Localization in Neurologic Diagnosis
Part 1
D. Joanne Lynn, MD
Associate Professor of Neurology
Associate Dean of Student Life
Joanne.Lynn@osumc.edu
Objectives
 Be able to accurately differentiate between examination findings
suggesting upper vs. lower motor neuron pathology
 Correlate neurologic signs and clinical features to the appropriate
level of the neuroaxis for the following neurologic localizations:
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Focal cortical disease, including a gross classification of aphasias;
Cerebellar disease;
Brainstem lesions;
Spinal cord disease;
Root and peripheral nerve disease;
Neuromuscular junction dysfunction;
Myopathy
Objectives – continued…
 Define dysarthria, dysphagia, aphasia, aphonia. Compare and
contrast Broca’s, Wernicke’s, conduction and global aphasia.
 List the primary functions of the frontal, parietal, temporal, and
occipital lobes.
 Correlate visual field deficits with lesions along the visual pathways.
 Describe abnormalities of clinical eye movements that will be
caused by lesions in cerebral and brainstem pathways that control
eye movements.
 Recognize clinical presentations that suggest brainstem pathology:
grouped cranial nerve palsies, crossed motor and sensory findings.
 Recognize clinical syndromes related to spinal cord pathology
based on examination findings of motor and sensorydeficits.
 Identify motor, sensory and reflex abnormalities that occur in C6,
C7, C8, L5 and S1 radiculopathies.
Holism vs. Cortical localization
Holism – all parts of the
brain are similar in
function, undifferentiated
and work together as an
aggregate field
Localism – the concept
that specific neurons and
areas of the brain have
specific functions
Connectionism – a view
that mental or behavioral
phenomena are the
product of interconnected
networks of simple units.
Cortical Localization vs. Holism
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Phineas Gage – 1848
Broca and M. Leborgne – 1861
Wilder Penfield – electrical stimulation results
Animal ablation studies
Functional studies by PET – 1990s
Phineas Gage and the frontal lobe
Paul Broca and M. Leborgne’s brain
Learning localization via pathological
observations
Wilder Penfield and Cortical Mapping
Penfield and cortical mapping
PET scan and mapping
Joanne Lynn MD
LOCALIZATION IN NEUROLOGIC
DIAGNOSIS
Levels of the nervous system
Central Nervous
System
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•
•
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Cerebrum / cortex
Basal ganglia
Cerebellum
Brainstem
Spinal Cord
Peripheral
Nervous System
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Roots
Plexus
Peripheral nerves
Neuromuscular
junction
• Muscle
Anatomical Localization
 History and physical examination
 Can the findings be explained by:
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One lesion?
Multiple discrete lesions?
A diffuse process?
 What level / levels of nervous system are affected?
 Beware false localizing signs, non-physiologic
(functional) disease
Levels of the
nervous system
Let’s start at the top with the cerebral cortex
Important cortical areas for clinical diagnosis
Cortical Functions - Language
 Aphasia/dysphasia – true language disturbance with
errors of grammar, word production and / or
comprehension
This should be differentiated from disorders of speech
production:
 Dysarthria – disorder of articulation due to the motor
function underlying speech in which language is intact
 Dysphonia – impairment of the ability to produce
sounds due to disorder of larynx or its innervation
 Aphonia – total loss of voice often due to bilateral
recurrent laryngeal nerve injury, resection of larynx, etc.
Cerebral Dominance / Lateralization
 90% of the population is definitely right handed

99% of these are strongly left hemisphere dominant for language
 The 10% who are left-handed are different:

80% have some degree of language representation in both
hemispheres
Language testing
 Handedness
 Spontaneous speech: fluency, articulation, prosody,
grammar, errors (paraphasias)
 Comprehension: single words, yes/no questions,
complex commands
 Repetition
 Naming
 Reading/ Writing
Broca’s aphasia
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Lesion in dominant inferior frontal gyrus
Nonfluent aphasia
Comprehension good
Associated contralateral hemiparesis if nearby
motor strip is involved
http://www.google.com/imgres?imgurl=http://www-rohan.sdsu.edu/~
Wernicke’s aphasia
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Lesion in dominant superior temporal gyrus
Speech fluent but nonsensical
Poor auditory comprehension
Poor awareness of problem
Aphasia- Localization
Vascular supply related to aphasias
Frontal Lobe
 Hemiparesis
 Personality changes: Apathy, euphoria, jocularity,
irritability, social inappropriateness
 Decreased executive functions
 Frontal micturation area – 2nd frontal gyrus – may
develop urinary incontinence (as in NPH)
 Disorders: tumors, head trauma, hydrocephalus
 Tests:
alternating sequences
alternating motor patterns
`
fist-palm-side test
Descending
Corticospinal and
Corticobulbar
tracts
Alternating sequencing tasks – impaired
in extensive frontal lobe disease
Frontal lobe function: alternating
sequences: Fist, side, palm
Temporal Lobe
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Bilateral lesions: profound memory loss
Dominant side: decreased verbal learning
Nondominant side: decreased visual learning
Visual field defects
Most common site of seizure focus for partial
seizures
Temporal lobe and memory
Parietal Lobe
 Either side: disturbance of sensation on the opposite
side of the body
Central sensory functions:
 Decreased 2 point discrimination
 Sensory inattention / extinction
 Sensory agnosia:
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Astereognosis
Agraphesthesia
Parietal Lobe
Pain pathways –
Spinothalamic tract
to thalamus
To parietal lobe
Parietal Lobe
Vibration and
proprioception input
Posterior or dorsal
columns
To Nucleus gracilis
and cuneatus
To Thalamus
To Parietal lobe
Parietal Lobe Syndromes
 Dominant hemisphere:
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Apraxias – inability to carry out an action in response to verbal
command in the absence of problems with comprehension,
impairment of motor function.
Gerstmann’s syndrome: impaired calculation, left-right
confusion, finger agnosia, dysgraphia
 Nondominant hemisphere:
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Neglect of opposite side
Impaired constructional ability
Neglect – parietal lobe dysfunction
Occipital lobe
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http://cerebrabraintech.com/alexia-turbobrain-technology/understanding-the-human-brain
Visual system
Optic nerves, tracts,
Radiations and cortex
And associated
visual field
defects
Laughter is the best medicine
Basal ganglia
 A whole set of clinical neurologic problems may be
associated with lesions of the basal ganglia.
 Clues to this localization include:
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Some types of tremor
Rigidity
Hypokinesia or hyperkinesia
Postural disturbances
 Many movement disorders caused by dysfunction in this
system are not associated with dramatic abnormalities
on routine imaging – so the clinician must recognize
typical syndromes by clinical features on history and
exam.
Cerebellum
Cerebellum – clinical signs
 Incoordination
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Dysdiadochokinesis
Terminal dysmetria
Intention tremor
Truncal and appendicular
ataxia
Hypotonia
Rebound
Oculomotor abnormalities
Dysarthria
commons.wikimedia.org
Ataxia
 Incoordination or clumsiness of movement not caused by
weakness or sensory loss – rather caused by a
disordered contractions of paired agonist and antagonist
muscles
 The word ataxia derives from Greek words meaning ‘lack
of order’
 Localization:
 True ataxia is Cerebellar
 Sometimes people speak of Vestibular ataxia or Sensory
(proprioceptive) ataxia because they are also associated
with staggering gait/ loss of balance
 So beware that this is a word that may mean different
things to different speakers
Cerebellar
modulation
Of descending
Corticospinal
tract
Brainstem level localization
Brainstem – Clues to Brainstem
Localization
 Grouped cranial nerve findings
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Brainstem site
Site within skull
Generalized disorder of nerve, NMJ
 Divergent eye movements with diplopia
 Vertigo
 Discrepancies in lateralization of motor or sensory
deficits – alternating sensory or motor findings
 Look for well-defined syndromes – like brainstem strokes
Brainstem wiring for eye movements
Joanne Lynn MD
FACIAL PALSIES – PLEASE LOCALIZE AS
UPPER VS. LOWER MOTOR NEURON
LESIONS
Facial palsy on the right….
Left facial palsy
Woman with a
peripheral facial
palsy –
note that the
Left side of the
forehead does
not wrinkle while
the
right does.
Brainstem stroke syndromes and
localization
Midbrain stroke syndromes
Laughter is the
best medicine
Spinal Cord
Simplified spinal cord for clinical
case analysis
Spinal cord
syndromes
 Complete transverse lesion
 Hemisection (BrownSequard)
 Posterior column loss
 Anterior spinal syndrome
 Central cord syndrome
Remember crossing of pain and
temperature fibers in cord
UMN vs LMN signs
 Upper motor neuron signs:
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Increased tone spasticity
Hyperreflexia
Extensor plantar response
 Lower motor neuron signs:
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Decreased tone
Hyporeflexia
Flexor plantar response
Muscle atrophy, fasciculations
Atrophy of Interossei muscles
Atrophy is more prominent with
weakness of LMN etiology
Reflexes
 Myotatic stretch reflexes
 Monosynaptic reflex: stretch muscle, stimulate Ia
sensory afferent, stimulate alpha motorneuron
Ankle
S1, S2
Patellar
L3, L4
Biceps
C5, C6
Triceps
C7, C8
Reflex arc
Stupid Neurology cartoon
Come back for Part 2 –
It is much shorter!
Thank you for completing this module
Questions? Contact me at:
Joanne.Lynn@osumc.edu
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