Brainstem and Cranial Nerve

臺北榮總神經內科李宜中

神經系統的作用

• 1. 接受訊息 (Afferent): 外在訊息,內在訊息 • 2. 處理訊息 (Processing): 有或無意識下 • 3. 回應訊息 (Efferent)

腦幹的功能

• 1. Conduit function: long tracts

• 2. Cranial nerve functions: afferent and efferent

• 3. Integrative functions: reticular formation 腦幹的外部構造腦幹的大略構造

basis basis tegmentumtegmentum tectumtectum midbrainmidbrain

ponspons

medullamedulla oblongataoblongata cerebellum pyramidpyramid cerebellum Figure 11-4 Medial surface of the right half of a hemisected brain, showing major features of the brainstem and cerebellum. (Courtesy Grant Dahmer, University of Arizona College of Medicine. Modified from Nolte J, Angevine JB Jr: The human brain in photographs and diagrams, ed 3, St. Louis, 2007, Mosby.)

Figure 11-3 Posterior (A), anterior (B), and lateral (C) aspects of the brainstem, shown at about 1.3 times actual size, after the cerebellum and cerebrum were removed. Cranial nerves are indicated by roman numerals. BP, basal pons; CP, cerebral peduncle; IB, brachium of the inferior colliculus; IC, inferior colliculus; ICP, inferior cerebellar peduncle; MCP, middle cerebellar peduncle; MG, medial geniculate nucleus; Pi, pineal gland; Pul, pulvinar; Pyr, pyramid; SC, superior colliculus; SCP, superior cerebellar peduncle. (Courtesy Grant Dahmer, University of Arizona College of Medicine. Modified from Nolte J, Angevine JB Jr: The human brain in photographs and diagrams, ed 3, St Louis, 2007, Mosby.)

• 1. Motor pathways: Corticospinal tract, coticonuclear tract • 2. Sensory pathways: medial lemniscus, spinothalamic tract (spinal lemniscus) • 3. Cerebellar pathway

Figure 12-18 Ascending trigeminal pathways from the spinal nucleus. The inset near the caudal medulla section indicates the arrangement within the spinal trigeminal tract of fibers from the three subdivisions of the trigeminal nerve, as well as those from cranial nerves VII, IX, and X that innervate the outer ear and some mucous membranes of the head and neck. (Trigeminal pain information, like pain information from the body, also projects to other parts of the thalamus and cortex not indicated in this figure.) VPL, ventral posterolateral nucleus; VPM, ventral posteromedial nucleus. Downloaded from: StudentConsult (on 2 August 2009 10:27 AM) © 2005 Elsevier Figure 12-16 Ascending trigeminal pathways from the main sensory nucleus. VPL, ventral posterolateral nucleus; VPM, ventral posteromedial nucleus. Downloaded from: StudentConsult (on 2 August 2009 10:27 AM) © 2005 Elsevier

CranialCranial NervesNerves Summary of Function of Cranial Nerves

Figure 13.5b

Cranial Nerve I: Olfactory

Figure I from Table 13.2 Cranial Nerve I: Olfactory Cranial Nerve II: Optic

Figure II Table 13.2

Visual field defect Cranial Nerve III: Oculomotor

Cranial Nerve IV: Trochlear Cranial Nerve VI: Abducens CN5 – Trigeminal nerve

• Sensation of face (不包括耳下，耳後) • Motor: • Masseter muscle • Pterygoid muscle • Temporalis muscle • Onion face • Corneal reflex: 5進7出 • Jaw jerk: 5進5出 Cranial Nerve V: Trigeminal

Onion face Cranial Nerve VII: Facial

• Fibers leave the pons, travel through the internal acoustic meatus, and emerge through the stylomastoid foramen to the lateral aspect of the face • Motor functions include; – Facial expression – Transmittal of parasympathetic impulses to lacrimal and salivary glands (submandibular and sublingual glands) • Sensory function is taste from taste buds of anterior two-thirds of the tongue Cranial Nerve VII: Facial

Figure VII from Table 13.2

Cranial Nerve VIII: Vestibulocochlear • Fibers arise from the hearing and equilibrium apparatus of the inner ear, pass through the internal acoustic meatus, and enter the brainstem at the pons-medulla border • Two divisions – cochlear (hearing) and vestibular (balance) • Functions are solely sensory – equilibrium and hearing Cranial Nerve VIII: Vestibulocochlear

Figure VIII from Table 13.2

Cranial Nerve IX: Glossopharyngeal • Fibers emerge from the medulla, leave the skull via the jugular foramen, and run to the throat • Nerve IX is a mixed nerve with motor and sensory functions • Motor – innervates part of the tongue and pharynx, and provides motor fibers to the parotid salivary gland • Sensory – fibers conduct taste and general sensory impulses from the tongue and pharynx

Cranial Nerve X: Vagus

• The only cranial nerve that extends beyond the head and neck • Fibers emerge from the medulla via the jugular foramen • The vagus is a mixed nerve • Most motor fibers are parasympathetic fibers to the heart, lungs, and visceral organs • Its sensory function is in taste • Paralysis leads to hoarseness • Total destruction incompatible with life Cranial Nerve X: Vagus

Cranial Nerve XI: Accessory

Figure XI from Table 13.2

Cranial Nerve XII: Hypoglossal

• Fibers arise from the medulla and exit the skull via the hypoglossal canal • Innervates both extrinsic and intrinsic muscles of the tongue, which contribute to swallowing and speech • If damaged, difficulties in speech and swallowing; inability to protrude tongue Cranial Nerve XII: Hypoglossal

Figure XII from Table 13.2

Reticular Formation

• The cell groups and fibers of the netlike reticular formation throughout the entire brainstem, where they fill up the interstices between the cranial nerve nuclei, olives, and ascending and descending pathways. Functions of Reticular Formation

• 1. Consiciousness: ascending reticular activating system. • 2. Maintenance of muscle tone and balance: descending reticular pathway (reticulospinal and vestibulospinal tract) • 3. Other autonomic functions: blood pressure, cardiac function, breathing, chewing, licking, sucking Figure 11-7 Locations of the corticospinal tract, medial lemniscus, spinothalamic tract, and reticular formation in the caudal and rostral medulla (A, B), caudal pons and midpons (C, D) and caudal and rostral midbrain (E, F). (Modified from Nolte J, Angevine JB Jr: The human brain in photographs and diagrams, ed 3, St. Louis, 2007, Mosby.)

Downloaded from: StudentConsult (on 2 August 2009 10:23 AM) © 2005 Elsevier Brainstem RAS (mid-pons rostrally) and its projections to the hemispheres Anatomic basis of coma (results from lesions that affect either the RAS or both hemispheres)

Abnormal respiratory patterns associated with pathologic lesions at various levels of the brain 腦幹的內部構造 Figure 11-6 Transverse planes defining the subdivisions of the brainstem and the planes of sections shown elsewhere in this chapter. In brief: (1) the medulla contains the pyramids, together with part of the central canal, in its caudal half and part of the fourth ventricle in its rostral half; (2) the pons contains the basal pons and part of the fourth ventricle, but only the caudal pons is physically attached to the cerebellum; (3) the midbrain contains cerebral peduncles and the aqueduct, together with the inferior colliculi in the caudal midbrain and the superior colliculi in the rostral midbrain.

Downloaded from: StudentConsult (on 2 August 2009 10:23 AM) © 2005 Elsevier Figure 11-17 Rostral midbrain, at the level of the superior colliculus. A, cerebral aqueduct; CP, cerebral peduncle; CTT, central tegmental tract; IB, brachium of the inferior colliculus; ML, medial lemniscus; PAG, periaqueductal gray; SC, superior colliculus; SCP, superior cerebellar peduncle (at this level, crossed and entering the red nucleus); SN, substantia nigra. Figure 11-14 Rostral pons, near the pons-midbrain junction. CST, corticospinal tract; CTT, central tegmental tract; 4V, fourth ventricle; M, medial longitudinal fasciculus; ML, medial lemniscus; SCP, superior cerebellar peduncle. Figure 11-13 Midpons, at the level of entry of the trigeminal nerve. CST, corticospinal tract; CTT, central tegmental tract; 4V, fourth ventricle; M, medial longitudinal fasciculus; MCP, middle cerebellar peduncle; ML, medial lemniscus; SCP, superior cerebellar peduncle; V, trigeminal nerve fibers. Figure 11-10 Rostral medulla, just rostral to the obex. 4V, fourth ventricle; ICP, inferior cerebellar peduncle; IO, inferior olivary nucleus; LCN, lateral cuneate nucleus; M, medial longitudinal fasciculus; ML, medial lemniscus; Py, pyramid; SpVn, spinal trigeminal nucleus; SpVtr, spinal trigeminal tract; STT, spinothalamic tract. Figure 11-9 Caudal medulla, just caudal to the obex. FC, fasciculus cuneatus; IO, inferior olivary nucleus (a small portion of the inferior olivary nucleus, a landmark of the rostral medulla, extends into the caudal medulla); M, medial longitudinal fasciculus; ML, medial lemniscus; NC, nucleus cuneatus; NG, nucleus gracilis; Py, pyramid; SpVn, spinal trigeminal nucleus; SpVtr, spinal trigeminal tract; STT, spinothalamic tract. Figure 11-8 Caudal medulla near the spinomedullary junction, at the level of the pyramidal decussation. AH, anterior horn (contains the accessory nucleus at this level); FC, fasciculus cuneatus; FG, fasciculus gracilis; NC, nucleus cuneatus; NG, nucleus gracilis; Py, pyramid; PyD, pyramidal decussation; SpVn, spinal trigeminal nucleus; SpVtr, spinal trigeminal tract; STT, spinothalamic tract. Localization Examples

Figure 12-29 Medial medullary syndrome. In this case, "a 60 year old man … sought neurological consultation for sudden onset of numbness over the left side of the body." Examination revealed deficits in tactile sensation on the left side of his body and weakness of the right side of his tongue (A). There was slight weakness of his left arm and leg; when he held both arms outstretched, the left arm drifted downward and rotated inward (pronator drift; inset, A). T2-weighted magnetic resonance imaging scans in coronal (B) and axial (C) planes revealed a small infarct in the medial part of the right rostral medulla. D, Vascular territory involved in the medial medullary syndrome (right side of the figure), and the structures whose damage would account for the resulting symptoms and signs (left side of the figure). CST, corticospinal tract; ML, medial lemniscus; XII, hypoglossal nerve; XIIn, hypoglossal nucleus. (A to C, from Nandhagopal R, Krishnamoorthy SG, Srinivas D: J Neurol Neurosurg Psychiatry 77:215, 2006.)

Looking to left

Looking to right

Convergence Internuclear Ophthalmoplegia (left MLF lesion)