Session 4:
Neuromuscular Disorders
Vignette
• 19 yo athlete has "tingling" in arms & legs for the
3 days with nl strength and coordination. Exam
in is normal.
• Two days later, he is admitted with rapidly
progressive weakness
• Exam shows tachycardia, nl pupils, EOM, facial
expression with a poor cough & gag. There is
proximal weakness, areflexia and nl sensation.
Bladder function is good as is rectal tone.
Questions
• Which motor subsystem: muscle,
neuromuscular junction, peripheral nerve,
plexus, root, anterior horn cell, spinal cord, or
brain is the problem located?
• Differential diagnosis?
• Tests
• CSF findings
• Management
• Significance of the tachycardia and
management
• Prognosis
• What if symptoms developed over 6 months?
Guillain-Barre Syndrome:
Acute Inflammatory Demyelinating
Polyneuropathy (AIDP)
Georges Charles Guillain
Jean-Alexandre Barre
André Strohl
Jean Landry
GBS
• Causes: In about 80% of the patients,
symptoms began about 5 days to 3 weeks
after a mild infection, surgery, etc. Some
have infection by Campylobacter jejuni
• Treatment includes plasmapheresis
(plasma exchange, PLEX) and/or highdose immunoglobulin therapy.
Prox/distal
Sensory
Prom fascic
Reflexes
EOM
Dysarth/dysph
Bladder
Muscle NMJNerveALS
P
P
D/P D/P
+
+
++
nc
+
+
+
+
+
+
+
+
+
-
Cord
D/P
+
+
+
???
diab neurop CIDP CMT I CMT II
Axonal vs Demyelin
A or D
Sens vs. sensmotor
Both
Length-dep
Yes
A or D
Muscle Tone:
Hypotonia/Atonia:
Increased tone
Rigidity
Reduce or absent tone; associated with LMN or
cerebellar lesions or acute UMN insult (e.g.,
spinal shock)
Present bidirectional – associated with basal
ganglia/extrapyramidal lesions (when
accompanied with tremor there is “cogwheeling”).
Changes in tone may be accentuated with
contralateral limb activation. Performed by
passively moving appendicular or axial structures
Spasticity
Velocity dependent; unidirectional increase in
tone; associated with UMN lesion
Paratonia
Also known as “gegenhalten”; which is apparent
increase in tone due to patient’s inability to relax;
often present in individuals with cognitive changes
Deltoid
Biceps
Triceps
Finger ext
APB
FDI
Iliopsoas
Quadriceps
Hamstrings
Tibialis ant
Gastroc
EHL
ext
Function
Sh ab
flex
C6
ext
abd
abd
Hip flex
Leg ext
Leg flex
Dorsi
Plantar
Dorsi
Root
C5
C5/6
Radial
C7
C8/T1
C8/T1
L12
L234
S1
L45
S1
L5
Nerve
Axillary
Musculocutan
Radial
Median
Ulnar
Upper plexus
Femoral
Sciatic
Peroneal
Tibial
Peroneal
Axillary Nerve
Median Nerve
Musculocutaneous
Nerve
Radial Nerve
Ulnar Nerve
Nerve
Peroneal Nerve
Femoral Nerve
Obturator Nerve
Tibial Nerve
Deltoid C5 Axillary N.
Biceps C6 Musculocutaneous N.
Triceps C7 Radial N.
Brachioradialis C6 Radial N.
Extensor Carpi Ulnaris C7 Radial (Posterior Interossious)
Extensor Digitorum C7 Radial (Posterior Interossious)
First Dorsal Interossious T1 Ulnar Nerve
Abductor Pollicis Brevis T1 Median N.
Psoas L1,2
Hamstring S1 Sciatic
Tibialis Anterior L4,5 Deep Peroneal N.
Ext. Hallucis Longus L5 Deep Peroneal N.
Extensor Digitorum Brevis L5 Deep Peroneal N.
Extensor Digitorum Longus L5 Deep Peroneal N.
Gastrocnemious S1 Tibial N.
Grading Strength
Deep Tendon Reflexes :
Adequate Relaxation
Stretch Tendon Suddenly
Reinforcement
Grading 0 to 4
Deep Tendon Reflex Technique:
Adequate Relaxation
Stretch Tendon Suddenly
Reinforcement
Grading 0 to 4
Segmental Reflex Innervation:
Muscle
•Biceps
•Triceps
•Brachioradialis
•Knee
•Knee (Alternate
techniques)
•Ankle
Primary Nerve Root
•C6
•C7
•C6
•L4
•L4
•S1
Reinforcement
•Grading 0 to 4
Reflex
Primary Nerve Root
Biceps
C6
Reflex
Primary Nerve Root
Triceps
C7
Reflex
Primary Nerve Root
Brachioradialis C6
Reflex
Primary Nerve Root
Patellar
L4
Reflex
Primary Nerve Root
Patellar
L4
Reflex
Primary Nerve Root
Achilles
S1
Abnormal Plantar Response:
Extension of the great toe and fanning of other toes implies
upper motor neuron dysfunction.
Babinski
Chaddock
Oppenheim
Gordon
Snout
Hoffman
Finger Flexors
Clonus
Definitions
• Allodynia: Pain due to a stimulus which does not
normally provoke pain.
• Dysesthesia: An unpleasant abnormal
sensation, whether spontaneous or evoked.
• Hyperalgesia: An increased response to a
stimulus which is normally painful.
• Neuropathic pain: Pain initiated or caused by a
primary lesion or dysfunction in the nervous
system.
• Paresthesia: An abnormal sensation, whether
spontaneous or evoked.
Management
• Neuropathic pain
– Tricyclic antidepressants
– Carbamazepine (tegretol)/trileptal
– Gabapentin (Neurontin)
– Opioids
– Other
Location
Ulnar at elbow
Radial at SG
Median at wrist
Peroneal at FH
Strength
Reflex
Sensation
ULNAR ENTRAPMENT AT ELBOW
SENSORY CHANGES: numbness along the little and ulnar half of the ring finger and
corresponding area of the palm and dorsum of the hand.
MOTOR: weakness of the grip, particularly in activities like using a tool. Patients with
more severe neuropathy would present with wasting of the intrinsic muscles of the hand
(Fig 7). They may have the classic Froment’s sign (Fig 8). Weakness of the deep flexors
to ring and little fingers as well as weakness of the flexor carpi ulnaris also point to
proximal ulnar nerve entrapment.
REFLEXES: no change
Fig 7; right FDI/ADM weakness
Fig 8; L thumb flexor weakness
(right side of picture)
Ulnar Nerve Lesion
With an ulnar nerve injury at the medial epicondyle of the humerus the muscles
paralyzed are the flexor carpi ulnaris, medial half of the flexor digitorum profundus,
medial two lumbricals, all interossei and the adductor pollicis. The appearance of the
hand is indicative of the muscles involved. The thumb is abducted and extended with
the distal phalanx flexed. The first two fingers are fully extended with a slight flexion of
the distal phalanges. The medial two fingers are hyperextended at the
metacarpophalangeal joints but flexed at the distal phalangeal joints. The hand
resembles a "claw" and is called a claw hand.
Radial nerve injury above the elbow =>
the patient cannot extend the wrist, but he
can minimally (passively) extend the
fingers by markedly flexing the wrist =>
therefore always test the radial nerve by
asking the patient to extend the wrist +
fingers simultaneously
Wrist Drop
The radial nerve may be injured as it passes along the spiral groove of the humerus
following factures of the humerus. The nerve has also been known to be injured due to
prolonged pressure of the back of the arm on the edge of an operating table.
Findings: The branches to the triceps are spared in this injury so that extension of
the elbow is possible. The long extensors of the forearm are paralyzed and this
will result in a "wrist drop". There is a small loss of sensation over the dorsal
surface of the hand and the dorsla sufaces of the roots of the lateral three fingers.
MEDIAN NERVE ENTRAPMENT AT THE WRIST
1. Commonly bilaterally and the dominant hand is often affected first and more severely.
2. Numbness over radial three and a half fingers; nocturnal numbness, improves with
shaking of hand; may be seen with pregnancy, acromegaly, etc.
3. Clumsiness/weakness of thumb; wasting/weakness of thenar muscles (Fig. 3)
4. Consider testing if appropriate for a systemic causes if there are features of a
neuropathy elsewhere, e.g. renal function,
blood sugar, thyroid function test. If history
of trauma consider xray of carpal tunnel.
Electrophysiological studies to determine
terminal motor latency, sensory nerve
conduction velocity, abnormal wave form
or amplitude of thenar muscle EMG.
5. Treatment: if the compression is mild,
the motor function is preserved and the
numbness is not severe, adjustment of
hand and wrist movements in work and
activity of daily living will help improve
symptoms. Resting splint during sleep
in neutral or in slightly dorsiflexion will
improve numbness. Some patients may
respond to ultrasound treatment or
diuretics. Others need surgery.
Fig 3; thenar atrophy of superior hand
The radial nerve may be injured in the axilla, in the spiral groove and in the posterior
compartment of the forearm.
•In the axilla the nerve can be compressed (by a crutch, or by a chair-back), or stretched
by dislocation of the shoulder joint. In this case the elbow extensors and extensors of the
wrist and digits are paralysed, resulting in wristdrop. There is a sensory loss to a narrow
strip of skin on the back of the forearm and on the dorsum of the hand and lateral three
and one half digits.
•Injury to the radial nerve in the spiral groove presents a different picture. Injury at
this site is either due to compression against the humerus or fracture of the
humerus. Injury most commonly occurs distal to the origin of the nerve supply to
the elbow extensors and the cutaneous supply to the forearm. The loss therefore
results in wristdrop and a small area of sensory loss on the dorsum of the hand
and digits.
•The radial nerve may also be injured in fractures of the proximal radius, resulting in loss
of the extensons of the digits. Extensor carpi radialis will be undamaged and may be
able to extend the wrist.
The Common Peroneal Nerve
The common peroneal nerve leaves the popliteal fossa between the tendon of biceps
femoris and the lateral head of gastrocnemius. It crosses behind the head of the fibula
and passes laterally around the neck of the fibula (where it may be palpated). The nerve
gives of the sural communicating branch to the sural nerve, and the lateral cutaneous
nerve of the calf. The nerve pierces the peroneus longus muscle to divide into deep and
superficial branches.
The deep peroneal nerve supplies the muscles of the anterior compartment - the tibialis
anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius and
extensor digitorum brevis. The deep peroneal nerve supplies cutaneous branches to the
cleft between the big toe and the second toe.
The superficial peroneal nerve supplies the muscles in the lateral compartment
(peroneus longus and brevis) and the skin over the anterior lower leg and dorsum of the
foot
“Sciatica” typical history:
• Sharp, burning, stabbing pain radiating down the posterior or lateral
aspect of the leg, to below the knee. Pain is generally superficial and
localized, and is often associated with numbness or tingling.
• In more advanced cases, motor deficit, diminished reflexes or
weakness may occur.
• The relatively uncommon central disc herniation provokes low back
pain and saddle pain in the S1 and S2 distributions.
• A central herniated disc may also compress nerve roots of the cauda
equina, resulting in difficult urination, incontinence or impotence. In
such cases, emergency surgery is needed to prevent permanent
loss of function.
• Pain caused by low back strain is exacerbated during standing and
twisting motions, whereas pain caused by central disc herniation is
worse in positions (such as sitting) that produce increased pressure
on the anular fibers. Questions about whether the patient's pain
became worse while driving to the appointment and sitting in the
waiting room may be revealing. The pressure on the intervertebral
disc is increased during sitting and bending postures, as opposed to
standing or recumbent positions.
Intervertebral disc herniation
The lumbar roots emerge from below their respective vertebrae. These roots are
vulnerable just above their exit foramina, as they are then the most ventral
(anterior) and most lateral root in the vertebral canal and lie in the immediate path
of a lateral disc herniation (L5 in the drawing on the right below). The
intervertebral disc lying between vertebrae L4 and L5 is called the L4/5 disc. The
disc between the L5 vertebrae and the sacrum is the L5/S1 disc. Since the L4
root emerges above the L4/5 disc, a lateral herniation of the L4/5 disc damages
the L5 root. Moreover, a lateral herniation of the L5/S1 disc damages the S1
root. KNOW THIS COLD!!
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Location of Pain, Sensory & Motor Deficits with Lumbosacral Nerve Root Involvement
Disc level
Location of pain
Motor deficit
T12-L1
Pain in inguinal
region and medial
thigh
None
L1-2
Pain in anterior and
medial aspect of
upper thigh
Slight weakness in
quadriceps; slightly
diminished
suprapatellar reflex
L2-3
Pain in anterolateral
thigh
Weakened
quadriceps;
diminished patellar or
suprapatellar reflex
L3-4
Pain in posterolateral
thigh and anterior
tibial area
Weakened
quadriceps;
diminished patellar
reflex
L4-5
Pain in dorsum of
foot
Extensor weakness
of big toe and foot
L5-S1
Pain in lateral aspect
of foot
Diminished or absent
Achilles reflex
W
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Sensory Changes
PAIN:
lines,
circles
and
gray
areas
SENSORY:
dots
Findings in a L5 root:
Motor:
ankle dorsiflexion
foot eversion
foot inversion*
hip abductors*
Reflexes:
none
Normal heel walking
Sensory
L5 = dorsum big toe
S1 = lateral foot
*Preserved in a peroneal
Neuropathy vs. L5 root
This patient was asked to
dorsiflex his feet. There was
loss of sensation in the
dorsum of the left foot and the
lateral aspect of the left shin.
Findings in a S1 root:
Motor: ankle plantar flexion + hip extensors
Reflexes: Achilles; S1, 2
Sensory
L5 = dorsum big toe
S1 = lateral foot
Normal toe walking
Potential Emergencies
• Consider a fracture
– Major trauma (motor vehicle accident, fall from height)
– Minor trauma or strenuous lifting in an older or osteoporotic patient
• Consider infection/tumor
–
–
–
–
–
–
Age >50 years or <20 years
History of cancer
Constitutional symptoms (fever, chills, unexplained weight loss)
Recent bacterial infection
Intravenous drug use
Immunosuppression (corticosteroid use, transplant recipient, HIV
infection)
– Pain worse at night or in the supine position
• Consider cauda equina syndrome
– Saddle anesthesia
– Recent onset of bladder dysfunction
– Severe or progressive neurologic deficit in lower extremity
Radiculopathy Practice question 1
Which of the following statements is TRUE regarding compression
radiculopathy?
the most common cause is vascular in origin
only dorsal roots are involved
only ventral roots are involved
they occur only near the intervertebral canal
intervertebral disc herniation is the most common cause*
Radiculopathy Practice question 2
Which of the following is the hallmark deficit resulting from root
compression?
anesthesia
analgesia
Pain*
spasticity
rootbeer
Questions
• Clinical findings in Bell’s palsy
• How is it distinguished from a stroke?
• Treatment of Bell’s palsy
Peripheral Seventh Nerve Lesions
CENTRAL LESION
PERIPHERAL LESION
Rt peripheral VII
Rt peripheral VII
Rt hemifacial spasm
Abnl vol central Rt facial weakness Nl invol central Rt facial control
Sl Abnl vol central Lt facial weakness Markedly abnl invol central Lt facial control
Gilden, D. H. N Engl J Med 2004;351:1323-1331
Gilden, D. H. N Engl J Med 2004;351:1323-1331
Treatment of Bell Palsy
Eye care. This is the primary concern in Bell palsy. Lubricating eye drops during the
day and an ointment-like petrolatum at night are usually effective. Taping the eye
closed when sleeping, or using an eye patch that will not abrade the cornea may
be required. Rarely, a temporary tarsorrhaphy may be used to protect the globe.
Prednisone. Prednisone therapy is probably of value in the treatment of Bell palsy
(Grogan and Gronseth 2001). Most quoted studies have agreed with these
findings, and although the benefit of steroids is modest, early intervention is
valuable in preventing denervation and, thus, disability. A reasonable protocol is to
use 1 mg/kg prednisone per day (up to 60 mg) for 5 days and if the paralysis is
incomplete, taper the prednisone over 5 days. If the paralysis is complete then
treatment is continued for 10 days and then tapered over a further 5 days.
Prednisone treatment should not be stopped abruptly because of the possible risk
of rebound edema and clinical worsening. To be of any value, it should be started
within 7 days of clinical onset, ie, before neuronal denervation is established.
Acyclovir treatment. This treatment is possibly of value in the early stages of Bell
palsy (Grogan and Gronseth 2001). Combination acyclovir (2000 mg/day in divided
doses) and prednisone has been shown in a single, small, double-blinded,
controlled study to be superior to prednisone alone. Thus, although early use of
prednisone is indicated, and combination acyclovir and prednisone may prove
superior to prednisone alone, at this time further pivotal combination studies are
warranted.
Laboratory Testing
• How are nerve conduction studies (NCS)
and electromyography (EMG; i.e., needle
examination) performed?
• What information is provided by them?
DEFINITION OF ELECTROMYOGRAPHY (EMG)/NERVE CONDUCTION
STUDIES (NCS)
The EMG/NCS examines nerves from just outside the spinal cord to the skin.
Nerves have long projections called axons that carry electrical signals. Axons are
surrounded by supporting cells called schwann cells, which produce myelin.
Myelin acts like an insulator for the axons and makes nerve signals travel faster.
In addition, because nerves go into muscles and give signals to muscles causing
muscle contraction, the EMG/NCS also tests muscles. Abnormalities with the
peripheral nervous system (all nerve tissue outside the brain and spinal cord),
including the insulating myelin and muscles, can all be evaluated with
EMG/NCS. While EMG/NCS can detect many different problems with nerves or
muscles, some of the more common are covered below.
Cervical or Lumbar Radiculopathy
A radiculopathy is the term used for pain radiating from the neck (cervical) or
low back (lumbar). There are many causes for radiculopathy; one is herniated
discs. The intervertebral discs are one of the weight bearing structures in the
neck and back. These discs can become degenerated and can herniate,
pressing on nearby nerves and causing the radiating pain. Often, herniated
discs squeeze nearby nerves as they pass causing damage. An EMG/NCS can
evaluate the severity of the nerve damage due to discs.
Peripheral Neuropathy
Many common medical conditions like diabetes can cause nerve damage. In
such cases, the longest nerves are usually affected first; hence the name
peripheral neuropathy. Whether the diabetes is controlled with diet, oral or
injectable medications, there is often nerve damage. An EMG/NCS can
evaluate the severity and monitor any progression of a peripheral neuropathy.
Myopathy
A myopathy is a disease that is localized to the muscle and muscle
supporting structures. Myopathies are hereditary (inherited from a mother or
father) or acquired (from infection or underlying medical condiction). A
patient will usually present with proximal muscle weakness and perhaps
myalgias (muscle aches). An EMG/NCS can localize the disease process in
such cases and aid diagnosis.
Focal Neuropathies
A focal neuropathy is when a single nerve suffers damage at a specific site
along the its course. There are an infinite number of possible focal
neuropathies in the body, but the most common example is carpal tunnel
syndrome. Carpal tunnel syndrome is when the nerve to the hand is
squeezed at the wrist causing numbness, tingling and pain. An EMG/NCS
evaluates the severity and location of such focal neuropathies.
Nerve Conduction Studies
Ulnar sensory / Vth
Distance = 11 cm
Stim points:
Elbow/Wrist
ELECTROMYOGRAPHY: NEEDLE EXAMINATION;
SOME EXAMPLES
Vignette
• 7 yo boy with 1 yr of progressive walking
problems;
• Older brother died of progressive
weakness five years ago
• Exam: moderate quadriparesis, preserved
but diminished reflexes, calf hypertrophy
and intact sensation.
Duchenne muscular dystrophy
Gower’s sign
Chromosome Xp21; Recessive; Genotype: Dystrophin
DMD: Hypertrophic
leg muscle
Duchenne Muscular Dystrophy
•
•
•
•
•
•
•
Onset 3 to 5 yrs
Weakness: Proximal > Distal’ Symmetric; Legs & Arms; Most involved
muscles: Adductor magnus in legs; relatively spared muscles: Gracilis &
Sartorius
Course: Reduced motor function by 2 to 3 years; steady decline in strength:
After 6 to 11 years ; Gowers sign: Standing up with the aid of hands pushing
on knees; failure to walk: 9 - 13 years; Later with steroid treatment
Features; muscle hypertrophy; epecially calves; contractures of the ankles,
hips and knees; scoliosis; dilated cardiomyopathy; mental retardation and
night blindness
Course: death between 15-25 yrs due to respiratory or cardiac failure
Laboratory findings: very high CK; elevated troponin I, AST and ALT
Diagnostic testing
– Muscle: Staining for dystrophin protein absent
– Genetic: Deletion, Duplication, Small mutation, Point mutation
Vignette
• 23 yo woman with fluctuating ptosis, diplopia,
dysarthria, and walking difficulty without sensory
symptoms.
Repetitive nerve stimulation: Decrement
Ptosis
Ocular Manifestations of Myasthenia Gravis
MG: Limitation of adduction
MG: Ptosis
Vignette:
59 yo man with 9 month h/o progressive gait
difficulty. Exam demonstrates mod-severe
weakness, atrophy, fasciculations in the LE s
but more severe on the right, crossed adductor
reflexes, 4 beats of ankle clonus and intact
sensation.
A normal spinal cord is shown compared to the cord of a patient with
ALS to highlight the difference in size of the nerve roots. The atrophy is
apparent in the ALS cord.
Vignette:
52 yo woman with 1 yr h/o burning pain & allodynia in the
feet. Exam demonstrates decreased pp and temp in both
forefeet.
Bilateral foot drop from neuropathy