2 CerebellumBrief anatomy and functions Functions – DANISH Pathology
3 Brief anatomy What do the lobes of the cerebellum do? Anterior cerebellum - unconscious proprioceptionPosterior cerebellum - fine motor controlFlocculonodular - head & eye movements
4 functions of the cerebellum Maintenance of balancePosture and muscle toneCo-ordinationEye movementsPlanning movementsLearning of motor skills.IMPORTANT: PROPRIOCEPTIONRecieves input from spinocerebellar tractRECAP from week 1 block 3:What is unconscious proprioception?Knowing where your body parts are in relation to space without looking. (eg MSK exams)
5 Blood supply Which 3 arteries supply the cerebellum? AICA – anterior inferior cerebellar artery (basilar)PICA – posterior inferior cerebellar artery (vertebral)SCA – superior cerebellar artery (basilar)NB LEARN YOUR CIRCLE OF WILLIS
7 What could cause damage to the cerebellum? Tumours Strokes Degeneration Haemorrhage Trauma Alcohol Hereditory disorders Viruses
8 DANISH Clinical features of cerebellar disease Dysdiadokinesia Ataxia NystagmusIntention tremorScanning dysarthriaHypotonia (and heel-shin test)NB IPSILATERAL SYMPTOMSAsk them in order of word DANISH.Ataxia: neurological term for problems related to your speech, coordination and balance.Nystagmus: how do you measure which direction a nystagmus is? Fast phase and slow phase – whichever side the fast phase flicks towards is the direction of the nystagmus.JERK NYSTAGMUS = repetitive eye movement with a fast and slow phaseSLOW PHASE – eyes slowly drift to the side of the lesionFAST PHASE – eyes move quickly back to the midline via action from SACCADE CENTRESJerk Nystagmus is named after the Fast Phase = opposite side to the lesion• RIGHT lesion = LEFT NystagmusScanning dysarthria – words broken up into separate syllables.
9 Damage to the cerebellum: REMEMBER THIS?What do the lobes of the cerebellum do?Anterior cerebellum - unconscious proprioceptionPosterior cerebellum - fine motor controlFlocculonodular - head & eye movementsWhat could cause damage?Effects of damageFlocculonodular lobeDizziness, nausea, vomiting and nystagmus.Central vermal region(Tumour in 4th Ventricle)Midline lesions result in truncal ataxia, limb co-ordination can be okAnterior lobe(alcoholic damage)Damage affects lower limbs - ataxic wide-based gaitNo heel toe walking or heel shin stroking with eyes openPosterior lobe (most of the cerebellum)Dysdiadochokinesia (inability to carry out rapid repeating movement)DysarthriaDysmetria (inability to calculate trajectory)Tremor (intentional)Wide-based unsteady gaitLinguistic incoordination - Grammar and syntax misuse
10 Important conditions to remember: PICA syndrome (Wallenberg syndrome, Lateral Medullary Syndrome) – KNOW FOR EXAMCause: Occlusion to PICA due to thrombosis or stroke.Symptoms: Ataxia, vertigo, nystagmus, facial pain, dysphagia, Horner’s syndrome. Loss of pain and temperature on contralateral side of the body and ipsilateral side of the face.Freidreichs AtaxiaMost common inherited ataxia – onset in teens before 25 yoCause: mutation in FRDA gene – reduced frataxin protein – tissues normally high in frataxin preferentially affected.Symptoms: above + muscle weakness.Outcome: Loss of ambulation at 25 – death in mid 30s.
15 Direct Pathway = Promotes movement VISUAL LEARNERS:Excitatory = glutaminergicInhibitory = GABAergicSubstantia Nigra pars compacta activates striatum via D1 receptorsCortexActivityActivates striatumActivityActivates Cortex(Premotor)Activates striatumStriatumGlobus Pallidus Internus & SNPRNormal activity Inhibits VLNTherefore removal causes activation of the VLNThalamusVentral Anterior/Lateral NucleusParkinsons – loss of dopamine from SNPC so lose striatal activation. Loss of movements as direct pathway eventually suppressed.Activity Inhibits GPIWORD LEARNERSInhibition of the inhibitory GPI allows the VLN to activate cortexSYMBOLIC LEARNERS
16 GABA and GLUTGreen= excitatory (go!) gluta-green-ergic (GABA is opposite)
17 Indirect Pathway = Inhibits Movement Normally Activates Cortex SNPC inhibits striatum via D2 receptorsCortexNormally Activates Cortex(Premotor)Activates striatumInhibits striatumD2StriatumGlobus Pallidus Internus & SNPRThalamusVentral Anterior/Lateral NucleusActivity Inhibits VLNHuntingtons = degeneration of striatal input to GPE and SNPCThalamus is overexcited.ActivityActivates GPI & SNPRActivity Inhibits GPEGlobus Pallidus ExternusNormal Activity Inhibits STN therefore removal causes activation of STNSubthalamic nucleus
18 Indirect Pathway = Inhibits Movement Normally Activates Cortex SNPC inhibits striatum via D2 receptorsCortexNormally Activates Cortex(Premotor)Activates striatumInhibits striatumD2StriatumGlobus Pallidus Internus & SNPRThalamusVentral Anterior/Lateral NucleusActivity Inhibits VLNActivityActivates GPI & SNPRHuntingtons = degeneration of striatal input to GPE and SNPCThalamus is overexcited.Activity Inhibits GPEGlobus Pallidus ExternusNormal Activity Inhibits STN therefore removal causes activation of STNSubthalamic nucleusWORD LEARNERSInhibiting the inhibitory GPE enables STN to activate GPI which inhibits the thalamusSYMBOLIC LEARNERS
19 Substantia nigra pars compacta promotes movement via dopaminergic signalling Activates direct pathwayDirect pathway normally activates movementSNPC(Dopaminergic)Inhibits indirect pathwayIndirect pathway normally inhibits movementParkinsons – can remove globus pallidusSNPC: A summary.SNPC releases dopamine which acts on:D1 in direct pathway to promote movement by activating that pathway.D2 in indirect pathway to promote movement by inhibiting that pathway.
20 BUILD YOUR PATHWAYSSplit into two groups and make up the pathways (we will be here to help)
21 Pathology of Basal Ganglia TRAP:Tremor (resting)RigidityAkinesiaPostural instabilityConditionCausesWhere is affectedEffects on basal ganglia pathwaysMain symptomsParkinsonsIdiopathic/iatrogenicSNPCInhibits direct pathway – to slow initiation of movement.TRAPHuntingtonsGeneticStriatumInhibits indirect pathway – to remove ability to suppress movements.Involuntary horeiform (writhing) movements + cognitive changesHemiballismusVascularSubthalamic nucleusUndesired flailing limbs (mainly proximal limb muscles)
22 THANKS FOR LISTENING Special effects: Andy /fb us with any questions you have.Special effects: Andy