial Nerves - Stino

EDX Evaluation of the Lower Cranial Nerves - Stino - Kushlaf

Pdf Summary

The EDX evaluation of the lower cranial nerves, specifically cranial nerves XI and XII, is an important complement to the clinical evaluation. This workshop provides a methodical approach to the electrodiagnostic evaluation of these nerves, covering topics such as electrode placement, stimulation site, needle insertion site, side-to-side testing, and the interpretation of normal and abnormal findings.<br /><br />The spinal accessory (CN XI) and hypoglossal (CN XII) nerves have unique anatomies that guide their clinical and EDX evaluation. CN XI features both cranial and spinal components, while CN XII arises from nuclei in the medulla oblongata. The common causes of CN XI mononeuropathy include surgery-induced trauma, while CN XII mononeuropathy can be caused by tumors, carotid endarterectomy, and other factors.<br /><br />The evaluation of CN XI and XII can be useful in the diagnosis and management of myasthenia and ALS. Repetitive nerve stimulation (RNS) studies in myasthenia are best performed proximally in the body, with CN XI evaluation revealing pathologic decrement. Needle EMG evaluation of muscles supplied by CN XI and XII is useful in evaluating ALS and other bulbar-predominant neuromuscular etiologies.<br /><br />In terms of NCS performance, CN XI evaluation is well-characterized, while CN XII techniques are less frequently used. For CN XI evaluation, a protocol used at the Mayo Clinic involves electrical stimulation posterior to the sternocleidomastoid muscle and placing electrodes on the upper body of the trapezius. Needle EMG testing can be performed on the upper trapezius for CN XI and the genioglossus for CN XII.<br /><br />Abnormal findings in NCS and needle EMG testing can indicate CN XI and XII mononeuropathy. Side-to-side comparison of CMAP amplitude for the upper trapezius can suggest CN XI abnormalities, while abnormal findings in CN XII testing can indicate various etiologies. However, there are limitations in the use of CN XI cutaneous NCS, and surgical exploration should be based on clinical weakness rather than NCS findings.<br /><br />In summary, the electrodiagnostic evaluation of cranial nerves XI and XII is a valuable tool in the assessment of neuropathies and neuromuscular disorders. This workshop provides guidance on the evaluation techniques and interpretation of findings for these lower cranial nerves.

Keywords

EDX evaluation

lower cranial nerves

cranial nerves XI

cranial nerves XII

electrodiagnostic evaluation

electrode placement

stimulation site

needle insertion site

side-to-side testing

interpretation of findings