Intro To The PNS Flashcards by Stephan Green

What’s the relationship between nerve fiber diameter vs conduction velocity? What’s the fastest type? Slowest?

Bigger the fiber, faster the conduction

Alpha motor neuron

Unmyelinated sympathetic nerves

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What is Wallerian Degeneration?

Results when a n fiber is cut or crushed > separation from neuron’s cell body > degeneration distal to the injury

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What is radiculopathy? Caused by what? Most commonly where?

Dysfunction of the spinal n roots (PNS) causing somatosensory (pain, radiates), LMN, and autonomic (rare) issues

Intervertebral discs, osteophytes, tumors, DM, infections

Commonly arm and leg (unilateral)

C5-C7
L4-S1

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What’s a sclerotome?

The innervation level to a bone

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What sclerotomes cover the scapula?

C5-C8

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What are the dermatomes of the hands?

C6 = 1st and 2nd digits
C7 = 3rd digit
C8 = 4th and 5th digits

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What dermatome controls finger flexion and leads to its weakness?

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What’s the sclerotome for L4, L5 and S1?

Sacral bone, pts present w/ deep posterior hip pain

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Lumbosacral radiculopathy involving L4 causes:

Pain: antlat thigh, knee, medial calf

Sensory: medial calf

Weakness: hip flexion, knee extension

DTR loss: patella

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Lumbosacral radiculopathy involving L5 includes:

Pain: dorsal thigh, lat calf

Sensory: lat calf, dorsal foot

Weakness: hamstrings, foot dorsiflexion, inversion, eversion

DTR loss: none

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Lumbosacral Radiculopathy involving S1 includes:

Pain: post thigh, post calf

Sensory: postlat calf, lat foot

Weakness: hamstrings, foot plantarflex

DTR loss: Achilles

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What are the peripheral neuropathy classifications?

Mononeuropathy (entrapments)

Polyneuropathy

Mononeuropathy multiplex (multiple mononeuropathy)

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What’s a positive vs negative sensory sx in PNDs?

Negative: loss of sensation

Positive: paresthesias, pain (burning sensation, hyperalgesia, dysesthesia, hyperpathia)

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What does dysesthesia mean? Hyperalgesia? Hyperpathia?

Dysesthesia: pain upon gentle touch

Hyperalgesia: lowered threshold to pain

Hyperpathia: pain threshold is elevated but pain is excessively felt

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In PND both large and small fibers can be affected. What sensations are associated w/ these?

Large: light-touch, two-point discrimination, vibration, joint position sense

Small: temp perception, pain (pin prick)

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Are fasciculations associated w/ upper or lower MN dysfunction?

Lower

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Are hyperactive DTRs associated w/ central or PNS dx? Babinski sign?

CNS

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What is the Babinski sign?

Stimulation of the sole of the foot w/ a sharp instrument, toes will fan and the big toe extends in positive tests (indicating a UMN lesion)

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What’s a way to differentiate median n entrapment by the flexor retinaculum vs pronator teres?

Teres has an absence of nocturnal awakening

Teres involves easy fatigue of the forearm muscles

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What sign may indicate anterior interosseous n (branch of median n) entrapment?

Positive OK sign where the pt is UNABLE to make the OK sign.. instead pointer and thumb cannot flex and lie flat

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What are the 3 entrapments associated w/ the median n?

Carpal tunnel
Pronator syndrome
Anterior interosseous syndrome

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What are sites of entrapment for the ulnar n?

Axilla
Elbow (between medial epicondyle and olecranon)
Cubital tunnel (tendinous arch of FCU)
Wrist (Guyon’s canal)

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What two bones form Guyon’s canal? What n entrapment is this associated w/?

Pisiform and hamate

Ulnar

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What is Froment sign? What’s it associated w/?

Pt must flex thumb to hold a piece of paper between their fingers

Ulnar n entrapment

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What mm are associated w/ ulnar mononeuropathy at the elbow?

``` 1 dorsal interosseous Abductor digiti minimi Adductor policis Flexor carpi ulnaris Flexor digitorum profundus ```

What two bones can the ulnar n get entrapped between in the elbow?

Medial epicondyle and olecranon

What are the 4 n entrapments associated w/ the radial n? Most common?

Axilla (Crutch Palsy) Humerus/Spinal Groove (Saturday Night Palsy) Supinator Wrist Saturday Night Palsy, goes away in a few weeks, may be confused w/ a stroke

What does humerus/spiral groove radial n entrapment (Saturday Night Palsy) cause?

Wrist drop (paresis of extensor mm of wrist, finger, and thumbs)

If a pt presents w/ foot drop, how do you differentiate between an L5 radiculopathy vs peroneal n (common fibular) entrapment?

Test inversion of the foot, if it's.. Normal, issue w/ peroneal n Abnormal, issue w/ L5 (peroneal n isn't responsible for inversion of the foot) Pt may also have back pain w/ L5, not so w/ peroneal .. so inversion issue and back pain = L5!

A nerve conduction study would show what in its findings regarding entrapment?

Below entrapment normal findings Above entrapment = lower conduction amplitude and decreased conduction velocity

What's the pattern of distribution in polyneuropathy? What's affected first/most severe?

Symmetrical in distal portion of limbs (stocking-glove) Legs affected first

What Hereditary Motor and Sensory polyneuropathy am I supposed to remember?

Charcot-Marie-Tooth Neuropathy, T1 & 2

What kind of neuronal dx is CMT T1? T2? Which is most common?

Demyelinating Axonal T1

What's the genetic transmission of CMT T1? Onset? Pt presentation?

Autosomal dominant 1st or 2nd decade ``` Difficulty walking/running Arreflexia Distal symmetric atrophy of legs > arms Sensory loss (mild) EMG shows slowing of motor n conduction velocities Scoliosis Hammer toes ```

What's the genetic transmission of CMT T2? Onset? Pt presentation?

Autosomal dominant Adulthood Distal symmetric atrophy (legs > arms) Arreflexia Sensory loss (mild) EMG is norm/nearly norm

What's another name for Guillain-Barre Syndrome?

Acute inflammatory demyelinating polyneuropathy

What precedes a Guillain-Barre Syndrome?

Illness - EBV - Mycoplasma pneumonia - Campylobacter jejuni

What type of weakness is associated w/ Guillain-Barre Syndrome?

Ascending symmetric

What are reflexes expected to be like in a pt w/ Guillain-Barre?

Hypo-responsive or absent

Are sensory sxs associated w/ Guillain-Barre?

No (if any, minimal)

What kind of polyneuropathy is Guillan-Barre?

Acquired acute inflammatory demyelinating

Prognosis for Guillain-Barre?

Pt likely to recover in 4-6w (up to a year or two) 25% req mech ventilator 20% experience persistent disability/fatigue 5-10% pass d/t resp failure

Tx for Guillain-Barre?

Supportive Plasma exchange or IVIg

What lab findings are key to a Guillain-Barre diagnosis?

CSF: protein inc, glucose and cell count norm NCV (neuronal conduction velocities): slowed, focal conduction block

What's the variant of Guillan-Barre that often occurs in kids? What part of the body does it involve? What anti-body is diagnostic?

Miller-Fisher Syndrome Eye muscles (ophthalmoplegia, ataxia, arreflexia, facial weakness, dysarthria, dysphagia) GQ1b

Multifocal Motor Neuropathy has what diagnostic lab result?

Elevated serum GM-1 antibody CSF norm

Multifocal Motor Neuropathy affects whom? What parts of the body? Are there sensory sxs or UMN signs? What's the tx?

Adult males Slowly progressive, hands > feet No IVIg

What's the most common peripheral neuropathy identified in the US?

PN d/t DM

What cranial nerves are traditionally affected by DM?

``` CN III (down and out) CN VI (affected eye turns inward), CN VII ```

What CD4 count would someone have if a polyneuropathy were to be affecting them d/t HIV? How many pts? What kind is it?

< 200 30-50% of AIDS pts Distal symmetrical polyneuropathy, AIDP, CIDP

What genetics are associated w/ Myasthenia Gravis?

HLA-B8 | HLA-DR3

In cervical radiculopathies, roots C6-8 cause pain in the arm (at different points). What are they?

``` C6 = proximal arm C7 = elbow and upper forearm C8 = medial forearm ```

Small sensory fibers are associated w/ what?

Pain and temp

What are some causes of brachial plexopathy?

Compression/stretch (birth, CABG surgery Inflammatory/Idiopathic (Parsonage-Turner syndrome = severe pain the shoulder) Radiation Injury (ex: F getting tx for breast CA) Neoplastic mass Traumatic Injury Ischemia (DM)

In pronator syndrome of the median n, what movement causes pain?

Forced forearm pronation

What 3 mm are associated w/ anterior interosseous syndrome?

FPL: flexor pollicus longus FDP: flexor digitorum profundus PQ: pronator quadratus

In anterior interosseous syndrome, what are the results expected in a NCS?

Normal EMG is not in FPL, FDP, PQ

What EDX findings are expected in Saturday Night Palsy?

NCS normal EMG in wrist extensors abnormal

Where is the peroneal n located?

Winds around the fibular head, hence the n's other name common fibular

What actions are weakened by peroneal n mononeuropathies?

Foot dorsiflection Foot eversion Toe extension Sensory loss to dorsum of the foot and lateral calf (winds back to L5)

What's the most common cause of peripheral neuropathy?

Regarding peripheral neuropathies, metabolic causes? Infectious causes? Immune-mediated caused? Deficiency states? Toxins? Drugs?

DM Lyme dx, HIV GBS, CIDP, monoclonal gammopathy (CA, multiple myeloma) B12 Alcohol, organophosphates Phenytoin, isoniazid (take w/ B6)

Is Charcot-Marie-Tooth a neuropathy or a myopathy? What does it kind of present as, but later on?

Neuropathy Kinda looks like DMD, but onset is later

What deformity is seen in CMT-1?

Hammer toes