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  <head>
    <title>081-02 Brainstem nuclei, cranial pathways, reticular formation, and cerebellar circuits</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Brainstem nuclei and cerebellar circuits">
      <outline text="Orienting the brainstem">
        <outline text="Small lesion gives crossed findings">
          <outline text="Ipsilateral cranial nerve, contralateral body"/>
        </outline>
        <outline text="Medulla: pyramids, olives, fourth ventricle opens"/>
        <outline text="Pons: ventral basis, dorsal tegmentum">
          <outline text="Middle cerebellar peduncles form lateral bulk"/>
        </outline>
        <outline text="Midbrain surrounds cerebral aqueduct">
          <outline text="Peduncles, substantia nigra, red nucleus"/>
          <outline text="Tectum: superior and inferior colliculi"/>
        </outline>
      </outline>
      <outline text="Cranial nerve columns">
        <outline text="Ventricle opening pushes sensory nuclei lateral"/>
        <outline text="Somatic motor nearest midline">
          <outline text="Hypoglossal, abducens, trochlear, oculomotor"/>
        </outline>
        <outline text="Branchial motor">
          <outline text="Nucleus ambiguus, facial, trigeminal motor"/>
        </outline>
        <outline text="Parasympathetic nuclei">
          <outline text="Dorsal motor vagus, salivatory nuclei"/>
          <outline text="Edinger-Westphal with oculomotor"/>
        </outline>
        <outline text="Sensory: solitary, vestibular, cochlear, trigeminal"/>
      </outline>
      <outline text="Trigeminal systems">
        <outline text="Principal nucleus: discriminative facial touch"/>
        <outline text="Spinal nucleus: pain and temperature"/>
        <outline text="Mesencephalic nucleus: primary neurons inside CNS"/>
        <outline text="Second-order fibres cross to ventral posteromedial"/>
        <outline text="Motor nucleus supplies mastication"/>
        <outline text="Lateral lesion: crossed pain-temperature loss"/>
      </outline>
      <outline text="Ocular motor integration">
        <outline text="Trochlear fibres cross before exiting dorsally">
          <outline text="Nuclear lesion contralateral, nerve ipsilateral"/>
        </outline>
        <outline text="Abducens nucleus holds interneurons">
          <outline text="Nuclear lesion: ipsilateral horizontal gaze palsy"/>
          <outline text="Fascicular lesion: isolated abduction weakness"/>
        </outline>
        <outline text="Paramedian pontine reticular formation: saccades"/>
        <outline text="Midbrain coordinates vertical gaze"/>
        <outline text="Medial longitudinal fasciculus lesion">
          <outline text="Internuclear ophthalmoplegia"/>
        </outline>
        <outline text="Pupil fibres superficial in third nerve">
          <outline text="Aneurysm compresses, microvascular may spare"/>
        </outline>
      </outline>
      <outline text="Medullary visceral networks">
        <outline text="Solitary nucleus integrates visceral reflexes"/>
        <outline text="Dorsal vagal and ambiguus: parasympathetic output"/>
        <outline text="Respiratory rhythm from distributed networks">
          <outline text="Pre-Bötzinger complex, respiratory groups"/>
          <outline text="Bilateral injury or opioids: respiratory failure"/>
        </outline>
        <outline text="Area postrema detects blood-borne emetics">
          <outline text="Hiccup and vomiting localise to medulla"/>
        </outline>
      </outline>
      <outline text="Auditory and vestibular pathways">
        <outline text="Cochlear nuclei at pontomedullary junction"/>
        <outline text="Bilateral ascending auditory projection">
          <outline text="Unilateral lesion rarely deafens one ear"/>
        </outline>
        <outline text="Vestibular nuclei stabilise gaze and posture"/>
        <outline text="Signs separate peripheral from central"/>
        <outline text="Nodulus and flocculus shape vestibulo-ocular function"/>
      </outline>
      <outline text="Cerebellar architecture">
        <outline text="Vestibulo-, spino-, cerebrocerebellum"/>
        <outline text="Cortex: molecular, Purkinje, granular layers">
          <outline text="Mossy fibres via granule and parallel fibres"/>
          <outline text="Climbing fibres convey error signals"/>
          <outline text="Purkinje cells inhibit deep nuclei"/>
        </outline>
        <outline text="Deep nuclei: fastigial, interposed, dentate"/>
        <outline text="Peduncles">
          <outline text="Inferior: spinal, vestibular, olivary input"/>
          <outline text="Middle: contralateral pontine input"/>
          <outline text="Superior: deep-nuclear output"/>
        </outline>
        <outline text="Double or no crossing, ipsilateral effect"/>
      </outline>
      <outline text="Cerebellar dysfunction">
        <outline text="Vermis: truncal and gait ataxia"/>
        <outline text="Hemisphere: ipsilateral limb dysmetria, tremor"/>
        <outline text="Flocculonodular: disequilibrium, ocular signs"/>
        <outline text="Gait inability may be the only stroke sign"/>
        <outline text="Cognitive-affective syndrome via cortical loops"/>
      </outline>
      <outline text="Reticular formation and consciousness">
        <outline text="Arousal, autonomic, pain, tone, sleep"/>
        <outline text="Ascending arousal via thalamus and hypothalamus"/>
        <outline text="Consciousness needs both hemispheres and arousal">
          <outline text="Small upper-brainstem lesion can impair it"/>
          <outline text="Unilateral cortical lesion usually does not"/>
        </outline>
        <outline text="Posturing reflects severe lesions, not precise level"/>
      </outline>
      <outline text="Vascular brainstem syndromes">
        <outline text="Paramedian and circumferential territories"/>
        <outline text="Posterior inferior cerebellar: lateral medulla"/>
        <outline text="Lateral medullary syndrome">
          <outline text="Vertigo, ipsilateral ataxia, facial loss"/>
          <outline text="Dysphagia, hoarseness, Horner syndrome"/>
        </outline>
        <outline text="Medial medullary syndrome">
          <outline text="Contralateral weakness, ipsilateral tongue"/>
        </outline>
        <outline text="Basilar thrombosis: locked-in syndrome">
          <outline text="Consciousness and vertical gaze preserved"/>
        </outline>
        <outline text="Examination builds anatomical hypothesis"/>
      </outline>
    </outline>
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