Download - Neuroanatomy (Handouts) Part 1
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Neuroanatomy untangled
Dr. Martin Turner MA MB BS MRCP PGCAP PhD [email protected] Registrar in Neurology (Oxford Deanery)5th Year Undergraduate Medical Students
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Localisation•Brain (stroke, MS, tumour)
•Cerebellum (stroke,MS, alcohol)•Spinal cord (tumour, MS)
•Neuromuscular junction (MG)
•NB always ask why not?•Muscle (dystrophy, myositis)•NB muscle wasting think nerve first•Autonomic nervous
system
•Peripheral nerve (GBS, vasculitis)
•Brain-stem (stroke, MS)
•Anterior horn (MND)
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Big clues
•Brain (hemi-body, cognitive involvement)•Brain-stem (CN involvement)•Cerebellum (ataxia, NB remember dorsal columns)•Spinal cord (legs not arms, sensory level)•Anterior horn (upper and lower motor neurone)•Peripheral nerve (asymmetrical, patchy)•Neuromuscular junction (non-specific, fatiguable)•Muscle (symmetry, family history)•Autonomic nervous system (postural hypotension,
diarrheoa, sweating)
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Upper vs. Lower Motor Neuron
UMN*
LMN
Brain
Brain-stem
Spinal cord
Peripheral nerves (including some CNs)
* Pyramidal (corticospinal) tract
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Common UMN/LMN conditions
UMN (central) conditions
Stroke
MS (demyelination)
Head injury
Cerebral palsy
LMN (“peripheral”) conditions
Entrapment neuropathies
Guillain-Barré
Diabetes
Vasculitis
UMN and LMN = anterior horn = MND
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Much rarer, but don’t forgetNeuromuscular junction
•Myasthenia Gravis
•Lambert-Eaton myasthenic syndrome (LEMS)
Clues:
•Generalised, fatiguable weakness
•Unexplained ptosis, bulbar problems
1º Muscle disease
•Dystrophies: Duchenne, FSH
•Inflammatory
Clues:
•Symmetrical wasting
•Retained reflexes
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The Examination elements
•The central nervous system–cranial nerve testing (brain-stem and brain)
–(cognitive testing – cortex: grey matter)•The peripheral nervous system
–limb function (spinal cord, neuromuscular junction, muscle)
•The autonomic nervous system–control of heart rate, BP, blood flow
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Cranial nerves
Twelve pairs
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The origins of the CNs
III, IVV, VI, VII, VIIIIX, X, XI, XII
III
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The course of the CNs
I – back of nose (trauma), frontal lobe (tumour)
II – visual fields
III, IV, VI,II, VI – cavernous sinus
V, VII, VIII – cerebellopontine angle (CPA)
VI – long, easily trapped under brain (false-localising)
IX, X, XI, XII – base of skull (jugular/hypoglossal foramina)
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II - Optic
Optic chiasm – bitemporal hemianopia – e.g. pituitary tumour
Optic radiation – homonymous hemianopia or quadrantanopia (lower parietal, upper temporal) – e.g. stroke
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Pupillary response to light•Inbound (afferent):
•II to midbrain
•Outbound (efferent):
•Parasympathetic on surface of III to both eyes
•So, testing the left pupil:
•Direct (left II and III working)
•Consensual (right II and left III working)
•“Pupil-sparing” III lesion:
•localises origin of pathology
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Eye movements – III, IV and VIVI (Abducens) – Lateral rectus: abducts eye
IV (Trochlear) – Superior oblique: depresses abducted eye
III (Oculomotor) – “everything else” and eyelid retraction
So, III palsy: “down and out” and ptosis:
Left complete IIIrd nerve palsy
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V - Trigeminal
Sensation to face and muscles of mastication
Corneal reflex, Jaw jerk (UMN sign)
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VII - Facial
Right LMN facial nerve palsy
•Muscles of facial expression
•(Taste to front 2/3 tongue)
•UMN e.g. stroke: only lower part of face affected (opposite side to stroke) as “back-up” supply from other side
•LMN e.g. Bell’s palsy: whole of face as lesion beyond point of back-up supply
•NB remember the close association to the ear (Ramsay-Hunt syndrome)
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The Cavernous
Sinus
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Uncal herniation
Right abducens palsy
VI
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Cerebello-pontine angle
VVIII
VII
Right acoustic neuroma
VI
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IX - Glossopharyngeal, X - Vagus
•XI - taste to back 1/3 tongue, pharyngeal sensation, afferent pathway for gag reflex, some palatal elevation
•X – efferent pathway for gag reflex,vocal cords, and main parasympathetic supply
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XI - Accessory
Motor to trapezius and sternocleidomastoid muscles
Right trapezius weakness
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XII - Hypoglossal
Right tongue wasting – LMN sign
Tongue movements
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The Peripheral Nervous System
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Spinal cord anatomy
•Terminates at L1 bone (LP below here)
•Everything below is LMN (cauda equina)
•Peripheral nerves enter like “Christmas tree” to centre (LL lateral to UL fibres)