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 and „ Locate in posterior cranial fossa beyond the foramen magnum

5 Divisions of brainstem „ Include (medulla), 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 „ „ Medial eminence „ Vestibular area „ Striae medullares „ : (genu of CN VII & abducens nucleus) „ (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) „

10 Dorsal view of brainstem Medulla

„ Fasciculus gracilis „ Fasciculus cuneatus „ Cuneate & gracile tubercles „ Tuberculum cinereum (spinal trigeminal tract & nucleus) „ (calamus scriptorius)

1 „ Closed & open parts of medulla „ (floor of 4th Ventricle) „ „ (Foramina of Luschka) „ Median aperture (Foramen of Magendie) „ Vagal & hypoglossal trigones „ – without BBB, site of vomiting (emetics) „ Inferior medullary velum ( 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) – : 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

„ „ 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