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Neuromuscular disease


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Title: Neuromuscular disease

Board Review- Neuromuscular Disorders
  • Which muscle fiber is characterized by
    fast-twitch oxidative metabolic properties?
  • (a) Type 1
  • (b) Type 2a
  • (c) Type 2b
  • (d) Type 3

  • (B) Humans have 2 primary types of muscle fiber.
    They are divided according to many different
    characteristics, including speed of contraction
    and sources of fuel. Type 1 muscle fibers are
    slow-twitch with oxidative metabolic pathways.
    Type 2 muscle fibers are fast-twitch fibers. The
    type 2 fibers can then be further divided into
    fast-twitch oxidative (type 2a) and fast-twitch
    glyclolytic (type 2b). There are no muscle fibers
    designated as type 3.

  • Duchenne/Becker muscular dystrophy is a defect
    within codes 4 dystrophy molecule located
  • XP 11
  • XP 16
  • XP 21
  • XP 18

  • C XP 21 X-linked recessive

  • Which one of the following characteristics is
    typically associated with Charcot Marie Tooth
    (CMT) disease type 2?
  • (a) minimal level of disability.
  • (b) minimal decrease in nerve conduction
  • (c) autosomal recessive inheritance.
  • (d) absence of sensory deficits.

  • (B) minimal decrease in nerve conduction
  • Charcot Marie Tooth (CMT) disease type 2 has
    greater variability and produces more disability
    than type 1. The disability can range from very
    mild to severe in CMT type 2. In addition to the
    weakness typical of the hereditary sensory motor
    neuropathy diseases, paresis of diaphragm, vocal
    cord, and intercostal muscle has been reported.
    CMT type 2 disease is characterized by less
    hypertrophic change in myelin, with more neuronal
    or axonal involvement. Sensory deficits are
    common to both forms. Both have autosomal
    dominant inheritance.

  • All of the following is true about ALS except
  • Characterized by progressive degeneration and
    loss of motor neurons and cortex, brain stem and
    spinal cord.
  • Spares bulbar function
  • Affects respiratory and limb musculature.
  • Results in both upper motor neuron and lower
    motor neuron signs.

  • B. Spares bulbar function
  • ALS does affect cranial nerves (bulbar function)

  • ALS typically affects males or females more
  • Males
  • Females

  • A Males 1.5-2.01 ratio approaching 11 with
    increasing age over 70.
  • Remember Lou Gehrig !

  • All of the following suggest a poor prognosis of
    the ALS patient except
  • Upper motor neuron signs at the time of
  • Short duration of time from onset of symptoms.
  • Older age of onset
  • Bulbar dysfunction early in disease course.
  • Pulmonary dysfunction early in disease course.

  • A Upper motor neuron signs at the time of
  • Typically it is lower motor neuron signs at the
    time of diagnosis not upper motor neuron signs to
    suggest a poor prognosis.
  • Older age at time of onset
  • Bulbar dysfunction early in disease course
  • Pulmonary dysfunction early in disease course
  • Short period of time from onset of symptoms to
  • Lower motor neuron signs at the time of diagnosis.

  • All of the following needle EMG findings in LMN
    dysfunction in ALS patients would be suspected
  • Increased MUAP amplitude, increased duration and
    polyphasic potentials.
  • Decreased MUAP amplitude, short duration,
    polyphasic potentials.
  • myotonic discharges
  • Increased jitter single fiber needle EMG.

  • A Youd expect a neuropathic pattern on needle
  • Increased MUAP amplitude, increased duration,
    decreased recruitment, polyphasic potentials.
  • Denervation potentials (fibrillations and
    positive sharp waves) would also be expected.
  • Jitter on single fiber EMG is more suggestive of
    myasthenia gravis.
  • Decreased MUAP amplitude, decreased duration is
    more suggestive of myopathies.

  • 72-year-old Caucasian male with PMH of
    hypertension, atrial fibrillation, BPH,
    aggressive weakness and functional disability
    from advancing ALS. Now progressive swallowing
    dysfunction and sialorrhea. He decided to manage
    his sialorrhea and the best choice would be?
  • Amitriptyline
  • Scopolamine
  • Bethenachol
  • Botox parotid gland injection

  • D Botox parotid gland injection
  • Anticholinergic medications have a relative
    contraindication in patients with glaucoma, BPH,
    and cardiac conduction disorders. Botox would
    probably be an excellent choice in this case.

  • A 70-year-old man presents with a 3-month history
    of numbness in patchy areas over the limbs and
    torso. His numbness began in the left foot, then
    the right hand, followed by numbness over the
    back and all the limbs. He has no complaints of
    bowel or bladder problems. He has a long history
    of smoking. His examination reveals normal
    strength, normal cranial nerve function, but
    sensation is decreased to pin prick, vibration,
    and position in the limbs. Deep tendon reflexes
    are absent. Electrophysiologic studies show
    normal motor nerve conduction and needle
    examination of the upper and lower limb muscles.
    The sensory nerve conduction studies show small
    or absent responses. Based on this information
    what test would you order next?
  • (a) Nerve and muscle biopsies
  • (b) Radiologic studies to assess for a tumor
  • (c) Skin biopsy to assess small nerve fibers
  • (d) Repetitive nerve conduction studies

  • (B) The clinical and electrophysiologic
    presentation is consistent with a sensory
    neuropathy. With no evidence to suggest motor
    involvement, the numbness is likely a disorder of
    the dorsal root ganglion. There are only a few
    distinct disorders associated with acute or
    subacute cases described by the history and
    physical in this clinical vignette. They may be
    part of a paraneoplastic syndrome, connective
    tissue disorder such as Sjogrens, a post
    infectious condition, pyridoxine intoxication, or
    as an isolated autoimmune process. In this
    patient with a history of smoking, a cancer work
    up would include obtaining anatomic studies of
    the chest. Biopsies of the nerve, muscle, or skin
    would not add much to the case. Repetitive nerve
    conduction studies would be considered if a
    neuromuscular junction disorder was suspected.

  • Which are the typical histologic characteristics
    of patients with post polio syndrome.
  • Motor units are 7-8 times larger.
  • High PMNs count found surrounding sarcolemma.
  • Muscle biopsy shows frequent, isolated, atrophic
    fibers rather than groups of atrophic fibers.
  • Fiber type grouping
  • A C
  • B D
  • All of the above

  • E A C
  • Histologic evidence indicates motor units are 7-8
    times larger than normal due to ongoing
    denervation reinnervation. Over time,
    denervation becomes permanent. Muscle biopsy
    shows frequent isolated atrophic fibers rather
    than groups of atrophic fibers.

  • Post polio muscle pain is thought to be secondary
  • Persistent muscle spasticity
  • Likely due to mechanical joint fatigue and
  • Neuropathic pain from spinal cord neuron damage.
  • Inflammatory myopathy

  • B. Likely due to mechanical joint fatigue and
  • Post polio muscle pain characterized often by
    superficial burning, cramping and tired feeling
    or a deep muscle ache commonly occurs with muscle
    overuse. Is likely due to muscle strain, fatigue
    and overuse of the joint and muscle. Usually it
    occurs at night or after activity. Neuropathic
    pain in PPS can occur but typically from
    entrapment neuropathies such as CTS or
    radiculopathy rather than spinal cord neuron

  • The polio foot is characterized by the
  • Atrophy, foot drop
  • Lymphedema
  • Erythema and burning foot pain.
  • Ankle contracture/soft tissue contracture

  • B. typical changes of post polio foot include
    skin changes, lymphedema. Secondary to polio
    vascular beds in the limb have not developed
    normally and lymphedema ensues.

  • All of the following are true about the use of
    steroids in the treatment of Duchenne muscular
    dystrophy except
  • Steroids are the only pharmaceutical palliative
    treatment available for Duchenne
  • Prolongs motor function
  • Reducing risk of scoliosis progression
  • Does not cause the problems of weight gain
    typically seen in the adult patient.

  • D steroids do in fact cause weight gain.
  • The steroids used in Duchenne muscular dystrophy
    is in fact the only pharmaceutical palliative
    treatment for Duchenne. It is not universally
    used. He does prolong motor function however
    there is a high incidence of side effects
    specifically weight gain and osteoporosis.

  • The patient in the picture above is seen in the
    outpatient clinic. Based on inspection respected
    physical diagnosis would be?
  • Disuse atrophy and weakness of the rhomboids and
  • Polyneuropathy especially affecting long thoracic
    nerve and dorsal scapular nerves.
  • FSH muscular dystrophy
  • bilateral frozen shoulder with scapulohumeral

  • C FSH muscular dystrophy

Q A patient with weakness in lower extremities
has a sural nerve biopsy. Diagnosis based on
  1. Peripheral neuropathy
  2. Werdnig Hoffman
  3. CMT-1
  4. Inflammatory myopathy


  • Spinal muscular atrophy is characterized by
    selective destruction of the anterior horn cells.
    SMA-1 and SMA-2 had similar effects and
    presentation. The primary difference between the
    two is
  • Findings on biopsy consisting of both
    hypertrophic and atrophic fibers.
  • Findings on EMG/MCV
  • SMA-1 patients never could sit
  • SMA-1 in the pediatric onset, SMA-2 is adult

  • C SMA-1 patients never gained the ability to
    sit. Fairborn A. floppy infant whereas SMA 2
    patients onset is 2-12 and therefore may be
    sitting and walking prior to onset.

  • What is the correct chronologic order that the
    following SMA syndromes occur based on onset of
  • Kugelberg Welander, SMA-2, Werdnig Hoffman
  • SMA-2, Werdnig Hoffman, Kugelberg Welander
  • Werdnig Hoffman, SMA-2, Kugelberg Welander
  • None are correct since two of these syndromes are
    not SMA syndromes.

C Werdnig-Hoffman, SMA 2, Kugelberg-Welander
  • type I (Also called Werdnig-Hoffman.) This is
    the most severe type of SMA and may be present at
    birth. Infants have problems holding their head,
    sucking, feeding, swallowing, and typically move
    very little. The muscles of the chest are also
    affected. The motion of the tongue is described
    as having "worm-like" movements. Death results
    usually by the age of two to six years from
    breathing problems.
  • type II (intermediate form) This form of SMA is
    seen in children from seven months to 18 months
    of age. They typically have generalized muscle
    weakness and may require braces, walkers, or a
    wheelchair for assistance. Life-expectancy may
    extend to the 20s and 30s.
  • type III (Also called Kugelberg-Welander.) This
    form of SMA affects children older than 18 months
    of age. These children show signs of clumsiness,
    difficulty walking, mild muscle weakness, and may
    be developmentally delayed. These children live
    long into their adult years.
  • type IV This form of SMA affects adults in their
    30s and 40s, resulting in a walking disability.

  • Which medication causes axonal neuropathy most
  • A) Vincristine
  • B) Vinblastine
  • C) Cisplatin
  • D) cyclophosphamide

  • A) Vincristine

  • A Duchennes muscular dystrophy patient has been
    describing morning headaches to his parents. On
    routine follow-up appointment you recommend for
    this complaint
  • a) MRI of brain
  • b) Nonsteroidal anti-inflammatory medications
  • c) Tylenol
  • d) Sleep study
  • e) Pulmonary function tests to rule out

  • D) Sleep study
  • Morning headaches may be a sign of sleep apnea.
    A sleep study may be more appropriate. Although
    pulmonary function tests are important for
    monitoring of Duchenne patients in this case you
    need to rule out sleep apnea.

  • All of the following myopathic conditions would
    typically demonstrate negative EMG except
  • Myophosphorylase deficiency
  • Steroid myopathy
  • Hyperthyroid myopathy
  • Inclusion body myositis

  • D inclusion body myositis are a group of
    inflammatory myopathies with MUAP and denervation
    potentials. Remember, endocrine myopathies and
    storage disease myopathies typically have
    abnormal EMG.

  • Which of the following potential neurotoxic
    agents cause axonal neuropathy?
  • Amiodarone
  • Arsenic
  • Gold
  • Tacrolimus
  • EtOH

  • E EtOH causes a typical axonal loss pattern with
    reduced SNAP and CMAP amplitudes. Neuropathies
    typically affect the legs gtarms.
  • Women her more susceptible to neuropathy
    secondary to EtOH
  • Substances the cause demyelinating disease
    include N- hexane, Suramin, amiodarone,
    chloroquine, cytosine arabinoside, tacrolimus,
    procainamide, goals, arsenic. The rest cause
    typically more axonal disease.

  • You are called to the ICU for a electrodiagnostic
    consultation to rule out critical illness
    polyneuropathy. The patient has failed weaning
    from the ventilator. She is on external pacing,
    she is on heparin for anticoagulation. The
    pulmonologist asks you to clarify whether or not
    the NCV can be done with the patient on
    pacemaker. The following is the most appropriate
  • EMG/NCV can be done on patients with pacemaker
    so long as is not done vicinity of the pacemaker.
  • EMG/NCV is contraindicated in this case.
  • EMG/NCV can be safely done without complications
    or precautions on patients with pacemakers.
  • Call the neurologist, maybe there crazy enough to
    do it.

  • B EMG/NCV is contraindicated. Why?
  • Because this patient has an external pacemaker
    and not an internal pacemaker. Patient with an
    external pacemaker should not have NCV testing.
  • AANEM recommends with implanted pacemakers there
    is little risk of harm to the patient with a
    pacemaker when performing NCVS testing unless you
    stimulate near the brachial plexus ipsilateral to
    the pacemaker .

  • Which of the following statements is true
    regarding needle EMG studies?
  • There is no contraindication to needle EMG in
    patients with prosthetic joints when sterile
    single use EMG needles are used
  • Prophylactic antibiotics are required with
    significant heart valve disease prior to the EMG
    / NCVS procedure
  • There is no significant concerns performing
    needle EMG and patients with lymphedema.
  • EMG NCV studies are contraindicated in pregnancy.

  • A There is no contraindication to needle EMG in
    patients with prosthetic joints when sterile
    single use EMG needles are used

  • What effect is having the active and reference
    electrodes closer than 3-4 cm apart?
  • Increased SNAP amplitude
  • Increased SNAP dispersion
  • Decreased SNAP amplitudes
  • This measurement will not matter as he will
    obtain the same values

  • C If the active and reference electrodes are
    placed less than 3 4 cm apart when performing a
    sensory conduction, then both electrodes will
    record similar information which is then canceled
    out leading to a decrease in the value for the
    SNAP amplitude

The potentials above are (a) complex repetitive
discharges. (b) myotonic discharges. (c)
neuromyotonia. (d) myokymia.
  • B) Myotonic discharges are single fiber
    discharges that wax and wane in frequency and

  • Which potentials have manifestations that CANNOT
    be observed on physical examination?
  • (a) Fasciculation potentials
  • (b) Myokymic discharges
  • (c) Complex repetitive discharges
  • (d) Cramp potentials

  • C CRDs can only be detected with EMG. The
    remainder of the discharges have manifestations
    that can be observed on physical exam

  • Which neuromuscular disorder is NOT usually
    associated with thyroid disease?
  • A. peripheral neuropathy
  • B. neuromuscular junction disorder
  • C. Myopathy
  • D. Radiculopathy

  • D. Thyroid disease is associated with several
    different aspects of the neuromuscular system.
    In both hypothyroidism and hyperthyroidism, there
    can be neuromuscular junction disorders
    (myasthenia), and myopathy. Hypothyroidism is
    associated with sensorimotor peripheral
    neuropathy and entrapment neuropathy, especially
    carpal tunnel syndrome. Thyroid disease is not
    associated with radiculopathy.

  • What condition casues the typical myopathic
    gait seen in a young boy with Duchenne muscular
    dystrophy with accentuated lumbar lordosis and
    toe walking?
  • (a) Hip and knee extensor weakness
  • (b) Hip flexion and ankle plantar flexion
  • (c) Hip extensor weakness and plantar flexion
  • (d) Hip flexion contracture and knee extensor

  • A) Hip and knee extensor weakness

  • Factors associated with poor prognosis in
    multiple sclerosis include
  • (a) female gender.
  • (b) age at onset less than 20 years.
  • (c) cerebellar involvement at onset.
  • (d) relapsing remitting course at onset.

  • C Patients have a poor prognosis if they are
    male, gt35 y/o, polysymptomatic, rapidly
    progressive, motor symptoms, ataxia, tremor, high
    rate of relapse

  • Which of the following neuropathies has the
    slowest conduction velocity?
  • A. dejerine sottas
  • B. friedreichs ataxia
  • C. fabrys disease
  • D. CMT type 1
  • E. CMT type 2

  • A. Dejerine Sottas CV is usually less than 10 m/s

  • MS patients experience a marked sensitivity to
    heat. This is called
  • A. Lhermittes sign
  • B. Uhthoffs phenomenon
  • C. Hoffmans sign
  • D. Kennedy phenomenon

  • B. Uhthoffs phenomenon

  • All of the following diseases may present with
    ptosis except
  • A. Myasthenia Gravis
  • B. Botulism
  • C. Myotonic Dystrophy
  • D. Fascioscapulohumeral dystrophy

  • D. Fascioscapulohumeral dystrophy
  • In FSH, the extraocular muscles are spared

(No Transcript)
  • A patient having difficulty late in the day
    getting up from a chair, going up or down stairs,
    and reaching with his arms presents for
    electrodiagnostic studies.
  • Physical exam demonstrates normal DTRs and normal
    findings on manual muscle testing.
  • Standard sensory and motornerve conduction
    studies are normal. Repetitive axillary nerve
    stimulation (RNS) performed at 2Hz demonstrates
    20 decremental response.
  • Immediately after exercise, the RNS decrement is
    no longer observed. Three minutes following
    exercise, however, the decrement is greater.
    Needle EMG results are normal.

  • (SAE)

  • Upon further investigation, you would most likely
    find what additional clinical finding?
  • (a) Asthma
  • (b) Dry mouth
  • (c) Ptosis
  • (d) Skin rash

  • C. Ptosis
  • The patient presents with myasthenia gravis
  • (MG), a postsynaptic neuromuscular junction
  • disorder. Ptosis and extraocular weakness often
  • occur in MG.
  • Lambert-Eaton myasthenic syndrome (LEMS), a
  • presynaptic neuromuscular junction disorder,
  • would demonstrate postexercise facilitation (at
  • least 100 increase in first response CMAP
  • immediately following exercise) and likely have
  • low-amplitude baseline CMAP results. Autonomic
  • symptoms such as dry mouth often accompany
  • LEMS.

  • Long-term steroid treatment for asthma may
  • cause myopathy without significant needle EMG
  • results, but RNS would be normal.
  • Although dermatomyositis typically presents with
    proximal weakness, no abnormalities
    characteristic of an inflammatory myopathy were
    seen on needle electromyography.

  • Which muscle group displays the earliest pattern
    of weakness in Duchenne muscular dystrophy?
  • A. Ankle dorsiflexors
  • B. Neck flexors
  • C. Shoulder flexors
  • D. Knee extensors
  • (SAE)

  • B. Neck flexors
  • In Duchenne muscular dystrophy, weakness is first
    seen in the neck flexors during preschool years.
    Pelvic girdle weakness precedes shoulder girdle
    weakness by several years.
  • Ankle dorsiflexors are weaker than
    plantarflexors ankle everters are weaker than
    inverters knee extensors are weaker than
    flexors hip extensors are weaker than flexors.

  • In performing motor nerve conduction studies,
    what is the effect on the compound muscle action
    potential (CMAP) of placing the recording
    electrodes (active and reference) closer
    together, over the same muscle?
  • A. No effect on the onset latency of the CMAP
  • B. An increase on the CMAP amplitude
  • C. A prolongation of the peak latency
  • D. A decrease in the calculated conduction

  • (SAE)

  • A. No effect on the onset latency of the CMAP
  • If the active and reference electrodes are placed
    too close together, similar waveforms will be
    recorded on both sites and these waveforms will
    be rejected. This will result in an CMAP
    amplitude drop. There is no effect on the onset

  • What feature is suggestive of polymyositis?
  • A. Distal symmetric weakness without pain
  • B. Reduced motor nerve conduction velocities and
    conduction block
  • C. Electromyography with low voltage, polyphasic
  • D. Brisk tendon reflexes
  • (SAE)

  • C. Electromyography with low voltage, polyphasic

  • Cognitive deficits are common in
  • A. Duchenne muscular dystrophy
  • B. Inclusion body myositis
  • C. Fascioscapulohumeral dystrophy
  • D. Becker muscular dystrophy

  • (SAE)

  • A. Duchenne muscular dystrophy
  • Brain isoform of dystrophin exists and there are
    documented mildly decreased Intelligence Quotient
    scores in people with Duchenne muscular
    dystrophy. These lower scores may be specific to
    deficits with tasks requiring attention to
    complex verbal information.

  • All hereditary sensory motor neuropathies are
    characterized by
  • A. Decreased intelligent quotient scores
  • B. Spinal deformities
  • C. Muscle weakness
  • D. Joint contractures

  • (SAE)

  • C. Muscle weakness
  • The residual muscle force in the later stages of
    the disease is 20-30 of normal. Intelligence
    quotient reduction, significant joint
    contractures, pulmonary/cardiac abnormalities and
    spinal deformities are not typical of HSMN.

  • Which symptom is most predictive of cardiac
    disease in Duchenne muscular dystrophy?
  • A. Palpitations
  • B. Syncope
  • C. Dyspnea
  • D. Cachexia

  • (SAE)

  • C. Dyspnea
  • The most frequent predictive symptom is dyspnea.
  • Absence of exertion dyspnea from lack of physical
  • activity allows myocardial impairments to remain
  • clinically silent and difficult to detect. A high
  • of suspicion is required.
  • Electrocdardiogram abnormalities in both
  • Duchenne and Becker muscular dystrophy patients
  • are attributed to progressive fibrosis of the
  • conduction system and impairment in the cardiac
  • autonomous nervous system.
  • Palpitations and syncope will be related to the
  • conduction abnormalities and occurs late in the
    disease process.

  • Cachexia is a late finding that occurs when
  • becomes difficult as a result of heart failure
  • dyspnea

  • A prominent feature of the most common form of
    CharcotMarie-Tooth disease is
  • A. Truncal ataxia
  • B. Sensory impairment
  • C. Severe proximal weakness
  • D. Mild mental retardation

  • (SAE)

  • B. Sensory impairment

  • A 36 year-old man has a known history of HIV.
    His family has observed worsening confusion and
    memory loss. He later develops progressive
    paraparesis, ataxia, posterior column sensory
    loss, and neurogenic bowel and bladder. The most
    likely diagnosis is
  • A. Viral myelitis
  • B. Multiple sclerosis
  • C. Cytomegalovirus (CMV) polyradiculopathy
  • D. Vacuolar myelopathy
  • (SAE)

  • D. Vacuolar myelopathy
  • Vacuolar myelopathy is the most common cause of
    spinal cord dysfunction in (HIV) patients, being
    found in 11 to 22 of acquired immunodeficiency
    disease (AIDS) cases, and demonstrable in as many
    as 40 of cases at autopsy. It is strongly
    associated with HIV dementia, and shares a
    virtually identical histopathology. The other
    diagnoses are less common, and can be ruled out
    or in with imaging, laboratory and
    electrodiagnostic studies.

  • A 40-year-old woman is currently
  • hospitalized for a severe flare of her
  • On consultation, you recommend that while in the
  • hospital she begin
  • (a) passive range-of-motion exercises to prevent
  • (b) isometric strengthening exercises at the
    bedside to maintain her strength.
  • (c) ambulation with a walker in the hallways
    supervised by her therapist.
  • (d) strengthening exercises with light hand and
    ankle weights.
  • (SAE)

  • (a) passive range-of-motion exercises to prevent
  • Passive range of motion to maintain joint
    movement is recommended during periods of acute
    flares. With resolution of the flare,
    active-assisted exercises may be started,
    progressing to strengthening exercises and

  • Which statement regarding glossopharyngeal
    breathing is TRUE?
  • A. It is typically useful in patients with weak
    oropharyngeal muscles
  • B. It is recommended therapy in a patient with
    laryngeal cancer
  • C. It is generally used when a patient has a
  • D. It is a useful backup for any mechanical
    failure of ventilatory assistance

  • (SAE)

  • D. It is a useful backup for any mechanical
    failure of ventilatory assistance