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Organization of Brainstem (I) Fu Jen Catholic University Department of Medicine

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Organization of Brainstem (I) Fu Jen Catholic University Department of Medicine 1 Organization of brainstem (I) Fu Jen catholic university Department of medicine 2 Basic directional terms 3 Development of brainstem 4 Location of brainstem (brain stem) Connect diecephalon rostrally, and cervical portion of spinal cord caudally Anterior (ventral) to the cerebrum and cerebellum Locate in posterior cranial fossa beyond the foramen magnum 5 Divisions of brainstem Include medulla oblongata (medulla), pons and midbrain Three continuous longitudinal laminae extend through the brainstem – tectum – tegmentum – basilar area Contains three types of structures: – nuclear groups – long fiber tracts (both motor and sensory) – reticular formation (RF) concerned with modulating awareness and behavior performance 6 External morphology of brainstem ventral view 7 External morphology of brainstem ventral view 8 External morphology of brainstem dorsal view 9 Dorsal view of brainstem Pons Median sulcus Sulcus limitans Medial eminence Vestibular area Striae medullares Facial colliculus: (genu of CN VII & abducens nucleus) Locus coeruleus (LC): noradrenaline containing neurons Cerebellar peduncles: superior (brachium conjunctivum), middle & inferior (restiform body) Midbrain Corpora quadrigemina: – superior & inferior colliculi (SC & IC) – superior & Inferior brachia Tectum Pretectum (pupillary light reflex) Trochlear nerve (CN IV) Superior medullary velum 10 Dorsal view of brainstem Medulla Fasciculus gracilis Fasciculus cuneatus Cuneate & gracile tubercles Tuberculum cinereum (spinal trigeminal tract & nucleus) Obex (calamus scriptorius) 1 Closed & open parts of medulla Rhomboid fossa (floor of 4th Ventricle) Lateral recess Lateral aperture (Foramina of Luschka) Median aperture (Foramen of Magendie) Vagal & hypoglossal trigones Area postrema – without BBB, site of vomiting (emetics) Inferior medullary velum (tela choroidea of the 4th ventricle) 11 Lateral view of brainstem 12 Lateral view of brainstem Medulla – Restiform body – Postolivary sulcus: CN IX, X, XII – Olive (inferior olivary nucleus) – Cerebellopontine angle: CN VII, VIIi, VIII – Posterior (dorsal) column: gracile and cuneate fasciculi, tubercles (nuclei) – Trigeminal tubercle (tuberculum cinereum): spinal trigeminal nucleus and tract Pons – Trigeminal nerve (motor and sensory root) – Sup. Mid. Inf. Cerebellar peduncles Midbrain – Brachium of sup. & inf. colliculi – Trochlear nerve – Cerebral peduncle = tegmentum + basis pedunculi (substantial nigra + crus cerebri) 13 Derivatives of alar and basal plates 14 Serial sections from Caudal to rostral subdivisions of brainstem 15 Internal structure of caudal medulla: Pyramidal (motor) decussation 16 Central canal Somatosensory system – Dorsal column: gracile & cuneate fasciculi – Dorsal column nuclei: gracile & cuneate nuclei (touch & proprioception of limb) – Spinal trigeminal tract & nucleus (pain & temperature from head) – Dorsal (uncrossed) & ventral (crossed) spinocerebellar tracts – for adjusting movements – Spinothalamic tract (pain & temperature from body) Motor system – Pyramids – Pyramidal decussation (corticospinal tract – for initiation of voluntary movement) Anterior horn – Accessory nucleus 17 Internal structure of mid-medulla: Sensory decussation 18 Central canal Hypoglossal nucleus Dorsal motor nucleus of vagus Tractus solitarius Nucleus of tractus solitarius (NTS) Fasciculus gracilis Fasciculus cuneatus Cuneate & gracile nuclei – internal arcuate fibers – medial lemniscus (ML) Dorsal column – medial lemniscus system External (lateral, accessory) cuneate nucleus Spinal trigeminal tract & nuclsus Dorsal & ventral spinocerebellar tract (DSC & VSC) Anterolateral system = Spinothalamic tract (spinal lemniscus) Inferior olivary nucleus Nucleus ambiguus Medial longitudinal fasciculus 2 (MLF) Pyramids (corticospinal fibers) Arcuate nucleus 19 Internal structure of rostral medulla: Inferior olivary nucleus 20 Fourth ventricle Hypoglossal nucleus Dorsal motor nucleus of vagus NTS & solitary tract Medial & inferior vestibular nuclei MLF & medial lemniscus Pyramid Cuneate nucleus External cuneate nucleus Inferior cerebellar prduncle Spinal trigeminal tract & nucleus Spinal lemniscus (SL): spinothalamic tract + spinotectal tract DSCT & VSCT Nucleus ambiguus Inferior olivary nucleus Central tegmental tract (CTT) 21 Internal structure of rostral medulla: lateral recess 22 Fourth ventricle Hypoglossal nucleus Dorsal motor nucleus of vagus NTS & solitary tract Lateral, medial & inferior vestibular nuclei MLF & medial lemniscus Dorsal & ventral cochlear nucleus (DC, VC) Glossopharyngeal nerve Nucleus ambiguus (NA) Inferior cerebellar prduncle (ICP) Spinal trigeminal tract & nucleus Spinal lemniscus (SL): spinothalamic tract + spinotectal tract DSCT & VSCT Ventral spinocerebellar tract (VSC) Inferior olivary nucleus Central tegmental tract (CTT) Pyramids 23 Internal structure of caudal pons: facial colliculus 24 Fourth ventricle MLF (v-shaped) Facial colliculus: Abducens nu. + internal genu Superior vestibular nucleus NTS & solitary tract CN VI (med) & CN VII (lat) Facial motor nucleus Superior olivary nucleus ML – horizontally oriented Anterolatero system: Spinothalamic tract Lateral lemniscus Trapezoid body (acoustic fibers) CTT in RF Spinal V tract & nucleus Pontine nuclei Pontocerebellar fibers (transverse) Longitudinal fibers: corticospinal, corticobulbar fibers Facial & abducens nerves Inferior cerebellar peduncle = restiform body + juxtarestiform body 25 Nervus intermedius and facial nerve 3 26 Overview of somatosensory system 1. Modalities: Pain, temperature, touch, vibration & position sense below head 2. Three-order pathway Dorsal root ganglion Interneuron in spinal cord Relay neuron in thalamus 3. Somatotopic organization 4. Most contralateral to cortex 27 Dorsal Column-Medial Lemniscus (DC-ML) System Lesions of DC-ML – Contralateral loss of tactile, two-point discrimination, and vibration sense 28 Anterolateral system (ALS) spinoreticular, spinotectal & spinothalamic tracts Lesions of ALS – Contralateral loss of pain and temperature from trunk and extremities 29 Overview of trigeminal sensory system 1. Modalities: Pain, temperature, touch, vibration & position sense from face & scalp 2. Three-order pathway CN V, VII, IX, X ganglion Interneuron in spinal V nucleus Relay neuron in thalamus 3. Somatotopic organization 4. Most contralateral to cortex 30 Trigeminal sensory pathway Lesions of Spinal V Tract & Nucleus – Ipsilateral loss of pain and temperature from face 31 Subdivisions of spinal V nucleus Pars caudalis – Extend from c3 to pyramid – Perception of pain and temperature from face Pars interpolaris – Extend from pyramid to rostal inf. olivary nucleus – Perception of pain from teeth and touch, discriminative touch from face Pars oralis – Extend from pars caudalis to pontine V nucleus – Perception of touch, discriminative touch from face 32 Overview of somatic motor system Course ipsilateral or contralateral Upper or lower motoneurons Somatotopic organization Crus cerebri contain three major fibers – Corticopontine tract – Corticobulbar tract – Corticospinal tract 33 Blood supply of medulla 4 34 35 Medial Medullary Syndrome Occlusion of Anterior Spinal Artery (ASA) CST – cotralateral spastic hemiparesis ML – contralateral loss of tactile & vibration from trunk & limbs CN XII – ipsilateral paralysis – tongue deviates to affected side 36 Lateral Medullary (Wallenberg’s) Syndrome Occlusion of posterior inferior cerebellar artery (PICA) Spinal trigeminal nucleus & tract - ipsiplateral loss of pain & temp from face (facial hemianesthesia) STT – contralateral loss of pain & temp from trunk & extremities NA – ipsilateral pharyngeal, laryngeal & palatal hemiparalysis Some vertigo and nystagmus (vestibular nu.) Loss of taste (NTS) Hoarseness (vagus nerve) Descending hypothalamospinal fibers in lateral medulla – ipsilateral Horner’s syndrome: interruption of cervical sym. innervation results in pupillary miosis, eyelid ptosis, anhydrosis, flushing of skin 37 Lab review 38 39 40 41 42 43 44 45 46 47 48 49 50 5.
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