Nerve Lesions 10Th Cranial
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TENTH CRANIAL NERVE LESIONS “The Nubian Giraffe”, oil on canvas, Jacques Laurent Agasse 1827 “The animal that the Pasha of Egypt is sending to the King is one of the happiest acquisitions that we have been able to make - never has a living giraffe arrived in France, and for eighteen centuries civilized Europe has not seen one, (…in fact the authors of this letter, unlike their colleague, the great Saint-Hilaire, were unaware of the giraffe that had been sent to Florence in the Fifteenth century)…we have no information at all on the state of this precious animal; we do not know if it is young or adult, large or small, feeble or in good health, wild or tame etc, etc. We beg you to have word written to us on these various points, and on the event that the giraffe should threaten to perish, have a drawing in colour made of it that will tell us exactly its proportions and the forms of its head viewed from the front and in profile. This will be with the skeleton and hide, a slight compensation for us if we have the misfortune to lose the giraffe before its arrival here” Professors & Administrators of the National Museum of Natural History, Paris, November 28, 1826. “She loves very much to leave her stable, and when she is walked in the garden of the prefecture on days of good weather, it often happens that she bounds like a young horse…sometimes she wants to launch herself into a gallop, dragging along with her the four Arabs who restrain her, and we have seen her in a moment of gaiety drag five strong men… …this animal has a very gentle disposition and has never been seen to manifest the slightest anger or malice. She distinguishes the Arab who usually feeds her, but she does not have an unusual affection for him. She allows herself to be approached by all who come to see her, she does not like to be touched, and it is only when she fears something or is bothered too much that she defends herself by kicking forward, whether with front or hind legs. She never tries to deal a blow with her head or her horns, on the contrary one sees her hold her head very high when one disturbs her or when she is afraid. She often licks the face the hands and the clothes of the Arab who cares for her. She appears fearful, heedful of noise; however she is not at all frightened by the presence of a great number of people who approach very close to her. She was shy though about drinking her milk in front of strangers.” Observations on the Giraffe, Monsieur Salze, Academy of Marseilles, 1826 On Tuesday, 31st of October 1826, the bustling port of Marseilles was presented with an astounding sight; a young Nubian Giraffe was coaxed off one of the docked ships having travelled from darkest Africa on the highland plains of Ethiopia on its long precarious 3,500 mile journey to its intended final destination at the Jardin des Plantes in Paris. Once in Paris the playful animal created an instant sensation, and became the envy of the rest of Europe, a stunning addition to the King‟s gardens. This was the first giraffe ever seen in France and the first to be seen in Europe in almost 350 years. So anxious were the king‟s naturalists over the well being of the legendary animal they had sent specific instructions to Marseilles when it arrived there to have a scientific portrait made of the animal in the event that it did not survive the trip to Paris, a trip which the animal would have to make by walking the entire distance. The giraffe, affectionately known to its handlers as Zarafa, was a politically motivated gift to Charles X from Muhammad Ali, the Ottoman viceroy of Egypt. The viceroy was at war with the Greeks, fiercely fighting at the time for their liberation from four centuries of Ottoman occupation and oppression. The western European powers felt a great shared cultural heritage with the Greeks and there was much sympathy for their struggle. By his spectacular gift the viceroy was hoping to win over some French sympathy to the Ottoman cause. It was a stunning success as a public relations exercise. The viceroy had correctly judged the new scientific enthusiasm of the post-Napoleonic French public. A generation previously the French under Napoleon Bonaparte had invaded and occupied Ottoman Egypt. The Ottomans had been powerless to resist Napoleon, and were only saved from complete subjugation when he was forced to return to France after Nelson‟s stunning defeat of the French fleet at the battle of the Nile in 1798. The returning soldiers brought back fabulous stories of archaeological ruins, of pyramids and sphinxes and temples of unimaginable age and exotic African animals which were only legends in the minds of most Europeans. Exotic animals such as giraffes had been relatively familiar in the ancient European world, however this was only in a most brutal and primitive context. Thousands of animals were captured in Africa, then transported to Rome to be slaughtered by gladiators in the Coliseum. Some were even slaughtered by the Emperor Commodus himself. The image of such a magnificent and gentle animal as the giraffe being terrorized by an immense crowd, and tortured by having its limbs hacked off then killed for the “entertainment” of the Roman masses simply leaves a sickening pit in the stomach of modern day sensibilities. Fortunately for these gentle creatures, they were left alone for over one and half millennia following the fall of Rome, until being “rediscovered” again in the late Eighteenth century. Fortunately again for these creatures this age was a far more enlightened one than the time of Commodus and they were greeted with affectionate curiosity by the general public and intense curiosity by the learned scientific community. Throughout the Nineteenth century our understanding of the natural world increased exponentially culminating in what the magisterial Richard Dawkins has proposed as possibly the “single most brilliant insight” in human history to date, the theory of evolution by natural selection. Before Darwin a powerful argument of the existence of God was the argument “by design” which said that the only possible explanation for such a complex creation as a living animal was the purposeful will of a divine creator. Darwin proposed that all living things were not individually designed by a creator but are descended, albeit in a modified form from a single distant and far simpler common ancestor. Intuitively it is difficult to see how a human and a giraffe could possibly have a common ancestor, yet that is precisely what Darwin proposed. As different as animals (including humans) look on the outside, when one dissects out the internal anatomy stunning similarities are seen. Some anatomical arrangements seem like very poor “design” indeed - an argument against a “intelligent” designer. Dawkins in his book, “The Greatest Show on Earth” gives numerous examples of poor design in animals, none more stunning than the pathway of the recurrent laryngeal branch of the vagus nerve. Not only do giraffes have one of these, just as do humans, but it also follows exactly the same completely non-sensiscal pathway it does in humans, but to an extreme degree in the case of a giraffe. This nerve takes a detour of many meters before its reaches its destination. The innervation of a giraffe‟s larynx comes from a cranial nerve via a pathway that travels from its brain to its chest back up to its larynx via the longest neck in the animal kingdom! Not a very „intelligent” design at all! Sharks are very primitive creatures, they also have a vagus nerve, but it supplies its posterior gills in a very logical and direct manner any intelligent designer would be proud of. Yet over the eons of time the changes that evolution has wrought has meant that the vagus nerve now supplies structures that in the distant geological past were gills, but are now larynxes! Humans and giraffes have exactly the same arrangement of their recurrent laryngeal nerves, a stunning evolutionary legacy of a far distant common ancestor that swam in Devonian oceans! Every living creature on the earth is our cousin in life - not to be senselessly slaughtered for “entertainment” - but for which we should feel the deepest shared kindred and respect for. TENTH CRANIAL NERVE LESIONS Introduction Cranial nerve X is also known as the Vagus nerve The vagus nerve caries motor, sensory and autonomic fibers, (a major part of the parasympathetic nervous supply of the body). Isolated lesions of the vagus nerve are rare. Lesions are usually seen in combination with other cranial nerves of the caudal brainstem. Anatomy Course of the Vagus nerve: The vagus nerve has a more extensive course and distribution than any of the other cranial nerves, coursing through the neck, and the thorax and on into the abdomen. The nuclei of the vagus nerves within the brainstem lie within the medulla oblongata, and include: Lateral medulla: ● Nucleus ambiguus: ♥ Somatic efferents for CN 9, 10, 11 ● Nucleus solitarius: ♥ Sensory relay nucleus for CN 7, 9, 10 Medial medulla: ● Dorsal vagal nucleus: ♥ Parasympathetic nucleus for CN 10 The vagus nerves emerge from the brainstem at the lateral aspect of the medulla oblongata within the posterior olivary suclus just caudal to the glossopharyngeal nerve and just rostral to the accessory nerve. The nerve then leaves the posterior fossa of the base of the skull through the jugular foramen together with CN 9 and 11 as well as the internal jugular vein and the inferior petrosal sinus), to enter the neck.