BMB 2 - Neuromuscular Disorders Flashcards
Define paresis.
Weakness of voluntary movement
Define fasciculation.
Muscle twitch
What are the major signs of an upper motor neuron injury?
Spastic paresis, increased reflexes
What are the major signs of a lower motor neuron injury?
Flaccid paresis, decreased reflexes, fasciculations and fibrillations
What term refers to injury to nerve myelin which spares the axon itself?
Neurapraxia
What term refers specifically to axonal damage?
Axonotmesis
What term refers to nerve injury that also extends to the surrounding connective tissue?
Neurotmesis
State whether the following nerve fiber is large or small, myelinated or unmyelinated, and also state the function: A-alpha
Large
Myelinated
Proprioception / vibratory sensation / motor function
State whether the following nerve fiber is large or small, myelinated or unmyelinated, and also state the function: A-beta
Large
Myelinated
Proprioception / vibratory sensation / motor function
State whether the following nerve fiber is large or small, myelinated or unmyelinated, and also state the function: A-gamma
Medium
Myelinated
Motor function
State whether the following nerve fiber is large or small, myelinated or unmyelinated, and also state the function: A-delta
Small
Myelinated
Pain / temperature / autonomics
State whether the following nerve fiber is large or small, myelinated or unmyelinated, and also state the function: C-fibers
Small
Unmyelinated
Pain / temperature / autonomics
Describe type 1 muscle fibers in terms of twitch speed, duration and intensity of use, and fatigue rate.
Slow-twitch, endurance / low fatigue rate
Describe type 2A muscle fibers in terms of twitch speed, duration and intensity of use, and fatigue rate.
Fast-twitch, moderate duration and intensity of use, moderate fatigue rate
Describe type 2B muscle fibers in terms of twitch speed, duration and intensity of use, and fatigue rate.
Fast-twitch, short duration and high intensity of use, quick fatigue rate
Which muscle fiber type is slow-twitch?
1
Which muscle fiber type is fast-twitch but still oxidative?
2A
Which muscle fiber type is glycolytic?
2B
Name the dermatome found at the following locations:
Bottom of the neck –
Nipples –
Umbilicus –
Inguinal area –
Knees –
Name the dermatome found at the following locations:
Bottom of the neck – C4
Nipples – T4
Umbilicus – T10
Inguinal area – L1
Knees – L4
Name the dermatome found at the following locations:
Thumb –
Middle finger –
Pinky and ring finger –
Name the dermatome found at the following locations:
Thumb – C6
Middle finger – C7
Pinky and ring finger – C8
Name the dermatome found at the following locations:
Great toe –
Middle three toes –
Pinky toe–
Name the dermatome found at the following locations:
Great toe – L4
Middle three toes – L5
Pinky toe – S1
Which nerve roots are tested using the triceps reflex?
C7, C8
Which nerve roots are tested using the biceps reflex?
C5, C6
Which nerve roots are tested using the brachioradialis reflex?
C5, C6
Which nerve roots are tested using the patellar reflex?
L3, L4
Which nerve roots are tested using the achilles reflex?
S1, S2
Which nerve is tested using the jaw jerk / masseter reflex?
CN V3
True/False.
The Babinski reflex is a polysynaptic motor reflex.
False.
The Babinski reflex is a polysynaptic cutaneous reflex.
How does one elicit a Babinski reflex?
Drag sensation along lateral foot and then across the ball of the foot
What is a normal Babinski reflex in an adult?
Toes curl downwards
What is an abnormal Babinski reflex in an adult (or most individuals over ~15 months)?
Toes curl upwards and fan out
An upward Babinski reflex in an adult suggest what?
UMN damage of the corticospinal tract
What is the normal motor function of the median nerve in relations to the hand?
Innervation of the abductor policis brevis and opponens policis
A patient experiences a tingling sensation in their hand when you tap on their median nerve. This is known as the ________ sign.
A patient experiences a tingling sensation in their hand when you tap on their median nerve. This is known as the Tinel sign.
If you can recreate a patient’s median nerve -related symptoms by flexing their wrist to 90° for one minute, this is known as a positive _________ test.
If you can recreate a patient’s median nerve -related symptoms by flexing their wrist to 90° for one minute, this is known as a positive Phalen test.
What might be indicated by numbness in the thumb area and an associated more proximal motor weakness in the biceps, deltoids, and forearm?
C6 lesion
(The C6 dermatome and myotome are both affected in this example.)
A patient is unable to extend her 2nd and 3rd digits. What is the cause?
Distal median n. injury
A patient is unable to flex her 2nd and 3rd digits. What is the cause?
Proximal median n. injury
A patient is unable to extend her 4th and 5th digits. What is the cause?
Distal ulnar n. injury
A patient is unable to flex her 4th and 5th digits. What is the cause?
Proximal ulnar n. injury
________ tunnel neuropathies affect branches of the median nerve, while ________ tunnel neuropathies affect branches of the ulnar nerve.
Carpal** tunnel neuropathies affect branches of the median nerve, while **cubital tunnel neuropathies affect branches of the ulnar nerve.
Ulnar neuropathies typically result in what sort of sensory and motor deficits?
Sensory changes in the hand only;
motor dysfunction in hand intrinsics (as well as some wrist/finger flexors)
(NOTE: C8 radiculopathies will be similar but also involve sensory loss of the forearm.)
Describe ‘Saturday night palsy.’
AKA radial palsy – loss of wrist/finger extension; loss of sensation to volar thumb and index finger
Where is the fibular nerve commonly compressed?
The fibular head
What is the fibular palsy presentation?
Flaccid foot drop (steppage gait), tendency to inversion
(NOTE: L5 radiculopathies will be similar but also involve gluteal weakness.)
What term refers to Herpes Zoster in the V1 distribution, resulting in blindness?
Herpes Zoster ophthalmicus
What eponymous term refers to Herpes Zoster + a facial palsy + lesions in the ear canal?
Ramsay Hunt syndrome (think Herpes zoster + Bell’s palsy)
(NOTE: treatment includes acyclovir and gabapentin)
Bell’s palsy is an idiopathic lesion of which nerve?
CN VII
Bell’s palsy is characterized by an inability to fully __________ the eye.
Bell’s palsy is characterized by an inability to fully close the eye.
Following a bicycle injury, a patient presents with an internally rotated arm and a flexed, pronated wrist. What is the eponymous term given to this condition?
Erb’s palsy
Erb’s palsy occurs due to a lesion in what?
The upper trunk of the brachial plexus (C5, C6)
Following a climbing injury, a patient presents with a claw-like hand affecting all the fingers. What is the eponymous term given to this condition?
Klumpke’s palsy
(NOTE: the elbow may be flexed and supinated as well if the C7 root is involved.)
Klumpke’s palsy occurs due to a lesion in what?
The lower trunk of the brachial plexus (C8, T1)
Upon pushing against the wall with their hands, a patient presents with a posteriorly protruding scapula. What nerve is injured and what nerve roots feed this nerve?
Long thoracic nerve
C5, C6, C7
Which muscle(s) lose innervation in lesions to the long thoracic nerve (resulting in a winged scapula)?
Serratus anterior
A suprascapular nerve palsy often leads to weakness in what two motions of the upper extremity?
Abduction;
external rotation
What is the cause of the loss of abduction and loss of external rotation seen in a suprascapular nerve palsy?
Loss of innervation of the supraspinatus and infraspinatus due to suprascapular n. impingement at thesuprascapular notch
Diabetic neuropathy typically affects which neurons more, sensory or motor?
Sensory
Diabetic neuropathy typically affects which tissue more, the axons or the myelin sheaths?
The axons
What are the main presenting features of diabetic neuropathy?
Foot ulcers, ascending numbness (starting in the toes), paresthesias
(NOTE: can also cause sweating and decreased GI mobility)
A patient with uncontrolled type II diabetes mellitus presents with proximal muscle weakness and pain in his hip and thigh. He reports that the pain started gradually and has improved over time. What is the diagnosis?
Diabetic amyotrophy
(an asymmetric, inflammatory motor neuropathy of the lumbosacral plexus)
True/False.
Hyperuremia, alcohol use, and thyroid disorders are all associated with the development of neuropathies.
True.
Hyperuremia is associated with sensorimotor issues; alcohol abuse is associated more with sensory issues (pain > numbness) than motor; etc.
Chemotherapy is associated with neuropathies, especially if containing __________.
Chemotherapy is associated with neuropathies, especially if containing platinum.
What is the classic presentation of lead poisoning -induced neuropathy?
Abdominal pain, wrist/foot drop, etc.
How do the neuropathies associated with vitamin B12 and/or copper deficiencies present?
Vibratory and sensory deficits
(subacute combined degeneration)
True/False.
Zinc deficiency can be caused by an excess in copper intake.
False.
Copper deficiency can be caused by an excess in zinc intake.
Monoclonal gammopathy of undetermined significance is associated with anti-MAG antibodies that can cause what sort of neuropathy?
Distal sensory demyelination
What disorder results due to an inherited misfolding of a vitamin A carrier, causing buildup of the carrier protein in body tissues?
Hereditary transthyretin amyloidosis
A teenage patient presents with high arches, hammer toes, and ‘champagne bottle’ legs. She reports having had balance issues and gait problems her entire life. What is the likely diagnosis?
Charcot-Marie-Tooth disorder
What is Charcot-Marie-Tooth disorder?
A demyelinating disease resulting in sensorimotor deficits
What is the most common gene involved in inheritance of Charcot-Marie-Tooth disorder?
CMT1A
(NOTE: PMP22 is the most common duplication)
30% of cases of Guillain-Barré syndrome cases are preceeded by infection with ______________, and another 10% of cases are preceded by _____________,
30% of cases of Guillain-Barré syndrome cases are preceeded by infection with Campylobacter jejuni, and another 10% of cases are preceded by CMV.
The influenza vaccine typically carries about a ____-case-per-1,000,000-vaccines-administered risk of triggering an episode of Guillain-Barré syndrome.
The influenza vaccine typically carries about a 1-case-per-1,000,000-vaccines-administered risk of triggering an episode of Guillain-Barré syndrome.
Name the most common subtype of Guillain-Barré syndrome in North America and Europe.
Acute inflammatory demyelinating polyneuropathy
True/False.
Guillain-Barré syndrome is purely a disease of ascending motor deficit due to demyelination.
False.
Guillain-Barré syndrome is a disease of ascending motor deficits and sensory loss due to demyelination.
The pathogenesis of Guillain-Barré syndrome is thought to be one of ___________ ___________.
The pathogenesis of Guillain-Barré syndrome is thought to be one of molecular** **mimicry.
Why may patients with Guillain-Barré syndrome require hospitalization?
To maintain respiration
Describe the likely lumbar puncture results in a patient with Guillain-Barré syndrome.
Elevated protein
(with < 10 WBCs / mm3)
How is Guillain-Barré managed?
IV Ig + plasmapheresis
Which demyelinating disorder is characterized by both proximal and distal muscle weakness that arises over a period of weeks, months, or even years?
Chronic inflammatory demyelinating neuropathy
(NOTE: there are variants that are purely sensory, only distal, multifocal motor and sensory, etc.)
What is the POEMS form of demyelination disorder?
Polyneuropathy
Organomegaly
Endocrinopathy
M-protein
Skin changes
Describe the basic end result of amyotrophic lateral sclerosis.
UMN and LMN damage
How does ALS typically present?
Mixed reflexes, spasticity, atrophy fasciculations;
bilateral tongue fasciculations;
jaw jerk reflex
You are presented with an infant who is increasingly ‘floppy’ and atonic. You rule out botulism and suspect what etiology?
A defect in the SMN1 gene (spinal muscular dystrophy)
Duchenne muscular dystrophy is caused by what structural etiology?
An absence of dystrophin
Becker muscular dystrophy is caused by what structural etiology?
A less functional form of dystrophin
What is the most common form of adult-onset muscular dystrophy? What is the etiology?
Myotonic dystrophy;
- CTG* repeats in the DM1 and DMPK genes
- (NOTE: shows anticipation)*
How does myotonic dystrophy present?
An adult developing myotonia (contracted muscles), atrophy of facial and temporal muscles, cardiac conduction blocks, cataracts, cognitive impairment
Most channelopathies present as what two forms?
- Periodic paralysis
- Myotonic
How do most channelopathies present? How are most managed?
Periodic paralysis;
correction of the metabolic disturbance
Which channelopathy mutation results in hyperkalemia and can be eased through a high-carb diet (which leads to increased insulin release, driving potassium into the intracellular space)?
SCN4A
Which channelopathy mutation results in hypokalemia?
CACNA15
Which channelopathy mutation is especially associated with thyrotoxicity?
KCNJ18
How do individuals with nondystrophic channelopathies typically appear?
Hypertrophic build, bulky jaws
(often heat- and/or cold-sensitive)
Name two forms of nondystrophic channelopathy.
Myotonia congenita (CLCN1);
paramyotonia congenita (SCN4A)
How are nondystrophic channelopathies typically treated?
Mexiletine or procainamide
A patient with fibromyalgia and uncontrolled diabetes presents with complaints that her ‘legs aren’t working right’ and her balance is off. What do you suspect?
Diabetic neuropathy
A diabetic patient presents with a painful, weak hip. What do you suspect?
Diabetic amyopathy
A patient presents with leg weakness one week after food poisoning.
What do you do next?
Send her to the ER for workup of Guillain-Barré syndrome
A patient presents with difficulty moving her arms over the past few months. What neuropathies do you most suspect?
Myasthenia gravis,
cervical myopathy
A patient presents with increasing issues with her balance. She is only taking over-the-counter supplements to prevent COVID infection. What do you suspect?
Zinc toxicity
(and subsequent subacute combined degeneration)
Charcot-Marie-Tooth disease mostly affects what portion of the body?
The feet
A patient presents with complaints that one of his legs has been dragging and he’s been choking on steak and hard bread over the past month.
What are you most concerned this might be?
Amyotrophic lateral sclerosis
