Neurology Block
Integration Lecture
Localization in Clinical Neurology
Remember: The Goal of
Neurology in Unit III
To produce a medical student entering
clerkship with a sufficient knowledge of
neurology to identify and treat neurologic
conditions that are


Common
Serious
Dr. Heather MacLean
Common, Serious or Both
•
•
•
•
•
•
•
•
•
•
•
Tumors
Stroke
Subarachnoid Hemorrhage
Head and Spinal trauma
Parkinson’s Disease
Wilson’s Disease
Huntington’s Disease
ALS
Sciatica
Carpal Tunnel Syndrome
Diabetic Polyneuropathy










Guillain Barre
Myasthenia Gravis
Multiple Sclerosis
Meningitis
HSV Encephalitis
Migraines
Tension Headaches
Cluster Headaches
Epilepsy
Sleep disorders
What are the 3 Golden Questions in
Neurology?
1.
2.
3.
Is it neurological?
Where is the lesion?
What is the lesion?
The tools we have given you to answer
those questions…
NeuroAnatomy
NeuroPathology
NeuroPhysiology
Answers
To Golden
Trio
NeuroRadiology
Clinical Neurology
NeuroAnatomy

Probably more than any other specialty,
Neurology REQUIRES a working
knowledge of relevant anatomy

It is the key to an accurate localization
Know your NeuroAnatomy Organized
by Regions…
Dr. Heather MacLean
And Organized by Systems

Eg: the
motor
system
Muscle
NMJ
Nerve
Dr. Heather MacLean
Elements of the Motor System

UMN





Pyramidal Tract (aka Direct
Pathway)
“Other” Tracts (aka Indirect
Pathway)
LMN
NMJ
Muscle
Diseases at Each
Level
Where in the Motor System is the Lesion?
(UMN,LMN,NMJ,Muscle)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Myasthenia gravis (MG)
Dermatomyositis (DM)
Myotonic Dystrophy (MD)
Spinomuscular Atrophy (SMA)
Amyotrophic Lateral Sclerosis (ALS)
Guillain Barre Syndrome (GBS)
Multiple Sclerosis (MS)
Left MCA stroke
Left Occipital Lobe Tumor
Benign Rolandic Epilepsy of
Childhood
L3/4 disc protrusion causing L4
distribution sciatica
C6 vertebral fracture causing a
complete traumatic myelopathy
1.
2.
3.
4.
5.
NMJ
Muscle
Muscle
LMN
UMN & LMN
10.
LMN
UMN (if the motor is affected!)
UMN
Neither!
UMN
11.
LMN (L4 motor root)
12.
UMN (CSTs) and LMN (Anterior Horn
Cells at level of C6 only)
6.
7.
8.
9.
The Pyramidal Tract – UMN Pathway For
Voluntary Movement
UMN Syndrome vs. LMN Syndrome
UMN Syndome
LMN Syndrome
weakness
yes
muscle bulk
fasciculations
normal
muscle tone
stretch reflexes
clonus
plantar reflex
none
increased
hyperactive
present
upgoing (Babinski)
Dr. Heather MacLean
yes
wasting
yes
decreased
hypoactive
absent
downgoing
Regarding the motor system, very
important to know spinal anatomy…



Corticospinal tract location,
decussation and
‘somatotopic
organization’
Anterior horn cells
Segmentation of spinal
cord
Spinal Cord Segmentation
Spinal Myotomes

Root innervation of muscles

Important Myotomes:

C5, C6, C7, C8/T1
 Innervate most of the arms

L4, L5, S1
 Innervate most of the legs
…AND need to know the very
complicated Brainstem

Where the CSTs run in the





Midbrain
Pons
Medulla
Which CN’s have motor
functions/nuclei
How to clinically differentiate
between UMN and LMN
facial weakness
LMN Facial Weakness
Regarding the Motor System, you must know the other
2 Circuits that modulate Movement…
Dr. Heather MacLean
Elements of the Somatosensory
System




Cutaneous Receptors
Peripheral Nerves
Dorsal Roots & Dorsal Root Ganglia
2 main sensory pathways




Spinothalamic tract (STT)
Dorsal Column Medial Lemniscal pathway
Both synapse in the contralateral thalamus on the way to
sensory cortex
Cortical Sensation

Aka corticosensory testing



2 point discrimination
Graphesthesia
Stereognosis
Dermatomes

Root innervation of skin

Important Dermatomes:




C5,C6, C7,C8
T4 (nipple line)
T10 (umbiliculus)
L4, L5, S1
The Visual System
Normal Anatomy of Vision
VF Defects Depending on
Lesion Location
Autonomic nervous system

Control of unconscious, visceral functions











Sympathetic system



Pupils
Tearing
Salivary glands
Breathing
Heart rate
Blood pressure
Stomach, intestines, gall bladder
Bladder, sex organs
Sweat glands, piloerector muscles
Adrenal glands
Fight and flight responses
Thoracolumbar levels
Parasympathetic system


Resting, vegetative functions
Craniosacral levels
Dr. Heather MacLean
Higher Cognitive Functions



Neglect
Anosognosia
Language



Left (dominant) hemispheric control
Analogue in the right (non-dominant)
hemisphere affects emotional aspects of
language
Memory

Declarative




Semantic
Episodic
Non-declarative (procedural)
Transient Global Amnesia

A temporary, largely anterograde memory
defect
Clinical Neurology

You must recognize patterns












Contralateral if hemispheric
Hemibody (face=arm=leg)
Optic nerves
Medial Longitudnal fasciculus


Basal ganglia

Brainstem



Dipoplia, dysarthria, vertigo
Crossed sensory deficits

Ipsilateral incoordination
Dysarthria, vertigo, nystagmus



Motor & Sensory areas affected
depend on specific nerve involved if
mononeuroapthy
Symmetric length dependent glove &
stocking sensory loss if polyneuropathy
NMJ

Hyper or hypokinetic sx/signs
Cerebellum



Symmetric
Sensory level
Motor level, UMN findings below this
Impaired bladder & bowel
Peripheral neuropathy
White matter pathology



Differential involvement of face&arm >leg
or leg> arm&face
Seizures
Sometimes headache
Sometimes dementia
Spinal lesions

Contralateral
Cortical homunculus



Gray matter pathology
Fatiguable
Face and Eye involvement
Only motor
Myopathy



Symmetric
Proximal muscles usually
Only motor
You need to systematically Create a
Differential Diagnosis









Congenital
Traumatic
Metabolic
Infectious, Inflammatory, Iatrogenic
Neoplastic
Degenerative
Stroke, seizure, sleep disorder
Vascular
Psychogenic
Dr. Heather MacLean
Let’s put our skills to the test…
Case 1

Mr. Brown is a 60 year old right handed auto mechanic who has
been referred for neck pain. He has had posterior neck pain
intermittently for 10 years but for the past 6 months it has been
nearly constant. 3 weeks ago after shovelling his driveway
following a heavy snowfall the pain in his neck started radiating into
his right shoulder and arm and his right lateral forearm and thumb
have become numb and tingly.

He also now finds his legs feel rubbery and weak when he walks
and he has had new problems with urination. His stream is hesitant
and he never seems to be able to completely empty his bladder.
Localize this lesion by history

Key symptoms:





Is his pain and numbness due to a central (CNS) cause?



Radiating pain from neck to right arm
Strip of numbness/paresthesias involving right thumb
Bilateral leg weakness
Bladder hesitancy
No. Although central lesions often produce numbness, they very less frequently
cause pain.
To have a “strip” of numbness would be unusual from a cortical source (think of the
homunculus) and would be nearly impossible from a subcortical source (think how
close the sensory fibres are in the internal capsule and how tiny that lesion would
need to be!)
In the PNS, does this fit with a root problem or a nerve problem?

Let’s look at this further…
Nerve Sensory Innervation of the
Hand

Median nerve


First 3 ½ fingers (conting from thumb)
SPLITS the ring finger
He has mainly the thumb
Involved, not first 3 ½ fingers
And his numbness spreads
Up higher than the wrist –
Doesn’t fit with median nerve
Dermatomes

C5


C6


fits nicely
Thumb
C7


Anterior Shoulder
Middle Finger
C8

“Pinky”
Radicular (root) Pain in the Arm
C5
C7
C5
C6
C8
C6
C8
BLACK= Pain, STIPPLED= Numbness/tingling
Radicular Pain in the Leg
S1
S1
L5
L5
L4
L4
BLACK= Pain, STIPPLED= Numbness/tingling
Dermatomes vs. Nerve Sensory
Innervation in the Leg Comparison
More Questions Case 1

Can his bilateral leg weakness and bladder
symptoms be explained by a C6 radiculopathy?


Where do these symptoms localize to?


No
Keys to a Spinal cord lesion are symmetric bilateral motor
involvement of legs (paraparesis) and bladder dysfunction
Let’s see if his physical exam confirms your
suspicion...
Case 1 continued

On examination he appeared in moderate discomfort but was pleasant and able to
give a concise history. Mental status, language and cranial nerve examinations
were normal.

Motor examination of the arms demonstrated atrophy and weakness of the right
biceps (mild), brachioradialis and wrist extensors (more pronounce). Shoulder
abduction and finger abduction and adduction were normal. Fasciculations were
seen in the right brachioradialis muscles. Motor examination of the legs revealed
spasticity and mild weakness of bilateral hip flexors, knee flexors and ankle
dorsiflexors. The extensors of the legs seemed strong.

Sensory exam of the left arm was normal. In the right arm, pin prick and fine touch
were reduced in the lateral forearm & thumb. You test temperature sensation and
he has a definite bilateral sensory level on the anterior trunk. Pulling out your
dermatome chart, you think it is between the C5 & T1 levels.
Simple as 1,2,3
Myotomes



L4,5
S1,2
Biceps (mostly C5)
Elbow flexion,
semipronated
(brachioradialis)
Wrist extension

L4


Elbow extension (triceps)

C8/T1

Hand intrinsics

Knee extension
L5
C7


Shoulder abduction, biceps
C6


L3,4
C5


L2,3
Ankle dorsiflexion, ankle
inversion and ankle
eversion
S1

Ankle plantarflexion
Case 1 continued

Tests of coordination/cerebellar function
were done well.

Left biceps and brachioradialis reflexes
were normal.
The right biceps reflex was present but
reduced, the right brachioradialis reflex
was absent.
His triceps, knee jerks and ankle jerks
were bilaterally brisk and he had
bilaterally upgoing plantar responses.


Root Innervation of Reflexes

As simple as
counting 1,2,3
Our case
And even more questions Case 1

Does this support a myelopathic process?


Yes
How do you get a C6 radiculopathy and a
myelopathy? What is the lesion?
Degenerative Disc Disease
(Mini)Case 2

You are on call for neurology and you hear a stroke code being called
overhead. You rush to the ER where Mrs. White is being assessed by the
ERP and is surrounded by nurses taking blood and getting an ECG.

The ERP tells you she is an 80 year old woman with a past history of HTN
who suddenly developed right-sided numbness 1 hour ago. There is no
headache, neck pain or apparent sensory loss.

You take over and examine her. She is alert and oriented and speaks
normally. Vision is normal. There is dense numbness involving the right
face, arm and leg to pinprick, temperature and fine touch but all strength
testing seems normal. Coordination and reflexes are normal. She can
walk without assistance.
Pure sensory loss
Where is the lesion?

CNS or PNS?


Brain or spinal cord?




Definitely not cerebellum (motor control)
No other brainstem sx or signs (diplopia, dysarthria, dysphagia, vertigo, crossed sensory findings)
Probably cerebrum
Which hemisphere?


Brain, hemisensory not sensory level
Cerebrum, brainstem or cerebellum?


CNS
Left
Cortex, white matter, thalamus or basal ganglia?



Not BG (motor control)
Cortex less likely as would have to involve a HUGE cortical surface area to equally involve face, arm and leg, yet
sparing any adjacent motor cortex or language area of the Left hemisphere??? IMPOSSIBLE!
Likely thalamus which functions as a huge sensory relay or retrolenticular part of the the internal capsule which
carries thalamic radiations to cortex.
What is the lesion?

Remember CT MIND SVP
Sudden onset, no ‘march’ to suggest seizure (seconds) or
migraine (minutes)
No hx of trauma or infectious symptoms
Negative symptoms (sensory loss) rather than positive (tingling)
seen in seizure or migraine
Older woman with HTN, stroke risk factor

Lacunar infarction of the left thalamus




Think lacune if stroke presents with
Pure hemisensory or pure hemimotor signs,
Especially if F=A=L distribution!
Minicase 3

A 35 year old female nurse notes that, at the end of her
shifts, she has difficulty enunciating her words, producing a
smile, and even holding her head up. Her symptoms
disappear with rest.

On prolonged upgaze she develops ptosis of the left eyelid.
While reading a long passage aloud, her speech gradually
becomes dysarthric. The rest of neuro exam including
sensory exam, strength, tone, bulk and reflexes are normal.
There are no fasciculations.
Based on this history, where is the
lesion?
Note:
Brainstem
Anterior horn cells
Multiple cranial neuropathies
Multifocal white matter (eg: MS)
Neuromuscular junction
1.
2.
3.
4.
5.





no UMN signs
no atrophy/fasics/LMN signs
no sensory abnormalities
the fatiguability
Dysarthria – can be UMN, cerebellar, LMN of CN 7, 9/10, 12 , NMJ or myopathy of
face/tongue
Facial weakness – can be UMN or LMN CN7, NMJ or myopathy of face/tongue
Ptosis -- can be LMN CN3 lesion or Horner’s syndrome, NMJ or myopathy
affecting eyes
Neck weakness – UMN or LMN CN11, NMJ or myopathy
Recall your patterns! Keys here are pure motor symptoms, fatiguability
and eye and face involvement
What is the lesion?


MG is the most common NMJ disorder
Fits clinically with her presentation
Minicase 4

A 68 year old man was walking from his bathroom
at 10am when he suddenly developed an
explosive headache. It is the “worst headache of
my life”. It began in the bifrontal area and over
the next few minutes spread all over his head and
down his neck. He denies nausea, vomiting, LOC
or vision changes. He is a heavy smoker and has
CAD.
Minicase 4 continued
What is the single most important diagnosis to rule out based on this
history

1.
2.
3.
4.
Meningitis
Encephalitis
Subarachnoid hemorrhage
Intracerebral hemorrhage
If SAH, what ‘extra’ neurologic sign do you need to look for on exam?

1.
2.
3.
4.
Nuchal rigidity
Straight leg raising
Dix-Hallpike maneuvre
Relative afferent pupillary defect
What investigation(s) should be ordered next?



CT head then LP if negative
If a SAH is proven  cerebral angiogram
Dr. Heather MacLean