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Localising The Lesion ‘where in the CNS’
Lauren O’Flynn
Learning objectives
• Definition of CNS and PNS• Definition of UMN and LMN• Function of each of the cerebral lobes• The homunculus• Circle of willis and blood supply to the cerebral
hemispheres• Motor tracts – lateral corticospinal• Sensory tracts – lateral spinothalamic and dorsal
columns• Clinical case scenarios
Definitions
• CNS– Brain and spinal cord• Protected by bone
• PNS– Everything else• Sensory, motor, autonomic
Homunculus
UMN vs LMN
• UMN– Entirely within CNS– symptoms
• Hyperreflexia• Spastic paralysis• Up-going plantar reflex
– Babinski’s sign
• LMN– Mostly outside of CNS– Symptoms
• Hyporeflexia• Flaccid paralysis• Muscle
wasting/fasiculations
Cerebral lobes
Cerebral function
• Frontal– Prefrontal cortex
• Personality• Reasoning/rationale• Cognition• Mood
– Motor area• Broca’s area
• Parietal– Sensory cortex– Visuospatial orientation
• Temporal– Auditory cortex
• Wernicke’s area
– Learning and memory– Emotional and affective
behaviour
• Occipital– Visual cortex– Meaning and
interpretation related to vision
Circle of Willis
Circle of Willis
Blood supply to the Brain
Spinal Tracts
Anterior Spinothalamic
• Sensory– Carries crude touch and
pressure
• Decussates at level of Spinal Cord
Lateral Spinothalamic
• Sensory– Carries pain and
temperature
• Decussates at level of Spinal Cord
Dorsal Columns
• Sensory– Carries vibration,
proprioception, and fine touch
• Decussates at level of the Medulla
Corticospinal
• Motor• Decussates at the level
of the Medulla
Brown-Sequard
Clinical scenario 1
• 75 year old • daughter noticed that he woke up with a left
facial droop and slurred speech• O/E– Left facial weakness– Unable to raise left arm– Upgoing left plantar
Stroke
• Aetiology– Thrombus in situ– Heart emboli– CNS bleed
• Risk factors– Hypertension– Smoking– DM– CVS disease– PVD– Past TIA– Hypercholesterolaemia
Stroke Syndromes
TACS – all 3 PACS – 2 of 3 LACS POCS
Hemiplegia/hemisensory loss
See left No visual field defect
Bilateral motor or sensory
Visual field disturbance
Pure motor Conjugate eye movement disturbance
Disturbance in higher function – e.g. dyphasia/dysphagia
Pure sensory Cerebellar dysfunction
Sensory-motor Hemiplegia or cortical blindness
Ataxia
Stroke - Ix
• Bedside– BP– ECG (+/- 24hr)
• Bloods
• Imaging– CT head– Carotid doppler– Echo– ?MRI head
• Special test– Swallow assessment
Stroke - Management
• Acute– A-E assessment– BP – only treat if >200– Throbolysis
• If <4.5 hrs after onset• Alteplase (tPA)
– NBM until swallow assessment– Fluid balance – beware cerebral oedema– Antiplatelets
• Aspirin 300mg OD for 2 wks
Stroke - Management
• Longterm– Antiplatelets
• Aspirin 75mg OD + Dipyridamole 200mg BD• Clopidogrel 75mg OD
– ?anticoagulation• If AF – warfarin
– Neurorehabilitation• Physio• OT• SALT• Stroke outreach team
Clinical scenario 2
• 26 year old female • 2 week history of bilateral leg weakness – started with pins and needles and numbness in
her hands and feet.• few days of urinary incontinence – resolved• Previous episodes?– episode of blurred vision and pain in the right eye
which lasted a month and fully resolved
Multiple Sclerosis
• Aetiology– Autoimmune?
• Epidemiology– Women > men– Onset ~30’s– Cold climates
Multiple Sclerosis
• Pathology– Chronic inflammatory condition of CNS
• CD4 mediated
– Characterised – multiple plaques of demyelination• Disseminated in TIME AND SPACE
• Types– Relapsing & remitting
• Demyelination heals incompletely
– Progressive• Prolonged demyelination and axonal damage
Multiple Sclerosis – clinical features
• Eyes– Unilateral optic neuritis
• Pain on eye movement• Rapid loss of central vision
– Intranuclear ophthalmoplegia• Weak primary abduction of
ipsilateral eye and nystagmus of contralateral eye
– Interrupted visual pursuit
• Urinary symptoms– Retention– incontinence
• Sensory disturbance– Parasthesia– Numbness– L’hermitte’s sign
• Electrical like shocks on neck flexion
– Decreased vibration sensation
– Trigeminal neuralgia
• Motor disturbance– Leg weakness– UMN signs
Multiple Sclerosis – clinical features
• Swallowing disorders• Balance problems• Constipation• Fatigue• Amnesia– Memory conversion
affected
• Erectile dysfunction• Cerebellar features– Ataxia– Nystagmus– Intention tremor– Monotonous speech
Multiple Sclerosis - Ix
• Bedside– Urine dip– LP
• Oligoclonal bands• Increased
– IgG– Protein– Lymphocytes
• Bloods
• Imaging– MRI head
• Plaques (periventricular)
• Special tests– Electrophysiology
Multiple Sclerosis
• Management– Acute
• Methylprednisolone– Decrease duration and severity of attacks
– Longterm• Biopsychosocial• B-interferon
– Relapsing and remitting
• Symptomatic
• Prognosis– Good features
• Female• Optic or sensory onset
Clinical scenario 3
• 59 year old male• 6 month history of progressive weakness of
his right hand– Also had problems with swallowing and has
choked whilst eating on several occasions• o/e – wasting of his R arm and both lower limbs – some fasciculation's were noted – Sensation was normal
Motor Neurone Disease
• Aetiology– Unknown
• Epidemiology– Men > women– Onset ~60yrs
• Pathology– Degenerative disease– Selective loss of neurons
in motor cortex
Motor Neurone Disease - patterns
• Amytrophic lateral sclerosis – UMN & LMN
• Progressive muscular atrophy – LMN only
• Progressive bulbar atrophy– LMN of CN IX-XII only
• Primary lateral sclerosis– UMN only
MND – clinical features
• Muscle weakness
• UMN signs (legs)– Beware if no UMN signs
above LMN signs
• LMN signs (arms)
• Bulbar palsy– Swallowing/speech
problems
• No Sensory disturbance
• No cognitive disturbance
• No eye or sphincter disturbance
Motor Neurone Disease- Ix
• Bedside– LP
• Rule out inflam causes
• Bloods– CK
• >600 excludes MND• Anti-GAD Abs
• Imaging– MRI head & spine
• Special tests– neurophysiology
Motor Neurone Disease
• Management– Anti-glutamate drugs
• Riluzole – Extends life by 3-5 months
– Symptomatic• Drooling – amytryptylline• Spasticity – baclofen• Pain – analgesia ladder• Resp failure – ventilation?• Surgical - gastrostomy
• Prognosis– Terminal– Usually die of resp failure rather than choking/aspiration
Questions?