Distribution of the internal branch of the human accessory nerve

A detailed review of the spinal accessory nerve and its anatomical variations with cadaveric illustration

The spinal accessory nerve, considered part of the eleventh cranial nerve, provides motor innervation to sternocleidomastoid and trapezius. A comprehensive literature review and two cadaveric dissections were undertaken. The spinal accessory nerve originates from the spinal accessory nucleus. Its rootlets unite and ascend between the denticulate ligament and dorsal spinal rootlets. Thereafter, it can anastomose with spinal roots, such as the McKenzie branch, and/or cranial roots. The spinal accessory nerve courses intracranially via foramen magnum and exits via jugular foramen, within which it usually lies anteriorly. Extracranially, it usually crosses anterior to the internal jugular vein and lies lateral to internal jugular vein deep to posterior belly of digastric. The spinal accessory nerve innervates sternocleidomastoid, receives numerous contributions in the posterior triangle and terminates within trapezius. Its posterior triangle course approximates a perpendicular bisection of the mastoid-mandibular angle line. The spinal accessory nerve contains sensory nociceptive fibres. Its cranial nerve classification is debated due to occasional non-fusion with the cranial root. Surgeons should familiarize themselves with the variable course of the spinal accessory nerve to minimize risk of injury. Patients with spinal accessory nerve injuries might require specialist pain management.

Is Immobile vocal fold Related to the Spinal Accessory Nerve Agenesis?: A Case Report

The spinal accessory nerve innervates the sternocleidomastoid and trapezius muscles, but the internal branch from the spinal accessory nerve is also contributing to the motor innervation of the larynx. For the first time, we report a case of an impairment of sternocleidomastoid, trapezius, and thyroarytenoid muscles from the same side. In our case, the anatomical variant that can explain this situation implies the cranial roots and some fibers from the spinal roots of the spinal accessory nerve to form the internal branch. In the case of agenesis of these spinal roots, the muscles reliant on it would be missing. For this reason, it is advisable to rule out laryngeal problems in patients with sternocleidomastoid and/or trapezius muscles impairment.

Palpation of the Respiratory System in Osteopathic Manual Medicine: From the Trachea to the Lungs

There is a lack of published literature in osteopathic manual medicine on how to perform palpation of the lower respiratory tree such as the trachea, main bronchi, and lungs. Several authors have studied the osteopathic effect and respiratory response of palpation but have failed to demonstrate how to perform palpation of the visceral areas involved in breathing, either in the context of a clinical trial or as a case report. This paper reviews the innervation of these anatomical areas, the mechano-metabolic weight of the passage of fluids and air in the respiratory tract, the anatomical topography, and the movements involved in respiration. Drawing from current knowledge, this article illustrates, for the first time, how to place the hands for an effective osteopathic assessment of the tracheal, bronchial, and pulmonary structures. Understanding how to perform palpation of the lower areas is a fundamental tool in the clinic and potential therapy in osteopathic manual medicine.

The metabolic role of vagal afferent innervation

The regulation of energy and glucose balance contributes to whole-body metabolic homeostasis, and such metabolic regulation is disrupted in obesity and diabetes. Metabolic homeostasis is orchestrated partly in response to nutrient and vagal-dependent gut-initiated functions. Specifically, the sensory and motor fibres of the vagus nerve transmit intestinal signals to the central nervous system and exert biological and physiological responses. In the past decade, the understanding of the regulation of vagal afferent signals and of the associated metabolic effect on whole-body energy and glucose balance has progressed. This Review highlights the contributions made to the understanding of the vagal afferent system and examines the integrative role of the vagal afferent in gastrointestinal regulation of appetite and glucose homeostasis. Investigating the integrative and metabolic role of vagal afferent signalling represents a potential strategy to discover novel therapeutic targets to restore energy and glucose balance in diabetes and obesity.