Improving surgical results in complex nerve anatomy during implantation of selective upper airway stimulation.

The following report presents a case of two late embedded hypoglossus branches during implantation of an upper airway stimulation device that caused a mixed activation of the tongue when included in the stimulation cuff. In the end, correct cuff placement could be achieved by careful examination of the hypoglossal nerve anatomy, precise nerve dissection, tongue motion analysis and intraoperative nerve monitoring.

Sternocleidomastoid innervation from an aberrant nerve arising from the hypoglossal nerve: a prospective study of 160 neck dissections.

BACKGROUND: Anatomical variants of the spinal root of the accessory nerve and cervical plexus are well known but other variants are exceptionally rare. METHODS: A prospective study of 160 selective neck dissections was undertaken following an index case, where a presumed C1 nerve (travelling with the hypoglossal nerve) was found to innervate sternocleidomastoid (SCM). A search was subsequently made for this variant while not compromising the neck dissection surgery itself. Eight cases could not be included due to metastatic disease precluding safe dissection in this area. A nerve stimulator was used to confirm the motor supply to SCM. RESULTS: This nerve variant was found in 4/160 necks (2.5 %). In all cases, it originated directly from the hypoglossal nerve and stimulation resulted in isolated SCM contraction. No accessory nerve anomalies were found. CONCLUSION: This finding adds to the knowledge of variants in this area. Meticulous dissection and preservation of all nerves, where possible, is important for optimising functional outcomes following surgery.

Atypical location of the hypoglossal nerve and its implications: a case report.

INTRODUCTION: Successful surgery in the neck is dependent on reliable anatomical relationships between nerves, vessels, and muscles. These landmarks and planes are also essential to avoiding undue morbidity and mortality. Anatomic variants of the hypoglossal nerve are rare, and their incidences are unknown. METHODS: We describe a case of a hypoglossal nerve found coursing superficial to the internal jugular vein in a 52-year-old woman treated with bilateral selective neck dissection for metastatic thyroid malignancy. RESULTS: The vulnerable nerve was protected, and she maintained excellent speech and swallow function post-operatively. CONCLUSIONS: The variant course of the nerve may pose higher risk for injury in neck surgery. Surgeons should be aware of the possibility of aberrant anatomy in this region and exercise extra caution to avoid nerve injury.

Different navigation of the hypoglossal nerve in the same patient: in the light of the literature.

The hypoglossal nerve appears typically between the internal carotid artery and internal jugular vein and down in the lateral groove between these 2 anatomical structures on to the right common carotid artery bifurcation. In this case report, we presented a patient that was operated on for laryngeal carcinoma, and abnormal navigation of hypoglossal nerve was observed during the neck dissection.

Aberrant anatomy of the hypoglossal nerve.

OBJECTIVE: Variant anatomy of the hypoglossal nerve is very rare. We report an unusual intra-operative finding of an aberrant branch of the hypoglossal nerve, encountered during a facial reanimation procedure. CASE REPORT: A 50-year-old man was referred to the head and neck surgery department by the neurosurgeons for hypoglossal-facial nerve anastomosis to treat his facial paralysis, which had occurred following the removal of an intracranial neoplasm. During surgery, we identified an aberrant branch of the hypoglossal nerve, which took a more ventral and superior course in the carotid triangle, prior to entering the base of the tongue. Following further dissection, we found the main trunk of the 'true' hypoglossal nerve. Several interconnecting strands were seen in the proximal aspect of both the aberrant branch and the main trunk of the hypoglossal nerve. These interconnecting fibres appeared to have tethered the main trunk into an abnormal anatomical position. CONCLUSION: As far as we can ascertain, this is the first report of an aberrant branch of the hypoglossal nerve. Although this variant would appear to be extremely rare, surgeons must consider all variations of this nerve during head and neck procedures, in order to minimise iatrogenic complications.

Lateral congenital anomalies of the pharyngeal apparatus: part III. cadaveric representation of the course of second and third cleft and pouch fistulas.

"Stepladder" surgery for fistula from second or third pharyngeal cleft and pouch is "blind." Neither intraoperative methylene blue injection and probing nor preoperative imaging (fistulogram ultrasound, computed tomography, magnetic resonance imaging) reveal three-dimensional anatomic relations of fistulas. This article describes the most common second and third fistula courses and demonstrates representation of their tracts with wires in human cadavers. A second cleft and pouch fistula, at its external opening, pierces superficial cervical fascia (and platysma), then investing cervical fascia, and travels under the sternocleidomastoid muscle, superficial to the sternohyoid and anterior belly of omohyoid. It ascends along the carotid sheath, and at the upper border of the thyroid cartilage it pierces the pretracheal fascia. Characteristically, it courses between the carotid bifurcation and over the hypoglossal nerve. After passing beneath the posterior belly of the digastric muscle and the stylohyoid, it hooks around both glossopharyngeal nerve and stylopharyngeus muscle. The fistula reaches the pharynx below the superior constrictor muscle. The course of a third cleft and pouch fistula is similar until it has pierced pretracheal fascia; then it passes over the hypoglossal nerve and behind the internal carotid, finally descending parallel to the superior laryngeal nerve, reaching the thyrohyoid membrane cranial to the nerve.

An ectopic cranial nerve identified during surgery in the posterior fossa for hemifacial spasm: a word of caution.

Variations of cranial nerve morphology may effect surgical technique and, if not appreciated, lead to complications and iatrogenic injury. The authors report an unusual course of the hypoglossal nerve within the posterior cranial fossa observed during microvascular decompression surgery for hemifacial spasm.

Unusual origin of the ansa cervicalis observed during carotid endarterectomy.

The surgical approach of the carotid artery for carotid endarterectomy demands knowledge of normal anatomy and anatomic variation. During carotid endarterectomy, a rare anatomic variant of the origin of the upper root of the ansa cervicalis was found. Contrary to commonly found anatomy, no upper root of the ansa cervicalis originating from the hypoglossal nerve was found. Instead, what seemed to be the ansa cervicalis originated from the vagus nerve and passed over the carotid bifurcation, branching to the infrahyoid muscles. Transection of this ansa cervicalis, for the purpose of good exposure, had no functional or cosmetic consequences.

Dual innervations of mylohyoid muscle: a case report.

Mylohyoid and anterior belly of the digastric muscles are supplied by a branch from the inferior alveolar nerve called the mylohyoid branch. Here we present an unusual finding in a 60-year-old male cadaver in which the mylohyoid muscle is supplied by a branch from hypoglossal nerve in addition to its usual nerve supply. Hypoglossal nerve after giving superior root of the ansa cervicalis and muscular branches to thyrohyoid and geniohyoid muscles gave another branch to supply the mylohyoid muscle. Any variation in the formation and/or branching pattern of ansa cervicalis or hypoglossal nerve can cause confusion and may complicate the procedures involving this nerve such as skull base surgery, neck dissection, and anterior cervical spinal approach. Developmentally mylohyoid muscle is from the mesoderm of the first arch, therefore, must be innervated by the mandibular nerve. Hence, we report this uncommon variation based on embryology and the clinical implications.

Communication between the vagus and hypoglossal nerves

Although the existence of the gross vagal-hypoglossal connection is known, no convincing role for the direct connection from the vagus to the hypoglossal nerve has been suggested. The purpose of this study was to investigate the anatomy of the vagal-hypoglossal connection. Forty human cadavers (22 males and 18 females), aged 25 to 75 years, were used. In 31 (75%) cadavers, there were two connections between the vagus and hypoglossal nerves, proximal to the inferior ganglion of the vagus and from the ganglion itself. In 8 (20%) cadavers there were only one connection joining the inferior ganglion of the vagus with the hypoglossal nerve. In 1 (2.5%) cadaver, the connection was by a thin intracranial vagal branch, proximal to its superior ganglion, joined the extracranial hypoglossal nerve. The communication was never from the vagus distal to the inferior ganglion. In 5 (12.5%) cadavers, the inferior ganglion of the vagus was bound to the trunk of the hypoglossal nerve and it was difficult to separate the nerve from the ganglion. Results suggest that the vagal-hypoglossal communication could be the afferent and efferent limbs for reflexes involving the tongue (AU)

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Monolateral hypoplasia of the motor vagal nuclei in a case of sudden infant death syndrome.

During the development of motor vagal nuclei (MVN), the neuroblasts of the myeloencephalic basal plate migrate in the dorsolateral direction to form the dorsal motor vagal nucleus (DMVN) and ventrolaterally to form the ventral motor vagal nucleus (VMVN). Those neuroblasts that remain close to the median sulcus will form the hypoglossal nucleus. In support of the congenital origin of the alteration of the MVN in sudden infant death syndrome (SIDS), we report the case of an 8-month-old female child who was found dead in her cot. The neuropathological assessment revealed that the medullary triangle of the 4th ventricle floor was asymmetric, owing to the presence of three prominences to the left side of the median sulcus. The medial prominence corresponded to the hypoglossal nucleus, which showed a marked increase in the number of large neurons; the intermediate prominence corresponded to the DMVN whose large neurons were reduced and were recognizable mainly at the level of the medial fringe; the lateral prominence corresponded to the solitary nucleus. The left solitary tract showed a reduction of the transverse diameter. Also, the left VMVN showed marked reduction in the number of neurons. Inflammatory and astrocytic reactions were absent. We suggest that in SIDS cases the hypocellularity of the MVN and the increased number of neurons of the hypoglossal nucleus are intimately related, indicating a congenital alteration due to incomplete migration of the vagal neuroblasts with abnormality of the autonomic cardio-respiratory control.

A case of the human sternocleidomastoid muscle additionally innervated by the hypoglossal nerve.

An anomalous nerve supply from the hypoglossal nerve (XII) to the sternocleidomastoid muscle (SM) was observed in the right neck of an 82-year-old Japanese female. This nerve branch arose from the hypoglossal nerve at the origin of the superior root of the ansa cervicalis. The nerve fiber analysis revealed that this branch consisted of fibers from the hypoglossal nerve, the first and the second cervical nerves and had the same component as the superior root of the ansa cervicalis. SM appeared quite normal and the most part was innervated by the accessory nerve and a branch from the cervical plexus. The anomalous branch from XII supplied the small deep area near the anterior margin of the middle of the sternomastoid portion of SM. It is reasonable to think that the small deep area of SM, which was innervated by the anomalous branch from XII, occurs as the result of fusion of the muscular component from infrahyoid muscles. If the muscular component does not fuse with SM, it is thought to appear as an aberrant muscle such as the superior sternoclavicular muscle (Hyrtl) which is also supplied from a branch of the superior root of the ansa cervicalis.

Anomaly of the hypoglossal nerve: embryologic, anatomic, and surgical considerations.

An anomaly of the hypoglossal nerve was discovered during a procedure to anastomose the 12th and 7th cranial nerves. This anomaly is described, and an embryologic mechanism is proposed to explain the occurrence of this particular anomaly. The surgical anatomy of the hypoglossal nerve is reviewed, and reasonable approaches to the surgical identification of the hypoglossal nerve are discussed.

About a very rare variation of the course and width of the vertebral arteries and the hypoglossal nerve.

Described are: 1. A very thin intracisternal part of the vertebral artery (0.9 mm). 2. A very rare course of the vertebral artery (dorsal to the hypoglossal nerve). 3. Rare anastomoses between the vertebral artery and the PICA. 4. A rare upwards coiling of the PICA and 5. The origin and prevertebral course of the vertebral arteries.