Cranial Nerves 11 & 12 PDF

Cranial Nerves- Accessory XI and Hypoglossal XII Dr. Moira Jenkins Spinal Accessory Nerve • Two components – Cranial root • Cell bodies are in the nucleus ambiguus; axons leave and travel with motor neurons of CN X to skeletal muscles of pharynx and larynx – Spinal root • Cell bodies are in the...

Cranial Nerves- Accessory XI and Hypoglossal XII Dr. Moira Jenkins Spinal Accessory Nerve • Two components – Cranial root • Cell bodies are in the nucleus ambiguus; axons leave and travel with motor neurons of CN X to skeletal muscles of pharynx and larynx – Spinal root • Cell bodies are in the ventral horn of the upper C1-5 segments; axons ascend to join cranial root fibers but branch off to ultimately innervate the trapezius and SCM muscles, GSE • Spinal root – Accessory nucleus (ventral horn of C1-5) • Cranial root – Nucleus ambiguus Spinal accessory nerve (CNXI) • general somatic efferent (GSE) – trapezius and sternocleidomastoid – Bilateral innervation from corticospinal tract to – Accessory nucleus is motor neurons in ventral horn of C1-C5 spinal cord Hypoglossal Nerve • The cell bodies of this nerve are located in the hypoglossal nucleus which is found in the tegmentum of the medulla. • Axons emerge from the medulla ventral to the olive as rootlets (preolivary sulcus) • Leave the skull through the hypoglossal canal and travel to the intrinsic and 3 extrinsic tongue muscles (all the muscles of the tongue except palatoglossus M.) Hypoglossal nucleus Hypoglossal nerve (CNXII) • general somatic efferent (GSE) – Muscles of the tongue – hypoglossal nucleus in 4th ventricular floor – Hypoglossal trigone Hypoglossal nerve (CNXII) – Genioglossus M. – Pusher – Contraction of genioglossus causes protrusion of the tongue towards the contralateral side – Typically, both genioglossus m. contract and tongue sticks out midline Hypoglossal nucleus Hypoglossal trigone- caudal medial floor of the 4th ventricle trigone Corticobulbar Fibers/Tract • Descending fibers from the motor cortex which influence cranial nerve motor nuclei directly or via reticular formation. • Fibers are others are bilateral providing dual innervation to muscles of the head and neck supplied by cranial nerves • EXCEPT lower part of the facial motor nucleus; and only slight in Hypoglossal, Vagus • There are no direct cortical fibers to motor nuclei of III, IV, or VI- medial longitudinal fasciculus or paramedian pontine formation weak • Central facial palsy (ex: stroke) • Muscles in upper half receive bilateral fibers • Muscles in lower half receive contralateral fibers • Lesions in the corticobulbar tract will cause paralysis in the contralateral lower quadrant muscles of facial expression Versus • Peripheral facial palsy • Entire facial nerve/face ipsilateral Genioglossus M. is a “pusher”, normal healthy →pushes to the opposite side Weakness/ lesion of nucleus or nerve - tongue deviates to side of lesion since it is unopposed from strong side Muscles of the soft palate are ‘pullers’ Innervated by Vagus N. Lesion in nucleus or nerve Deviate AWAY from side of lesion UvulA- Away lesion Tongue- Towards lesion