Hypoglossal nerve identification during head and neck surgery

Hypoglossal Nerve Neuropathies-Analysis of Causes and Anatomical Background

The hypoglossal nerve is the last, and often neglected, cranial nerve. It is mainly responsible for motor innervation of the tongue and therefore the process of chewing and articulation. However, tumors, aneurysms, dissections, trauma, and various iatrogenic factors such as complications after surgeries, radiotherapy, or airway management can result in dysfunction. Correct differential diagnosis and suitable treatment require a thorough knowledge of the anatomical background of the region. This review presents the broad spectrum of hypoglossal neuropathies, paying particular attention to these with a compressive background. As many of these etiologies are not common and can be easily overlooked without prior preparation, it is important to have a comprehensive understanding of the special relations and characteristic traits of these medical conditions, as well as the most common concomitant disorders and morphological traits, influencing the clinical image. Due to the diverse etiology of hypoglossal neuropathies, specialists from many different medical branches might expect to encounter patients presenting such symptoms.

Unilateral aberrant anatomy of the hypoglossal nerve

PURPOSE

Neck dissection is often performed in patients with oral cancer to both treat and reduce the risk of subsequent neck metastases. Injury to the hypoglossal nerve may result in dysarthria, dysphagia, and profound difficulty with upper airway control. Although surgical landmarks facilitate intra-operative identification of vital structures to be preserved, they should not be an absolute measure, due to anatomical variants. We present a rare case of unilateral aberrant anatomy of the hypoglossal nerve, passing superficial to the internal jugular vein.

METHODS

A 70-year-old female presented to the emergency department with an indurated and ulcerated floor of mouth lesion, later confirmed to be a squamous cell carcinoma. She was treated with wide local excision, bilateral selective neck dissection of levels I to III, surgical tracheostomy, anterior mandibulectomy and reconstruction with a left composite radial forearm free flap.

RESULTS

A nerve-like structure was identified crossing superficially and perpendicular to the internal jugular vein within the left neck, which was later determined to be an anatomical variant of the hypoglossal nerve. This was carefully dissected and preserved, and the remainder of the surgery completed uneventfully. On the right, the hypoglossal nerve followed its normal anatomical course. The patient made a good recovery and suffered no neurological complications.

CONCLUSION

Identification, meticulous dissection and preservation of the hypoglossal nerve is essential in lymphadenectomy involving levels I and II. Detailed knowledge of both normal and variant anatomy is fundamental for surgeons, which will allow for identification and protection of important neurovascular structures, thereby minimising surgical morbidity.

Hypoglossal Nerve Palsy After Anterior Cervical Spine Surgery: A Case Report and Literature Review

CASE

A 37-year-old man was found to have hypoglossal nerve palsy after undergoing anterior cervical spine surgery at C3-C5, an injury that would cause him severe disability and further complications.

CONCLUSION

Knowledge of the hypoglossal nerve is crucial for cervical spine surgery even at lower levels (C4-C7), including variations in its course and potential displacement during the induction of anesthesia.