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Cranial Nerves Lesion and Blood Supply 29/04/2017 The Accessory Nerve XI It's a purely motor nerve and it has 2 motor roots: spinal and cranial roots, which they unite together in the posterior cranial fossa to exit from jugular foramen. The Cranial root : Originate from the lower part of the nucleus ambiguous in the medulla and its axons emerge between the olive and the inferior cerebellar peduncle. ! The nucleus ambiguous is seen at the level of the medulla, level of the olive, and gives also the motor roots for the glossopharyngeal VII and Vagus X nerves. The Spinal root : As the name indicates it originates from the spinal cord, specifically from the spinal nucleus in the anterior horn of the gray mater which is located in the upper 5 cervical segments, then the axons of the spinal nucleus enter through foramen magnum till they reach the posterior cranial fossa to unite with the cranial root. Then, the 2 roots unite and exist from the jugular foramen but after a short distance, the spinal root separates from the cranial root. The cranial root joins the Vagus nerve and is distributed in its pharyngeal and recurrent laryngeal branches to the muscles of the pharynx and the larynx. The spinal root descend downward to supply both sternoclediomastoid and trapezius muscle. 1 Cranial Nerves Lesion and Blood Supply 29/04/2017 2 Cranial Nerves Lesion and Blood Supply 29/04/2017 The Hypoglossal Nerve XII It's a purely motor nerve, supplies the intrinsic and the extrinsic muscles of the tongue except the palatoglussal muscle. The hypoglossal nucleus is seen the most medially to the midline at the level of the olive in the medulla then the axons of the nucleus emerge between the pyramids and the olive. ! The fibers of the hypoglossal nerve considered as General somatic efferent fibers (GSE) that innervate skeletal muscles of tongue except the palatoglussal muscle that is supplied by the pharyngeal plexus. 3 Cranial Nerves Lesion and Blood Supply 29/04/2017 The lesion of the Cranial Nerves Trigeminal nerve The Trigeminal nerve has both sensory and motor root. We test the motor function by asking the patient to clench his teeth, then the masseter and the temporalis muscles are felt harden as they contract; that is the normal state since these muscle are supplied by branches from the mandibular motor division of the trigeminal. We test the sensory function by using a pin over the areas that are supplied by the sensory divisions of the trigeminal nerve. Trigeminal Neurogelia It's a disease affecting the sensory part of trigeminal nerve characterized by a stapping pain which is felt over the skin areas that are innervated by the maxillary and the mandibular divisions of the V, rarely the pain is felt in the area supplied by the opthalmic. This pain occurs with no reason or suddenly by simple contraction of the masticatory muscles when chewing or shaving, treated by an anticonvulsant or antidepressants. It's a serious disease because the pain symptom last from second to several minutes, 3 minutes to be precise, and occurs for hundred of times during the day especially after touching specific areas in the face. 4 Cranial Nerves Lesion and Blood Supply 29/04/2017 The Facial Nerve We know that the facial nerve has motor, sensory and parasympathetic nuclei. The motor nucleus of the facial nerve give arise to the fibers that supply the muscles of the facial expressions, and the part of the motor nucleus - that supplies the muscles of the upper part of the face - receives corticonuclear fibers from both cerebral hemispheres, also the part of the motor nucleus - that supplies the muscles of the lower part of the face- receives only corticonuclear fibers from the opposite cerebral hemisphere. 1 2 1- In upper motor neuron injury ( injury to the corticonuclear fibers or the cerebral cortex ) : The lower part of the face is the only part that is affected on the opposite side to the injured area. Its sign is deviation of the 5 Cranial Nerves Lesion and Blood Supply 29/04/2017 angle of the mouth downwardly on the opposite side to the injured area, the muscles of the forehead are not affected and we will find normally working orbicularis oculi. ! Explanation The part of the motor nucleus that controls the muscles of the upper part of the face is not affected, because this part of the motor nucleus receives corticonuclear fibers from both hemispheres, so any injury to one bundle of the corticonuclear fibers won't affect this part, since it's also under the control of the other bundle from the other hemisphere, and as a result, it won't affect the upper part of the face, but the injury affects hugely the part of the motor nucleus that control the lower part of the face, since it receives the corticonuclear fibers only from the contralateral hemisphere ,that means, there is only one relay of the corticonuclear on this part of the motor nucleus contralaterally, hence affecting the lower part of the face markedly. 2- In lower motor neuron injury ( injury to the facial motor nucleus itself, its fibers or the facial nerve ): The upper and the lower parts of the face are affected on the same side to the injured area. The muscles of the face on the same side would be paralyzed and its signs: deviation is in lateral angle of the eye and the corner of the mouth at the same side to the injured area ,tears will flow over the lower eyelid, and saliva will dribble from the corner of the mouth leading to the a dry mouth. The patient will be unable to close the eye and will be unable to expose the teeth fully on the affected side.. To test the facial nerve, IThe patient is asked to show the teeth by separating the lips with the teeth clenched. Normally, equal areas of the upper and lower teeth are revealed on both sides. If a lesion of the facial nerve is present on one side, the mouth is distorted. A greater area of teeth is revealed on the side of the intact nerve, since the mouth is pulled up on that side. 6 Cranial Nerves Lesion and Blood Supply 29/04/2017 II- We ask the patient to close both eyes firmly, then we open the eyes gently raising the patient's upper lids, normally if there is no lesion, we feel some resistance the patient shows to open his eye . On the side of the lesion, the orbicularis oculi is paralyzed so that the eyelid on that side is easily raised. Bell Palsy Facial paralysis, usually temporally but in some cases it's permanent , it's a lower motor neuron lesion that result from compression on the facial nerve within the facial canal. It's classified as one category ; it is usually unilateral probably due to a viral infection or cold draft. It has the signs of lower motor neuron lesion. Facial Nerves and Related Cranial Nerves i. The facial nerve injury may affect the abducens since the axons of the facial nuclei wind around the abducens nucleus forming the facial colliculus on the posterior surface of the pons. Case I: A patient with a problem with some muscles of the eye, specifically the extraoclular muscles, and has Bell palsy. In this case: Bell palsy indicates that there is a lower motor neuron facial nerve injury, and the extraocular muscles problem that is due to the trochlear (supplying the superior oblique), abducens (supplying the lateral rectus) or occulomotor (supply all of the muscles of the eye except the superior oblique and the lateral rectus) , so if it's "some extraocular muscles" then the nerve affected is either the IV or VII but the one that is related to the facial nerve is the abducens at the level of the pons as mentioned earlier, so the level of injury would be at the level of pons. ii. Facial nerve injury may affect the vestibulocochlear nerve at the level of the junction between the pons and the medulla 7 Cranial Nerves Lesion and Blood Supply 29/04/2017 oblongata or when the cochlear and vesibular nerves enter internal acoustic meatus in accompany with the facial nerve. Case II: A pataint with Bell palsy and has deafness or vertigo. In this case: Since the patient has Bell palsy then he has a facial nerve injury. Deafness or vertigo is due to an injury to the cochlear or vestibular nerves respectively, that are located lateral to facial nerve at the lower border of the pons. Hence the lesion is at the level between the pons and the medulla oblongata or at the level of internal auditory meatus. iii. The facial nerve exists the internal auditory meatus and gives branches within the parotid gland, so any infection or cancer in the parotid gland would affect the facial nerve. The Vestibulocochlear Nerve It consists of the vestibular and cochlear nerves. The vestibular lesion cause vertigo, nystagmus and affects the balance state. The cochlear nerve lesion causes deafness and tinnitus. ! Nystagmus Rhythmic oscillation of the eyeball that is due to an injury in the vestibular nerve since the vestibular nuclei emit efferent fibers to the nuclei of the occulomotor, trochlear and abducens nerve – the 3 nerves control the extraocular muscles- through the medial longitudinal fasciculus. Glossopharyngeal Nerve Lesions of the glossopharyngeal nerve usually associated with Vagus nerve lesions and rarely we find it as isolated injuries. Since the sensory fibers of the glossopharyngeal nerve innervate the posterior one-third of the tongue so we test it's lesion via asking the patient to taste something on the posterior third of his tongue. 8 Cranial Nerves Lesion and Blood Supply 29/04/2017 The Vagus Nerve The Vagus nerve innervates the smooth muscles of many important organs, that some of them are not obvious, so we examine it by testing the function of the branches to the pharynx, soft palate, and larynx. We test the injury via: I. We ask the patient to say "ah" to observe the soft palate and the uvula. Normally the soft palate rise and uvula move backward in the midline normally, but if there a deviation in the uvula to any side so there is a lesion in the Vagus. II. The pharyngeal or gag reflex may be tested by touching the lateral wall of the pharynx with a spatula. This should immediately cause the patient to gag; that is, the pharyngeal muscles will contract. ! For the larynx, Hoarseness or absence of the voice may occur as a symptom of vagal nerve injury. !! All the muscles of the larynx are supplied by the recurrent laryngeal branch of the Vagus, except the cricothyroid muscle, which is supplied by the external laryngeal branch of the superior laryngeal branch of the Vagus. Accessory Nerve Since the spinal root of the accessory nerve descend downwardly to supply both trapezius and sternoclediomatiod, we examine the injury by asking the patient to rotate his head to one side against resistance, causing the sternocleidomastoid of the opposite side to come into action. Also we ask him to shrug his shoulders, causing the trapezius muscles to come into action. If there is a lesion in the XI, the shoulder will droop on that side due to the atrophy of the trapezius muscle, and will be weakness in turning the head to the opposite side due to atrophy in the sternocleidomastoid muscle. 9 Cranial Nerves Lesion and Blood Supply 29/04/2017 Hypoglossal Nerve The hypoglossal nerve supplies the intrinsic and extrinsic muscles of the tongue except the palatoglussal muscle. ! The greater part of the hypoglossal nucleus receives corticonuclear fibers from both cerebral hemispheres but the part of the nucleus that supplies the genioglossus receives corticonuclear fibers only from the opposite cerebral hemisphere. The lesion can be tested by asking the patient to put out his tongue forward and this occurs under the action of the genioglossus muscle. The lesion can be: 1- lower motor neuron lesion The tongue will be smaller on the side of the lesion, owing to muscle atrophy, and it will deviate toward the paralyzed side. 2- upper motor lesion ( Corticonuclear fibers lesion ) There will be no atrophy of the tongue, and on protrusion, the tongue will deviate to the side opposite the lesion. Blood Supply of the Spinal Cord Arteries of the Spinal Cord The spinal cord receives its arterial supply from 3 arteries that run longitudinally: 1- The 2 posterior spinal arteries: supply the posterior part of the spinal cord. 2- The anterior spinal artery: supplies the anterior part of the spinal cord. Other arteries originate as branches from outside the vertebral column are called the segmental arteries. As the name indicates they enter each segment of the spinal cord and divides into 10 Cranial Nerves Lesion and Blood Supply 29/04/2017 anterior and posterior radicular arteries, to supply the anterior and posterior parts of the spinal cord respectively - especially the white and the gray mater - that accompany the anterior and posterior spinal arteries. The posterior spinal arteries branch directly from the main trunk of the vertebral arteries or indirectly from the posterior inferior cerebellar arteries (the largest branch of the vertebral artery). The anterior spinal artery is formed by the union of two arteries, each of which arises from the vertebral artery. Veins of the Spinal Cord The drainage is mainly through the internal vertebral venous plexus or epidural venous plexus. Blood Supply of the Brain 11 Cranial Nerves Lesion and Blood Supply 29/04/2017 Arteries of the Brain The brain is supplied by the 2 internal carotid and the 2 vertebral arteries. The four arteries lie within the subarachnoid space, and their branches anastomose on the inferior surface of the brain to form the circle of Willis. The internal carotid artery The common carotid artery bifurcate giving arise to the internal carotid artery where it usually has a localized dilatation, called the carotid sinus. It ascends the neck passing through the carotid canal. The artery then runs horizontally forward through the cavernous sinus and emerges on the medial side of the anterior clinoid process. It now enters the subarachnoid space. Finally, it terminates into the small anterior and large middle cerebral arteries. 12 Cranial Nerves Lesion and Blood Supply 29/04/2017 Branches of the Cerebral Portion I. II. III. IV. V. The ophthalmic artery arises as the internal carotid artery emerges from the cavernous sinus. It enters the orbit through the optic canal to supply the eye and other orbital structures. The posterior communicating artery, originates from the internal carotid artery and runs posteriorly to join the posterior cerebral artery, thus forming part of the circle of Willis. The choroidal artery. The anterior cerebral artery is the smaller terminal branch of the internal carotid artery and it supplies all the medial surface of the cerebral cortex The middle cerebral artery, the largest branch of the internal carotid and it supplies the entire lateral surface of the hemisphere. 13 Cranial Nerves Lesion and Blood Supply 29/04/2017 ! The 2 anterior cerebral arteries are joined by the anterior communicating artery, which is so important because it form part of the circle of Willis. 14 Cranial Nerves Lesion and Blood Supply 29/04/2017 Vertebral Artery The vertebral artery, a branch of the first part of the subclavian artery, ascends the neck by passing through the foramina in the transverse processes. It enters the skull through the foramen magnum and pierces the dura mater and arachnoid to enter the subarachnoid space. Branches of the Cranial Portion I. The meningeal branches ,supplies the dura in the posterior cranial fossa. II. The posterior spinal artery may arise directly from the vertebral artery or indirectly from the posterior inferior cerebellar artery. It descends on the posterior surface of the spinal cord. III. The anterior spinal artery is formed from a contributory branch from each vertebral artery near its termination. The single artery descends on the anterior surface of the spinal cord. ! Both anterior and posterior spinal artery are reinforced by radicular arteries anteriorly and posteriorly respectively IV. The posterior inferior cerebellar artery, the largest branch of the vertebral artery, passes between the medulla and the cerebellum.. It supplies the medulla, both posterior and the inferior surfaces of the cerebellum beside the nuclei in the cerebellum. V. The medullary arteries are very small branches that are distributed to the medulla oblongata. 15 Cranial Nerves Lesion and Blood Supply 29/04/2017 Basilar Artery Formed by the union of the two vertebral arteries, ascends in a groove on the anterior surface of the pons (= basilar groove ). At the upper border of the pons, it divides into the 2 posterior cerebral arteries. Branches I. II. III. IV. V. The pontine arteries , supplies the pons. The labyrinthine artery, supplies the internal ear. It often arises as a branch of the anterior inferior cerebellar artery. The anterior inferior cerebellar artery, supplies the anterior and inferior parts of the cerebellum. The superior cerebellar artery , supplies the superior surface of the cerebellum. The posterior cerebral artery Circle of Willis It is formed by the anastomosis between the 2 internal carotid arteries and the 2 vertebral arteries. The anterior communicating, 16 Cranial Nerves Lesion and Blood Supply 29/04/2017 proximal pars of the anterior cerebral, internal carotid, posterior communicating, proximal parts of the posterior cerebral, and basilar arteries, that all contribute to the circle. Arteries to Specific Brain Areas The corpus striatum and the internal capsule are supplied mainly by the medial and lateral striate central branches of the middle cerebral artery; the central branches of the anterior cerebral artery supply the remainder of these structures. The thalamus is supplied mainly by branches of the posterior communicating, basilar, and posterior cerebral arteries. 17 Cranial Nerves Lesion and Blood Supply 29/04/2017 The midbrain is supplied by the posterior cerebral, superior cerebellar, and basilar arteries. The pons is supplied by the basilar and the anterior, inferior, and superior cerebellar arteries. The medulla oblongata is supplied by the vertebral, anterior and posterior spinal, posterior inferior cerebellar, and basilar arteries. The cerebellum is supplied by the superior cerebellar, anterior inferior cerebellar, and posterior inferior cerebellar arteries. Done By : Rawan Hamdan 18