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BRAIN STEM, CEREBELLUM and NEURO-OPTHALMOLOGY Submitted to:- AskTheNeurologist.Com in 2007

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GROSS ANATOMY

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LATERAL VIEW

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LOCATION OF CRANIAL NERVE NUCLEI WITHIN BRAINSTEM

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CRANIAL NERVE 5 Note that although all fibres enter the brainstem at the level of the pons, those concerned with pain and temperature descend as low as C3

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PATHWAYS INVOLVED IN HORIZONTAL GAZE LEFT FRONTAL EYE FIELD

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INTERNUCLEAR OPTHALMOPLEGIA ( INO)

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THE FACIAL NERVE

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The Long Tracts Note sites of decussation of major tracts : Spinothalamic Cuneate / Gracile Corticospinal

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Blood supply of Brainstem and Cerebellum <ul><li>Ant. cerebral </li></ul><ul><li>Internal carotid </li></ul><ul><li>Middle cerebral </li></ul><ul><li>Post. communicating </li></ul><ul><li>Sup. cerebellar </li></ul><ul><li>Basilar </li></ul><ul><li>Ant. Inf. cerebellar </li></ul><ul><li>Vertebral </li></ul><ul><li>Ant. Spinal </li></ul><ul><li>Post. Spinal </li></ul><ul><li>Post. Inf. Cerebellar </li></ul><ul><li>Post cerebral </li></ul><ul><li>Mesencephalic </li></ul>

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Somatotopy of cerebellum posterior <ul><li>Midline lesions: </li></ul><ul><ul><li>nystagmus </li></ul></ul><ul><ul><li>Titubation </li></ul></ul><ul><ul><li>Trunk / gait ataxia </li></ul></ul><ul><li>Hemispheric lesions: </li></ul><ul><ul><li>nystagmus </li></ul></ul><ul><ul><li>ipsilateral limb signs </li></ul></ul>

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Basic Plan of Cerebellar connections DN= Dentate nucleus T = Thalamus RN = Red nucleus Each cerebellar cortex controls ipsilateral side of body Efferents to cortex leave cerebellum via superior cerebellar peduncle Note: red nucleus is present in midbrain and ultimately controls contralateral half of body

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DSCT= dorsal spinocerebellar tract VSCT= ventral spinocerebellar tract VSCT is crossed in the cord but crosses back within cerebellum

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Which of the following patients cannot have MG? <ul><li>Right eye totally paralysed, left eye moves freely but with ptosis </li></ul><ul><li>Inability of both eyes to move to left with no diplopia </li></ul><ul><li>Bilateral inability to look up with bilateral ptosis </li></ul><ul><li>Left eye deviated down and laterally with ptosis on left and left pupil larger than right </li></ul>

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Anisocoria <ul><li>“ Inequality between the 2 pupils” </li></ul><ul><li>Pupils may be : </li></ul><ul><li>- equal ( to within 1mm) </li></ul><ul><li>- unequal due to surgery ( usually irregular) </li></ul><ul><li>- unequal due to neurological disease </li></ul>

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The 2 neurological causes of anisocoria <ul><li>One pupil too big </li></ul><ul><li>One pupil too small </li></ul>Parasympathetic---------------------------------------Sympathetic Constricts (Ach) III Dilates (Nad) Symp fibres

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Anisocoria rules <ul><li>Darkness exaggerates failure of dilation </li></ul><ul><li>Bright light exaggerates failure of constriction </li></ul><ul><li>If unilateral ptosis is present assume that the eye with the ptosis is sick! </li></ul>

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Sphincter pupillae muscle

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Left RAPD AKA Marcus-Gunn pupil For example a patient with multiple sclerosis who is suffering from acute left sided optic neuritis

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Sphincter pupillae muscle

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